Fundamentals of
Remote Sensing
Do we have To
characterize
Remote Sensing
REMOTE SENSING is the process of sensing and
measuring objects from a distance without physical
contact with them
Sensing
1.Scanning
2.Characterizing
3.Classification
4.Identification/ Quantification
5.Analysis
REMOTE SENSING
• "Remote sensing is the science of acquiring
information about the Earth's surface without actually
being ...
SIX STAGES IN REMOTE SENSING
Stage-1. Source of energy
Stage-2. Transmission of EMR towards the Object
Stage-3. Interactio...
Solar Energy
Incident Radiation
Absorption
Scattering
Reflected energy
Thermal emission
Transmission
Platforms
& Sensors
G...
Rate of transfer of Radiant Energy ( Joules) = Flux ( watts)
Energy response from surface of earth = radiant emittance Wm-...
Area Features
Spatially distributed entities, activities or
events
• Areas (Polygons) are a series of geographic
coordinat...
Types of RS system
Active RS
system
Passive RS
system
Artificial Energy
source
Natural Energy
source
e.g. radar systems
SL...
Sensor Detection
1.Passive Detection
• sensors measure levels of energy that are
naturally emitted, reflected, or transmit...
Active detection
1. Active Sensors provide their own energy source for
illumination of the target by directing a burst of ...
• IMAGING SENSORS
– Sensors which provide output to create an
image
– Eg : LISS I,LISS II, LISS III etc.
• NON IMAGING SEN...
IRS 1C Sensors overview
PAN
LISS III
WiFS
ORBIT
The path followed by a satellite
Two types of Orbits are
1) Geostationary Orbits
2) Near Polar Orbits
ORBIT
The path followed by a satellite
Two types of Orbits are
1) Geostationary Orbits
2) Near Polar Orbits
GEOSTATIONARY ORBITS
at altitudes of approximately 36,000 kilometres
revolve at speeds which match the rotation of the
E...
NEAR-POLAR ORBITS
• The inclination of the orbit relative
to polar axis.
 Some of these satellites’ orbits
are also sun-s...
• As the satellite revolves around the Earth, the sensor
"sees" a certain portion of the Earth's surface.
• The width of t...
PLATFORM
CHARACTERISTICS
USUAL PLATFORMS
• Aircraft
– Helicopters
– Microlites
– Low altitude aircrafts
– High altitude aircraft
• Satellites
– Orb...
CHARACTERISTICS OF
PLATFORMS
• Aircraft
– Defence permission needed
– Imagery can be obtained at the time and place of
our...
• Satellite
– Global coverage
– No fuel needed(for 3 years operation)
– Defence permission not needed
– Usually used for s...
Platform/Sensor /
Launch Year
Image
Cell Size
Image Size
(Cross x
Along-
Track)
Spec.
Bands
Visible
Bands
(m)
Near IR
Ban...
Pixels and Digital Number
Resolution of a Sensor
• Spatial Resolution – ‘Area’ aspects
• Spectral resolution – ‘ Band
aspect’
• Radiometric resoluti...
Spatial Resolution
• refers to the size of the smallest possible feature that
can be sensed
IRS 1C/D – 5.8m
(PAN)
IKONOS –...
PIXELS (Picture + elements)
Black - 0
White - 255Pixel
Grey
values
Spatial
Resolution
LANDSAT
30 m
LISS III
23.5
PAN
5.8 m
IKONOS
1m
60 cm spatial
resolution
Spectral Resolution
• Ability of a sensor to define fine wavelength intervals.
• The finer the spectral resolution, the na...
IRS 1C PAN IMAGE OF VIZAG STEEL PLANT, 1996IRS 1C PAN IMAGE OF VIZAG STEEL PLANT, 1996
IRS 1C LISS III IMAGE OF VIZAG STEEL PLANT, 1996IRS 1C LISS III IMAGE OF VIZAG STEEL PLANT, 1996
IRS 1C PAN, LISS III MERGED IMAGE
OF VIZAG STEEL PLANT, 1996
4 3 2 Composite of Landsat 7
7 4 2 Composite of Landsat 7
The image to the right is a "true color" image of the desert around the Salton
Sea and Imperial Valley in Southern Califor...
