PDPU STUDENT MATERIAL

1. 3/10/2016
1
Remote Sensing & its
Applications in Civil
Engineering
Akshay Jain
www.akshayjain.co.in
by
What is Remote Sensing
Remote sensing is the science (and to
some extent, art) of acquiring
information about the Earth's surface
without actually being in contact with it.
This is done by sensing and recording
reflected or emitted electromagnetic
energy and processing, analyzing, and
applying that information.
Since our birth, Remote sensing activities have
been carried out by each one of us
listening music (Activity) – ears (sound energy) - Head (Sensor)
Reading book (Activity) – eyes (light energy) - Head (Sensor)
Nervous system carries information to brain
Brain (interpreter) identify the object
sensors are not in contact with object
Measurement of Temperature with thermometer is
in-situ measurement

2. 3/10/2016
2
Elements of RS
 Energy Source or Illumination
(A)
 Radiation and the Atmosphere
(B)
 Interaction with the Target (C)
 Recording of Energy by the
Sensor (D)
 Transmission, Reception, and
Processing (E)
 Interpretation and Analysis (F)
 Application (G)
Elements of RS
 Energy Source or Illumination (A)
The first requirement for remote sensing is to have
an energy source which illuminates or provides
electromagnetic energy to the target of interest.
 Radiation and the Atmosphere (B)
As the energy travels from its source to the target, it
will come in contact with and interact with the
atmosphere it passes through. This interaction may
take place a second time as the energy travels from
the target to the sensor.
 Interaction with the Target (C)
once the energy makes its way to the target through the
atmosphere, it interacts with the target depending on
the properties of both the target and the radiation.
 Recording of Energy by the Sensor (D)
after the energy has been scattered by, or emitted from
the target, we require a sensor (remote - not in contact
with the target) to collect and record the
electromagnetic radiation.
Elements of RS

3. 3/10/2016
3
Transmission, Reception, and Processing (E)
The energy recorded by the sensor has to be
transmitted, often in electronic form, to a receiving and
processing station where the data are processed into an
image (hardcopy and/or digital).
Interpretation and Analysis (F)
The processed image is interpreted, visually and/or
digitally or electronically, to extract information about
the target which was illuminated.
Elements of RS
Application (G)
The final element of the remote sensing process is
achieved when we apply the information we have
been able to extract from the imagery about the
target in order to better understand it, reveal some
new information, or assist in solving a particular
problem.
Elements of RS
Different Remote Sensing Systems
Passive system
 The source of the object
illumination is independent of
the sensor and it is a natural
source.
 Passive sensors used when
naturally energy is available.
during the time when the sun is
illuminating the Earth.
 No reflected energy available
from the sun at night.

4. 3/10/2016
4
Active Remote Sensing
Active system
 Own energy source of illumination
 sensor emits radiation
 which is directed toward the target to be
investigated. The radiation reflected from
that target is detected and measured by the
sensor
 Ability to obtain measurements anytime, day
or season.
 Active sensors can be used for examining
wavelengths that are not sufficiently
provided by the sun, such as microwaves,
 Active systems require the generation of a
fairly large amount of energy to adequately
illuminate targets.
 Laser Fluorosensor, Synthetic Aperture
Radar (SAR).
Electromagnetic Radiation
Energy source to illuminate the target
This energy is in the form of electromagnetic
radiation.
Energy Source
 All electromagnetic radiation has
fundamental properties and behaves in
predictable ways according to the basics of
wave theory.
 Electromagnetic radiation consists of an
electrical field (E) which varies in magnitude
in a direction perpendicular to the direction
in which the radiation is traveling.
 Magnetic field (M) oriented at right angles to
the electrical field. Both these fields travel at
the speed of light (c).

