Embed Size (px)
Citation preview
-- 1 ·..,..,..g ; j 29 109@ &@:_
TA
7 .W34 1966 c. 1
lERf\A\N ANALYSlS CENTER
f\LE COP\/ TECt-lNICAL REPORT NO. 3-727
FEASIBILITY STUDY OF THE USE OF RADAR
TO DETECT SURFACE AND GROUND WATER
by
B. R. Davis
J. R. Lundien
A. N. Williamson, Jr.
April 1966
Sponsored by
Advanced Research Projects Agency
Directorate of Remote Area Conflict
Service Agency
U. S. Army Materiel Command
Conducted by
U. S. Army Engineer Waterways Experiment Station
CORPS OJ= ENGINEERS
Vicksburg, Mississippi
T'tris-docnroeoi is i»Yl3jeet to special export controls and each transrnlttal to fmeig11 gouernm�B -m: foceign Aati0i:ials may -mrmaae urlly with prior app�011al of bl. S. A,my Eugi11eer Waterways 'Expe,i111e11t Station. ----
� E.ARTH SCH:J•'=FS DIVISIOJFILE COPY 13 JUN 1966
i��li1i�ll\111i1i�l1ii�il1il llli�@i 3 4215 0018442
Destroy this report when no longer needed. Do not return it to the originator.
The findings in this report are not to be construed as an official Department of the Army position unless so designated
by other authorized documents.
TECI-INICAL REPORl
TA 7 .W34 1966 c. 1
Davis, Billy R.
Feasibility study of the use of radar to detect surface
FEASIBILITY STUDY OF THE U�I:. Ut- t<AUAt<
TO DETECT SURFACE AND GROUND WATER
by
B. R. Davis
J. R. Lundien
A. N. Williamson, Jr.
Iii PROPERTY OF U.S. ARMY
OPOGRAPHIC ENGJN.EERING CENTER
ATTN: LIBRARY 7701 TELEGRAPH ROAD
ALEXANDRIA, VA�15 - 3864
April 1966
Sponsored by
Advanced Research Projects Agency
Directorate of Remote Area Conflict
Order No. 400
Service Agency
U. S. Army Materiel Command
Conducted by
U. S. Army Engineer Waterways Experiment Station
CORPS OF ENGINEERS
Vicksburg, Mississippi
ARMV•MRC VICKSBURG, MISS.
FOREWORD
The study reported herein constitutes a portion of the Mobility
Environmental Research Study (MERS), sponsored by the Office, Secretary
of Defense (OSD), Advanced Research Projects Agency (ARPA), Directorate
of Remote Area Conflict, for which the U. S. Army Engineer Waterways Exper
iment Station (WES) is the prime contractor, and the U. S. Army Materiel
Command (AMC) is the service agency. The broad mission of Project MERS is
to develop a significant research effort to study the physical environment,
particularly as it affects the design and employment of materiel systems,
with special emphasis being given to Southeast Asian environments. The
funds employed for this study were allocated to the WES through AMC under
ARPA Order No. 400. This study was performed during the period January
through May 1964 under the general guidance and supervision of the MEES
Branch of WES, the staff element responsible for the technical management
and direction of the MERS program.
Acknowledgment is made to the representative of Science Services
Division, Texas Instruments Incorporated, who under Contract No. DA-22-
079-eng-295 assisted in the initiation of this test program.
The tests were conducted under the general supervision of Messrs. W. G.
Shockley, S. J. Knight, and A. A. Rula. Mr. B. R. Davis directed the study
and, with Messrs. J. R. Lundien and A. N. Williamson, Jr., prepared this
report.
Col. Alex G. Sutton, Jr., CE, and Col. John R. Oswalt, Jr., CE, were
Directors of the WES during this investigation and the preparation of this
report. Mr. J. B. Tiffany was Technical Director.
iii
CONTENTS
FOREWORD
GLOSSARY .
SUMMA.RY
PART I: INTRODUCTION
Bae kground . . . • . • • • . . . . • . Purpose and Scope of Test Program Previous and Current Investigations Definitions • . • . . . . • . .
PART II: DESCRIPI'ION OF EQUIPMENT
Radar Test Facility Radar Sets • • • . System Calibration .
PART III: TEST PROGRAM
Materials Used Preparation of Soil Samples Measurement of Reflectivity
PART IV: DATA ANALYSIS
Basis of Analysis . . • • . . . . •Analysis of Depth-of-Penetration Test Data Analysis of Signature Test Data • • • . . • • .Discussion of Test Results . • • . . . • • .
PART V: PROPOSED RADAR DETECTION SYSTEM •
Monopulse Radar System . . • . . .FM Radar System • • • . . • . .Variable-Frequency Radar System
PART VI: CONCLUSIONS AND RECOMMENDATIONS
Conclusions Recommendations
V
Page
iii
vii
xi
l
l
2
2
3
6
6
8
l4
18
18 18 19
24
24
24
37
38
43
43 43 44
48
48
48
LITERATURE CITED TABLES 1-6 PLATES 1-18
CONTENTS
. . . . . . . . . . . . . . . . . . . . . . . . . . Page
50
APPENDIX A: CALCULATION OF NORMALIZED ECHO AREA . . . . . . . . . . Al
vi
A a
A. l
C
cc
d
db
dbm
d-c
DC
E
E.
E m
E r
f
FM
G
Antenna aperture area, sq m
Area of illumination, sq m
GLOSSARY
Speed of electromagnetic waves through free space or air, m/sec
Coaxial cable loss, db
Diameter of antenna, m
Decibel
Decibels referred to one milliwatt
Direct current
Directional coupler loss, db
Electric field intensity of the wave reaching the metal plate, volt/m
Electric field intensity incident on the sample surface, volt/m
Electric field intensity of the wave returning to the radar receiver from the subsurface metal plate reflection, volt/m
Electric field intensity of the wave returning to the radar receiver from the soil surface reflection, volt/m
Electric field intensity transmitted through the sample surface, volt/m
Frequency, cps
Frequency modulation
Antenna gain, dimensionless
vii
j
k
K
n
p
R
RA
T
TA
V
X
ex
'Y
€
€ r
E V
e
A
µ
Antenna constant for effective antenna area, dimensionless
Radar system constant, db
An integer
Normalized power
Received power, watts or dbm
Pulse repetition frequency, pulses/sec
Transmitted power, watts or dbm
Surface power reflectance
Range from radar system to sample, m
Receiver attenuator loss, db
Time, sec
Transmitter attenuator loss, db
Velocity of electromagnetic wave through any material, m/sec
Sample depth, m
-1Attenuation constant, m
-1Phase factor, m
Normalized echo area, dimensionless
Dielectric constant, farad/m
Relative dielectric constant or apparent relative dielectric constant, dimensionless
Dielectric constant of free space or air, farad/m
Antenna beam width, deg
Wavelength, m
Electromagnetic pernieabili ty, henry/m
viii
a Conductivity, mho/m
¢ Phase shift, radian
w Angular frequency, radian/sec
ix
SUMMA.RY
A study was made of the feasibility of using radar sensors as a means of detecting the presence and measuring the depth of surface water, and detecting the presence of and measuring the depth to ground water. A secondary purpose was to continue previously begun studies to relate radar returns and the electrical soil constants they provided to soil moisture content.
Large laboratory soil samples were prepared at various moisture contents and with various depths of surface water and various depths to ground water. Standard pulsed radar sensors, operating with frequencies of 297, 5870, and 9375 megacycles per sec and directed at various angles of incidence to the surface, were employed.
The results of this laboratory study indicate that the standard pulsed radar sensors can provide information which will permit detection of surface water and an estimate of the moisture content of deep homogeneous soil samples. However, such sensors used monochromatically cannot provide information to predict depth of surface water, presence of ground water, or depth to ground water.
The systematic manner in which the surface-water depths and depths to ground water were varied in this study permitted an analytical solution of the problem of measuring surface- or ground-water depths, and .led to the conclusion that properly designed radar systems could measure surface- and ground-water depths. Three such systems are proposed.
xi
FEASIBILITY STUDY OF THE USE OF RADAR TO
DETECT SURFACE AND GROUND WATER
PART I: INTRODUCTION
Background
1. To make acceptable estimates of soil trafficability conditions,
information on the characteristics of the surface and of the subsurface to
a depth of approximately 2 ft is required. Instruments and techniques are
available for measuring soil trafficability by contact means.1* Technology
of modern warfare, however, makes it increasingly difficult, if not impos
sible, to precede movement of men and materiel with ground reconnaissance
parties to obtain adequate soil measurements by contact means. A need
therefore exists for a remote sensor capable of gathering and integrating
information on surface and subsurface soil conditions with an acceptable
degree of accuracy and speed.
2. Aerial photography in the visible and infrared portions of the
electromagnetic spectrum is sensitive only to differences in surface char
acteristics because reflection of these wavelengths is almost entirely
dependent upon the characteristics of the air-soil interface. Information
about the surface is useful in a trafficability analysis, but soil con
sistency at the depth most important from the trafficability standpoint
(6 to 12 in.) must be inferred from surface manifestations. At the present
time, the techniques for inferring subsurface soil consistency from surface
indications are more in the realm of art than science, and the results are
dependent greatly upon the knowledge and skill of the photo analyst.
3. Electromagnetic radiation at radio frequencies is capable of pene
trating soil to some depth even though a portion of the radiation is re
flected at the air-soil interface. A significant portion of the radiation
that penetrates the soil may be reflected further by a subsurface interface.
*Raised numbers refer to similarly numbered items in the Literature Cited
at the end of this report.
1
The possibility exists therefore that radar sensors can be used to determine the presence of a discontinuity in material beneath the soil surface. Water-soil interfaces, such as those associated with water on the surface or with ground water, are such discontinuities.
Purpose and Scope of Test Program
4. The tests reported herein are part of a comprehensive study to determine the feasibility of utilizing sensors operating in various portions of the electromagnetic spectrum as airborne sensors of terrain character-istics. The specific objectives of this study were to determine the abil-ity of standard pulsed radar sensors operating under laboratory conditons in the X- (9375 megacycles per sec), C- (5870 megacycles per sec), and P-band (297 megacycles per sec) radar portions of the spectrum to:
a. Determine the feasibility of detecting the presence of and measuring the depth to ground water in common soil types at various moisture contents.
b. Determine the feasibility of detecting the presence of and measuring the depth of surface water.
c. Determine the feasibility of measuring soil moisture content.
Previous and Current Investigations
Previous investigations 5. Previous laboratory investigations have been conducted to deter-
mine if electromagnetic sensors operating in the near- and middle-infrared (0.76- to 12-micron) portions of the spectrum could be used to measure soil
2 parameters for trafficability purposes. A report on investigations con-ducted using active infrared sensors has been published, and a report on tests utilizing a passive infrared sensing device is scheduled for publica-tion soon. Current investigations
6. In addition to the surface- and ground-water studies reported herein, studies are being conducted to determine the capabilities of gamma-ray frequencies for delineating soil type and soil moisture content. Other
2
studies are being conducted using radar frequencies to determine the amount
of power transmitted through vegetation samples.
Definitions
7. For clarity, certain pertinent terms used in this report are de
fined as follows.
Angle of incidence
Angle of reflectance
Antenna gain
Attenuator
Back-to-back
Band
Bore sight
db
Delay line
Depth-ofpenetration test
Dielectric constant
The angle between the normal to the surface at the point of incidence and the line of propagation approaching the surface.
The angle between the normal to the surface at the point of reflection and the line of propagation leaving the surface.
For a directional antenna, the average of the power radiated through the half-power angle of the antenna divided by the power radiated in the direction of maximum radiation by a half-wave dipole.
A device that reduces the amplitude of an electrical signal without introducing appreciable phase or frequency distortion.
A circuit connection in which a portion of the transmitted radar signal is fed directly into the receiver. This connection is used in calibration of the radar system.
A range of radio frequencies of specific limits designated by a letter; e.g. C-band includes frequencies from 3900 to 6200 megacycles per sec.
The act of aligning the transmitting and receiving antennas so that their patterns overlap on the sample surface.
A dimensionless unit (decibel) for expressing the ratio of two amounts of electric or acoustic signal power equal to 10 times the common logarithm of this ratio.
A real or artificial transmission line or equivalent device designed to delay a signal or wave for a predetermined length of time.
A test in which power reflected from the test sample at vertical incidence is measured as layers of the sample are removed.
That property of a material that determines the electrostatic energy stored per unit volume for unit potential gradient. Synonymous with permittivity.
3
Directional coupler
Lobe
Magnetron
Microwave
Normalized echo area
Power received
Incident power
A device that splits the input signal into two output signals. Both output signals, one being much larger than the other, are proportional to the input signal.
One of the three-dimensional rounded or elongate portions or sections of the radiation pattern of an antenna.
A transmitting tube that generates microwave energy. A tunable magnetron can be varied in frequency over a limited range.
Radio waves that are so short they exhibit some of the properties of light.
A measure of the quantity of energy reflected by a sample being interrogated by a radar beam.
The amount of power (watts or dbm) that is incident on the receiving antenna. Power returned differs from power received in that returned power refers to the situation at the sample and received power refers to the situation at the radar receiver.
Power from the radar transmitter incident on the sample surface.
Power reflectance The ratio of power returned to incident power.
Power returned The amount of power (watts or dbm) that is reflected by the sample and returned to the receiving antenna. (See definition for "power received" above.)
Pulse An abrupt change in voltage, either positive or negative with respect to a reference, that conveys information to a circuit. This change is characterized by a rise and decay of a finite duration.
Pulsed radar A radar system in which the transmitted signal consists of a series of pulses of microwave energy.
Pulse width The time in seconds of the duration of the pulse measured between the half-power points of the pulse.
Receiver gain An adjustment in the receiver that allows changes to be made in the amplification of the input signal.
Reflectivity The ratio of the reflected electric field intensity at the surface divided by the incident electric field intensity. Also called reflection factor.
Relative dielectric The ratio of the dielectric constant of a material constant
Saturation
to that of a vacuum. The relative dielectric constant of a vacuum is equal to 1.
A circuit condition for which an increase in the driving or input signal no longer produces a change in the output.
4
Side lobe
Signature test
Surface reflection
Trigger
A portion of the beam from an antenna other than the
main lobe. It is usually much smaller than the main
lobe.
Test in which reflected power from the test sample
is measured as the transmitting and receiving systems
are moved through a range of incidence angles from
0 to 60 deg.
The energy coming from a sample due to first-surface
phenomena only. Surface reflectance refers to the
ratio of first-surface reflection to incident energy.
A pulse that activates a circuit or starts action in
another circuit which then functions for a certain
length of time under its own control.
5
PART II: DESCRIPTION OF EQUIPMENT
Radar Test Facility
General characteristics
8. The radar sets used in these studies are installed in the radar
test facility shown in fig. 1. The principal parts of the facility are the
Fig. 1. Radar test facility
wooden arch structure, the antenna carriage, and the instrument room. Fig. 1
also shows the cart that contains a soil sample whose reflectivity character
istics are to be measured, and microwave-absorbent material that is used to
reduce extraneous signals from the area surrounding the soil cart. The soil
cart is located in the center of the arch and is mounted on a hydraulic
lift (not shown) that is used to align the soil cart properly relative to
the antennas.
Wooden arch structure
9. The wooden, open-end, 50-ft-radius arch 44 ft in length is the
main structure of the test facility. Wood was used in the construction
6
wherever possible to reduce spuriou radar refle tions. A track-pulley
cable assembly is attached to the underside of the two enter supporting
arches to permit movement of the antenna carriage.
Antenna carriage
10. The antenna carriage system is shown in more detail in fig. 2.
Fig. 2. Antenna carriage system
The major portions of each of the radar sets are mounted on this arriage
assembly. A transmitting antenna and a re eiving antenna for each of the
radar bands are mounted on the front of the carriage as shown in fig. 2,
while the transmitter and portions of the receiver sections re mounted in
an environment-control chamber on the back of the carriage. This chamber
eliminates the effects of environmental changes on radar operation 1 charac
teristics by maintaining a constant temperature and humidity. The arriage
system is capable of traversing a 105-deg segment of the arch stru ture
from horizontal to 15 deg past verti al. This arrangement llows the radar
systems to collect reflectivity and reradiation data from fixed soil samples
at a number of aspect angles.
Instrument room
11. The instrument room contains (a) the amplifier, video detector,
7
range gate delay line, boxcar detector, log converter, and recorder portions
of each radar band's receiver se tion (described later), (b) power supplies
for the radar sets, and (c) the test control console (fig. 3). Using the
BAND SELECTOR
Fig. 3. Test control console
test control console, the operator conducting the tests can (a) control
power to all radar sets, (b) select the radar band that he wishes to oper
ate, (c) adjust the gain of the receiver, (d) adjust the frequency of the
local oscillator, (e) monitor the video output pulse and range gating pulse
by means of an oscilloscope, (f) adjust the range gate delay line, and
(g) monitor the data results being recorded on the X-Y recorder.
Radar Sets
General characteristics
12. A multifrequency pulsed radar system capable of measuring re
flectivity characteristics of terrain specimens at various angles of inci
dence was used in this study. The system is composed of three radar sets*
operating independently but not simultaneously at the following frequencies:
(a) X-band at 9375 megacycles per sec, (b) C-band at 5870 megacycles per
sec, and (c) P-band at 297 megacycles per sec.
Operational characteristi s
13. The signal flow diagram in fig. 4 illustrates the principal
* Initially Ka-band at 34,483 megacycles per sec was to be included in thetest program, but the magnetron of Ka-band malfunctioned at the beginningof this test program and could not be replaced in time for this band tobe utilized.