Spectral bands of Landsat 7
Band Number Wavelength Interval Spectral Response
1 0.45-0.52 µm Blue-Green
2 0.52-0.60 µm Gre...
• Landsat 7
Land Number Applications
• 1coastal water mapping, soil/vegetation discrimination, forest classification,
man-...
• Ability of the sensor to discriminate very slight
differences in energy.
• The finer the radiometric resolution of a
sen...
256 Level Grey Scale
Temporal Resolution
• Time interval between two successive visits of
the satellite for the same place.
• Spectral characte...
SCANNERS
CHARACTERISTICS OF SCANNER
• Output in digital form
• Highly amenable for computer processing
• No consumables
• Flexible ...
ACROSS-TRACK SCANNERS
• Scan the Earth in a series of lines.
• The lines are oriented perpendicular to the
direction of mo...
ALONG-TRACK SCANNERS
• Along-track scanners also use the forward motion of the
platform to record successive scan lines an...
CHARACTERISTICS OF RADAR
• All weather capability, day and night
observing capability
• Sensitive to moisture
• Soil depth...
Spectral reflectance curve
SPECTRAL REFLECTANCE OF
VEGETATION,SOIL AND WATER
Strong absorption in
blue and red bands.
Reflection depends on
the amount of
chlorophyll in the leaf.
SPECTRAL REFLECTANCE...
Reflectance peaks in
green, corresponds
with solar maximum
SPECTRAL REFLECTANCE OF VEGETATION
Major reflectance
peaks in NIR,
provides energy
balance for
vegetation
SPECTRAL REFLECTANCE OF VEGETATION
Water absorption at
1.4 and 1.9 microns
due to leaf moisture
SPECTRAL REFLECTANCE OF VEGETATION
Soil reflectance generally increases gradually from
visible to infrared.
SPECTRAL REFLECTANCE OF SOIL
Molecular water
absorptions at 1.4 and 1.9
microns
SPECTRAL REFLECTANCE OF SOIL
Spectral Signature Curves
B1 B2 B3 B4 B5 B6 B7
0
15
30
45
60
75
90
105
120
135 CLASS:WATER
Ambazari
Phutala
Gorewada
Gandh...
Electromagnetic Radiation
AN ELECTROMAGNETIC WAVE
Electromagnetic radiation consists of an electrical field(E)
which varies in magnitude in a direct...
THE ELECTROMAGNETIC
SPECTRUM
Electromagnetic Spectrum
• Covers the wavelength range from approximately 0.7
mm to 100 mm
• Divided into two categories based on their radiation
p...
REFLECTED IR
• Radiation in the reflected IR region is used for remote
sensing purposes in ways very similar to radiation ...
• The thermal IR region is quite different than the
visible and reflected IR portions, as this energy is
essentially the r...
INTERACTION WITH
THE ATMOSPHERE
 Radiation used for remote sensing reaches the Earth's
surface it has to travel through some distance of the
Earth's atmo...
SCATTERING
• Scattering occurs when particles
or large gas molecules present in
the atmosphere interact with and
cause the...
• Rayleigh scattering occurs
particles are very small compared
to the wavelength of the radiation
 Small specks of dust o...
MIE SCATTERING
• Mie scattering occurs when
the particles are just about the
same size as the wavelength of
the radiation....
NONSELECTIVE SCATTERING
• This occurs when the particles are
much larger than the wavelength of
the radiation. Water dropl...
Raman Scatter
• Any particle of any size
• Elastic collision of energy with
molecule resulting in loss or gain
in energy
•...
RADIATION - TARGET INTERACTIONS
• Radiation that is not absorbed or scattered in the
atmosphere can reach and interact wit...