5. 3/10/2016
5
Electric Field
Magnetic Field
Direction of
propagation
- Wavelength(λ)
- Frequency
Wavelength is the length of
one wave cycle, which can
be measured as the distance
between successive wave
crest
Wavelength usually measured
in metres or some factor of
metres such as nanometres
(nm, 10-9 m) or micrometres
(μm, 10-6 metres) or
centimetres (cm, 10-2
metres).
Frequency 3 Hz
t = 0 sec
t = 1sec
Two important characteristics of EMR
Frequency 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.
Wavelength and Frequency are related by the
following formula:Wavelength and frequency are
related by the following formula:
Wavelength and Frequency are inversely proportional to each other

6. 3/10/2016
6
Electromagnetic Spectrum
 Ultraviolet
 Visible - 0.4 to 0.7 mm
 Infrared (IR) - 0.7 mm to 100
mm
Reflected IR - 0.7 mm to 3.0
mm
Thermal IR - 3.0 mm to 100
mm
 Microwave Region - 1 mm to
1 m
Visible Spectrum
 Called Light waves
 Occupies only small portion of electromagnetic
spectrum
 Wavelength between 0.4 μm to 0.7 μm
Optical Infrared Region (OIR)
Visible 0.4 to 0.7 μm
Near Infrared 0.7 to 1.5 μm
Shortwave Infrared 1.5 to 3 μm
Mid-wave infrared 3 to 8 μm
Long wave Infrared (Thermal Infrared-TIR) 8 to 15 μm
Far Infrared (FIR) Beyond 15 μm
Marginal Differences in the range of wavelength in different literature

7. 3/10/2016
7
Sun and Atmosphere
Before radiation used for remote sensing
reaches the Earth's surface it has to travel
through some distance of the Earth's
atmosphere.
Particles(Aerosols, dust particles) and
gases (CO2
,H2O, Vapour,O3) in the
atmosphere can affect the incoming light
and radiation. These effects are caused
by the mechanisms of scattering and
absorption.
Scattering
 Scattering occurs when
suspended particles or large
gas molecules present in the
atmosphere interact
 Cause the electromagnetic
radiation to be redirected from
its original path.
 Depends on several factors
 Wavelength of the radiation the
 Abundance of particles or gases
 Distance the radiation travels
through the atmosphere
Types of Scattering
Rayleigh Scattering
Occurs when particles are very small compared to the
wavelength of the radiation.
Particles such as small dust or nitrogen and oxygen
molecules.
Shorter wavelengths of energy to be scattered much
more than longer wavelengths.
Rayleigh scattering is the dominant scattering
mechanism in the upper atmosphere.
Sky appears "blue" during the day is because of this
phenomenon. Shorter wavelengths (i.e. blue) of the
visible spectrum are scattered more than the other
(longer) visible wavelengths.
Rayleigh Scattering is the most important type of
scattering and cause high path radiance at the blue-end
of spectrum.
It leads to haze on images and photographs, which
results in contrast and unsharp pictures
Effects can be reduced by the filters to eliminate shorter
wavelength radiation

8. 3/10/2016
8
 Mie scattering occurs when the particles (Spherical) are
just about the same size or larger than the wavelength of
the radiation
 Dust, smoke and water vapour are common causes of
Mie scattering
 Mie scattering occurs in the lower altitude of the
atmosphere
 Mie Scattering influences the entire spectral region from
Near UV to Near IR
 It has greater affect on larger wavelengths than Raleigh
scattering
 Mie Scattering depends on factors such as ratio of the
size of scatterer particle to the wave length incidence.
 Dominates when cloud conditions are overcast
Nonselective scattering
Occurs when the particles are much larger
than the wavelength of the radiation.
Due to water droplets and large dust
particles
Nonselective scattering gets its name from
the fact that all wavelengths are scattered
about equally
This type of scattering causes fog and
clouds to appear white to our eyes
Absorption
Absorption
This phenomenon causes molecules in the atmosphere to
absorb energy at various wavelengths.
Ozone, carbon dioxide, and water vapour are the three main
atmospheric constituents which absorb radiation.
Ozone serves to absorb the harmful UV radiation from the
sun.
Carbon Dioxide tends to absorb radiation strongly in the far
infrared portion of the spectrum - that area associated with
thermal heating - which serves to trap this heat inside the
atmosphere.
Water vapour in the atmosphere absorbs much of the
incoming longwave infrared and shortwave microwave
radiation (between 22µm and 1m).
water vapour in the lower atmosphere varies greatly from
location to location and at different times of the year.
For remote sensing, area of spectrum which is very much
useful is visible region because atmospheric absorption is
less in this area