8
,---------------1-----------------------------7
PRF
GENERATOR
I TRANSMITTER SECTION I RECEIVER SECTION
MODULATOR
RADAR
SIGNAL
OSCILLATOR
VARIABLE
ATTENUATOR
TRANSMITTING
ANTENNA
I I
TRIGGER
LOCAL
OSCILLATOR
CRYSTAL
MIXER
VARIABLE
ATTENUATOR
AMPLIFIER V IDEO
DETECTOR
BOXCAR
DETECTOR
Fig. 4. Typical radar set signal flow diagram
LOG
CONV ERTOR RECORDER
components of a typical radar set used in these studies. Each radar set is
comprised of two major subassemblies, i.e. the transmitter and receiver
sections. The purpose of the transmitter section is to generate a radar
signal that is transmitted toward the soil sample being investigated. A
portion of the radar signal reflected by the soil sample is received by the
receiver section which processes this signal and displays it in a usable
form, such as a graph of the change in radar signal returned versus change
in the angle of incidence. Details of how these various functions are per
formed are presented in the following paragraphs.
14. Pulse repetition frequency (PRF) generator. When an area is
being scanned by a pulsed radar system, a sufficient number of pulses of
radar energy must be transmitted by the system for each small increment of
distance traveled by the antennas to ensure continuous monitoring of the
reflectivity characteristics of the terrain. The PRF generator is the com
ponent in a pulsed radar system that controls this rate of transmission.
In laboratory radar systems, the PRF is not a critical factor since the
antennas move slowly. For these studies, the PRF generator was arbitrarily
adjusted for approximately 1800 pulses per sec. The output of this gener
ator, which is a 200-volt positive pulse produced at a rate of 1800 pulses
per sec, is used to trigger the modulator portion of the radar transmitter.
15. Modulator. For each 200-volt positive pulse received from the
PRF generator, the modulator produces two output voltages. One output is a
radar trigger pulse used in the receiver section's boxcar detector to
sample specific time increments of the received pulse (see paragraph 24 for
details). The other output is a 10,000-vo.lt negative pulse with a pulse
width for each of the radar bands as follows:
Radar Band
X
C
p
Pulse Width, microsec
o. 54
0.50
0.82
16. Signal oscillator. The 10,000-volt negative pulse is used to
trigger the signal oscillator which generates a pulse of microwave energy
at a fixed tuned frequency (paragraph 12). The X- and C-band radar sets
10
utilize nontunable magnetrons as signal oscillators while the P-band radar
set uses a ceramic triode tube oscillator. The signal oscillator emits
microwave energy for a period of time equivalent to the pulse width of the
modulator output. The power level of the output microwave energy which is
determined by the design of the signal oscillator is as follows for each of
the bands used.
Radar Band Peak Powerz watts Peak Powerz dbm
X 4787 66.8
C 93 49.7
p 269 54.3
17. Transmitter variable attenuator. The microwave energy pulse
emitted by the signal oscillator is introduced into the transmitting
antenna through a variable attenuator that can be used to adjust the
power level of the transmitted signal. This attenuator is adjusted to
reduce the transmitted power level in such a way that the level of
energy received by the receiver can be processed in a usable form.
18. Transmitting antenna. After passing through the variable
attenuator, the pulse of microwave energy is propagated into space by
means of a parabolic antenna that is boresighted toward the center of the
top surface of the soil sample. When the transmitted wave strikes the
sample, a portion of the microwave energy is reflected toward the receiv
ing antenna.
19. Receiving antenna. The receiving parabolic antenna, which is
also boresighted toward the center of the top surface of the sample,
collects a portion of the reflected microwave energy and passes it through
a variable attenuator in the receiver section.
20. Receiver variable attenuator. The function of this variable at
tenuator is identical with that of the attenuator used in the transmitter
section (paragraph 17), except that here the received microwave energy is
reduced to a level that will not saturate the receiver section. In normal
practice the attenuator in the transmitter section is adjusted so that the
maximum amount of power permissible is transmitted toward the soil sample
with the receiver attenuator range available. This maximum level is
11
determined by the reflectivity of the sample and the attenuation range of
the receiver section attenuator.
21. Crystal mixer. Frequencies as high as those used in radar trans
mission (i.e. 9375 megacycles per sec for X-band) cannot be processed
through standard electronic wiring and amplifier tubes. Wave guides must
be used to route the high-frequency signals efficiently from one point to
another. To simplify the processing of these radar signals, the crystal
mixer reduces the frequency of the received radar energy. It does this by
mixing the frequency of the received signal with the output of the local
oscillator that is tuned to produce a signal having a frequency 60 mega
cycles per sec higher than that of the received signal. The output fre
quency of the crystal mixer is the difference between the frequency of the
received signal and the frequency of the local oscillator. The following
tabulation gives the input and output frequencies of the crystal mixers for
each of the radar bands used.
Radar Band
X
C
p
Frequency of Received Signal
megacycles per sec
9375
5870
297
Frequency of Local Osci�lator Signal megacycles per sec
9435
5930
357
Output of Crystal Mixer
megacycles per sec
60
60
60
22. Amplifier. The input from the crystal mixer to the amplifier is
a pulse having a frequency of 60 megacycles per sec, an amplitude propor
tional to that of the energy received, and a time duration proportional
to that of the transmitted signal. The amplifier, which is tuned to receive
signals having a frequency of approximately 50 to 70 megacycles per sec,
amplifies the 60-megacycle-per-sec signal input and passes it on to the
video detector portion of the receiver.
23. Video detector. The video detector rectifies the 60-megacycle
per-sec signal input into a d-c pulse proportional to the amplitude of the
input signal and applies this pulse to the boxcar detector.
24. Boxcar detector. The boxcar detector has two inputs as follows:
(a) the signal from the video detector, and (b) a range gate that is
12
produced by passing the radar trigger through a delay line. Unless both
of these inputs are present at the same time, the boxcar detector has no
output. When both inputs are present at the same time, the output of the
boxcar detector is a d-c voltage proportional to the amplitude of the
detected video pulse that is coincident with the range gate (see fig. 5).
RANGE GATE
�PORTION OF VIDEO PULSE PASSED
I - BY BOXCAR DETECTOR
TIME
( RANGE GATE PULSE WIDTH 100 NANOSEC)
Fig. 5. Boxcar detector inputs; voltage versus time
The range gate can be adjusted to coincide with any portion of the video
pulse. The trigger that produces the range gate is generated by the modu
lator portion of the transmitter section at the same time that the signal
oscillator is triggered to transmit a signal to�ard the soil sample. In
order to pass the detected video signal due to the soil sample through the
boxcar detector, the range gate must be delayed by a period of time equiv
alent to the time that it takes the transmitted signal to travel from the
transmitting antenna, through space to the sample, and back through space
to the receiving antenna. The time required for the transmitted pulse to
travel through space to and from the sample is computed as follows:
where
T = time required, sec
T = 2R
C
R = distance from antenna to soil sample, m
c = speed of electromagnetic waves through air, m per sec
13
(1)
With the test facility used in these studies, R equals 13.7 m and T is
computed as follows:
T 2(13.7 m)
8 3 x 10 m/sec
T -89 x 10 sec
T = 0.09 microsec
The range gate is adjusted so that it is coincident with the portion of the
video pulse that represents a time delay of 0.09 microsec from the time
the radar signal is propagated by the transmitting antenna. All of the re
mainder of the video pulse shown in fig. 5 is a combination of (a) reflec
tions from objects other than the sample and (b) reflections from the sample
due to the trailing edge of the transmitted pulse.
25. Log converter. The log converter receives the d-c signal from
the boxcar detector and converts it to a logarithmic output voltage. This
permits compression of the high-�nergy-level signals received at vertical
incidence and expansion of the low-energy signals received off vertical
incidence. This is necessary because the return signal off vertical inci
dence is of such a low level that any changes in the quantity of reflected
energy due to changes in sample parameters will be only slight, and these
changes must be amplified if the data are expected to be of any value.
26. Recorder. The output of the log converter is recorded by the X-Y
recorder as a function of the radar energy reflected from the sample versus
the angle of incidence.
System Calibration
Calibration of X-Y recorder
27. As stated in paragraph 26, variations in the quantity of radar
energy reflected by the soil samples were recorded on an X-Y recorder. To
interpret the recorder deflections in terms of actual power received, the
recorder must be calibrated for each of the radar bands by inserting known
amounts of radar power into the receiving system and measuring the resulting
14
voltage output on the X-Y recorder. To accomplish this, the transmitted
power of each radar transmitter was measured using a standard power meter.
Next, the transmitter and receiver were coupled back-to-back as shown in
fig. 6. With the equipment connected in this manner, the radar energy
TRANSMITTER 1----�-1
VARIABLE ----
ATTENUATORS
RECEIV ER t---1111----------1
Fig. 6.
COAXIAL CABLE
r::CEIVING \.:TENNA
Radar sets connected back-to-back
being received by the receiver section came directly from the transmitter
through a directional coupler instead of being received through the re
ceiving antenna. Attenuation was then added between the transmitter and
receiver by means of the variable attenuators (paragraphs 17 and 20) until
the power level being received resulted in a minimum reading on the re
corder. Next, the attenuation was removed in carefully measured increments
until the receiver became saturated and further increases in power did not
result in an increase in recorder deflection. Throughout this calibration
procedure, the attenuation value of each of the variable attenuators was
recorded along with the corresponding recorder deflection. To ensure
accuracy, it was necessary to go through the calibration procedure period
ically (paragraph 30). Typical calibration recordings are given for each
of the radar sets in the first three columns of tables 1, 2, and 3.
28. The power received PR that corresponds to each of the recorder
deflection values can be calculated and plotted versus recorder deflection
to provide a receiver calibration curve. PR for each recorder deflection
was found by subtracting all power losses between the transmitter and
15
receiver from the transmitted power. These losses were due to the fixed
losses of the directional coupler and the coaxial cable and to the losses
due to the variable attenuators. Therefore, PR for a given recorder
deflection was calculated using the following equation:
where
PR = PT - (DC+ CC+ TA+ RA)
power received, dbm
power transmitted, dbm
(2)
loss in directional coupler, db (X-, C-, and P-band losses were 9.6, 20.0, and 20.0 db, respectively)
CC = loss in coaxial cable, db (X-, C-, and P-band losses were 5.5, 3.7, and O db, respectively)
TA = loss due to the transmitter attenuator, db
RA= loss due to the receiver attenuator, db
Calculated values for PR are given in the last column of tables 1� 2,
and 3, and plots of the resulting calibration curves are illustrated in
plate 2 for each of the radar sets used.
Daily calibration checks
29. In order to check and maintain system accuracy, a daily calibra
tion check was performed. Twice each day, once in the morning at the
beginning of operation and again in the evening at the end of operation,
each of the radar receivers was coupled back-to-back with its respective
transmitter. A standard amount of attenuation was inserted, using the
variable attenuators between the transmitting and receiving units, and the
transmitter was tuTned on. The output voltage of the receiver resulting
from the input power of the transmitter was monitored on the X-Y recorder.
By measuring the output power of the transmitter and subtracting all
subsequent power losses between the transmitter and receiver, the amount
of power reaching the receiver could be calculated. This value was com
pared with the one obtained by converting the output voltage of the re
ceiver to power by use of the receiver calibration curve shown in plate 2.
In this way, any changes in the system were detected and corrected.
16
30. It was realized that in setting up the system each day there
would be a certain amount of human error. Also, a certain amount of inher
ent fluctuation in the radar systems was to be expected. Therefore, as
soon as a sufficient nwnber of data points were available, the mean devia
tion of the daily readings from the values obtained during the calibration
of the X-Y recorder was calculated and confidence limits were established
for the calibration check. These confidence limits were used to ascertain
if the system was functioning properly. If the value obtained from the
daily check was between these confidence limits, the system was considered
to be functioning satisfactorily. If the value fell outside these limits,
the operator first checked to ascertain if the system was set up properly,
and second, checked for system malfunctions. If both checks were positive,
the system was asswned to have drifted due to aging of components and it
was recalibrated. In this way, the daily calibration check not only moni
tored system accuracy, but also e;ave a convenient indication of the proper
time to recalibrate each of the radar systems.
31. The daily checks revealed that the mean deviations of the
measured values, using all data points, of the X-, C-, and P-bands were
�0.5 dbm, �LO dbm, and �0.9 dbm, respectively. The average differences
between the two dai1y readings, again using all data points, were 0.5 dbm
for both the X- and P-bands and 0.8 dbm for the C-band.
17
PART III: TEST PROGRAM
32. The test program consisted of using the multifrequency pulsed
radar system operating in the X-, C-, and P-band regions of the spectrum
to measure and record the proportion of transmitted radar energy that was
reflected from samples prepared in the laboratory. Tests in which the
sample depth was varied (depth-of-penetration tests) and tests in which
the incidence angle was varied (signature tests) were used to determine the
feasibility of measuring soil moisture content. The depth-of-penetration
tests were also used to detect the presence of and measure the depth of
surface water, and detect the presence of and measure the depth to ground
water.
Materials Used
33. Four materials were used in this test program, i.e. three soils
(clay, sand, and silt) and tap water. The source, classification under the
Unified Soil Classification System (uses) and the United States Department
of Agriculture (USDA) classification system, specific gravity, average
Atterberg limits, and grain size curves for the three soils are shown in
plate 1.
Preparation of Soil Samples
Soil sample container
34. A cross section of the radar test cart in which· the soil samples
were prepared is shown in fig. 7. The cart was constructed of wood and had
the following inside dimensions: 12-ft length, 6-ft width, and 2-ft depth.
The walls of the cart were constructed in 4-in. segments to facilitate
removal of the soil in layers during the depth-of-penetration tests
(paragraph 40).
Construction of ground-water samples
35. The method used for simulation of ground water in these studies
was as follows. A polyethylene membrane material was placed in the bottom
18
4" THICK SIDEBOARD
WATER TABLE - COMPOSED OF SOIL SATURATED WITH WATER
Fig. 7. Cross section of test cart
of the test cart (fig. 7), and the cart was filled with saturated test soil
to a depth of approximately 4 in. Additional free water was added to this
saturated layer to bring the level of material to the top surface of the
bottom 4-in. sideboard. Another piece of polyethylene material was placed
on top of this soil layer, and the edges of the upper and lower polyethylene
sections were glued together to confine the soil and water in the lower
section of the test cart. The sides of the test cart were built up to the
normal height of 2 ft, using tne 4-in. sideboards. The cart was then
filled with soil in at least two lifts, and the soil was compacted with a
pneumatic-tired roller after each lift was added. Moisture content and dry
density measurements were taken at intervals during the construction of the
soil sample to ensure uniformity. No attempt was made to obtain a specific
value for density, but the moisture content was varied from sample to sample
over a broad range of moisture content values for each soil type.
Construction of surface-water samples
36. The process used for simulation of the surface-water samples
consisted first of placing a 4-in. layer of the test soil in the bottom of
the test cart. The interior of the cart was lined with polyethylene mem
brane, and water was added in varying increments until the cart was filled.
Measurement of Reflectivity
Soil sample signature tests
37. Once it was established that the radar sets were functioning
19
properly, the test cart containing the soil sample w s moved into position
under the wooden arch structure and placed on a hydraulic-lift system
located in the center of the ar h. The surface of the sample was elevated
43 in. above the ground. This height corresponded to the point in space
at which the transmitting and receiving antennas for all three radar bands
had been boresighted. The sample then was surrounded with microwave
absorbent material, as shown in fig. 8, to reduce reflections from areas
other than the sample.
Fig. 8. icrowave-absorbent material layout
38. Signatures of the soil sample were determined by measuring and
re ording the quantity of radar energy reflected by the sample as the radar
antenna carriage moved from vertical incidence through an angle of inci
ence of 60 deg. A typical soil sample signature is shown in fig. 9. The
quantity of energy refle ted is a measure of the sample's normalized echo
20
+3.1
-1.5 INDEX NO. 6764-2-18-4WM
DATE 18 FEB 1964 TIME t 730 HRS
5.0 -8.3 SAMPLE: NO.£ TYPE .filb.I. M.C.
TEMPERATURE: SAMPLE � AMBIENT�
..£__ BAND HORIZONTAL POLARIZATION
PEAK TRANSMITTED POWER 4S.0 DBM 0
TRANSMITTED FREQUENCY 5.87 KMC
4.0 1-- -16.1 RECEIVER ATTENUATION 9.4 DB
<
RECEIVER GAIN SETTING _§Q_
� w RECORDER GAIN SETTING .. 10 MILLI VOL TS,'INCH
z"' � Q
3.0 l: -22.2 u
w
0
0 N
a::
� 2.0 < -28.2
�
1.0 -33.7
0 -39.1 .__ ____ _.__ _____ _.__ _____ -'------....l.------L-------l 10 20 30 40 50 60
ANGLE OF INCIDENCE, DEG
Fig. 9. Typical radar sample signature
area3
r , expressed in db. r is used as the radar return parameter
because it is not dependent on radar system constants and is a measure of
the sample properties only. The method of computing r is described in
Appendix A. Since the antenna carriage did not move at a constant speed,
it was necessary to record the position of the carriage at certain incre
ments. This was accomplished by devices on the antenna carriage that were
actuated every 10 deg by spacers mounted on the track of the arch. These
devices broke the recorder circuit, which caused an event mark to appear
on the signature.
Microwave-absorbent material signature tests
39. After the radar signatures from the soil samples were obtained,
additional microwave-absorbent material was placed on top of the soil sample
to cover the entire surface. With the addition of this microwave-absorbent
material, the soil sample effectively was removed from the field of view of
the radar antennas and any radar return measured was due only to the
21
microwave-absorbent material and background areas. Radar signatures were
again measured and recorded as described in paragraph 38. The signatures
obtained were similar to those for soils except that the amplitude of the
return signal normally was much lower. In this manner, effects contributed
by the soil sample were isolated by computing the true signature of the
soil sample as the vector difference between the signatures obtained with
and without microwave-absorbent material covering the surface of the sample.