Incident energy (I) from the source
Absorption (A) occurs when radiation (energy) is absorbed
into the target
Transmission...
TWO TYPES OF
REFLECTION
When a surface is smooth we get
specular or mirror-like reflection
where all (or almost all) of the
energy is directed awa...
• Because certain gases absorb electromagnetic energy in
very specific regions of the spectrum, they influence the
wavelen...
The transmission and absorption phenomenon varying with the
wavelength
Thermal Infra
Red Image (TIR )
True Color Thermal Infrared
CHARACTERISTIC OF IR IMAGES:
ON MOST TIR IMAGES, BRIGHTEST TONE ( HIGHER DN
VALUE ) REPRESENT THE WARMEST RADIANT
TEMPERAT...
RADAR WAVELENGTHS : WAVELENGTHS AND FREQUENCIES USED IN RS
BAND DESIGNATION WAVELENGTHS FREQUENCY
 ( CM ) GHZ
KA 0.8 –1.1...
Radar
• A Radar is an active remote sensing system
operating in the microwave portion of the spectrum
• Radar is an acrony...
Some definitions:
Target :
Ground objects of interest in a radar image
Backscatter :
Returned signal from surface targets
...
Principles of Imaging Radars
• A radar sensor operates by transmitting
microwaves towards the earth's surface in a
directi...
The radar creates an electromagnetic energy pulse which is focused
by an antenna and transmitted through the atmosphere. O...
TRANSMITTER
DUPLEXER OBJECT
CONTROL
ANTENNA
RECEIVER
Basic Structure of Radar System
CRT MONITOR
Film
Data Tapes
Data Proc...
DEPRESSION ANGLE
Pulse length
RANGE DIRECTION
TARGET A B
RANGE RESOLUTION( RR) OF RADAR :
RANGE RESOLUTION OR RESOLUTION I...
How Radar Works
A typical radar system consists of the following components:
(1) a pulse generator that discharges timed p...
RADAR CHARACTERISTICS : RADAR RECORDS MAY BE DIVIDED INTO FEATURES
CHARACTERISTIC OF AN RADAR IMAGE . THESE ARE :
1.HIGHLI...
Elements of Interpretation
 Tone
 Size
 Shape
 Pattern
 Shadow
 Texture
 Location / Site
 Association
 Resolution...
Red, Green Blue Display
R G B R G B R G B
1.Tone
•Relative Brightness or Color of the Objects
•On Panchromatic imagery - Shades of Gray
•On True / False Color Image...
2.Size •Spatial dimension of the object
3.Shape •General form, Configuration of the object
4.Pattern •Spatial arrangement ...
FINE
MEDIUM
TEXTURE
COARSE
7. Association •Occurrence of certain features in
relation to other
• Building and shadow
8.Location/Site •Geographic or T...
1.Data Selection & Screening
•Quality & Contrast
•Cloud, Fog etc free or minimal %
2.Mapping Scale
•For Country - 1:1Milli...
Ground Truthing
•Process of establishing correlation between spectral
signatures and ground information
•Scene dependant
H...
• REAL TIME
• SPATIAL LOCATIONS
AND EXTENTS OF
FEATURES CAN BE
COLLECTED
ACURATELY
• CHEAPER
• FASTER
• DIFFERENT SCALES
•...
1. Readily available at range of scales
2. Cheaper and more accurate than field surveys
3. Gives Synoptic view
4. Remote s...
Photogrammetry
• Photogrammetry is defined as the technique of
obtaining reliable measurements of objects from
photographs...
Principles of Photogrammetry
Principal Point
The amount of the relief displacement, d, is:
directly proportional to the difference in elevation, h,
between the top of ...
RESOURCESAT
SPECIFICATIONS
IRS-P6 (RESOURCESAT-1) is the most advanced
remote sensing satellite built by ISRO.
The tenth satellite of ISRO in IRS ser...
