APPLICATION OF REMOTE SENSING AND

GEOGRAPHICAL INFORMATION SYSTEM IN

CIVIL ENGINEERING

Date:

INSTRUCTOR

DR. MOHSIN SIDDIQUE

ASSIST. PROFESSOR

DEPARTMENT OF CIVIL ENGINEERING

� Remote Sensing (RS)

� Remotely sensing the usefulinformation of object (earth)

� Geographic Information

System (GIS)

� A system that deals with alltypes of geographicallyreferenced data

Application of Remote Sensing and Geographical

Information System in Civil Engineering2

� Remote Sensing (RS)

� Remotely sensing the usefulinformation of object (earth)

� Process of recording, measuring andinterpreting imagery and digitalrepresentations of energy patterns

derived from noncontact sensor

systems

� Geographic Information

System (GIS)

� A system designed to capture,store, manipulate, analyze,manage, and present all typesof geographically referenceddata

Application of Remote Sensing and Geographical

Information System in Civil Engineering3

Can you recall Google Earth ?

While the representation and management of remotely sensed data on geographical locations is made possible through GIS

The information in the Google earth is obtained through Remote Sensing

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Can you recall Google Earth ?

Lets look at small movies about Google earth to learn more about the remotely sensed information and its geographical referencing of the information

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� Remote sensing has been variously defined but basically it is the art or scienceof telling something about an object without touching it. (Fischer et al.,1976, p. 34)

� Remote sensing is the acquisition of physical data of an object without

touch or contact. (Lintz and Simonett, 1976, p. 1)

� Remote sensing is the observation of a target by a device separated from itby some distance. (Barrett and Curtis, 1976, p. 3)

� The term “remote sensing” in its broadest sense merely means“reconnaissance at a distance.” (Colwell, 1966, p. 71)

� Remote sensing is the art, science and technology of obtaining reliable

information about physical objects and the environment, through theprocess of recording, measuring and interpreting imagery and digitalrepresentations of energy patterns derived from noncontact sensor systems

(Lecture Note by Wataru Takauchi, 2009)

Remote Sensing

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� Remote sensing is the science of deriving information about an object frommeasurements made at a distance from the object, i.e., without actually

coming in contact with it. The quantity most frequently measured in present-day remote sensing systems is the electromagnetic energy emanating fromobjects of interest, and although there are other possibilities (e.g., seismicwaves, sonic waves, and gravitational force), our attention . . . is focused uponsystems which measure electromagnetic energy. (D. A. Landgrebe, quoted inSwain and Davis, 1978, p. 1)

� Remote sensing is the practice of deriving information about the Earth’s land and

water surfaces using images acquired from an overhead perspective, using

electromagnetic radiation in one or more regions of the electromagnetic

spectrum, reflected or emitted from the Earth’s surface. (James B.

Campbell, Randolph H. Wynne (2011): Introduction to Remote Sensing)

Remote Sensing

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Is remote sensing limited to use of electromagnetic radiation ?

Various Steps in RS

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(A) Energy Source(B) Radiation and the Atmosphere(C) Interaction with the Target(D) Recording of Energy by the Sensor(E) Transmission, Reception, and Processing(F) Interpretation and Analysis(G) Application

Source of Electromagnetic Radiation9

� Nuclear reactions within the Sun produce a full spectrum of

electromagnetic radiation, which is transmitted through space without

experiencing major changes.As this radiationapproaches the Earth, itpasses through theatmosphere before reachingthe Earth’s surface.Some is reflected upwardfrom the Earth’s surface; itis this radiation that formsthe basis for photographsand similar images. Othersolar radiation is absorbedat the surface of the Earthand is then reradiated asthermal energy.

Source of Electromagnetic Radiation

By recording emitted or reflected radiation and applying knowledge of its

behaviour as it passes through the Earth’s atmosphere and interacts with

objects, remote sensing analysts develop knowledge of the character of

features such as vegetation, structures, soils, rock, or water bodies on the

Earth’s surface.

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Remote sensing of reflected radiation Remote sensing of emitted radiation

� The electric and magnetic components are oriented at right angles to one

another and vary along an axis perpendicular to the axis of propagation

� Magnetic field (H) oriented at right angles to the electrical field is

propagated in phase with the electrical field (E)

Electromagnetic Radiations (EMR)

λfc =

Electric (E) and magnetic (H) components of EMR.

smc /103 8×=

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� Two characteristics of electromagnetic radiation are particularly important for understanding remote sensing. These are the wavelength and frequency.