9. 3/10/2016
9
Those areas of the spectrum which are not
severely influenced by atmospheric
absorption and thus, are useful to remote
sensors, are called atmospheric
windows
Atmospheric Emission
Atmosphere emits EM radiation due to its thermal
state ( All bodies above absolute temperature,
emits EM radiation)
Path Radiance : The part of signal emanating from
the atmosphere is called path radiance
Path radiance reduce the contrast of the image
generated by the sensor, hence visual sharpness of
the image will reduce (Radiometric Error)
Energy Interaction Mechanism on
the Ground
Radiation that is not absorbed or scattered in
the atmosphere can reach and interact with
the Earth's surface.
EM Energy incident (Eiλ) on the earth surface
may be absorbed (Eaλ); transmitted (E tλ); and
reflected (E rλ).
Eiλ = Eaλ + E tλ + E rλ
Absorption ,Transmission and Reflection are
differ for different objects at different
wavelength and condition
We are interested in reflected energy from the
target
 specular reflection
 Diffuse reflection
 semi-diffused reflection

10. 3/10/2016
10
Specular or Mirror-like reflection
smooth surface, where all or almost all of the energy is
directed away from the surface in a single direction.
Diffuse reflection
Rough surface, where the energy is reflected almost
uniformly in all directions.
Most earth surface features lie somewhere between
perfectly specular or perfectly diffuse reflectors.
Whether a particular target reflects specularly or
diffusely, or somewhere in between, depends on the
surface roughness of the feature in comparison to the
wavelength of the incoming radiation.
If the wavelengths are much smaller than the surface
variations or the particle sizes that make up the
surface, diffuse reflection will dominate.
For example, fine-grained sand would appear fairly
smooth to long wavelength microwaves but would
appear quite rough to the visible wavelengths.
SPECTRAL REFLECTION
DIFFUSED REFLECTION
Leaves
A chemical compound in leaves called chlorophyll
strongly absorbs radiation in the red and blue
wavelengths but reflects green wavelengths.
Leaves appear "greenest" to us in the summer, when
chlorophyll content is at its maximum.
In autumn, there is less chlorophyll in the leaves, so
there is less absorption and proportionately more
reflection of the red wavelengths, making the leaves
appear red or yellow (yellow is a combination of red
and green wavelengths
The internal structure of healthy leaves act as
excellent diffuse reflectors of near-infrared
wavelengths.
If our eyes were sensitive to near-infrared, trees
would appear extremely bright to us at these
wavelengths. In fact, measuring and monitoring the
near-IR reflectance is one way that scientists can
determine how healthy (or unhealthy) vegetation may
be.
Water: Longer wavelength visible and near infrared
radiation is absorbed more by water than shorter visible
wavelengths. Thus water typically looks blue or blue-green
due to stronger reflectance at these shorter wavelengths,
and darker if viewed at red or near infrared wavelengths.
If there is suspended sediment present in the upper layers
of the water body, then this will allow better reflectivity and
a brighter appearance of the water. The apparent colour of
the water will show a slight shift to longer wavelengths.
Suspended sediment (S) can be easily confused with
shallow (but clear) water, since these two phenomena
appear very similar.
Chlorophyll in algae absorbs more of the blue
wavelengths and reflects the green, making the water
appear more green in colour when algae is present.
The topography of the water surface (rough, smooth,
floating materials, etc.) can also lead to complications for
water-related interpretation due to potential problems of
specular reflection and other influences on colour and
brightness.

11. 3/10/2016
11
Single Channel/Multi Channel Concept
Information from a narrow wavelength range is
gathered and stored in a channel (band)
We can combine and display channels of
information digitally using the three primary colours
single channel or range of wavelengths, we are
actually displaying that channel through all three
primary colours. Because the brightness level of
each pixel is the same for each primary colour, they
combine to form a black and white image, showing
various shades of gray from black to white.
When we display more than one channel each as a
different primary colour, then the brightness levels
may be different for each channel/primary colour
combination and they will combine to form a colour
image.
Single Channel
Multi Channel
Sensor and Platform
Platform where the
sensors are placed
Sensors may be
 Ground based
 Aircraft
 Space shuttle
 Satellites
Sun Synchronous
Geo Stationary

12. 3/10/2016
12
Resolution, Pixel Size and Scale
Spatial resolution of the sensor and refers
to the size of the smallest possible feature
that can be detected.
Spatial resolution of passive sensors
depends primarily on their Instantaneous
Field of View (IFOV).
The IFOV is the angular cone of visibility of
the sensor (A) and
Determines the area on the Earth's surface
which is "seen" from a given altitude at one
particular moment in time (B).
The size of the area viewed is determined
by multiplying the IFOV by the distance
from the ground to the sensor (C)
Data Resolution
 Spatial resolution - size of the smallest
possible feature that can be detected
 Spectral resolution - Ability of a sensor
to define fine wavelength intervals
 Radiometric resolution - Ability to
discriminate very slight differences in
energy
 Temporal resolution
SATELLITE SYSTEMS
 LANDSAT
 SPOT
 IRS