Senso
r
Spatia
l Resn
m
Steera
blity
Swat
h
Km
Spectral
Bands
Radiom
etric
Resn
LISS-3 23.5 No 140
B2, B3, B4
& B5
7 bits
...
Salient Features :
• Orbit : Circular Polar Sun Synchronous
• Orbit height : 817 km
• Orbit inclination : 98.7 deg
• Orbit...
IRS 1C/1D RESOURCESAT OCEANSAT
LISS III PAN WiFS LISS III LISS IV AWifs OCM
(Ocean
Colour
Monitor)
No of
Spectral
bands
4 ...
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
Fundamentals of remote sensing
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Fundamentals of remote sensing

  1. 1. Fundamentals of Remote Sensing
  2. 2. Do we have To characterize Remote Sensing
  3. 3. REMOTE SENSING is the process of sensing and measuring objects from a distance without physical contact with them
  4. 4. Sensing 1.Scanning 2.Characterizing 3.Classification 4.Identification/ Quantification 5.Analysis
  5. 5. REMOTE SENSING • "Remote sensing is the science 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 energy and processing, analyzing, and applying that information." Sensor Object to be sensedElectro Magnetic Radiation Three Essential Things for Remote Sensing
  6. 6. SIX STAGES IN REMOTE SENSING Stage-1. Source of energy Stage-2. Transmission of EMR towards the Object Stage-3. Interaction of EMR with the Object Stage-4. Transmission of Interacted EMR towards the Sensor Stage-5. Recording of the Image by the Detector Stage-6. Analysis of the Imagery 1 2 3 4 5 (Film) 6 3 3 4
  7. 7. Solar Energy Incident Radiation Absorption Scattering Reflected energy Thermal emission Transmission Platforms & Sensors Ground Borne Air Borne Space Borne Antenna Data Processing Data Products Soft Copy Data Products Hard Copy Visual Interpretation Digital Interpretation Outputs Softcopy Outputs Hard Copy Decision Making
  8. 8. Rate of transfer of Radiant Energy ( Joules) = Flux ( watts) Energy response from surface of earth = radiant emittance Wm-2 Radiance = radiant flux density from small area = Wm-2 Sr -1
  9. 9. Area Features Spatially distributed entities, activities or events • Areas (Polygons) are a series of geographic coordinates joined together to form a boundary such as: – Lake – Soil types
  10. 10. Types of RS system Active RS system Passive RS system Artificial Energy source Natural Energy source e.g. radar systems SLAR,SAR e.g.sensors on satellites Landsat,SPOT
  11. 11. Sensor Detection 1.Passive Detection • sensors measure levels of energy that are naturally emitted, reflected, or transmitted by the target object. • Passive sensors are those which detects naturally occurring energy. Most often, the source of radioactive energy is the sun. • Detection of reflected solar energy, for example, can only proceed when the target is illuminated by the sun, thus limiting visible light sensors on satellites from being used during a nighttime pass. • The Thematic Mapper, the primary sensor on the Landsat satellites, is a good example of a passive sensor.
  12. 12. Active detection 1. Active Sensors provide their own energy source for illumination of the target by directing a burst of radiation at the target and use sensors to measure how the target interacts with the energy. 2. Most often the sensor detects the reflection of the energy, measuring the angle of reflection or the amount of time it took for the energy to return. 3. Active sensors provide the capability to obtain measurements anytime, regardless of the time of day or season. 4. They can be used for examining energy types that are not sufficiently provided by the sun, such as microwaves, or to better control the way a target is illuminated. However, active systems require the generation of a fairly large amount of energy to adequately illuminate targets. Doppler radar is an example of an active remote sensing technology.
  13. 13. • IMAGING SENSORS – Sensors which provide output to create an image – Eg : LISS I,LISS II, LISS III etc. • NON IMAGING SENSORS • Sensors which provide numerical output with respect to the quantum of radiation • Eg: Radiometer,Scatterometer etc.