Electromagnetic Radiations (EMR)

f

c=λ

Wave length (λ) is the length of one wave

cycle, which can be measured as the

distance between successive wave crests.

Wavelength is measured in metres (m)

Frequency (f) refers to the number of

cycles of a wave passing a fixed point per

unit of time. Frequency is normally

measured in hertz (Hz), equivalent to one

cycle per second, and various multiples of

hertz

Remember ! Two are inversely related to each other. The shorter the wavelength, the higher the frequency. The longer the wavelength, the lower the frequency

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Units used in RS13

Electromagnetic (EM) Spectrum14

The most familiar form of EMR is visible light, which forms only a small (but

very important) portion of the full EM spectrum.

The large segments of this spectrum that lie outside the visible range require our

special attention because they may behave in ways that are quite foreign to our

everyday experience with visible radiation.

Electromagnetic (EM) Spectrum15

� Two important categories are not shown in above Table. The optical spectrum,

from 0.30 to 15 µm, defines those wavelengths that can be reflected andrefracted with lenses and mirrors. The reflective spectrum extends from about

0.38 to 3.0 µm; it defines that portion of the solar spectrum used directly forremote sensing.

Electromagnetic (EM) Spectrum

reflective

spectrum

Optical

spectrum

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The Visible Spectrum

The color of an object is defined by the color of the light that itreflects . Thus a “blue” object is “blue” because it reflects bluelight.Intermediate colors are formed when an object reflects two ormore of the additive primaries.

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� Wavelengths longer than the red portion of the visible spectrum are designated as the infrared region

The Infrared Spectrum

Infrared

(0.7-15µm)

Near infrared

(0.72-1.3µm)

Mid infrared

(1.3-3.0µm)

Far infrared

(3-15µm)

A photo of the Orion constellation in visible (left) and infrared (right). Although the

infrared provides little indication to the exact location of the stars, it detects gas clouds

throughout the constellation and other features totally invisible in the optical spectrum

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� The portion of the spectrum ofmore recent interest to remotesensing is the microwave regionfrom about 1 mm to 1m.

� This covers the longest wavelengthsused for remote sensing.

� The shorter wavelengths haveproperties similar to the thermalinfrared region while the longerwavelengths approach thewavelengths used for radiobroadcasts.

Microwave Spectrum

The remote sensing using microwave spectrum is termed as microwave sensing

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� Basic Definitions

� The rate at which photons (quanta) strike a surface is the radiant flux,

measured in watts (W); this measure specifies energy delivered to a surface ina unit of time.

� Irradiance is defined as radiant flux per unit area (usually measured as wattsper square meter). Irradiance measures radiation that strikes a surface

� Radiant exitance defines the rate at which radiation is emitted from a unit area(also measured in watts per square meter).

Radiation Laws20

� Black Body Radiation

Radiation Laws

A blackbody is a hypothetical source of energy that behaves in anidealized manner. It absorbs all incident radiation; none is reflected. Ablackbody emits energy with perfect efficiency; its effectiveness as aradiator of energy varies only as temperature varies.

where B is the spectral radiance, T is the absolute temperature of the blackbody, k is the Boltzmann constant, h is the Planck constant, c is the speed oflight and λ is the wavelength.

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� Wein’s Displacement Law

Radiation Laws22

� Stephan Boltzmann Law

Radiation Laws23

� Kirchhoff law

Radiation Laws24

� Emissivity

Radiation Laws25

All these radiation laws are important for understanding

electromagnetic radiation. They have special significance of detection of

radiation in the far infrared spectrum

� All radiation used for remote sensing

must pass through the Earth’s

atmosphere

� Atmospheric effects may have

substantial impact on the quality of

images and data that the sensors

generate

� Therefore, the practice of remote

sensing requires knowledge of

interactions of electromagnetic energy

with the atmosphere

Radiation Interaction with the Atmosphere

As solar energy passes through the Earth’s atmosphere, it is subject tomodification by several physical processes, including

(1) scattering,(2) absorption,and (3) refraction

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� Scattering is the redirection of electromagnetic energy by particlessuspended in the atmosphere or by large molecules of atmosphericgases

