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Military University of Technology Institute o f Optoelectronics. Correction of reflectance characteristics of chosen natural and anthropogenic materials for airborne laser scanning system. Mirosława Szopa. INCIDENT LIGHT. REFLECTION. EMISSION. ABSORPTION. TRANSMISSION. - PowerPoint PPT Presentation
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Mirosława Szopa
Electromagnetic radiation which interact with boundary of two media
characterized by different refractive index, undergo four various phenomena:
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INCIDENT LIGHT
EMISSION
TRANSMISSION
ABSORPTION
REFLECTION
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SPECULAR BACKREFLECTION SPECULAR-DIFFUSE
DIFFUSE REAL
Characteristics of reflection are depended on physical properties of optic materials,
characteristics of boundary layer, and wavelength of incident radiation
Reflectance is a proportion between power of reflected beam and incident beam of radiation and can be expressed
as a fraction (R1),
as a percent (R2),
or decibels (R3):
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INC
REF
P
PR 1
%1002
INC
REF
P
PR
INC
REF
P
PR 103 log10
Effective Target Cross Section Effective Target Cross Section (ETCS) (ETCS)
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SOLID ANGLE
SOURCEOF LIGHT
PARAMETERS OF REFLECTING MATERIAL
AR
4
reflectancein decibels
target area
solid angle
Values of reflectance Values of reflectance of chosen materialsof chosen materials
613
0,5 1,0 1,5 2,0 2,5 WAVELENGTH [um]
RE
FLE
CT
AN
CE
[
%]
0
2
0
40
60
8
0 ICE
GREEN PLANT
CONCRETE
Reaching receivers signal, which carries information on analyzed material reflectance is subject to weakness on the path in atmosphere(extinction)caused by phenomena of light absorption and scattering,
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ReII 20
METEOROLOG
ICAL
VISIBILITY
EXTINCTION COEFFICIENT [km-1]
λ1 = 850 nm λ2 = 900 nm λ3 = 1500 nm
10 km 0.234 0.216 0.097
15 km 0.154 0.142 0.064
20 km 0.114 0.106 0.047
23 km 0.09860 0.091 0.041
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Extinction of light for analyzed wavelengths :λ1 = 850 nm, λ2 = 900 nm, λ3 = 1500 nm
with chosen atmospheric conditions (described by meteorological visibility)
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Extinction of radiation on the path in atmosphere causes disorders of signal proportions for chosen wavelengths.
Meteorological visibility = 10 km
SIGNAL PROPORTIONS 850/1500 nm
without extinctionwith extinction
SIGNAL PROPORTIONS 900/1500 nm
without extinctionwith extinction
SIGNAL PROPORTIONS 850/900 nm
without extinctionwith extinction
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Correction was carried out with allowance of character of reflection obtained from materials, various atmospheric
conditions stated by meteorological visibility, and spectral characteristics of atmospheric extinction.
SIGNAL PROPORTIONS 850/1500 nm
without extinctionwith correction
SIGNAL PROPORTIONS 900/1500 nm
without extinctionwith correction
SIGNAL PROPORTIONS 850/900 nm
without extinctionwith correction
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The proposed method of correction provides minimization
of real values falsification and decrease in obtained measurement
errors, which do not exceed the value of 5%
for the analyses from a distance of 0.5 km with atmospheric visibility of 10 km,
and for the analyses from a distance of 1 km with atmospheric visibility of 20 km.
CONCLUSIONCONCLUSIONBasing on the fundamental assumption
of the remote sensing technique, which says that every material has its own
specific spectral characteristics, and after precise analysis of reflectance
of chosen materials, it is possible to elaborate the airborne laser scanner.
The aim of this scanner would be detection and localization of materials and objects
in analyzed area of space on the basis of reflection signal analysis
using proposed method of signal correction .
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Tytuł 13/13