  14. 14. IRS 1C Sensors overview PAN LISS III WiFS
  15. 15. ORBIT The path followed by a satellite Two types of Orbits are 1) Geostationary Orbits 2) Near Polar Orbits
  16. 16. ORBIT The path followed by a satellite Two types of Orbits are 1) Geostationary Orbits 2) Near Polar Orbits
  17. 17. GEOSTATIONARY ORBITS at altitudes of approximately 36,000 kilometres revolve at speeds which match the rotation of the Earth so that they seem stationary, relative to the Earth's surface This allows the satellites to observe and collect information continuously over specific areas
  18. 18. NEAR-POLAR ORBITS • The inclination of the orbit relative to polar axis.  Some of these satellites’ orbits are also sun-synchronous. This means that they cover each area of the world at a constant local time of day called local sun time.  Platforms
  19. 19. • As the satellite revolves around the Earth, the sensor "sees" a certain portion of the Earth's surface. • The width of the strip imaged is referred to as the swath width. SWATH
  20. 20. PLATFORM CHARACTERISTICS
  21. 21. USUAL PLATFORMS • Aircraft – Helicopters – Microlites – Low altitude aircrafts – High altitude aircraft • Satellites – Orbiting satellites – Geostationary satellites
  22. 22. CHARACTERISTICS OF PLATFORMS • Aircraft – Defence permission needed – Imagery can be obtained at the time and place of our choice – Expensive – Usually used for cameras – Narrow limited view – Platform less stable – Large scales(1:1000 to 1:30000) – Flexible repeat coverage – High spatial resolution – Less cost effective
  23. 23. • Satellite – Global coverage – No fuel needed(for 3 years operation) – Defence permission not needed – Usually used for scanners and radars which transmit information in electronic format – Wide,synoptic view – Very stable paltform – Small scale(>1:50000) – Limited repeat coverage(3 to 26 days) – Low spatial resolution – Highly cost effective
  24. 24. Platform/Sensor / Launch Year Image Cell Size Image Size (Cross x Along- Track) Spec. Bands Visible Bands (m) Near IR Bands (m) Ikonos-2 VNIR 1999 4 m 11 x 11 km 4 B 0.45-0.52 G 0.52-0.60 R 0.63-0.69 0.76-0.90 Terra (EOS-AM-1) ASTER 1999 15 m (Vis, NIR) 30 m (MIR) 90m (TIR) 60 x 60 km 14 G 0.52-0.60 R 0.63-0.69 0.76-0.86 SPOT 4 HRVIR (XS) 1999 20 m 60 x 60 km 4 G 0.50-0.59 R 0.61-0.68 0.79-0.89 SPOT 1, 2, 3 HRV (XS) 1986 20 m 60 x 60 km 3 G 0.50-0.59 R 0.61-0.68 0.79-0.89 IRS-1C, 1D LISS III 1995 23.6 m 70.8 m (MIR) 142 x 142 km 70 x 70 km Pan 3 G 0.52-0.59 R 0.62-0.68 0.77-0.86 Landsat 7 ETM+ 1999 30 m 185 x 170 km 7 B 0.45-0.515 G 0.525- 0.605 0.75-0.90 Landsat 4, 5 TM 1982 30 m 185 x 170 km 7 B 0.45-0.52 G 0.52-0.60 R 0.63-0.69 0.76-0.90 IRS-1A, 1B LISS I, II 1988 36.25 m (LISSII) 72.5 m (LISS 1) 148 x 148 km 4 B 0.45-0.52 G 0.52-0.60 R 0.63-0.69 0.77-0.86 Landsat 4, 5 MSS 1982 79 m 185 x 185 km 4 G 0.5-0.6 R 0.6-0.7 0.7-0.8 0.8-0.9 IRS-1C, 1D WiFS 1995 189 m 810 x 810 km 2 R 0.62-0.68 0.77-0.86
  25. 25. Pixels and Digital Number
  26. 26. Resolution of a Sensor • Spatial Resolution – ‘Area’ aspects • Spectral resolution – ‘ Band aspect’ • Radiometric resolution – ‘Radiance’ aspect • Temporal resolution – ‘Frequency’ aspect
  27. 27. Spatial Resolution • refers to the size of the smallest possible feature that can be sensed IRS 1C/D – 5.8m (PAN) IKONOS – 1m (PAN) RESOURCESAT – 5.8m MULTISPECTRAL
  28. 28. PIXELS (Picture + elements) Black - 0 White - 255Pixel Grey values
  29. 29. Spatial Resolution LANDSAT 30 m LISS III 23.5 PAN 5.8 m IKONOS 1m
  30. 30. 60 cm spatial resolution
  31. 31. Spectral Resolution • Ability of a sensor to define fine wavelength intervals. • The finer the spectral resolution, the narrower is the wavelength range for a particular channel or band.