Depth-of-penetration tests for ground-water samples
40. After the soil sample signature tests and the microwave-absorbent
material signature tests were run, the depth-of-penetration capabilities of
the radar waves as influenced by soil type and moisture content were deter
mined for the three radar bands. With the sample in position under the arch
and surrounded by microwave-absorbent material, measurements were taken
with the antenna carriage at vertical incidence. The quantity of microwave
energy reflected by the sample at vertical incidence was recorded for each
of the radar sets. A thin layer of soil, usually 1/2 in. thick,* was
removed from the sample, the sample surface was raised to the original
height of 43 in., and another recording was taken of the radar return
energy with each of the radar sets at vertical incidence. This process of
removing thin layers of soil and recording the microwave energy returned
from the soil sample was repeated until the water table at the bottom of
the sample was exposed. Results of depth-of-penetration tests for ground
water samples are shown in plates 3-11.
Depth-of-penetration tests for surface-water samples
41. The procedures used to determine depth of penetration for
surface-water samples were similar to those described in paragraph 40 for
ground-water samples, except that different depths of water were obtained by
adding increments of water in the test cart. Initially, the 4-in.-thick
* At the start of the test program, the thickness of the layers of soil tobe removed was not well established due to insufficient data. As moredata were accumulated, 1/2 in. was determined as the thickness that wouldproduce the best data.
22
soil sample had no water standing on it. This thin layer of soil mate
rial was scanned by the radar sets, and the quantity of microwave energy
reflected at vertical incidence was recorded. A small quantity of water,
normally a sufficient amount to increase the depth of water by 1/2 in.,
was then added to the sample, the sample surface was lowered to the
original height of 43 in., and another recording taken of the quantity of
microwave energy reflected at vertical incidence. This process was re
peated until the test cart contained water to a depth of approximately
2 ft. Results of depth-of-penetration tests for surface-water samples
are sho1tm in plates 12 and 13.
23
PART IV: DATA ANALYSIS
Basis of Analysis
42. Radio waves transmitted in a completely homogeneous medium will
be propagated with a constant rate of attenuation, until they disappear,
having been consumed as heat. When the waves strike a sudden discontinuity
in the medium such as the boundary between two materials with differing
electrical properties, some of the waves are reflected, while the remainder
continue their penetration but at a modified rate of attenuation and
velocity. In this program, the attenuation occurring in air in the 50-ft
distance between the test medium (soil or water) and the antennas was
assumed to be zero and the velocity of the waves was assumed to be equal
to that of light in free space. Thus, the first and most important
reflection-causing discontinuity was the surface of the soil or water
itself. The remainder of the waves traveled through the surface into the
sample until they encountered another discontinuity and a second reflection
of the waves was produced. The phase shift between the first and second
reflections varied with sample depth due to the longer path length for the
second reflection. The analysis of the data collected in the program from
the depth-of-penetration tests and the signature tests was based on the
measurement of the proportion of emitted energy which was reflected upon
contact with the various discontinuities, the phase shifts which occurred
between reflections of radio waves from the various discontinuities, and
the change in wavelength that occurred following radio wave entry into
different media.
Analysis of Depth-of-Penetration Test Data
43. The radar returns from the surface of a sample, the subsurface
soil-water interface, and the area surrounding the sample can be thought of
as three separate vectors. The phase of each vector depends on the distance
the wave travels, and its magnitude depends on the reflectivity of the area,
the distance the wave travels, and the electrical properties of the material
24
through which the wave travels. These three vectors combine to form a
vector sum whose phase and magnitude are influenced by the depth to the
soil-water interface (fig. 10). As this depth is decreased, the phase of
a. REINFORCEMENT
r FROM AREASURROUNDINGSAMPLE
b. DESTRUCTION
DIRECTION OF ROTATION FOR DECREASING
270°
90°
r FROM SAMPLESURFACE
RESULTANT OF TOTAL r
NOTE: r = ELECTRIC WAVE REFLECTANCE.
/ r FROM SAMPLE SUR FACE
/ RESULTANT FROM r OFDEP TH , ( SAMPLE SURFACE AND
180°----+------,i,�-- ------�-> AREA SURROUNDING
_________ --:;? SAMPLE
SOIL-WATERINTERFACE
270°
----RESUL TANT OF TOTAL r r FROM AREA SURROUNDING SAMPL £
Fig. 10. Radar return phaser diagrams
the subsurface soil-water interface vector advances in a counterclockwise
direction and its magnitude steadily increases. The phase and magnitude
of the surface reflection vector and the vector from the area surrounding
the sample remain constant during the test. A maximum power return or
reinforcement is produced when the rotating vector is in phase with the
resultant of the constant vectors, and a minimum power return or destruc
tion is produced when the rotating vector is out of phase with the re
sultant of the constant vectors. Furthermore, it can be seen that there
25
will be a reinforcement and a destruction for every 360-deg rotation of the
rotating vector. The pulsed radar systems used in these tests, however,
are sensitive only to the magnitude of the total radar return, and individ
ual pulse returns cannot be analyzed directly to determine the contribution
being made by each reflecting surface. It was possible to make this type
of Qnalysis indirectly because the depth of the sample was controlled in
the test program. In the following paragraphs, the procedures will be dis
cussed for the determination of the existence of subsurface water-soil
interface reflections, calculation of electrical constants of soils from
interference patterns, and calculation of electrical soil constants from
surface radar return.
Determination of existence of subsurface water-soil interface reflections
44. As the sample thickness was reduced in the depth-of-penetration
tests (paragraph 40), the phase of the subsurface interface reflection
advanced, thereby producing oscillations in the total radar return. This
situation is illustrated in fig. lla for a sample composed of Yuma sand
overlying a metal plate. Test results on a sample with a conductive metal
plate bottom are used for illustration purposes as a metal plate exhibits
th';_' highest reflection possible from a second medium. Obviously, a plot of
this type by itself is of very limited use as a calibration or reference
chart for measuring depth to an interface. The appearance of this uniform
cyclic pattern together with the fact that the in-soil wavelength is shorter
than the in-air wavelength of the radar used is, however, enough proof that
the radar wave is penetrating through the upper material in the sample, re
flecting from the interface, and returning to the radar receiver. For the
example in fir,. lla, the oscillations indicate that a wave at P-band fre
quencies penetrated through the entire 0.56-m sample. In this example and
in 0-.ll succeeding tests, the actual depth to a soil-water interface could
not be measured directly with any one band of the type of radar system
used. The depth at which the oscillations first appear indicates the limit
at which a depth-measuring system (such as the variable-frequency system
described in Part V) coula be expected to operate assuming a sensitivity
equivalent to that of the systems tested for this report.
26
aJ 0
'o' w N ...J � -5 .__--h--+--+-----1.1----l�+----+-n,/,,,/---____;!lllc---H.,&::I.L-----+-�=8'-=------t a: 0 ,b
a: w � � -10 1-----+1-/---------------1--------1--------1----o w tu w ...J � w
/
a: -15 1,_ ____ ......_ ____ ...1,,,_ ____ ....._ ____ ....._ ____ ......_ ___ ___,,
a. TOTAL RADAR RETURN
aJ 0
0----------------------------------
15' w
N
...J < � -10 0
b
a: w � SLOPE = 3 8.1 ....Q.L
,-suRFACE REFLECTION
0 M �-2ot-----+-----+-----+------i1�-+-----+-------1
0 w t-
u w
...J � w
a:
Cl) z < 0 <a:
�--� :I: Cl)
w
-30 "-----""-----""----------------....._ ___ ___,
IOT'r
5,r
00 0.1
b. COMPONENTS OF RADAR RETURN
0.2
RADIANS
M
0.3
SOIL DEPTH1 M
0.4
c. PHASE SHIFT OF RADAR RETURN
0 . .5 o.e
Fig. 11. P-band depth-of-penetration test results for Yuma sand; moisture content = 19.27j
27
Calculation of electrical properties from interference patterns
45. Phase-shift method of calculating electrical constants of soils.
The radar return that produced the type of oscillations illustrated in
fig. lla can be separated into two components, as follows: (a) a constant
surface reflection (a small amount of background reflection was present)
(fig. llb), and (b) a metal plate reflection which varied in magnitude
(fig. llb) and in phase (fig. llc) with depth of overlying soil. The wave
that reaches the metal plate in the bottom of the sample has a phase and
magnitude which are functions of depth. The equation for the intensity of
this wave at an instant in time is given below.4,5
where
-0'.X -j�X E = Et
e e
E = electric intensity of the wave reaching the metal plate, volt per m
Et= electric intensity of the wave transmitted through the airsoil surface boundary, volt per m
-1a = attenuation factor of the soil,
t3 phase factor of the wave, -1= m
X = soil depth, m
j =J=I
(3)
In these studies the radar wave traveled twice the soil depth as it pene
trated through the surface boundary to the metal plate and was reflected
back through the surface of the sample. When equation 3 is adjusted by
this factor, added to the surface reflection, and written in terms of
power, it becomes:
where
p = Er + Em (
R )
2
E. E. R + x l l
-2ax e -j2e>xe
2
P = normalized power of the wave returning to the radar receiver from the soil
28
(4)
E r
= electric field intensity of the wave returning to the radarreceiver from the soil surface reflection, volt per m
E. = electric field intensity of the incident wave striking thel surface of the soil, volt per m
E m = electric field intensity of the wave returning to the radar
receiver from the subsurface metal plate reflection, volt per m
R = range from radar system to sample, m
The constant surface reflectance term in this equation is E/Ei
; the
magnitude of the metal plate reflection, which varies with soil depth, is
Em (
R)
2
E. R + X -20'.x e ; and the phase shift of the metal plate reflection,
which also varies with soil depth, is -j2t3xe • By using every data point
obtained in the depth-of-penetration test (fig. lla) as a solution to
equation 4 and solving the equations simultaneously, a, t3 , E/Ei
, and
E /E. can be evaluated. This method requires many calculations and is m l
best suited for us8 with a digital computer. A much simpler method can be
used to demonstrate the procedure and evaluate the unknown quantities in
equation 4 by using the maximum and minimum points from the cyclic depth
of-penetration curve as solutions to the equation. The maximum points are
given by the equation
r m R -20'.x[
E E 2 ]
2
p max = Ei + E i ( R + x) e
and the minimum points are given by the equation
Equations 5 and 6 describe the envelopes of the maximum and minimum
points, respectively, as shown in fig. lla and are obtained by setting
e-j23x
in equation 4 equal to +l to obtain equation 5 and -1 to obtain
equation 6. As an example of the calculations used to separate the
29
(5)
(6)
components of the total radar return, consider the point at a soil depth
x of 0.165 m in fig. 11. The minimum point as shown in fig. lla is -7.7 db
or a power ratio P of 0.17 (db= 10 log P), and by extrapolation to the
maximum point envelope, a maximum point at this soil depth would have been
approximately -1.3 db or a power ratio of 0.74. Substituting these values
in equations 5 and 6 gives:
and
0.74 =[Er+
Em (-R-) 2 e-2ax]2
Ei Ei
R + x
[E E 2
] 2
0 . .17 = _.!: - � (-R--) e-20'.x E. E. R + X
l l
Taking the square root of both sides and solving two simultaneous equations,
the reflections in terms of voltage ratios are
and
....E = o.64E. l
Em
(R
x )2
e -20'.x = E. R + 0.23l
or in terms of power ratios
2 2 10 log (E/Ei) = 10 log (o.64) = -3-9 db= surface power reflection
2 [ / ( R ) 2 -2ax] ( ) 2 10 log Em Ei R + x e = 10 log 0.23 = -12.8 db= metal plate
power reflection
The above solutions for the metal plate reflections and the surface reflec
tions along with solutions from other maximum and minimum points are
plotted in fig. l.lb. Although not used in any calculations, the value
for (E✓Ei) can be found by extrapolation and is the point where soil
depth x is zero. In fig. llb, this value is the point where an extension
of the metal plate reflection curve (straight line) crosses the vertical
axis at zero soil depth.
30
46. The attenuation factor a varies with soil composition, moisture
content, density, etc., and is computed using the term in equation 4 in
volving the magnitude of the metal plate reflection as follows:
. m R -2ax [E 2
]
2
Return signal from the metal plate = Ei ( R + x) e
or expressed in db:
Return signal from the metal plate, db 10 log [:: (R ! x
) 2 e -2ax] 2
(7)
= 20 log E� + 40 log R - 40 log (R + x) + 20 (log e)(-2ax) (8)l
To find the slope of this expression, the derivative with respect to x
must be taken.
Slope of the metal plate return signal (db/m) = - 40 (R � x) log e
+ 20 (log e)(-20'.) = -(17.372)(R ! x) - (17.372)(a) (9)
The value of x varies between 0 and 0.5 m, and when compared with the
range (R = 13.7 m) it is negligible. Thus, the exp
(
re1
si)
on R � x can be
approximated by 1/R , and the expression (17.372) R + x becomes 1.3 db/m.
Equation 9 then reduces to
Slope of the metal plate return signal (db/m) + 1.3 db/m -17.372a (10)
Using the srunple in fig. 11 for illustration purposes, a can be calculated
by inserting -36.1 db/m (the measured slope of the metal plate reflection
curve, fig. llb) into equation 10 as follows:
-36.l db/m + 1.3 db/m = -17,3720'. -1or a= 2.0 m
47. The phase shift of the radar return (fig. llc) is shown in-j2t3x equation 4 by the term e . It is found by inspection of the
oscillations in fig. lla and the prior knowledge that there are n radians
31
of phase shift between a maximum and a minimum or 2n radians between
successive minimums or maximums. The pbase factor e can then be obtained
from the cycling effect (fig. lla) or phase shift shown in fig. llc as
follows:
R = (1/2)(phase shift slope, radian per m) (11)
where phase shift slope is equal to the number of oscillations occurring
over a change in depth of 1 m multiplied by 2n. Using the sample in
fig. 11, f, can be calcu.lated by inserting 17.1n radians/m (the measured
value of the slope of the phase shift curve, fig. llc) into equation 11.
or
s = (1/2)(17.1n radians/m)
t:· = 26. 8 -.1
m
48. Of the factors influencing the normalized power, the relative
dielectric constant is of primary interest because it can be sbown to be
re.lated to the moisture content of the soil. The equations5 for determin-
ing relative die.lectric constant
soils ar0 as follows:
E and conductivity a for nonmagneticr
0: = (1)
8 :.- (1)
�(8-1) µ2€
( l + i2 + 1)
Solving equations 12 and 13 simultaneous]y yields:
2 Er = c2 (�2 - cl-)
20:f> a = rnµ
32
(12)
(13)
(14)
(15)
where
E
E
-1a= attenuation factor, m
(D =
µ =
E =
a
B =
= r
= V
=
angular frequency, radian/sec
electromagnetic permeability of the soil (assumedto that of free space), 4n x 10-7 henry/m
dielectric constant
conductivity, mho/m
phase factor, -1m
relative dielectric
dielectric constant
( E/E = E ) , farad/m V r
constant (dimensionless)
of free space, l/(3611 X 109 ) 8 speed of light in free space, 3 x 10 m/sec
to be equal
farad/m
The assumption that the electromagnetic permeability µ for soils is equal
to that of free space is valid because the soils tested are known to be
nonmagnetic. Only traces of magnetic materials have been found in these
soils.
49. Again using the sample in fig. 11 for illustration purposes,
the following calculations can be made. Substituting the previously cal
culated values for a and B into equations 14 and 15 yields values for
E and o . The angular frequency m is equal to 2n x 297 x 106 radians
p:r sec where 2 97 x 106 is the frequency in cycles per sec of the P-band
radar system.
E r
E r
( 8
I )2
C -1
)2
C -1
)2
= 3 x 10 m sec [ 26.8 m · - 2.0 m · J (2n x 2 97 X 106 radians/sec)
2
= 18.5
a = (2n x 2 97 x 106 radians/sec) (4n x 10-7 henry/m)
a = 45.8 x 10-3 mhos/m
50. Wavelength method for computing electrical constants of soils.
The relative dielectric constant of a soil sample also can be calculated
from the wavelength of the radar wave in the material. Examination of the
radar return phasor diagram shown in fig. 10 indicates that a maximum and
33
minimum will occur in the oscillations of the reflected power from a
soil sample every 360 deg. Since the wave travels through two soil depths
(down and back) to produce the oscillations, one need only measure the
distance between two successive minimums or maximums of the depth-of
penetration test results and double the value obtained to determine the
wavelength of a radar wave in a medium. In the sand sample used for
illustration of these oscillations (fig. lla), P-band frequencies had a
wavelength of 0.234 m as compared to 1.01 m in air. A numerical value for
the attenuation constant a is not always attainable from the sample data
since this determination requires that very little system drift occur dur
ing the entire depth-of-penetration test. The phase factor � is not as
readily obscured because the minimums and maximums are usually available
even under the most undesirable conditions. From prior tests, the dissipa
tion factor cr/mE (equations 12 and 13) has been found to be small at
P-band frequencies and can be neglected when calculating the relative
dielectric constant without causing much error. For example, the value
� 2 2 2 of l + a /m E for silt at 4.9 percent moisture content and P-band
frequencies is 1.03 (see table 5 for conductivity factor). This is the
largest value obtained for soils tested so far. Equations 12 and 13 then
reduce to the following expressions:
Since
a = ill ✓ µ; ( .J 1 + O - 1)
a = o
S = m.Jµe
� = 2n/i , E = E E V r
2C
1
µE V
, and ro = 2nf , substituting in
equation 16 gives:
2 2 2 E = c /f )... r
34
(16)
(17)
where
E r
apJ)arent relative dielectric constant ( terminology changed to "apparent" since dissipation factor is being neglected)
C speed of light in free space, 3 x 108
m/sec
f frequency, cps
A= wavelength in the mediwn, m
Using the wavelength value determined from the oscillations (fig. lla),
the apparent relative dielectric constant for Ywna sand at a moisture
content of 19. 2 percent was calculated as fol.lows:
€ r
E r
= (3 X 108 )2
(297 X 106)
2 (0.234)2
18.7
When the above value for apparent relative dielectric constant is compared
with the r-?lc1tive dielectric constant calculated previously (E = 18.5)
in equation 14, it differs by only 0. 2 . Similar differences were noted
for other samples.