13. 3/10/2016
13
Indian Remote Sensing satellite
(IRS)
Earth Observation satellites, mostly built,
launched and maintained by Indian Space
Research Organisation (ISRO)
Father of Space Technology in India
Dr.Vikarmbhai Sarabhai
National Natural Resources Management
System (NNRMS) for which the Department of
Space (DOS) is nodal agency
Bhaskara 1 satellites launched in 1979
Bhaskara 2 satellites launched in 1981
largest constellation of remote sensing satellites for
civilian use in operation today
IRS
Is
Sun Synchronous and Provides variety of
spatial, spectral and temporal resolutions
 IRS-1D,
 OCEANSAT-1
 Technology Experiment Satellite (TES)
 RESOURCESAT-1
 CARTOSAT-1, CARTOSAT-2
 CARTOSAT-2A
 IMS-1
IRS Satellites are

14. 3/10/2016
14
Serial
No.
Satellite Date of Launch Launch Vehicle Status
1 IRS 1A 17 March 1988 Vostok, USSR Mission Completed
2 IRS 1B 29 August 1991 Vostok, USSR Mission Completed
3 IRS P1 (also IE) 20 September 1993 PSLV-D1 Crashed, due to
launch failure of
PSLV
4 IRS P2 15 October 1994 PSLV-D2 Mission Completed
5 IRS 1C 28 December 1995 Molniya, Russia Mission Completed
6 IRS P3 21 March 1996 PSLV-D3 Mission Completed
7 IRS 1D 29 September 1997 PSLV-C1 In service
8 IRS P4 (Oceansat-1) 27 May 1999 PSLV-C2 In service
9 Technology Experiment
Satellite (TES)
22 October 2001 PSLV-C3 In service
10 IRS P6 (Resourcesat 1) 17 October 2003 PSLV-C5 In service
11 IRS P5 (Cartosat 1) 5 May 2005 PSLV-C6 In service
12 Cartosat 2 (IRS P7) 10 January 2007 PSLV-C7 In service
13 Cartosat 2A (IRS P7) 28 April 2008 PSLV-C9 In service
14 IMS 1 (IRS P7)
Integrated Mission for
Sustainable Development
28 April 2008 PSLV-C9 In service
Data Acquisition and Analysis
National Remote Sensing Agency (NRSA)
Hyderabad
 Reception
 Archival
 Processing
 Dissemination
IRS Data applications
 Preharvest crop area and production estimation of major crops.
 Drought monitoring and assessment based on vegetation
condition.
 Flood risk zone mapping and flood damage assessment.
 Hydro-geomorphological maps for locating underground water
resources for drilling well.
 Irrigation command area status monitoring
 Snow-melt run-off estimates for planning water use in down
stream projects
 Land use and land cover mapping
 Urban planning
 Forest survey
 Wetland mapping
 Environmental impact analysis
 Mineral Prospecting
 Coastal studies
 Integrated Mission for Sustainable Development (initiated in 1992)
for generating locale-specific prescriptions for integrated land
and water resources development in 174 districts

15. 3/10/2016
15
REMOTE SENSING DATA
ANALYSIS
FCC OF ROORKEE AREA IRS LISS III
DATA
IKONOS DATA OF ROORKEE DATA

16. 3/10/2016
16
PROCESSING & ANALYSIS
INTERPRETATION
Visual - Human based
Digital - Computer assisted
COMPARISON
VISUAL ANALYSIS
 Single band or as FCC
 Slow
 Analyst Bias
 Subjective
DIGITAL ANALYSIS
 Multi Image
 Fast with many options
 Free of Analyst bias
 Objective
Elements of Image Interpretation
Primary Elements
Black and White Tone
Color
Spatial Arrangement of Tone & Color
Size
Shape
Texture
Pattern
Based on Analysis of Primary
Elements
Height
Shadow
Contextual Elements
Site
Association