  32. 32. IRS 1C PAN IMAGE OF VIZAG STEEL PLANT, 1996IRS 1C PAN IMAGE OF VIZAG STEEL PLANT, 1996
  33. 33. IRS 1C LISS III IMAGE OF VIZAG STEEL PLANT, 1996IRS 1C LISS III IMAGE OF VIZAG STEEL PLANT, 1996
  34. 34. IRS 1C PAN, LISS III MERGED IMAGE OF VIZAG STEEL PLANT, 1996
  35. 35. 4 3 2 Composite of Landsat 7
  36. 36. 7 4 2 Composite of Landsat 7
  37. 37. The image to the right is a "true color" image of the desert around the Salton Sea and Imperial Valley in Southern California. The American/Mexican border is clearly visible.
  38. 38. Spectral bands of Landsat 7 Band Number Wavelength Interval Spectral Response 1 0.45-0.52 µm Blue-Green 2 0.52-0.60 µm Green 3 0.63-0.69 µm Red 4 0.76-0.90 µm Near IR 5 1.55-1.75 µm Mid-IR 6 10.40-12.50 µm Thermal IR 7 2.08-2.35 µm Mid-IR
  39. 39. • Landsat 7 Land Number Applications • 1coastal water mapping, soil/vegetation discrimination, forest classification, man-made feature identification • 2vegetation discrimination and health monitoring, man-made feature identification • 3plant species identification, man-made feature identification • 4soil moisture monitoring, vegetation monitoring, water body discrimination • 5vegetation moisture content monitoring • 6surface temperature, vegetation stress monitoring, soil moisture monitoring, cloud differentiation, volcanic monitoring • 7mineral and rock discrimination, vegetation moisture contentFor more details see: Lillesand, T. and Kiefer, R., 1994. Remote Sensing and Image Interpretation. John Wiley and Sons, Inc., New York, p. 468.
  40. 40. • Ability of the sensor to discriminate very slight differences in energy. • The finer the radiometric resolution of a sensor, the more sensitive it is to detecting small differences in reflected or emitted energy. Radiometric Resolution 0 255 0 127 0 63
  41. 41. 256 Level Grey Scale
  42. 42. Temporal Resolution • Time interval between two successive visits of the satellite for the same place. • Spectral characteristics of features may change over time and these changes can be detected by collecting and comparing multi-temporal imagery.
  43. 43. SCANNERS
  44. 44. CHARACTERISTICS OF SCANNER • Output in digital form • Highly amenable for computer processing • No consumables • Flexible w.r.t. radiometric and spectral resolutions
  45. 45. ACROSS-TRACK SCANNERS • Scan the Earth in a series of lines. • The lines are oriented perpendicular to the direction of motion of the sensor platform (i.e. across the swath). • Each line is scanned from one side of the sensor to the other, using a rotating mirror (A).