� The amount of scattering depends on the sizes of these particles, theirabundance, the wavelength of the radiation, and the depth of theatmosphere through which the energy is travelling

� The size of a scattering particle is parameterized by the ratio α of itscharacteristic dimension D and wavelength λ:

� α = πD/λ

� Rayleigh scattering (α < 0.4)

� Mie scattering (0.4 < α < 3)

� Nonselective scattering /Discrete dipole approximation (α > 3)

Scattering27

� Rayleigh scattering occurs when atmospheric particles have diametersthat are very small relative to the wavelength of the radiation.Typically, such particles could be very small specks of dust or some ofthe larger molecules of atmospheric gases, such as nitrogen (N2) andoxygen (O2)

� Mie scattering is caused by large atmospheric particles, including dust,pollen, smoke, and water droplets. Such particles may seem to be verysmall by the standards of everyday experience, but they are manytimes larger than those responsible for Rayleigh scattering

� Non-selective scattering is caused by particles that are much largerthan the wavelength of the scattered radiation. For radiation in andnear the visible spectrum, such particles might be larger waterdroplets or large particles of airborne dust

Scattering

Rayleigh scattering of sunlight in clear atmosphere is the main reason why the sky is blue

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� Scattering behaviors of three classesof atmospheric particles.

� (a) Atmospheric dust and smokeform rather large irregularparticles that create a strongforward-scattering peak, with asmaller degree of backscattering.

� (b) Atmospheric molecules aremore nearly symmetric in shape,creating a pattern characterizedby preferential forward- andbackscattering, but without thepronounced peaks observed in thefirst example.

� (c) Large water droplets create apronounced forward-scatteringpeak, with smaller backscatteringpeaks.

Scattering

Lynch and Livingston (1995)

Mie

Rayleigh

Non-selective

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Principal components of observed brightness

I = Is + Io + Id

Is: reflected from the groundIo: scattered by the atmosphere directly to the sensorId: diffuse light directed to the ground then to the atmosphere

scattered

reflected Diffused/refracted

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Changes in reflected, diffuse, scattered, and observed radiation over wavelength

for dark (left) and bright (right) surfaces.

� Atmospheric effects constitute a larger proportion of brightness for

dark objects than for bright objects especially at short wavelengths

Magnitude of brightness components31

� Absorption is the other main mechanism when electromagnetic radiationinteracts with the atmosphere.

� In contrast to scattering, this phenomenon causes molecules in the atmosphereto absorb energy at various wavelengths.

� Ozone, carbon dioxide, and water vapour are the three main atmosphericconstituents which absorb radiation.

Absorption32

Absorption

After passingfrom atmosphere

Original EMspectrum

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� Refraction is the bending of light rays at the contact area betweentwo media that transmit light.

� Refraction occurs at the lenses of cameras, magnifying glasses and inatmospheric layers of varied clarity, humidity and temperature

Refraction34

� As electromagnetic energy reaches the earth’s surface, it must bereflected, absorbed or transmitted

� The proportions of these processes depend on three components;

� nature of the surface

� wavelength of the energy

� angle of illumination

� Reflection occurs when a ray of light is redirected as it strikes anon-transparent surface.

� It depends on sizes of surface irregularities (roughness orsmoothness) in relation to the wavelength of the radiation

� If surface is smooth relative to wavelength, specular reflection

occurs. If surface is rough, diffuse or isotropic reflection occurs

Interaction with the surface35

Reflection

Specular (a) and diffuse (b) reflection. Specular reflection occurs when a

smooth surface tends to direct incident radiation in a single direction.

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� Lambert’s cosine law, which states thatthe observed brightness (I) of such asurface is proportional to the cosine of theincidence angle (θ), where I is thebrightness of the incident radiation asobserved at zero incidence:

� I′ = I/cos θ

� This relationship is often combined with theequally important inverse square law,which states that observed brightnessdecreases according to the square of thedistance (D) from the observer to thesource:

� I′ = (I/D2) (cos θ)

Illumination37

� Transmission of radiation occurs when radiation passes through asubstance without significant attenuation

� From a given thickness, or depth, of a substance, the ability of amedium to transmit energy is measured as the transmittance (t):

� t = Transmitted radiation/Incident radiation

Transmission38

Incident radiation passes throughan object without significantattenuation (left), or may beselectively transmitted (right).The object on the right would act asa yellow (“minus blue”) filter, as itwould transmit all visible radiationexcept for blue light.