51. Surface-reflection method for computing electrical constants
of soi.ls. If radar waves are not reflected from a subsurface layer such
as a water table, the total energy reflected by a soil will be due to
f fl t . d b d f 11 f t . 1 . . d 5sur ace re ec ions an can e expressc as o. ows or ver 1ca. 1nc1 ence:
E rr =
E.l
If the dissipation factor
before:
a
WE
�( 1 - j1/2
:E ) 1
.£....)1/2+1WE
( 18)
is considered to be very small as asswned
r -· Afr - 1 �+l
or the power reflectance is 2 r ( � - l)
�-(19) af; + 1
* Equation must be squared because power as measured with the radar setsis in terms of watts while equation 19 is in terms of volts.
35
A graphical illustration of the relation between the power reflectance and
the apparent relative dielectric constant is shown in fig. 12. For example,
water is known to have a high relative dielectric constant of approximately
81. When this value is inserted in equation 19, the power reflectance is
found to be 0.64, or -1.94 db, a high value compared with that of soil
L "' t-z
<
z
0 u
� a: t-u UJ ...J UJ
0
UJ >
t-< ...J II.I a:
t-z II.I
a: <Q. Q.
<
100
90
80
70
60
�o
40
30
20
10
9
8
7
6
5
4
3
2
I
0
\ \
\ \
\ \
\ \
\ \ \\
-5
\ \ '
'Ii\.
�
�
� -----10 -rs -20
POWER REFLECTANCE r2, OB -25 -30
Fig. 12. Power reflectance versus apparent relative dielectric constant
as determined from r 2 ·--( � - 1. )2
�+ 1
(see table 5). In the case of actual sample measurements, the power 2
reflectance r was taken to be the average soil surface power reflection
in watts divided by an average bare metal plate power reflection in watts. 2 The power reflectance r taken from the depth-of-penetration data
(table 5) was inserted in equation 19 so that a solution for apparent
relative dielectric constant E could be obtained.
Analysis of Signature Test Data
52. Signature tests were run to determine the feasibility of pre
dicting soil electrical constants which in turn could be related to soil
properties. It is possible to calculate one electrical constant, apparent
relative dielectric constant, from the signature tests at angles of
incidence near 0 deg(� 10 deg). This requires modification of the surface
reflection method for computing soil electrical constants described in
paragraph 51 to include changes in incidence angle. At angles of incidence
greater than 10 deg, the surface of the samples appeared specular to the
waves that were transmitted in each of the three radar bands, and the
amplitude of the radar return rrom the soil sample was often less than the
noise level of the system. This noise level was made up primarily of
(a) return from the microwave-absorbent material surrounding the soil
sample, (b) return produced by the antenna side lobes which strike areas
outside the immediate test area, and (c) electronic noise in the electrical
circuits. It should be noted that these radar sets are being used inside
a test facility that will contribute to the noise of the system due to
multiple reflections within the arch. Efforts thus far to develop valid
techniques for analyzing these data have been unsuccessful because of the
noise present in the signal as described above and because the shapes of
the signature curves change drastically with changes in surface texture of
the soil.6 Although much care was taken to make the surface of the test
specimen smooth prior to running the signature test, pits and scratches
were unavoidably left on the surface. It was found that even these slight
changes in the surface texture would alter the signature curves more than
would large changes in soil constants. For these reasons, results of the
signature tests are not discussed herein.
37
Discussion of Test Results
Ground-water tests
53. The ability of radar sensors to detect the presence of ground
water is determined not only by the radar frequencies being used, but also
by the electrical properties of the first (soil) and second (e;round water)
media in which the wave is traveling after entering the sample. Results
of the tests for each of the soils used are summarized in tables 4 and 5
and are shown graphically in plates 3-11 as plots of normalized echo area
y (see Appendix A for method used to compute r) versus soil depth above
water table.
54. Sand. Graphs illustrating the results of tests conducted using
sand samples with Eround water at three moisture contents are shown in
plates 3-5. Plate 3 illustrates the penetration and detection capabilities
of P-band frequencies in sand having moisture contents of 0.6, 5.0, and
14. 3 percent. 'rhe pattern of oscillations described in paragraph 50 was
fairly well defined at all three moisture contents and indicated that this
particular frequency is capable of penetrating through at least 20 in. of
sand and detecting the presence of ground water. It should be reemphasized
at this point that the power measured by the radar receiver was in terms of
relative power and is expressed in db; therefore, oscillations such as
those shown in plate 3c, that appear to be only minor, were actually pro
duced by rather large changes in the quantity of radar energy being re
flected from the soil. For example, there was approximately a 60 percent
increase in power between the maximum and minimum signals received that
define the oscillation for the soil depth of 14 to 19-1/4 in. Plates 4 and
5 illustrate the results of tests conducted using C- and X-band frequencies,
respectively. Although there were distinct fluctuations in the relative
quantities of power received as the depth of the soil material overlying
the ground water was reduced, no well-defined pattern of oscillations com
patible with the wavelengths to be expected in soils for these frequencies
could be established. This probably can be attributed to the relatively
short wavelengths of the C- and X-bands.
5:5. The pattern of oscillations produced by P-band in the
comparatively dry sand sample (plate 3a) indicates that there were appro�i
mately two oscillations produced at this frequency (297 megacycles per sec)
for depths from Oto 20 in. The number of oscillations in a test is roughly
proportional to frequency, and therefore for C- (5870 megacycles per sec)
and X-band (9375 megacycles per sec) frequencies, a total of approximately
40 and 63 oscillations, respectively, should be produced for the same change
in depth if penetration were achieved. With so many oscillations present,
the 1/2-in. increments of sample depth were not thin enough to define the
pattern. Assuming that it would take at least four data points per cycle
for good definition of the pattern, the sample would have to be cut in
layers as thin as 1/8 in. or less to define a pattern of oscillations. For
wet sand samples (plate 3c) in which the number of P-band cycles produced
is double that in dry sand, cuts as thin as 1/16 in. or less would have to
be made to resolve the patterns produced by C- and X-band frequencies if
they were penetrating. Cutting thin layers of soil with this degree of
accuracy is impractical. Deviations in elevation of points on the soil
surface in excess of 1/10 of the wavelength cause serious fluctuations in
the return energy and are most pronounced when short wavelengths, such as
those at X- and C-band frequencies, are used. Greater deviations probably
would obscure any pattern of oscillations that might be present. In actual
testing, deviations as large as 5/10 of a wavelength for X-band and 3/10 of
a wavelength for C-band were not uncommon. Therefore, data from the X- and
C-band depth-of-penetration tests were considered inadequate for determin
ing penetration to ground water.
56. Silt. Graphs illustrating the results of tests conducted with
ground water in silt samples at three moisture contents are shown in
plates 6-8. Plate 6 shows the penetration achieved by P-band frequencies
in silt having moisture content values of 10.7, 15.7, and 25.4 percent.
The pattern of oscillations is fairly well defined for a moisture content
of 10.7 percent (plate 6a), indicating that P-band frequencies can penetrate
through 20 in. of silt at this moisture content. The pattern shown in
plate 6b for silt at 15.7 percent moisture content is well defined for
depths between O and 12-1/2 in. but is considered inconclusive of penetra
tion results at depths greater than 12-1/2 in. P-band, therefore, is
39
considered to be capable of penetrating through 12-1/2 in. of this material
at a moisture content of 15.7 percent. In plate 6c, no well-defined pattern
of oscillations was apparent and penetration of the silt at 25.4 percent
moisture content by P-band wavelengths was considered negligible. The
data presented in plates 7 and 8 represent the results of the C- and X-band
tests on silt samples. Again considerable fluctuation in the return signal
was noted as the sample thickness was decreased, but no pattern of oscilla
tions could be defined. In the tests conducted for C- and X-bands on the
silt sample at a moisture content of 25.4 percent, attempts were made to
cut the layers in 1/8-in. thicknesses for a total of 2 in. to define the
pattern of oscillations of these two bands. This proved unsuccessful; no
pattern of oscillations was apparent, probably because of surface roughness.
C- and X-bands must therefore be considered inadequate to predict penetra
tion to ground water.
57. Clay. Plates 9-11 illustrate the results of tests conducted
on clay samples with ground water at three moisture contents. In plate 9
the patterns of oscillations produced at P-band frequencies are shown for
clay having moisture contents of 7.3, 19.3, and 49.1 percent. The pattern
of oscillations is fairly well defined for the 0- to 10-in. depth for clay
at 7.3 percent moisture content and for the 0- to 8-1/2-in. depth for clay
at 19.3 percent moisture content. P-band frequencies therefore can be con
sidered to have penetrated to these depths. In plate 9c, a pattern of
oscillations could not be discerned, thus indicating that no appreciable
penetration was made in clay at a moisture content of 49.1 percent. Plates
10 and 11 illustrate the results of tests using C- and X-band frequencies.
Again fluctuations in the received power were indicated, but no pattern of
oscillations that was compatible with these short wavelengths could be
established. Therefore, C- and X-band data must be considered inadequate
to predict penetration to ground water.
58. Correlation of soil moisture content with soil electrical
constant. Soil moisture contents were compared with values of wavelength,
apparent relative dielectric constant, and conductivity computed from the
depth-of-penetration test data as described in paragraphs 51 to 57. The
results of these tests are summarized in table 5 and shown graphically in
40
plates 14-18. (To have sufficient data to establish these correlations,
data from earlier radar studies were included.)
59. The results reported for P-band were derived from the cycling
pattern of the depth-of-penetration tests. Since penetration of the radar
waves into the samples was achieved, the electrical properties were indi
cative of subsurface or internal conditons as well as surface conditions.
60. All the results from the X- and C-band wavelengths were obtained
from the analysis of surface power reflectance at normal incidence. There
fore, the results may be influenced by surface drying, roughness, or temper
ature fluctuations. These surface conditions may or may not be indicative
of subsurface or internal conditions of the sample.
61. In most instances, the plots show good correlation between the
moisture content of the soil and (a) the wavelength of the radar wave
inside the soil (plate 14), (b) the apparent relative dielectric constant
(plates 15-17), and (c) the conductivity of the soil (plate 18). The
correlation is best at the longer wavelength of P-band frequencies (plates
14, 15, and 18), probably because the effect of surface roughness of the
sample was proportionally less at these longer wavelengths.
Surface-water tests
62. Tests were conducted on one sample to determine the feasibility
of using radar sensors to detect the presence and measure the depth of
surface water both over clay and over a metal plate. The results of this
study are summarized in table 6 and shown graphically in plates 12 and 13.
The pattern of oscillations shown in plate 12a with the clay under the
surface water indicates that with this material as the subsurface layer,
P-band frequencies can detect the presence of the soil layer from approxi
mately Oto 13 in. in depth. At depths greater than this, insufficient
energy was reflected from the clay to produce a pattern of oscillation.
The patt�rn of oscillations obtained with a metal plate under the water
(plate 12b) is still apparent at a depth of 24.5 in., and it becomes evident
that the type of material underlying the surface water has an important
influence. As the reflectivity of the subsurface layer increases, the
depth-detection capability increases. The results obtained for C- and
X-band tests (plate 13) show a slight pattern of oscillations but they are
41
not compatible with the frequency of oscillation that theory indicates would
be exhibited (see paragraph 50) if these wavelengths actually were penetrat
ing. Therefore, these tests for X- and C-bands must be considered inade
quate for determining the depths of surface water.
42
PART V: PROPOSED RADAR DETECTION SYSTEM
63. For reasons discussed in paragraph 43, a single monochromatic
standard pulsed radar system which is sensitive only to the magnitude of
the return radar energy cannot be used practically to make depth measure
ments in layered materials. In order to measure the thicknesses of layered
media, a radar system capable of measuring the time delay between surface
and subsurface reflections would be needed. There are at least three
systems that may give satisfactory results, but the relative dielectric
constant must be known before a depth can be determined. The three systems
are (a) a monopulse radar system, (b) an FM radar system, and (c) a
variable-frequency radar system. In all three systems a signal would be
transmitted perpendicular to the ground and the return to the receiver would
be composed of both surface reflections and subsurface reflections.
Monopulse Radar System
64. The monopulse system has the simplest operating procedure. A
single pulse of electromagnetic energy with a very short pulse width is
transmitted. The surface radar reflection is the first to return, and the
subsurface reflection is delayed because of the longer distance traveled.
The time delay between the two reflections is measured, and the depth is
calculated using the relative dielectric constant. A monopulse type
system has been used successfully to measure ice thickness.7
FM Radar System
65. In an FM radar system, a constant-amplitude pulse of many cycles
is transmitted. The pulse is linearly frequency modulated from an initial
frequency f1 at the beginning of the pulse to a final frequency f2 at
the end. The radar return, sampled at one instant in time, is made up of
individual frequencies of various amplitudes. The frequency difference
between the surface and subsurface reflections can be interpreted as time
delay and converted to a measure of depth.
43
Variah1e-Frequency Radar System
66. A variab 1 e-frequency raclar system probably would give good
results and requires the simplest radar equipment. The system would con
sist of an ordinary radar receiver and a transmitter with a variable
frequency output. This system could operate with either a pulsed or a
continuous wave transmitter output. The speed of the frequency variation
is not critical, but must be slow enough so thrrt the frequencies of the
returns from the surface and the subsurface layers are essentially the
same. To operate, the transmitter and receiver are positioned at vertical
incidence to the soil and the frequency is varied from lowest to highest.
The return received would decrease with frequency to a minimum, increase
to a maximum, and then repeat the cycle over and over. The only measurement
required is the frequency difference between either two adjacent maximums
or two adjacent minimums. A block diagram of the variable-frequency radar
system is shown in fir,. 13 and the derivation of the depth-determination
formula is shown below. For the geometry shown in fig. 14, the return to
CONTINUOUS WAVE (cw)
TRANSMITTER �Q U£ IV � � \ I II / ,,c �
'd '---..___""T"""-_ __,J
i--------�,�E]I WIDE �
I BAND a: vvv I RECEIVER �
II
� �
LLl FREQUENCY _..I\_ ___ ./
SUBSURFACE
INTERFACE
Fig. 13. Variable-frequency radar system block diagram
TRANSMITTED WAVE
RECEIVED WAVE
t
Fig. 14. Wave phase change in soils SURFACE
SUBSURFAC£ INTERFACE
the receiver will be a minimum. The phase shift between the surface and subsurface reflections is given by:
¢ 2x (2rt) = 4rtx A. A. (20)
and c
A. f
(21)
where
rf phase shift, radian x depth of the medium, m
A. wavelength of wave in the medium, m
c speed of light, 300 x 106 m per sec E relative dielectric constant r
f frequency of radar wave, cps
The term c gives the speed of an electromagnetic wave in a medium with
the conductivity term neglected (the conductivity term has little effect on wave velocity at frequencies above 200 megacycles per sec for the samples thus far tested). From equations 20 and 21
4rtx c (22)
For a minimum, ¢ must be some odd multiple of n: such as rt , 3rt , 5rt , etc. This can be shown by ¢ = 2rtn - rt where n is an integer. There will
45
be two adjacent minimums as the frequency is increased from f1 to f2when n is increased by one unit.
¢2
= 2n(n + 1) - n =C
Subtracting equation 23 from equation 24 yields
or
(4nx) � (f2
- f1
)
C
X = 1 (300 X 106 )
2 � f2 - fl
(23)
(24)
(25)
(26)
This derivation is good for either a pair of minimums at f1 and f2 or
a pair of maximums at f1 and f2 because only the frequency difference
is used in the calculation for depth. From the formula, the only other vari-
able besides the frequencies is that of relative dielectric constant
The relative dielectric constant can be calculated from the average power
reflectance of this variable-frequency radar system. From the limited num
ber of studies conducted, the relative dielectric constant of soils appears
to vary between 3 and 50. If, for purposes of illustration, it is assumed
that (a) the dielectric constant is 9, (b) f1 is 300 megacycles per sec,
and (c) f2
is 350 megacycles per sec, tfie predicted depth to a subsurface
discontinuity from equation 26 would be l m. If f1 were 300 megacycles
per sec and f2 305 megacycles per sec, for the same dielectric constant
the indicated depth would be 10 m.
67. An advantage of a system of this type is that no calibration
of the radar system is needed if the relative dielectric constant of
the medium being tested is known. All measurements are relative. The
accuracy of such a system would depend mainly on the ability to measure the
transmitter frequencies. For best results, the following conditions should
apply to the area being measured:
a. The change in dielectric constants between layers should beabrupt.
46
b. The reflecting planes should be parallel to each other and
p�rpendicular to the line of sight to the radar system.
c. The surface should be smooth with respect to the wavelengths
used.
d. The conductivity shoulu be negligible at the frequencies
being used.
It is obvious that the above conditions would not be encountered in nature
at all times and some adjustments in the analysis technique would probably
have to be made.