17. 3/10/2016
17
Elements of Visual Interpretation
 Tone - relative brightness or colour of objects in
an image.
.
Generally, tone is the
fundamental element for
distinguishing between different
targets or features.
Variations in tone also allows the
elements of shape, texture, and
pattern of objects to be
distinguished
Elements of Visual Interpretation
 Shape - general form, structure, or outline of
individual objects
Shape can be a very distinctive clue
for interpretation.
Straight edge shapes typically
represent urban or agricultural (field)
targets.
Natural features, such as forest edges,
are generally more irregular in shape,
except where man has created a road
or clear cuts.
Elements of Visual Interpretation
 Size - to assess the size of a target
A quick approximation of target
size can direct interpretation to
an appropriate result more
quickly.
Large buildings factories or
warehouses would suggest
commercial property,
Small buildings would indicate
residential use.

18. 3/10/2016
18
Elements of Visual Interpretation
 Pattern - spatial arrangement of objects
Spatial arrangement of surface
features
Similar features under similar
condition reflects similar pattern
Linear – road, railway, canal
Nonlinear- Stream, River, Creeks
Clustered – Settlement
Dispersed – forest blanks, salt
affected patches
Regular pattern - Orchard
Elements of Visual Interpretation
 Texture - arrangement and frequency of tonal
variation
Rough textures would consist of a
mottled tone where the grey levels
change abruptly in a small area,
whereas smooth textures would have
very little tonal variation.
Smooth textures are most often the
result of uniform, even surfaces,
such as fields or grasslands.
Elements of Visual Interpretation
 Shadow - provides an idea of the profile and
relative height of a target or targets which
may make identification easier
shadows can also reduce or eliminate
interpretation in their area of
influence
•useful for enhancing or identifying
topography and landforms

19. 3/10/2016
19
Location
Geographical Site and Location of object
 Building near sea – Light House
 Salt affected land – Near sea
 Glacier – mountain peaks
Elements of Visual Interpretation
 Association - relationship between other
recognizable objects
a lake is associated with boats, a
marina, and adjacent recreational
land.
Canal with agricultural field
Marsh or swamp with flood plain
or tidal flats
DIGITAL IMAGE PROCESSING

20. 3/10/2016
20
Preprocessing
 When remotely sensed data is received from the
imaging sensors on the satellite platforms it contains
flaws and deficiencies.
 Pre-processing refers to those operations that are
preliminary to the main analysis.
1. Radiometric Corrections
2. Geometric Corrections
3. Atmospheric Correction
4. Feature Extraction
Radiometric Corrections
 Radiometric Corrections are carried
out when an image data is recorded
by the sensors they contain errors in
the measured brightness values of
the pixels. These errors are referred
as radiometric errors.
Geometric Corrections
 Raw digital images often contain serious geometrical
distortions that arise from earth curvature, platform motion,
relief displacement, non-linearity in scanning motion.

21. 3/10/2016
21
Atmospheric Corrections
 The path radiation coming from the
sun to the ground pixel and then
being reflected to the sensor is
effected by atmosphere.
 In this on going process, absorption
by atmospheric molecules takes
place that converts incoming energy
into heat.
 In particular, molecules of oxygen,
carbon-di-oxide, ozone and water
attenuate the radiation very strongly
in certain wavelengths.
 Scattering by these atmospheric
particles is also the dominant
mechanism that leads to radiometric
distortion in image data.
Image Classification and Analysis
 Spectral pattern recognition
 Digital image classification uses the spectral
information represented by the digital numbers in
one or more spectral bands, and attempts to
classify each individual pixel based on this
spectral information
 The resulting classified image is comprised of a
mosaic of pixels, each of which belong to a
particular theme, and is essentially a thematic "map"
of the original image.
Common classification procedures
 Supervised classification
 Unsupervised classification

22. 3/10/2016
22
Comparison
Supervised classification
 Training areas
 the analyst identifies in the
imagery homogeneous
representative samples of the
different surface cover types
 To determine the
numerical "signatures”
 Once the computer has
determined the signatures for
each class, each pixel in the
image is compared to these
signatures and labeled as the
class it most closely "resembles"
digitally
Unsupervised classification
 reverse of supervised classification
 Spectral classes are grouped first
 Then matched to information classes
 the analyst specifies how many
groups or clusters
 It is iterative in nature
 not completely without human
intervention

23. 3/10/2016
23
Applications of RS in Civil
Engineering
Self Study