� Fluorescence occurs when an object illuminated with radiation of onewavelength emits radiation at a different wavelength.

� The most familiar examples are some sulfide minerals, which emitvisible radiation when illuminated with ultraviolet radiation

� Reflectance� For many applications of remote sensing, the brightness of a surface is

best represented as reflectance.

� Reflectance is expressed as the relative brightness of a surface as measured for a specific wavelength interval:

� Reflectance = Observed brightness/Irradiance

Fluorescence

Note: Irradiance measures radiation that strikes a surface

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� The polarization of electromagnetic radiation denotes the orientation of the oscillations within the electric field of electromagnetic energy

Polarization

Schematic representation of horizontally and vertically polarized radiation.

The smaller arrows signify orientations of the electric fields.

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Spectral characteristics of Energy sources, Atmospheric

Effects and Sensing Systems

Spectral sensitivity range of eye coincides with an atmospheric window

and peak level of energy from the sun

Photography Thermal Scanner

Multispectral Scanner Radar and Passive Remote Sensing

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� Earth’s atmosphere is by no means completely transparent to

electromagnetic radiation because the gases (O3, O2, CO2 & H2O )

together form important barriers to transmission of electromagnetic

radiation through the atmosphere.

� Atmosphere selectively transmits energy of certain wavelengths; those

wavelengths that are relatively easily transmitted through the atmosphere

are referred to as atmospheric windows.

Atmospheric Windows

Atmospheric windows are vitally important to the development of sensors

for remote sensing.

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� Everything in nature has its own unique distribution of reflected, emitted andabsorbed radiation.

� These spectral characteristics can – if ingeniously exploited - be used todistinguish one thing from another or to obtain information about shape, size,and other physical and chemical properties.

� A set of observations or measurements that constitutes a spectral response pattern is called the spectral signature of an object.

Concept of Spectral Signature43

� Which bands are most useful for distinguishing between these classes ?

Spectral response patterns (spectral patterns)44

Spectral response patterns45

� Both types of trees will appear as similar shades of green to the naked eye

� Imagery (or photography) using the visible portion of the spectrum may not be useful

� In near-infrared, they are clearly separable

Spectral response pattern (Reflectance curves)46

Reflectance curves

Oblique normal color aerial photograph

showing portion of Univ. of Wisconsin-

Madison

Oblique Infrared aerial photograph

showing portion of Univ. of Wisconsin-

Madison

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� Assignment: Discuss the spectral reflectance of each category in accordance with division of EM spectrum

Typical Spectral Reflectance curves for Vegetation, Soil and

Water48

� Spectral sensitivity of thesensors available

� Presence or absence ofatmospheric windows in thespectral range(s) in whichone wishes to sense

� Source, magnitude, andspectral composition of theenergy available in theseranges

� Manner in which the energyinteracts with the featuresunder investigation (Spectralsignature and spectralpatterns)

Sensor Selection49

Type of Remote Sensing (RS)50

�Passive RS� Natural (EMR from Sun)

� Example� Optical and thermal remote sensing (passive)

(A technology to measure reflected and emitted energy in visible and thermal wavelength)

RS using reflected solar radiation RS using emitted terrestrial radiation

Type of Remote Sensing (RS)51

�Active RS

� Technological Assisted

Radiation

�Example� Microwave remote sensing (active)

(A technology to measure a time (distance) between sensor and an object)

RS using senor’s transmitted radiation

� Uniform Energy Source

� Source would provide energyover all wavelengths, at aconstant, known, high level ofoutput, irrespective of time andplace

� Non interfering atmosphere

� Atmosphere would not modify theenergy from the source in anymanner

� Unique Energy/ Matter Interactions

at the Earth's Surface

� Reflectance is invariant andunique to each and every earthsurface feature

Ideal Remote Sensing System52

� Super Sensor

� Highly sensitive to all wavelengths

� Simple, reliable, require virtuallyno power or space, be accurate,and economical to operate

� Real-Time Data Handling System

� Derived data would provideinsight into the physical-chemical-biological state of each featureof interest

� Multiple Data Users

� Knowledge in subject domain & RSimage interpretation

� Same set of data would becomevarious forms of information

� Energy Source

� Solar energy

� Microwave for Active remotesensing

� RS at specific local time

� Atmosphere

� Atmospheric windows

� Energy/Matter Interactions

� Spectral signature and Spectralsimilarity

� Sensor

� All sensors have fixed range ofspectral sensitivity

� Limitation on spatial resolution

Real Remote Sensing System53

� Real-Time Data Handling

System

� Capability of currentremote sensors to generatedata far exceeds the currentcapacity to handle thesedata

� Multiple Data Users

� No single combination ofdata acquisition andanalysis procedures willsatisfy the needs of all datausers

Comments….