47
PART VI: CONCLUSIONS AND RECOMMENDATIONS
Conclusions
68. The following conclusions are based on the data from the tests
reported and the measurement techniques described herein.
a. Standard pulsed radar systems such as used in this studyare amplitude sensitive only, and an individual returnsignal obtained using this type of system cannot be separated into the components resulting from surface and subsurface reflections. Therefore, this type of radar systemcannot be used to measure the depth of surface water,detect the presence of ground water, or measure the depthto ground water (paragraphs 43 and 44).
b. If only surface reflections are present in the returnsignal from a standard pulsed radar system, it is possibleto detennine the presence of surface water from the largereflectance values or large relative dielectric constantscalculated from the reflectance values (paragraph 51).
c. Radar sensors, including standard pulsed radar sensors,provide information which can be used to calculate electricalproperties of soil (paragraphs 45-51). Since correlationsexist between the electrical properties of soil and soilmoisture content (paragraph 58), radar sensors are capableof providing infonnation upon which to base estimates ofsoil moisture content.
d. Long wavelength radar waves (P-band) will reflect from asubsurface soil-water interface. This indicates that it isfeasible to measure depths of layered materials, such assurface-water depth or depth to ground water, with aspecially designed radar system operating at P-band frequencies (paragraphs 53-57 and 62), i.e. 225 to 390 megacycles per sec.
e. Data produced by this program were not sufficient to showthat short wavelength radar waves (C-band or shorter) areas effective as long wavelength radar waves (P-band) formeasuring the depth of layered materials (paragraphs 53-57and 62).
Recommendations
69. Based on the findings of this study, it is recormnended that:
a. Comprehensive tests be initiated to determine the basic
48
electrical properties of soils at high radio frequencies
and to establish correlations between these properties and
soil moisture contents.
b. Field tests be conducted using a variable-frequency radar
set to determine its ability to detect and measure the depthto ground water and the depth of surface water.
LITERATURE CITED
.1. Department of the Army, Soils 1rrafficabili ty. Technical Bulletin ENG 37, July 1959.
2. U. S. Army Engineer 'i-Jaterways Experiment Station, CE, Terrain Analysisby Electromagnc.tic Means; Laboratory Investigations in the 0.76- to5.00-Micron Spectral Region, by B. R. Davis, E. B. Lipscomb, andS. J. Knight. Technical Report No. 3-693, Report 1, Vicksburg,I-1iss., October 1965.
:"). Cosgriff, H. L. , p,�:1k,2, vJ. II. , and 1]1ay.lor, R. C. , Electromagnetic Reflection Properti<2s of Natural Surfaces with Applications to Design of Racbrs am1 Other s�nsors. Ohio State University Research Foundation, Department of Electrical Engineering, Report 694-9, Air Force Contract No. 23U_;16) 3649, Tar,k No. 41136, Columbus, Ohio, February 1959.
4. Von Hippel, A., Dielectrics and Waves. John Wiley and Sons, Inc.,New York, N. Y., 1954.
5.
6.
7.
Jordan, Edward C., Electromagnetic Waves and Radiating Systems.Prentice-Hall, Inc., Englewood Cliffs, N. J., 1950.
,
Beckmann, Petr, and Spizzichino, Andre, The Scattering of Electro-magnetic Waves from Rough Surfaces. The McMillan Company, New York,N. Y., 1963, vol 4.
Barrin1;er Re search Limited, Scientific Reports No. 4 and 5, ContractNo. AF 19 (628)-2998, 145 Belfield Road, Rcxdale, Ontario, Canada,dated 15 February and 15 April 1964.
50
Table 1
Calibration Data2
X-Band
Recorder Receiver Transmitter Deflection Attenuation Attenuation Power Received
in. db db dbm
o.oo 32.40 36.60 -17.3
0.52 32.40 34.20 -14.9
1.20 32.40 31.90 -12.6
1.83 30.10 31.90 -10.3
2.38 30.10 29.60 -8.o
2.88 27.80 29.60 -5.7
3.48 27.80 27.40 -3.5
3.90 25.55 27.35 -1.2
4.32 25.60 25.20 0.9
4.73 23.40 25.20 3.1
5.18 23.40 23.20 5.1
5.58 21.30 23.20 7.2
6.00 21.30 21.20 9.2
6.21 19.30 21.20 11.2
6.25 19.30 19.20 13.2
6.28 17.40 19.20 15.1
6.29 17.40 17.30 17.0
Table 2
Calibration Data, C-Band
Recorder Receiver Transmitter Deflection Attenuation Attenuation Power Received
in. db db dbm
0.00 36.2 36.0 -47.2o.42 34.o 36.0 -45.00.80 34.o 33.7 -42.71.20 31.8 33.7 -40.51.60 31.8 31.4 -38.22.05 29.5 31.4 -35-9
2.41 29.5 29.2 -33-72.77 27.4 29.2 -31.63.11 27.4 27.1 -29.53.46 25.2 27.1 -27.33.75 25.2 25.1 -25.34.04 23.6 25.1 -23.7
4.27 23.6 23.2 -21.84.51 22.7 23.2 -20.94.74 22.7 21.4 -19.14.94 20.0 21.4 -16.45.12 20.0 19.7 -14.75.31 18.3 19.7 -13.0
5.44 18.3 18.0 -11.35.57 16.6 18.0 -9.65.66 16.6 16.3 -7-95.74 15.0 16.3 -6.35.82 15.0 14.8 -4.85.86 13.6 14.8 -3.4
5.90 13.6 13.3 -1.95.92 12.2 13.3 -0.55.94 12.2 11.9 0.95.96 10.9 11.9 2.25.98 10.9 10.6 3.55.99 9.6 10.6 4.8
Table 3
Calibration Dataz P-Band
Recorder Receiver Transmitter Deflection Attenuation Attenuation Power Received
in. db db dbm
0.00 50 8 -23.70.10 50 7 -22.7o. 50 50 6 -21.70.60 50 5 -20.70.80 50 4 -19.71.00 50 3 -18.71.20 40 12 -17.71.40 40 11 -16.71.60 40 10 -15.71.80 40 9 -14.72.05 40 8 -13.72.30 40 7 -12.72.50 40 6 -11.72.70 4o 5 -10.72.90 40 4 -9-73.10 40 3 -8.73.30 30 12 -7.73.50 30 11 -6.73.70 30 10 -5-73.90 30 9 -4.74.05 30 8 -3-74.24 30 7 -2.74.40 30 6 -1.74.55 30 5 -0.74.70 30 4 0.34.85 30 3 1.35.00 20 12 2.35.15 20 11 3.35.30 20 10 4.35.43 20 9 5.35.55 20 8 6.35.70 20 7 7.35.80 20 6 8.35.90 20 5 9.36.00 20 4 10.36.10 20 3 11.36.20 10 12 12.36.25 10 11 13. 36.30 10 10 14.36.31 10 9 15.36.35 10 8 16.36.35 10 7 17.36.40 10 6 18.36.40 10 5 19.3
Soil Depth Above Water Table
in.
19-9/1618-3/418-1/417-3/417-1/416-3/416-1/415-5/815-1/814-1/21413-1/21312-1/21211-1/21110-1/2109-1/48-1/24-3/40
19-3/419-3/818-7/818-3/817-7/817-3/816-3/416-1/415-5/814-1/212-1/210-3/48-3/4
Table 4
Data on Ground-Water Studies
Normalized Echo Area, db X-Band C-Band
Sand at 0.6 Percent Moisture Content
13.5 8.3 12.7 8.214.6 8.3 12.5 8.1 14.5 8.1 16.1 8.7 14.3 8.9 16.3 10.9 14.6 9.0 15.2 9.9 12.8 9.8 13.2 10.1 17.6 9.7 14.6 9.3 17.2 8.9 17.6 8.5 13.9 7.5 13.7 7.1 12.7 7.5 12.7 8.7 13.3 8.5 19.6 13.9 22.5 18.6
Sand at 5.0 Percent Moisture Content
13.0 16.8 15.4 15.1 18.5 16.6 17.6 17.1 16.8 10.5 13.5 15.213.9 (Continued)
11.6 12.4 14.7 16.0 .16.1 15.5 13.7 18.7 18.9 10.9 12.4 9.7
11.7
P-Band
-8.6-6.3-7.2-7.7-8.6-8.7
-10.5-11.5-9.2-7.1-7.3-7.1-4.5-3-9-3.6-3.8-4.4-4.7-4.6-4.4-4.8-9-9-2.5
-4.8-4.8-4.5-4 .1+-4.o
-4.5-4.9-6.l-6.6-8.l-8.5-6.4-4.5
(1 of 8 sheets)
Soil Depth Above Water Table
in.
Table 4 (Conttnued)
Normalized Echo Area, db X-Band C-Band P-Band
Sand at 5.0 Percent Moisture Content (Continued)
8 7 6-1/26
5-1/254-1/243-1/232-1/221-1/20
19-3/419-1/418-1/21817-1/21716-1/21615-1/21514-7/1613-3/413-lj}+12-1/21211-1/21110-1/210
9-1/298-1/27-3/47-1/4
16.8 13.0 18.5 13.9 18.0 13.2 17.0 13.2 18.2 12.2 16.6 12.7 17.3 12.2 16.9 13.6 17.9 13.918.8 14.719.9 16.121.9 16.219.9 18.322.0 16.9
Sand at 14.3 Percent Moisture Content
20.0 18.7 21.1 20.9 21.5 20.8 20.9 20.5 22.3 22.l21.622.119.820.919.920.522.222.6
9.0 12.2 14.8 19.7 19.2 21.2
(Contjnued)
15.9 15.2 17.6 16.6 _17.6 18.0 16.2 16.4 18.9 17.6 17.2 17.6 16.4 17.0 17.3 17.2 18.7 18.0 15.3 16.2 17.4 16.2 16.4 17.3
-4.2-4.8-5.1-5.6-6.4-7-3-8.3-9-3-9.8-7.6-6.9-5.8-4.2-3.0
-3.5-4.5-3.8-3.1-2.5-3.0-2.8-2.6-2.8-3.0-3.4-3-9-3.8-3.8-3.1-3.1-3.5-2.9-3.1-2.6-3.0-2.7-2.6-1.3
(2 of 8 sheets)
Soil Depth Above Water Table
in.
Table 4 (Continued)
Normalized Echo Area, db X-Band C-Band P-Band
Sand at 14.3 Percent Moisture Content (Continued)
6-3/4 20.0 16.6 -1.86-1/4 20.8 16.8 -2.05-3/4 20.4 16.1 -1.55-1/4 20.4 16.5 -1.34-3/4 20.4 16.8 -1.70 22.6 19.5 0.7
Silt at 10.7 Percent Moisture Content
20 10.6 10.8 -5-919-1/2 12.5 12 .4 -5-719 13.8 13.2 -5.418-1/2 12.8 12.4 -6.318 12.7 13.2 -6.317 15.4 14.7 -5.416-1/2 16.1 14.9 -5.8.16 13.8 12.4 -5.515-3/8 11.8 12.6 -5.714-7/8 12.8 12.8 -5-914-3/8 12.9 11.8 -6.o13-7/8 12.9 13.8 -6.113-3/8 14.6 14.3 -6.812-13/16 14.7 15.3 -7-512-1/4 14.3 13.8 -8.511-3/4 7.4 4.1 -7.011 6.5 10.0 -7.710-3/8 13.1 10.5 -7.110 8.o 10.3 -6.39-1/2 8.o 8.5 -5.89 11.2 9.6 -5.28-5/8 15.8 12.4 -3-54-1/2 14.o 12.2 -4.8
3/4 17.6 15.7 -2.80 21.8 20.7 -1.5
Silt at 15.7 Percent Moisture Content
19-3/4 13.1 13.4 -5.6(Continued) (3 of 8 sheets)
Soil Depth Above Water Table
in.
Table 4 (Continued)
Normalized Echo Area, db X-Band C-Band P-Band
Silt at 15.7 Percent Moisture Content (Continued)
19-1/418-3/418-.1/417-3/417-1/416-7/81615-1/21514-1/21413-1/21312-1/411-3/41110-1/2.109-1/298-1/287-.1/26-3/46-1/!+5-3/45-1/44-1/243-1/232-1/21-3/41-1/4
3/40
19-3/4
10.4 11. 515.3 15.715.9 14.614.9 15.217.7 16.113.2 16.016.3 17.715.0 14.213. 9 15.34.8 15.37.9 10.86.7 11.71.9 12.67.5 1.1.1
14.4 14.913.2 13.613.7 13.911.4 13.816.4 14.516.8 13.915.0 15.716.1 15.314.8 13.911.8 13.010.6 13.310.2 13.012.3 14.710.5 14.312.4 15.09.0 14.1
10.5 14.25.4 13.07.7 13.94.7 13.19.3 14.9
12.9 17.8
Silt at 25.4 Percent Moisture Content
15.9 (Continued)
17.6
-4.8-4.5-5.0-5.1-4.8-4.5-4.4-4.o-4.1-4.9-4.4-4.6-5.0-5.3-2.8-3.8-4.2-4.9-5.5-5.9-5.7-5.8-4.5-4.6-3.6-3.6-4.o-3-9-4.4-4.4-5.1-5.9-6.1-5.7-5.3-3.8
-2.8(4 of 8 sheets)
Soil Depth Above Water Table
in.
Table 4 (Continued)
Normalized Echo Area, db X-Band C-Band P-Band
Silt at 25.4 Percent Moisture Content (Continued)
18-1/8 22.3 15.8 -2.216-1/8 12.7 14.6 -2.414-1/4 21.6 18.5 -2,912-3/8 12.8 15.3 -3.310-1/2 21.9 19.6 -3.18-1/2 19.4 18.7 -3.18-3/8 21.4 17.6 -3.78-1;?+ 22.7 18.7 -3.68-1/8 22.4 17.6 -3.l8 24.4 20.9 -3.07-7/8 21.0 18.2 -2.97-3/4 23.4 19.6 -3,37-5/8 20.5 17.9 -3.87-3/8 22.6 18.8 -3.27-1/8 21.0 17.1 -3.56-7/8 22.5 19.3 -3.26-3/4 21.7 18.5 -3.86-3/8 21.9 17.9 -3-36-3/16 19.6 17.3 -3.64-1/2 21.8 16.9 -2.32-3/4 21.6 16.1 -2.40 20.8 16.7 -1.2
Clay at 7.3 Percent Moisture Content
19-3/4 9.8 8.o -3,719-1/4 10.8 10.0 -3.418-3/4 10.9 8.3 -3.618-1/4 12.9 7.8 -3,917-3/!+ 14.3 9.1 -3.717-1/4 10.4 9.7 -3.716-3/4 9.9 10.2 -4.316-1;?+ 10.4 10.4 -3.515-3/4 10.8 10.4 -4.o15 10.7 11.0 -4.l14-1/2 10.8 11.3 -4.o14 10.8 10.3 -4.213-1/2 9.6 10.4 -5.012-3/4 9.4 10.3 -4.312-1/4 10.2 10.0 -5.2
(Continued) (5 of 8 sheets)
Soil Depth Above Water Table
in.
Table 4 (Continued)
Normalized Echo Area, db X-Band C-Band P-Band
Clay at 7.3 Percent Moisture Content (Continued)
11-1/2
1110-1/2
109-1/2
98-1/2
87-1/2
6-3/46-1/!+5-5/85-3/854-7/84-1/2
43-1/82-1/221-3/8
3/40
16 15-5/815-1/814-1/81413-1/2
1312-1/411-3/411-1/410-3/410-1/!+
9-1/2
9-1/16
11.5 11.8 11.6 12.2
11.6 11.1 13.4 10.4 11.6 9.4 12.6 11.0 12.9 12.2 15.2 10.8 11.8 10.4 11.5 10.0 11.6 10.8 10.2 10.2
7.4 9.6 9.3 9.1
11.6 10.2
12.1 11.0 7.4 8.6
12.1 10.4 12.7 9.9 10.4 10.4
9.8 10.4 13.4 11.4 12.4 11.0
Clay at 19.3 Percent Moisture Content
9.9 9.4
11.1 10.3 11.0 12.2 10.8 11.6 16.0 14.6 14.o14.912.612.5
(Continued)
7.6 6.5 8.2
10.3 9.5 8.6 5.6 4.9
10.2
10.2
13.8 14.1 12.8 12.5
-5.0-5.6-4.8-5.2-4.8-4.3-3-5-3.7-3.2
-3.0-2.9-3.4-5.1-3.8-4.3-4.6-5.2
-3.8-3-9-3,4-2.4-1.4-1.2
-3.1-1.3-1.7-2.0-2.0-1.8-1.5-2.0-3.4-3-9-3.1-3.1-3.0-3-3
(6 of 8 sheets)
Soil Depth Above Water Table
in.
Table 4 (Continued)
Normalized Echo Area, db X-Band C-Band
Clay at 19.3 Percent Moisture Content (Continued)
8-1/28-1/87-1/26-7/86-3/85-7/85-1/44-5/843-1/232-3/81-3/41-1/4
3/40
19-3/419-3/818-7/818-3/418-1/417-3/417-1/416-5/81615-1/214-7/814-3/813-3/413-1/412-5/811-5/8.11-1/21110-1/29-7/89-1/4
12.4 11.9 10.5 10.3 13.9 14.7 14.3 13.9 13.0 14.o14.4 14.213.9 14.o11.8 13.019.9 16.0.17.4 15.916.1 14.416.0 13.315.8 10.213.1 12.916. 5 .14.o13.1 .11. 7
Clay at 49 . .1 Percent Moisture Content
15.6 17.4 5.2
12.3 15.6 11.6 8.5
19.7 19.6 16.8 20.0 16.8 14.5 18.0 17.6 13.0 18.8 15.4 18.5 21.5 21.7
16.2 17.1 i2.2 15.7 19.4 15.0 14.9 18.6 17.0 20.2 19.6 19.4 22.8 14.7 17.3 13.1 17.1 16.7 12.5 16.6 19.0
P-Band
-3.3-2.8-1.7-1.8-1.4-1.4-1. l
-2.0-2.9-3-5-3-3-2.0-0.50.71.51.9
-1.4-2.1-1.8-1.8-2.0-2.0-1.8-1.7-1. 6
-1.2
-1.7
-1. 6-1.7
-2.0-2.1-2.4-2.1-2.2-2.1-2.3-1.9
(Continued) (7 of 8 sheets)
Soil Depth Above Water Table
in.
Table 1+ (Concluded)
Normalized Echo Area, db X-Band C-Band P-Band
Clay at 49.1 Percent Moisture Content (Continued)
8-3/4 _17.4 15.4 -2.28 1.1. 8 12.0 -2.37-3/8 11.6 1.1. 0 -2.06-3/4 17.3 18.6 -2.26-1/4 12. l 11.7 -2.15-3/4 17.8 16.7 -2.25-1/!+ 17.l 9.0 -2.04-7/8 20.4 14.5 -1.34-3/8 .l7.0 17.2 -0.33-3/4 _17.4 15.9 -0.43-1/4 16.3 17.3 -0.12-1/2 14.2 16 . .1 -0.32 16.5 15.9 -0.51-1/}+ 16.1 .17.1 -0.7
5/8 18.5 19.5 -4.10 17.3 19.7 -4.7
(8 of 8 sheets)
Table 5
Soil Electrical Pro�erties
P-Band Conductivity Wave-Moisture Power Reflectance length Apparent Relative for P-Band*
Test Item Content db in Soil Dielectric Constant Frequencies
22:._ ..!!?.:. ___L_ � � ---1E.:._ � C-Band � mhosLm x 10-3
Sand-Ground Water Studies
62 1 o.6 -10,5 -14.1 22.6 3.4 2,2 3.1 5,61 66 2 5,0 -7,6 -8.5 17.8 5.8 4.9 5.0 13.9 64 3 14.3 -3,4 -5,7 11.2 26.7 10.0 12.6 30,5
�
20 4 0,5 -8.9 -10.4 22.4 4,5 3,5 3,2 2lt 5 0,5 -10.0 -10.4 20,7 3,7 3,5 3, 7 68t 6 0,5 -11.0 -8.9 22,0 3.2 4.5 3.3
T-10 7 o.6 -11,9 -11.0 23.0 2.8 3,2 3.0 4.50 23 8 3.9 -9,7 -9,5 18.8 3.9 4.o 4.5
9 5,5 -8.6 -9,7 16.4 4.8 3,9 5,9 15.3 22t 10 5.6 -8.9 -7,9 17.4 4.5 5,5 5.2 30 11 6.o -7,5 -7,7 16.8 6.o 5,8 5,6 40 12 7.3 -8.2 -7.3 15.8 5.1 8.o 6.3 36 13 9.6 -7.6 -6.3 15.0 5.9 8.3 7,0 37 14 11.8 -7.8 -6.o 13.4 5.6 9,0 8.8 38 15 15.1 -6.o -5,3 11.0 9,0 11.4 13.1 39 16 17.8 -5,3 -3,0 10.0 11.4 34,2 15.8
T-9 17 19.2 -5.6 -5,0 9,2 10.3 12,7 18.7 45,9
Silt-Ground Water Studies
63 18 10.7 -10.9 -9,2 17.3 3,2 4.2 5,3 23.1 65 19 15.7 -8.5 -6.8 13,5 4.8 7,2 8.7 33,6 67 20 25,4 -5,0 -4.o 8.o 12.7 19,5 24,7
Silt**
80 21 4.9 -11.4 -11.8 19.0 3.0 2.9 4.38 17.6 81 22 5,5 -10.4 -11.1 19.0 3,48 3,13 4.38 18.2
T-llt 23 5.8 -13,9 -14.o 20.0 2.3 2,2 4.o 15.1 24 24 7,0 -11.5 -9,8 19.6 3.0 3,8 4.127 25 8.9 -8.o -8.4 18.4 5.4 5,0 4.7 25 26 15.3 -5,3 -4.9 14.o 11.5 13.2 8.1 28 27 20.6 -3,5 -3,8 10.8 25,3 20,5 13.6 82 28 20.9 -5.4 -4.3 9.4 11.0 17.0 17,9 50,8 29 29 24.1 -3,0 -3,3 9.0 34.2 28.4 19,5 83 30 25.2 -3,6 -3,2 6.9 24.o 30,2 33.2 72,3
T-12 31 25.6 -3,9 -4.o 8.0 21.9 19.5 24.7 6o.6 26 32 26.6 -4.4 -4.o 7,6 16.3 19.5 27.4
Clar-Ground Water Studies
70 33 7.3 -12.6 -8.6 12.0 2,5 4.8 11.0 31.8 72 34 19.3 -12.0 -8.9 11.0 2.8 4,5 13.1 43.4 71 35 49.1 -5.0 -3,9 12.7 20.5
�
75 36 8.o -12.4 -8.3 12.5 2.7 5,1 10,1 31.9 T-13 37 8.2 -14.o -10.4 14.o 2,2 3.5 8.1 30.8
74 38 8.3 -13,1 -10.9 13.0 2.5 3.2 9.4 31.7 18 39 10,1 -11.4 -10,5 3.0 3.4 17 40 15,0 -10.7 -8.o 3,3 5,4 76 41 18.6 -8.9 -6.8 10.5 4.5 7,2 14.3 46.4 73 42 19.8 -6.5 -6.9 11.5 7,5 7,0 11.9 41.4 16 43 24.2 -5,5 -6.5 10.6 7,5 31 44 30.1 -4.4 -5.0 16.3 12. 7 78 45 34.1 -5.4 -4.6 9,7 11.0 14.9 16.8 57,5 32 46 34.3 -5.0 -3.8 12.7 20.6 79 47 44.6 -2.9 -3,9 6.2 36.5 20,5 41.2 91.2 15 48 44.7 -2.5 49.0 19 49 46,7 -2.6 -2,5 45.3 49.0
T-14 50 48.2 -4.o -4.4 6.5 19.5 16.3 37,4 86.9
* Techniques for computing this parameter only recently developed. Therefore, data on earlier samples are notavailable for computation.
** Metal plate on bottom of test cart in lieu of ground water, t No metal plate or water table, bottom of test cart.
Table 6
Data on Surface-Water Studies
Normalized Echo Area db Water Metal Plate Depth Underlying Water Clay Underlying Water
in. P-Band X-Band C-Band
o.o -0.5 15.4 10.60.5 -5.8 17.7 14.9LO -5.4 18.3 15.21.5 -1.2 18.3 15.02.0 -0.7 18.2 15.42.5 -0.6 16.8 16.13.0 -3.6 16.6 15.83.5 -1.2 15.5 16.34.0 0.2 16.0 14.84.5 -0.1 16.0 15.25.0 -2.7 15.5 15.35.5 -1.4 15.7 15.16.o -0.1 15.5 l4.66.5 o.8 15.6 15.37.0 -0.1 14.9 14.97.5 -1.8 16.1 15.38.o 0.0 15.7 15.88.5 1.6 .15.7 15,09.0 1.4 15.1 15.79.5 -0.3 14.5 15.3
10.0 0.5 15.4 14.610.5 1.7 15.7 15.311.0 1. 8 15,3 14.811.5 0.5 15.2 15.612.0 -0.1 15.4 15.312.5 1.3 15.5 15.213.0 1.8 16.3 15.213.5 1.2 16.3 15.514.o -0.5 16.1 15.314.5 o.8 .16.7 15.515.0 1.9 15.9 15.315.5 1.4 16,7 15. 716.0 0.1 16.8 16.216.5 0.3 16.7 15,3 17.0 1.2 15.6 15.9 17.5 1.7 16.6 15.7 18.0 o.8 16.7 .15.5 18.5 0.3 17.2 15,3 19.0 1.1 16.7 15.2 19.5 1.3 16.1 15.4 20.0 1.3 .16.4 15.8 20.5 '). 5 16.4 14.6 21.0 1.021.5 1.222.0 1.222.5 o.823.0 0.823.5 1.424.o 1.524.5 1.7
Note: Blank spaces in column denote depths occupied by soil.
P-Band
o.8-0.9-1.10.50.65
-0.8-1.l0.650.15
-0.35-1.2-0.65o.60.05
-1.2-1.0-0.35-0.85-1.45-1.05-0.5-0.6-1.05-1.6-1.1-0.9-1.1-1.55-1.35-0.8-0.5-0.45-0.35-0.2-0.05-0.05-0.10.150.150.150.1
-0.35
U. S Standard Sieve Openings in Inches U. S Standard Sieve Numbers Hydrometer
100 3 2 It l l ½ 1 3 4 6 10 1, 16 2C 30 40 50 70 100 140 ''" 1 1 I I I I I 1 . I 0
' -�,... ,...� .....------
90 \ r-.� r-,.....r-... 1 ...
..... ,10
� _.,--CLAY
\ r\ " ( 80 ' "'
20
\
70 \ "" 30
\ \ �, --\ \ � "'�
� � _,,...-SILT 40 � "ii 60
\ \ "'i\. >.
\ \ \. � � 50
Q)
C
\ ' 'I\.
50 1!! �
u -C
\ ... SAND \ "' -
..... -� 40 60 Q)
r .. \ '
30 \ \ 70 ' \
20 \ \ 1
�, 80
' ",� 10 \
90
0 I I ' I ' I I I I I I 100
100 50 10 5 1 0.5 0.1 0.05 0.01 0.005 0.001 Grain Size in Millimeters
GRAVEL SAND I SILT or CLAY Coarse I Fine Coarse Medium l Fine I
Soil Type Source L.L. P.L. p .I. Sp Gr uses USDA Classification Classification
CLAY MISSISSIPPI RIVER ALLUVIUM 71 23 48 2.69 CH sic GRADATION AND
SAND YUMA, ARIZONA, DUNES NOt,IPLASTIC 2.66 SP s CLASSIFICATION DATA
SILT VICKSBURG, MISSISSIPPI, LOESS 31 23 8 2.63 ML SiL
20.------,----...------------�----------
� -20 L---.....1.---...1.-------"---....L...---,L.._--.....I...--____J m o 1.0 2.0 3.0 4.0 s.o 6.0 1.0
0
o" w � w
RECORDER DEFLECTION, IN.
Cl. X - BAND ( 3 APR 64)
� -10,--------.----...--------,.-----r----.---------a:: a::
Q. -20 t-----+-----+------4-----+----�--..D-------1
-60._ __ ____._ ___ _,_ __ ___. ___ _.... ___ 1.-__ ......_ __ ____.
0 1.0 2.0 3.0 4.0 5.0 RECORDER DEFLE CTION, IN.
c. P - BAND ( 3 APR 64)
6.0 7.0
10
0
� 10 m 0
0 ..
� � -20 w a:: a:: w
� -30
-40
,V v'-'
-50 0 1.0
I
}
I/ �
y V
2.0 3.0 4.0 5.0 RECORDER DEFLECTION, IN.
b.C - BAND (29 NOV 63)
6.0 7.0
CALIBRATION CURVES
201-----+---------+-------,f-----4-----4-------4---------1
101-----+---------+-------,f-----4-----4-------4---------1
0�---+-----+-----+-------,f-----+----+----+--�
""'� � 0 a:: <
0 ::c I,) ....
0 .... N
:J < ::I:
g 10
z
0
-10
-20
:I....
0
--........
10 15
SOIL DEPTH ABOVE WATER TABLE, IN.
d. 0.6 PERCENT MOISTURE CONTE NT
A • • fl. ---
�•A
I
• • A - .. -- a_ a. A A •
�
5 10 15 SOIL DEPTH ABOVE WATER TABLE, IN.
c. 14.3 PERCENT MOISTURE CONTENT
20 0
��
20
5 10 15
SOIL DEPTH ABOVE WATER TABLE, IN.
b. 5.0 PERCENT MOISTURE CONTENT
NORMALIZED ECHO AREA VS SOIL DEPTH
FROM P-BAND DEPTHOF-PENETRATION TESTS
SAND
20
01-----+-----+----------------<----------+-----I---�
O -101------+--------+------l------l-------_j__----1--------l
?--< w 0 a:: <
w
w
J < ,:
5 10 15
SOIL DEPTH ABOVE WATER TABLE, IN.
a. 0.6 PERCENT MOISTURE CONTENT
20 0
� 20n-----+------1---------+-----�----l-------+------l-----------1
101------+--------+---�----l-------_j__----l-------l
01-----+------1-------�--------+-------------1
-101-----+------i---------+-----.__--....j..._--_J_--___J_----1
0 5 10 15
SOIL DEPTH ABOVE WATER TABLE, IN.
c. 14.3 PERCENT MOISTURE CONTENT
20
5 10 15
SOIL DEPTH ABOVE WATER TABLE, IN.
b. 5.0 PERCENT MOISTURE CONTENT
NORMALIZED ECHO AREA VS SOIL DEPTH
FROM C -BA ND DEPTH -OF-PENETRATION TESTS
SAND
20
o----+------+-----+--------,1-----+-----+-----+------
o -10----+------+-----+--------,1-----+-----+-----+-------1
?-. <w 0
< 0 ::r
0 ILi
N
:i < � a: 0 z
5 10 15
SOIL DEPTH ABOVE WATER TABLE, IN.
a. 0.6 PERCENT MOISTURE CONTENT
0--------------1-----+----+-----+-------t
-10----+------+-----+---1-----+-----+-----+-------1
0 10 15 20
SOIL DEPTH ABOVE WATER TABLE, IN.
c. 14.3 PERCENT MOISTURE CONTENT
SOIL DEPTH ABOVE WATER TABLE, IN.
b. 5.0 PERCENT MOISTURE CONTENT
NORMALIZED ECHO AREA
VS SOIL DEPTH
FROM X-BAND DEPTH -
OF-PENETRATION TESTS
SAND
1) r
� fTI
0) 20
10
0
·�
o -10
'?'-. < .... 0 a:
<
0 :I:
0 I.J N
< � a: 20 0 z
10
0 -
-:IO
0
A
�- � � �
-- - u -
. - A
!, 10 I!> SOIL DEPTH ABOVE WATER TABLE, IN.
ct 10 :7 PERCENT MOISTURE CONTENT
!,
.A A - -
& .... - -
A .
10 SOIL DEPTH ABOVE WATER TABLE, IN.
A
I!>
c.25.4 PERCENT MOISTURE CONT�NT
Ao A� �
20 0
.
-
20
�
!,
A A --.!1"""'-,
. .
� ,-..-
10
A � ..A�
I!> SOIL DEPTH ABOVE WATER TABLE,IN.
A A -- �
20
b. 15.7 PERCENT MOISTURE CONTENT
NORMALIZED ECHO AREA
vs SOIL DEPTH
FROM P-BAND DEPTH-OF-PENETRATION TESTS
SILT
2Ul"r----+------+----1--------1---------+---�---l------------1
o----+----+--------+---------<e----�-----+--------+------+
o -10----+----+--------+---------<e----�-----+--------+--------I
?--
� 0 a: < 0 X u
:J < � � 20 z
IL
10
0
-10
0
-
5 10 15 SOIL DEPTH ABOVE WATER TABLE, IN.
a. IO. 7 PERCENT MOISTURE CONTENT
--D-
rll
-d1°Y �m- �� � ..r-\.0 I"-.
5 10 15 SOIL DEPTH ABOVE WATER TABLE, IN.
lJ
c. 25. 4 PERCENT MOISTURE CONTE NT
20 0
�
20
5 10 15 SOIL DEPTH ABOVE WATER TABLE, IN
b. 15.7 PERCENT MOISTURE CONTENT
NORMALIZED ECHO AREA
VS SOIL DEPTH
FROM C-BAND DEPTH
OF-PENETRATION TESTS
SILT
20
"'t) r
� fTI
O>
'rt-. <
a:
<
0
<
a:
0
40---+-----+----+-----+-----+------+----t-------1
30---+-----+-----+-----+------+------+------+----
o---+----+-----+-----+------+------+----------1
0
2
10
5 10 15 SOIL DEPTH ABOVE WATER TABLE, IN.
a. 10. 7 PERCENT MOISTURE CONTENT
20 0
0----------------------------
-10---+-----+-----+-----+-----+----+-------lf------t
0 10 15 20
SOIL DEPTH ABOVE WATER TABLE, IN.
c. 25.4 PERCENT MOISTURE CONTENT
10 15
SOIL DEPTH ABOVE WATER TABLE• IN.
b. 15.7 PERCENT MOISTURE CONTENT
NORMALIZED ECHO AREA
VS SOIL DEPTH
FROM X-BAND DEPTHOF-PENETRATION TESTS
SILT
20
"'O r
�rn U)
201-----+-----+-----+-----+-----+----+--�---
101-----+-----+-----+-----+-----+----+--�---
?-. < .... 0
:J < ::l � 20
10
0
. f--10
0
I
-
5 10 15
SOIL DEPTH ABOVE WATER TABLE, IN.
a. 7.3 PERCENT MOISTURE CONTENT
� . .- .
I
I
I
I I
• A • 1-
-
I
-
10
I I
I
i
I
. . .- I
I
. . .
SOIL DEPTH ABOVE WATER TABLE, IN.
A•
15
c. 49.1 PERCENT MOISTURE CONTENT
I
I
& A
-�
20 0
A A A • .A -
20
� �
A • J\..__,_ ...--. i'-A A -�- �� -
- -
5 10 15
SOIL DEPTH ABOVE WATER TABLE, IN.
..A
b. 19.3 PERCENT MOISTURE CONTENT
NORMALIZED ECHO AREA VS SOIL DEPTH
FROM P-BAND DEPTHOF-PENETRATION TESTS
CLAY
20
201---------------------1---+-----+----+-------t
0t-----------+--------1---------1---+-----+----+------+
a -I0f----+--------+------+------+---+------+-----+------1
?-.
� 0 5 10 15 a:: < 0 ::c u
SOIL DEPTH ABOVE WATER TABLE, IN.
a. 7.3 PERCENT MOISTURE CONTENT
�2��---+---------1-- -���----����--�------1
0t-----+-----+------+----.,t----+-----+-----+------t
-I0t-----+-----+------+------,f----+----+------+-----i
0 5 10 15
SOIL DEPTH ABOVE WATER TABLE, IN,
c. 49.1 PERCENT MOISTURE CONTENT
20
5 10 15
SOIL DEPTH ABOVE WATER TABLE• IN.
b. 19.3 PERCE NT MOISTURE CONTE NT
NORMALIZED ECHO AREA
VS SOIL DEPTH
FROM C-BAND DEPTH -
OF-PENETRATION TESTS
CLAY
20
201----+----+-------+-------l---+-----+-------+------I
Ot----+-----+--------+-------1---+-----+-------+------1
o -101------r-----+--------+-------l---+-- --+-------+------I
'?-.