Questions….

Suggestions….

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I am greatly thankful to all the information sources(regarding remote sensing and GIS) on internet that Iaccessed and utilized for the preparation of presentlecture.

Thank you !

Feel free to contactsmohsin@uet.edu.pk

� Assignment: Discuss the spectral reflectance of each category in accordance with division of EM spectrum

Typical Spectral Reflectance curves for Vegetation, Soil and Water

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� 'Peak and Valley' configuration

� VISIBLE RANGE

� Valleys in the visible portion are dictated by the pigments in plant leaves

� Chlorophyll strongly absorbs energy in 0.45-0.65 μm (Chlorophyll Absorption band)

� If Vegetation is subjected to stress, chlorophyll content reduces and red reflectance increases

� NIR RANGE (0.7 to 1.3 µm)

� Very high reflectance (50%)

� Remaining energy transmitted (very little absorption)

� Depends on Plant leaf structure

� Useful for identification of different species

� Useful for vegetation condition monitoring

VEGETATION (Healthy Green Vegetation)56

Spectral reflectance of oak leaves57

Reflectance from Forest canopy and Layered vegetation58

Leaf Structure and Reflectance59

� BEYOND 1.3 μm

� Essentially reflects or absorbs with little transmittance At 1.4, 1.9, and 2.7µm water in leaf absorbs strongly

� (Water Absorption Bands)

� Leaf reflectance is approximately inversely related to the total waterpresent in a leaf

VEGETATION (Contd..)

Reflectance of a leaf to decreased relative water content

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� Factors affecting soil reflectance

� Moisture content

� Soil texture (proportion of sand, silt, and clay)

� Surface roughness (reduces reflectance)

� Iron oxide (reduces reflectance)

� Organic matter content (reduces reflectance)

� Inter-related

� Coarse textured dry soils will have more reflectance than fine textured soils (reverses if water is present)

� Rocks

� Aggregates of minerals

� Reflectance depends on mineral composition

� Weathered surface

SOIL (Dry Bare Soil – Grey-brown Loam)61

� Most of the energy is either absorbed or transmitted

� VISIBLE RANGE

� Little energy is reflected only in this range

� Water quality studies

� Shallow Vs Deep water

� Clear Vs Turbid water

� Rough Vs Smooth

� NIR RANGE (0.7 to 1.3 µm)

� Completely absorbs

� Useful for delineating water bodies

� Algal bloom and/ or Phytoplankton results in reflection

WATER (clear deep water body)62

Water surface, subsurface, volumetric and bottom

radiance63

Attenuation in pure water by absorption and

scattering

Water Penetration

� Ability to view large parts of the globe at different scales

� Capability to monitor regions which may be very remote or where access isdenied

� Ability to analyse different surfaces at wavelengths not detectable to thehuman visual system

� Ability to obtain imagery of an area at regular intervals over many years inorder that changes in the landscape can be evaluated

� Capability to see human-induced effects on our planet

� Disadvantages� Certain skill level is required to interpret the imagery

� Interpretation based solely on remotely sensed data should be treated withcaution unless supported by ground verification data.

Advantages of Remote Sensing66

� Exploring both geographical and thematic components of data in a holistic way

� Stresses geographical aspects of a research question

� Allows handling and exploration of large volumes of data

� Allows integration of data from widely disparate sources

� Allows analysis of data to explicitly incorporate location

� Allows a wide variety of forms of visualisation

� Disadvantages of GIS � Data are expensive

� Learning curve on GIS software can be long

� Shows spatial relationships but does not provide absolute solutions

� Origins in the Earth sciences and computer science. Solutions may not be appropriate for humanities research

Advantages of GIS67

Thank you