� 0 5 10 15 20 0 a: < 0 :c I.) LJ
LJ
< :l: a: 0 z
SOIL DEPTH ABOVE WATER TABLE, IN.
d. 7.3 PERCENT MOISTURE CONTENT
o----+----+-------.------------+-------
-101----+----+-------+---------,f-----+----+-------+-------i
0 5 10 15 SOIL DEPTH ABOVE WATER TABLE, IN.
c. 49.1 PERCENT MOISTURE CONTENT
20
5 10 15 SOIL DEPTH ABOVE WATER TABLE, IN.
b. 19.3 PERCENT MOISTURE CONTENT
NORMALIZED ECHO AREA
VS SOIL DEPTH
FROM X-BAND DEPTH -
OF-PENETRATION TESTS
CLAY
20
m 0
�<
10..-------,,---------.--------.-------------.----------.------.------------r------,
� -100..__ __ _____.'---__ _____.5 ___ _____. ___ _____.,o ___ -----L,. ____ ___._,5 ___ -----L,. ____ 2....1...o ___ ----L.. __ __.125 <
0 I
u LLJ
0 LLJ
a. CLAY AT 48.2 % MO ISTUR E CONTENT IN BOTTOM OF CART
� IOr------,,-------.------.---------.------.------.-----------.-------r------< � a:: 0 z
WATER DEPTH I IN.
b. METAL PLATE IN BOTTOM Of' CART
NORMALIZED ECHO AREA
VS WATER DEPTH
P-BAND DEPTH-Of'
PENETR ATION TESTS
SURFACE WATER
m 0
.,.. ...
w 0----------------------------------------------------
� 0
0 :::c 0
0
j 20
<
0
z
I C 10
0 0
- -- ""
_. ..- - ,..._ .. - n
- - �
NOTE: SURFACE WATER OVER CLAY A T 48.2 � MOISTURE CONTENT.
10
� 1'\... --
V lT
10
15
a, X-BAND
rt r,,. - - � 1\. -
� � .... -
15 WATER DEPTH, IN.
b. C-BAND
20 25
- _I\ - - -- - - -
20 25
NORMALIZED ECHO AREA
VS WATER DEPTH
DEPTH-OF-PENETRATION TESTS
X- AND C-BANOS
z
J:
r c., z lo.I
..J
lo.I
>
.J
0 II) I
z
2�r-------r-----r----.-----,------,------,-----"T-----r-----,-------.
2
25
20
15
10
5
4 6 8 10 12 MOISTURE CONTENT, "I,
a. SAND
A
ti-r----a
� � -
14 16 18 20
---
r--:.. ---
10 15 20 25 30
MOISTURE CONTENT, "I.
c. CLAY
r----t. �
35 40 45 50
0
a
0
5 10 15 20 MOISTURE CONTENT, "I,
b.SILT
LEGEND
METAL PL ATE BETWEEN SOIL AND TEST CART BOTTOM WATER TABLE BETWEEN SOIL AND TEST CART BOTTOM NOTHING BETWEEN SOIL AND TEST CART BOTTOM
25
IN-SOIL WAVELENGTH VS
MOISTURE CONTENT
FROM P-BAND DEPTH
OF- PENETRATION TESTS
30
50
40
30
20
10
8
6
5
I L �
)
_c/
H
<j' 4
3 �
� 2
� z 0 u
-
u ii: t-
'o
..J UJ 0
UJ >
� ..J UJ
o:: 50 t� 40 0:::
10 20 30
a. SAND
/
4
a:>/
40
,-
50 0 MOISTURE CONTENT, %
n /
/0
10
J:Y
,T
/
I
o/
I
1 I
20 30
b. SILT
40 50
� 30 a. c(
20 /
10
8
6
5
4
3
2
I
A,.,
�
0
0
/' /
10
I
I
I
i
20 30
MOISTURE CONTENT,%
c. CL AY
-
-- -�----
40 50
0 METAL PLATE BETWEEN SOIL AND TEST CART BOTTOM
A WATER TABLE BETWEEN SOIL AND TEST CART BOTTOM
□ NOTHING BETWEEN SOIL AND TEST CART BOTTOM
APPARENT REL ATIVE
DIELECTRIC CONSTANT V S
MOI STURE CONTENT
P-BAND DEPTH-OF
PENETRATION TESTS
PLATE 15
50
40
30
20
10
8 - ("
0
/
/o
,J -
r
6
5 IY
4
3
I- 2 z
z 0 u
P/_ �, rv
�
I � 0 a: I-
-' w 0
w >
-' w a: 50 I-
� 40 a: � 30 Q.
10 20 30
a. SAND
I"\
40
--
50 0
-
-,,
n/
la
10 MOISTURE CONTENT, %
vu
/
/A
,J
n 7_ lr -
o/
IA
I
I
20 30
b. SILT
40
20
/ 0
10
8
6
5
4
3
2
PLATE 16
I"\
0 V _/
8 1>
10
/
/
/ I"\, /0 /
J:T �
20 30 MOISTURE CONTENT,%
c. CLAY
- ----
40 50
0 METAL PL ATE BETWEEN SOIL AND TEST CART BOTTOM
6 WATER TABLE BETWEEN SOIL AND TEST CART BOTTOM
□ NOTHING BETWEEN SOIL AND TEST CART BOTTOM
APP A RENT REL ATIVE
DIELECTRIC CONSTANT VS
MO ISTURE CONTENT
C-BAND POWER
REFL ECTANCE T ES TS
50
50
40
30
20
10
8
_,.. .J.
U"',/'
.,. 6 5
4
o_)f
3
t- 2 z
z 0 IJ
D
u 'o�
LIJ .J LIJ
i5 LIJ >
.J LIJ er 50 I-� 40
f 30 a. <
10
/l
I
/-/
0
20 30
a. SAND
0 / ,v
_o/ �
40
7,-
50 0 MOISTURE CONTENT, %
0
0/
/
10
0 /
p i
V/ o Jo
/
Q
20 30 40 50
b. SILT
20
10
8
0 ''/ u
/l
6 5
4
3
2
'o
/ C /
/
/
'.../6
�
7
10
lJ
20 30
MOISTURE CONTENT,%
c. CL AY
40 50
0 METAL PL ATE BETWEEN SOIL AND TEST CART BOTTOM
/l WATER TABLE BETWEEN SOIL AND TEST CART BOTTOM
□ NOTHING BETWEEN SOIL AND TEST CART BOTTOM
AP PARENT RELATIVE
DIELECTRIC CONSTANT VS
MOI STURE CONTENT
X-BAND POWER
REFLEC TANCE TESTS
PLA.TE 17
100
80
60
40
20
0 0
f 120 5
� 100 u
80
60
40
10
c/
20 30 MOISTURE CONTENT, cg.
a. SAND
40
�v Vo
tg-�
20
PLATE 18
0 0 10 20 30
MOISTURE CONTENT,�
c. CLAY
40
50 0
0
/0
50
10 20 30 MOISTURE CONTENT I aro
b. SILT
LEGEND
40
0 METAL PL ATE BETWEEN SOIL AND TEST CART BOTTOM
t,. WATER TABLE BETWEEN SOIL AND TEST CART BOTTOM
□ NOTHING BETWEEN SOIL AND TEST CART BOTTOM
CONDUCTIVITY VS
MOISTURE CONTENT
P-BAND
APPENDDC A: CALCULATION OF NORMALIZED ECHO AREA
1. The normalized echo area r of a material is determined by means
of the following equation:
where
PR= power received, watts
PT= power transmitted, watts
2 2 PTG 1 Ai
r
(4n)3R4
G = antenna gain, dimensionless
1 = wavelength, m
(Al)
A. = cross-sectional area of radar-beam at a distance equal to R ,l sq m
r = normalized echo area, dimension.less
R = range, m
Equation Al can be written in a more convenient form by dividing PR and
PT by 10-3 watts, taking ten times the .logarithm of both sides of the
equation, and solving for 10 logy.
10 log r
where
10
10
log p:3
+ 2(10 log G) + 10 log [ A
2A� 4] �
10 1 ( 4n) R '
10 logy= normalized echo area (ydb), db
PR power received, dbmlog --= 10-3
PT power transmitted, dbmlog--= 10-3
(A2)
The values for the terms in equation A2 were established as described in
the following paragraphs.
Al
Power Received
2. To establish the quantity of power received from a particular ma
terial at a given angle of incidence (reference fig. 9 of the main text),
the recorder deflection for that angle was converted to power received by
the radar receiver through the use of the appropriate calibration curve
shown in plate 2 of the main text. Any attenuation in the receiver due to
coaxial cables, wave guide, and the variable receiver attenuation, which
had been adjusted to the optimum operating value (see data in upper right
corner of fig. 9), was added to the value obtained from the calibration
curve. This yielded the amount of power actually reaching the receiving
antenna.
Power Transmitted
3. The quantity of power transmitted was measured by means of a
standard power meter and was recorded on each signature curve (fig. 9).
Antenna Gain
4. The gain of the antenna G was calculated using the following
equation:
where
10 log G =
4rtA k 10 1 og ----2
---
a--l
k = 0.6 (constant for a parabolic antenna)
l = wave.length for each band as follows:
X-band: l = 0.0321 mC-band: l = 0.051 m
(A3)
P-band: l = 1.01 m2
Aa
= antenna aperture area =:rt(;) where d is the diameter of the
antenna.
X-band:C-band:P-band:
The following values are obtained for each band:
d = o.456 m and Aa = 0.163 sq m d = 0.71 m and Aa = 0.292 sq m d = 2.438 m and Aa = 4.66 sq m
A2
Substituting these wavelength and antenna radius values in equation A3
yields the following values for antenna gain:
X-band: 10 log G = 30.8C-band: 10 log G = 29.3P-band: 10 log G = 15.4
Range
5. The range R was fixed by the design of the radar facility and
has a value of 13.7 m. This is equal to the radius of the arch (50 ft)
minus the distance that the antenna carriage and antennas were mounted in
from the outer edge of the arch.
Cross-Sectional Area of Radar Beam
6. The cross-sectional area A. of the radar beam at verticall
incidence was calculated using the following equation:
where
Ai � n ( R tan ; )2
e = antenna beam width for each radar band as follows:
X-band:C-band:P-band:
e = 4.93 deg e = 5.86 deg e = 29.0 deg
(A4)
Substituting these beam width values in the above equation A4 yields the
following cross-sectional areas:
X-band: C-band: P-band:
A. = 1.1 sq m A� = 1.6 sq m A
l. 40
l = sq m
Using the above values established for the variables in equation A2, the
following sample calculation was made for the soil signature shown in
fig. 9. The value for the power transmitted for C-band, 45.0 dbm, was
obtained from the soil signature curve (paragraph 3).
A3
or
10 log l
PR= 10 log --10-3
2
! 10 log p':3
+ 2(10 log G) + 10 log [ AA� 4] �f 10 (4n) R '
\ 4 5 • 0 + 2 ( 2 9 • 3 ) + 10 log [ ( O • O 51)
2( 1. 6 )]
. l
� (4n)3 (13.7)4 �
PR ldb = 10 log --
3- 1.3
10- (A5)
One inch of deflection on the X-Y recorder corresponds to a power received
value of -41.8 dbm (plate 2b). Correcting this value of power received by
the amount of attenuation in the receiver at the time of the test, +9.4 db
(fig. 9), yields the following value of rdb for a deflection of 1 in.:
Ydb (-41.8 + 9.4) - 1.3
)'db= -33.7 db
Similar calculations for recorder deflections of o, 2.0, 3.0, 4.o, 5.0,
6.o, and 6.8 in. yield the following values of corrected power received and
rdb
Recorder Deflection Corrected Power db in. Received, dbm rdb'
0.0 -37.8 -39.1
LO -32.4 -33-7
2.0 -26.9 -28.2
3.0 -20.9 -22.2
4.o -14.8 -16.1
5.0 -7.0 -8.3
5.5 -0.2 -1.5
5.8 4.4 3.1
A4
DISTRIBUTION LIST
Address
Secretary of Defense, ATTN: ARPA/AGILE, Pentagon Building, Washington, D. C.
No. of Copies
4
Commanding General, U. S. Army Materiel Command, ATTN: AMCRD-RV-E, 2 Washington, D. C.
Dr. Daniel C. Drucker, Physical Sciences Council, Brown University, 1 Providence, R. I.
Dr. Emil H. Jebe, Operations Research Dept., Institute of Science 1 and Technology, The University of Michigan, Box 618, Ann Arbor, Mich.
Prof. Kenneth B. Woods, Head, School of Civil Engineering, Purdue 1 University, Lafayette, Ind.
Director, Land Locomotion Laboratories, ATTN: SMOTA-RCL, Warren, 3 Mich.
Dr. Ralph E. Fadum, Dean, School of Engineering, North Carolina 1 State College of the University of North Carolina, Raleigh, N. C.
Prof. Robert Horonjeff, 3643 Brook St., 1 I.a.fayette, Calif.
Director, JRATA, APO San Francisco 96243 1
Director, Combat Development & Test Center, APO San Francisco 2 96243
Director, MRDC, APO San Francisco 96346 6
Chief, USMAC, APO San Francisco 96346 2
Dr. Clark N. Crain, Dept. of Geology, University of Denver, 2 Denver, Colo.
Prof. J. A. Russell, University of Illinois, Urbana, Ill. 1
CINCPAC, Camp H. M. Smith, Oahu, Hawaii 2
Dr. Howard Mills, Marshall University, Huntington, w. Va. 1
Dr. Peter Krunkel, Vanderbilt University, Nashville, Tenn. 1
Dr. Robert Stevenson, Florida State University, Tallahassee, Fla. 1
Mr. A. C. Orvedal, USDA, Hyattsville, Md. 3
Commanding General, USAMC Natick Laboratories, ATTN: Curator, Basic Data Collection, Natick, Mass.
Dr. F. R. Fosberg, US Geological Survey, Washington, D. C.
Director, ARFO(LA), P. 0. Drawer 942, Ft. Clayton, Canal Zone
1
2
1
1
Address
Director, ARFO(FE), Beirut, Lebanon, APO New York 09694
Director, U. S. Army Engineer Geodesy, Intelligence & Mapping Research & Development Agency, ATTN: Mr. Gillis, Fort Belvoir, Va.
Wilson, Nuttall, Raimond Engineers, Inc., ATTN: Mr. Nuttall, Chestertown, Md.
No. of Copies
1
1
2
Dr. Jack R. Van Lopik, Geosciences Dept., Texas Instruments, Inc., 1 Exchange Bank Building, Dallas, Tex.
Chrysler Corp., Defense Operations Division, P. 0. Box 1316, 1 Detroit, Mich.
Dr. Richard 0. Stone, Dept. of Geology, University of Southern 1 California, Los Angeles, Calif.
Library, CRREL, P. 0. Box 282, Hanover, N. H. 1
Mr. Robert E. Frost, Photographic Interpretation Research Division, 2 CRREL, P. 0. Box 282, Hanover, N. H.
President, U. S. Army Armor Board, Fort Knox, Ky. 1
President, U. S. Army Air Defense Board, Fort Bliss, Tex. 1
President, U. S. Army Infantry Board, Fort Benning, Ga. 1
President, U. S. Army Infantry Board, Tactical Section, TIS, 1 Fort Benning, Ga.
Commanding Officer, ATTN: Technical Library, Building 313, 2 Aberdeen, Md.
President, u. S. Army Artillery Board, Fort Sill, Okla. 1
President, u. S. Army Airborne and Electronic Board, Fort Bragg, 1 N. C.
Director, Development & Proof Services, ATTN: STEAP-DS-TU, Aberdeen, Md.
Commanding Officer, Aber�een Proving Ground, ATTN: STEAP-DS-D, Aberdeen Proving Ground, Md.
Comm.anding General, u. s. Army Weapons Command, ATTN: AMSWE-RDR, Rock Island, Ill.
Commanding Officer, Yuma Proving Ground, Yuma, Ariz. ATI'N: STEY-TGM
Chief of Engineers, ATTN: ENGAS-I, DA, Washington, D. c.
Chief of Engineers, ATTN: ENGTE-AS, DA, Washington, D. c.
Chief of Engineers, ATTN: ENGMC-ER, DA, Washington, D. C.
2
, ..L
1
1
2
2
1
2
No. of Address Copies
Commander, U. s. Army Southern Command, ATI'N: Engineer, Fort 1 Amador, Canal Zone
,
u. s. Army Attache, American Embassy, U. S. Navy 100, Box 36, 2 FPO, New York
Commanding Officer, u. s. Army Engineer Research & Development 1 Laboratories, ATI'N: Technical Documents Center, Fort Belvoir, Va.
Engineer School Liaison, Fort Belvoir, Va. 1
Transportation Corps Liaison Officer, Fort Belvoir, Va. 2
Commander, U. S. Army Combat Development Command ENGINEER AGENCY, 1 ATTN: CAGEN-SC, Fort Belvoir, Va.
U. S. Army Continental Army Command, ATTN: Engineering Section, Fort Monroe, Va.
U. S. Army Continental Army Command, ATTN: Combat Development (ATSND), Fort Monroe, Va.
President, U. S. Army Aviation Board, Fort Rucker, Ala.
Asst. Chief of Staff for Force Development, Hqs, Dept. of the Army, ATTN: FORDS SSS, Washington, D. C.
Chief of Research and Development, Headquarters, Department of the Army, ATTN: Director of Army Technical Information, Washington, D. C.
Commanding Officer & Director, U. S. Naval Civil Engineering Laboratory, Port Hueneme, Calif.
Offfce of Naval Research, ATTN: Code 463, ND, Washington, D. C.
Commanding Officer, U. S. Naval Photographic Interpretation Center, ATTN: Librarian, 4301 Suitland Road, Washington, D. C.
Geography Branch, Office of Naval Research, DN, Washington, D. C.
Commandant, Marine Corps Hqs., ATTN: A04E, Washington, D. C.
Chief, Bureau of Yards & Docks, ATTN: Code 70, ND, Washington, D. C.
Director, Coastal Studies Institute, Geology Building, Louisiana State University, Baton Rouge, La.
Commanding Officer, F'HIBCB One, u. s. Naval Amphibious Base, Coronado, San Diego, Calif.
Commanding Officer, IBIBCB Two, u. s. Naval Amphibious Base, Little Creek, Norfolk, Va.
Director, Naval Warfare Research Center, Stanford Research Institute, Menlo Park, Calif.
Library, U. S. Army Signal School, Fort Monmouth, N. J.
3
1
1
1
1
3 copies of Form 1473
1
1
1
1
1
1
1
1
1
1
1
Address
Library, Arctic, Desert, Tropic Information Center, Research Studies Institute, Maxwell Air Force Base, Ala.
Commanding General, U. S. Army Transportation Research Command, ATTN: Mr. H. P. Simon, Fort Eustis, Va.
Defense Documentation Center, ATTN: Mr. Myer Kahn, Cameron Station, Alexandria, Va.
New York University, College of Engineering, Research Division, University Heights, New York, N. Y.
No. of
Copies
1
5
20
1
The Chief Signal Officer, ATTN: SIGGE-M-3, Radar & Meteorological 1 Branch, Washington, D. C.
Director, California Forest and Range Experiment Station, P. 0.
Box 245, Berkeley, Calif.
Military Geology Branch, U. S. Geological Survey, Room 4225, GSA
Building, Washington, D. C.
Davidson Laboratory, Stevens Institute of Technology, 711 Hudson
Street, Hoboken, N. J.
Librarian, U. S. Military Academy, West Point, N. Y.
Research Analysis Corporation, ATTN: Library, Bethesda, Md.
1
2
1
1
1
Commandant, Command & General Staff College, ATTN: Archives, Fort 1 Leavenworth, Kans.
Library, Armed Forces Staff College, Norfolk, Va.
U. S. Army Combat Developments Command Experimentation Center, Fort Ord, Calif.
Commanding General, U. S. Army Tank Automotive Center, ATTN: SMOTA-R, Warren, Mich.
Hqs, U. S. Army Mobility Command, ATTN: ASMO-R, Warren, Mich.
Massachusetts Institute of Technology, ATTN: Soil Engineering Library, Cambridge, Mass.
Library of Congress, Documents Expediting Project, Washington, D. C.
National Tillage Machinery Laboratory, U. S. Dept. of Agriculture, P. 0. Box 792, Auburn, Ala.
Heavy Construction Section, Dept. of Engineering, Pavements & Materials Group, U. S. Army Engineer School, Fort Belvoir, Va.
4
1
1
3
1
1
3
1
1
Address
Commander, U. S. Army Electronic Proving Ground, ATTN: Chief, Radar and Electronics Division, Fort Huachuca, Ariz.
No. of Copies
1
Director, Project Michigan, Willow Run Laboratories, Ypsilanti, 2 Mich.
Clark Equipment Co., Construction Machinery Div., Pipestone Plant, 1 Benton Harbor, Mich.
Prof. L. C. Stuart, University of Michigan, Ann Arbor, Mich. 1
Engineering Societies Library, 345 E. 47th Street, New York, N. Y. 1
University of Arkansas, College of Engineering, Fayetteville, Ark. 1
Library, Division of Public Docwnents, U. S. Government Printing 1 Office, Washington, D. C.
Martin Company, ATTN: Technical and Research Staff, Mail 1
No. MP-28, Orlando, Fla.
Commander, Picatinny Arsenal, ATTN: Ammunition Research Lab- 1 ortory, Engr Res Section, Dover, N. J.
Caterpillar Tractor Co., ATTN: Research Library, Peoria, Ill. 1
Commanding Officer, Rock Island Arsenal, Rock Island, Ill. 1
Office of AC of s, ATTN: Engineer Intelligence, 1 Hqs, Fourth U. S. Army, Fort Sam Houston, Tex.
Defense Research Laboratories, General Motors Corporation, Box T, 1 Santa Barbara, Calif.
Office of the Engineer, USAREUR, Intelligence, APO New York 1 09403
Commander, U. S. Strike Command, ATTN: J4-E, McDill AFB, Fla. 1
Headquarters, USAF, (AFRSTC) Astronautics Division, Des/Research 1 and Development, Washington, D. C.
Headquarters, USAF, Base Structures Branch, Directorate of Civil 1 Engineering, ATTN: AFOCE-GC, Washington, D. C.
Headquarters, USAF, Director of Civil Engineering (AFOCE-KA), 2 Washington, D. C.
Commander, Air Proving Ground Command, ATTN: :FGABAP-1, Eglin AFB, 1 Fla.
Systems Engineering Group, Deputy for Systems Engineering, 1 Directorate of Technical Publications and Specifications (SEPRR), Wright-Patterson AFB, Ohio
Commander, SEG (SEHB), Wright-Patterson AFB, Ohio 1
5
Address
Commander, MATS, Andrews AFB, ATTN: Air Installations Officer, Washington, D. C.
No. of Copies
1
Terrestrial Sciences Laboratory (CRJlI'), Air Force Cambridge 1 Research Laboratories, L. G. Hanscom Field, Bedford, Mass.
Dr. A. R. Barringer, President, Barringer Research Limited, 1 145 Belfield Road, Rexdale, Ontario, Canada
Dr. F. C. Bates, Associate Professor, Saint Louis University, 1 3621 Olive Street, Saint Louis, Mo. 63108
Dr. R. N. Colwell, Professor of Forestry, School of Forestry, 1 University of California, Berkeley, Calif.
Dr. L. H. Lattman, Department of Geology and Geophysics, 1 The Pennsylvania State University, University Park, Pa.
Mr. J. 0. Morgan, Research Physicist, Institute of Science and 1 Technology, The University of Michigan, Ann Arbor, Mich.
Dr. Allen Martin Feder, Chief, Terrain Analysis Section, 1 Texas Instruments Inc., P. O. Box 5621, Dallas, Tex. 75222
Mr. George D. Whitmore, United States Department of the Interior, 1 Geological Survey, Washington, D. C.
Mr. Eugene P. Kennedy, Chief, Information Retrieval Section, MS-112, 1 Library Branch, Federal Aviation Agency, Washington, D. C.
Mr. J. C. Brasheer, Tennessee Valley Authority, Division of 1 Chemical Development, Wilson Dam, Ala.
Mr. Carlton E. Molineux, Air Force Cambridge Research Laboratories 1 (CRZG), Office of Aerospace Research, Laurence G. Hanscom Field, Bedford, Mass.
Mr. W. J. Roberts, Engineer, Illinois State Water Survey, 1 P. 0. Box 232, Urbana, Ill. 61802
Mr. Olin W. Mintzer, The Ohio State University, Department of 1 Civil Engineering, 2036 Neil Avenue, Columbus, Ohio 43210
Dr. Peter C. Badgley, Chief, Advanced Missions, Manned Space 1 Science Division, NASA (Code SM), Washington, D. C. 20546
6
Address
Notice of Availability
Director, Naval Research Laboratory, ATTN: Code 5270, Mr. Frank C. McDonald Washington, D. C.
Pneumo Dynamics Corporation, Instrumentation and Control Division, ATTN: Mr. S. L. Varner, Grand Rapids, Mich.
Geophoto Services, Inc., 2149 South Holly Street, P. 0. Box 22196, Denver, Colo.
Mr. Bruce W. Hapke, Center for Radiophysics and Space Research, Phillips Hall, Cornell University, Ithaca, N. Y.
Mr. Robert A. Cummings, Jr., Registered Engineers, P. O. Box 1135, Pittsburgh, Pa.
Mr. Paul Bock, Director, Hydrology and Water Resources Division, The Travelers Research Center, Inc., 650 Main Street, Hartford, Conn.
Chief, U. S. Weather Bureau, U. S. Department of Commerce, Washington, D. C.
Mr. R. L. Lane, Group Engineer, Electronic Support Equipment Group, Electro-Dynamics Staff, Transport Division, The Boeing Company, P. O. Box 707, Renton, Wash.
Mrs. Marjorie Henderson, Librarian , United Electrodynamics, Inc., 200 Allendale Road, Pasadena, Calif.
Commanding Officer, Picatinny Arsenal, ATTN: S:MlJPA-DR4, Mr. R. Aaron, Dover, N. J.
Dr. William H. Peake, Antenna Laboratory, Department of Electrical Engineering, Ohio State University, 2024 Neil Avenue, Columbus, Ohio
Mr. David W. Strongway, Bear Creek-Mining Company, 1498 South Lipan Street, Denver, Colo.
Mr. E. Azmon, Planetary Physics and Chemistry Laboratory, Astro Sciences, Northrop Corporation, Norair Division, 1001 East Broadway, Hawthorne, Calif.
Mrs. Peggy V. Church, University of California, Scripps Institution of Oceanography, La Jolla, Visibility Laboratory, San Diego, Calif.
7
Address
Notice of Availability (Continued)
Mr. Donald G. Rea, University of California, Lenschner Observatory, Berkeley, Calif.
Space Electronics Corporation, ATTN": Mr. Edwin H. Heimer, 930 Air Way, Glendale, Calif.
Mr. M. Slavin, United Geophysical Corporation, P. 0. Box M, 2650 East Foothill Boulevard, Pasadena, Calif.
Mr. Frederick J. Doyle, Intelligence Systems Division, Broadview Research Corporation, 2139 Wisconsin Avenue, N. W., WashinGton, D. C.
Socony Mobil Oil Company, Inc., Field Research Laboratories, ATTN: Library, Box 900, Dallas, Tex.
Mr. C. A. Pugh, Area Engineer, U. S. Department of the Interior, Bureau of Reclamation, Phoenix, Ariz. 85004
Mr. L. S. Collett, Chief, Electronic Instrument Development and Research, Geophysics Division, Geological Survey of Canada, Department of Mines and Technical Surveys, 601 Booth Street, Ottawa, Ontario, Canada
Professor R. J. P. Lyon, Department of Geophysics, Stanford University, Stanford, Calif.
8
Unclassified Security Classification
DOCUMENT CONTROL DAT A · R&D (Security claesillcallon ol lllle, body ol abstract and indexing annotation must be entered when the overs/I report is classified)
I. ORIGINATING ACTIVITY (Corporate author) 2 a. REPORT SECURITY C L.ASSIFICATION
u. s. Anny Engineer Waterways Experiment Station Unclassified
Vicksburg, Mississippi 2 b GROUP
3. REPORT TITLE
FEASIBILITY STUDY OF THE USE OF RADAR TO DETECT SURFACE .AND GROUND WATER
4, D ESCRIPTIVE NOTES (Type ol report and Inclusive datee)
Final report s. AUTt!OR(S!{�ast nltme, I/rat name, Initial) Davis, illy R. Lundien, Jerry R. Williamson, Albert N., Jr.
6, REPO RT DATE 7a, TOTAL. NO. OF PAGE!' 1
7b. NO. OF REFS
April 1966 93 7 Sa. CONTRACT OR GRANT NO. 9a. ORIGINATOR'S REPORT NUMBER(S)
b. PROJECT NO. Technical Report No. 3-727
c. ARPA Order No. 400 9b. OTHER REPORT NO(S) (.Any other numbers thstmaybeessillfled this report)
d.
1 O. A V A IL ABILITY/LIMITATION NOTICES l!ah dOCJll:lHiA:t i� �n,1°Gjeei; tie sreeia:l:- � cont1 ols
li,BQ ��g� i;Pa.A9ffli=t,��i to fo?e±gII got'e�HmeRt� e�:i �H aa:Meaa.J.� ma�c be�-
, 9:R3:;'9 ,,i;;:a :i;i:i:: :i ef e:pp! O'Oa:I O! t1. S1 '� EB1!5i�se� Ha:teP�il� :Elxpe:r :i.ms:at 8�
11. SUPPL EMENTARY NOTES 12. SPONSORING MILITARY ACTIVITY
Advanced Research Projects Agency, Direc-torate of Remote Area Conflict; Service Agency, u. s. Anny Materiel Command
13- ABSTRACT
A study was made of the feasibility of using radar sensors as a remote means of detecting the presence and measuring the depth of surface water, and detecting the presence and measuring the depth to ground water. Also, previously begun studies were continued to relate radar returns, and the electrical soil con-stants they provided, to soil moisture content. Large laboratory soil samples were prepared at various moisture contents and with various depths of surface water and various depths to ground water. Standard pulsed radar sensors operat-ing with frequencies of 297, 5870, and 9375 megacycles per sec through variousangles of incidence were employed. Results indicate that the standard pulsed radar sensors can provide information to permit detection of surface water and an estimate of the moisture content of deep homogeneous soil samples. However, such sensors do not permit prediction of depth of surface water, presence of ground water, or depth to ground water. Systematic variation of surface-water depths and depths to ground water permitted an analytical solution for measur-ing surface- or ground-water depths, and led to the conclusion that properly designed radar systems could measure surface- and ground-water depths. Three such systems are proposed.
DD FORM
1 JA N 114 1473 Unclassified
Security Classification
Unclassified Security Classificatio_n _ ____ _
14. LINK A LINK B LINK C KEY WORDS
ROL.E WT ROL.E WT ROL.E WT
Radar
Soils
Trafficabili ty
V Surface water
.,.... Ground water
V ��-J..._7'.,... c-:":� . . .
INSTRUCTIONS
1. ORIGINATING ACTIVITY: Enter the name and address of the contractor, subcontractor, grantee, Department of Defense activity or other organization (corporate author) issuing the report.
2a. REPORT SECURITY CLASSIFICATION: Enter the overall security classification of the report. Indicate whether "Restricted Data" is included. Marking is to be in accordance with appropriate security r�gulations.
2b. GROUP: Automatic downgrading is specified in DoD Directive 5200.10 and Armed Forces Industrial Manual. Enter the group n umber. Also, when applicable, show that optional markings have been used for Group 3 and Group 4 as authorized.
3. REPORT TITLE: Enter the complete report title in all capital letters. Titles in all cases should be unclassified. U a meaningful title cannot be selected without classification, show title classification in all capitals in parenthesis immediately following the title.
4. DESCRIPTIVE NOTES: If appropriate, enter the type of report, e.g., interim, progress, summary, annual, or final. Give the inclusive dates when a specific reporting period is covered.
5. AUTHOR(S): Enter the name(s) of author(s) as shown on or in the report, Enter last name, first name, middle initial, If military, show rank and branch of service, The name of the principal author is an absolute minimum requirement.
6. REPORT DATE: Enter the date of the report as day, month. year; or month, year, If more than one date appears on the report, use date of publication.
7a. TOTAL NUMBER OF PAGES: The total page count should follow normal pagination procedures, i. e,, enter the number of pages containing information.
7b. NUMBER OF REFERENCES: Enter the total number of references cited in the report,
8a. CONTRACT OR GRANT NUMBER: If appropriate, enter the applicable number of the contract or grant under which the report was written.
8b, 8c, & 8d. PROJECT NUMBER: Enter the appropriate military department identification, such as project number, subproject number, system numbers, task number, etc.
9a. ORIGINATOR'S REPORT NUMBER(S): Enter the official report number by which the document will be identified and controlled by the originating activity. This number must be unique to this report,
9b. OTHER REPORT NUMBER(S): If the report has been assigned any other report numbers ( either by the originator or by the sponsor), also enter this number(s).
10. AVAILABILITY/LIMITATION NOTICES: Enter any limitations on further dissemination of the report, other than those imposed by security classification, using standard statements such as:
(1) "Qualified requesters may obtain copies of this report from DOC."
(2) "Foreign announcement and dissemination of this report by DDC is not authorized. "
(3) "U. S. Government agencies may obtain copies of this report direct! y from DOC. Other qualified DOC users shall request through
(4) "U. S. military agencies may obtain copies of this report directly from DDC. Other qualified users shall request through
(5) "All distribution of this report is controlled. Qualified DOC users shall request through
If the report has been furnished to the Office of Technical Services, Department of Commerce, for sale to the public, indicate this fact and enter the price, if known.
11, SUPPLEMENTARY NOTES: Use for additional explanatory notes.
12. SPONSORING MILITARY ACTIVITY: Enter the name of the departmental project office or laboratory sponsoring (payina for) the research and development, Include address,
13. ABSTRACT: Enter an abstract giving a brief and factual summary of the document indicative of the report, even though it may also appear elsewhere in the body of the technical report. If additional space is required, a continuation sheet shall be attached.
It is highly desirable that the abstract of classified reports be unclassified. Each paragraph of the abstract shall end with an indication of the military security classification of the information in the paragraph, represented as (TS), (S), (C), or (U).
There is no limitation on the lenl(lh of the abstract. However, the suggesteci len(lth is from 150 to 225 words .
14. KEY WORDS: Key words are technically meaningful terms or short phrases that characterize a report and may be used as index entries for catalo11:inl!I: the report. Key words must be selected so that no security classification is required. ldenfiers, such as equipment model designation, trade name, -nilitary project code name, 1!1:eov,raphic location, may be used as key words but will be followed by an indication of technical context. The assignment of links, rules, and weights is optional.
Unclassified
Security Classification
TA 7 .W34 1966 c. IDavis, Billy R.
Feasibility study of the useof radar to detect surface