  46. 46. ALONG-TRACK SCANNERS • Along-track scanners also use the forward motion of the platform to record successive scan lines and build up a two-dimensional image, perpendicular to the flight direction. • Instead of a scanning mirror, they use a linear array of detectors (A) located at the focal plane of the image (B) formed by lens systems (C), which are "pushed" along in the flight track direction (i.e. along track). • Also referred to as pushbroom scanners • Principle of MSS.
  47. 47. CHARACTERISTICS OF RADAR • All weather capability, day and night observing capability • Sensitive to moisture • Soil depth penetration to certain extent
  48. 48. Spectral reflectance curve
  49. 49. SPECTRAL REFLECTANCE OF VEGETATION,SOIL AND WATER
  50. 50. Strong absorption in blue and red bands. Reflection depends on the amount of chlorophyll in the leaf. SPECTRAL REFLECTANCE OF VEGETATION
  51. 51. Reflectance peaks in green, corresponds with solar maximum SPECTRAL REFLECTANCE OF VEGETATION
  52. 52. Major reflectance peaks in NIR, provides energy balance for vegetation SPECTRAL REFLECTANCE OF VEGETATION
  53. 53. Water absorption at 1.4 and 1.9 microns due to leaf moisture SPECTRAL REFLECTANCE OF VEGETATION
  54. 54. Soil reflectance generally increases gradually from visible to infrared. SPECTRAL REFLECTANCE OF SOIL
  55. 55. Molecular water absorptions at 1.4 and 1.9 microns SPECTRAL REFLECTANCE OF SOIL
  56. 56. Spectral Signature Curves B1 B2 B3 B4 B5 B6 B7 0 15 30 45 60 75 90 105 120 135 CLASS:WATER Ambazari Phutala Gorewada Gandhi sagar Lendi talav DNVALUES BANDS Class: Water 0 2 4 6 8 20 40 60 80 100 120 140 160 CLASS: THICK VEGETATION BANDS DNVALUES VNIT NEERI Koradi Road 20 40 60 80 100 120 140 160 Seminary Hills Class: Thick vegetation
  57. 57. Electromagnetic Radiation
  58. 58. AN ELECTROMAGNETIC WAVE 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, and a magnetic field (M) oriented at right angles to the electrical field. Both these fields travel at the speed of light (c).
  59. 59. THE ELECTROMAGNETIC SPECTRUM
  60. 60. Electromagnetic Spectrum
  61. 61. • Covers the wavelength range from approximately 0.7 mm to 100 mm • Divided into two categories based on their radiation properties – the reflected IR(0.7-3.0 µm), NIR(0.7- 1.1µm), SWIR(1.55-1.7 µm) and TIR(3-14 µm). INFRARED (IR) REGION
  62. 62. REFLECTED IR • Radiation in the reflected IR region is used for remote sensing purposes in ways very similar to radiation in the visible portion. The reflected IR covers wavelengths from approximately 0.7 µm to 3.0 µm. • Photographic IR ranges from 0.7 to 0.9 µm
  63. 63. • The thermal IR region is quite different than the visible and reflected IR portions, as this energy is essentially the radiation that is emitted from the Earth's surface in the form of heat. The thermal IR covers wavelengths from approximately 3.0 µm to 100 µm. But the heat energy is sensed in windows at 3 to 5.5 µm and 8 to 14 µm. THERMAL IR MICROWAVE REGION •The microwave region from about 1 mm to 1m
  64. 64. INTERACTION WITH THE ATMOSPHERE
  65. 65.  Radiation used for remote sensing reaches the Earth's surface it has to travel through some distance of the Earth's atmosphere.  Particles and gases in the atmosphere can affect the incoming light and radiation.  These effects are caused by the mechanisms of scattering and absorption.
  66. 66. SCATTERING • Scattering occurs when particles or large gas molecules present in the atmosphere interact with and cause the electromagnetic radiation to be redirected from its original path.
  67. 67. • Rayleigh scattering occurs particles are very small compared to the wavelength of the radiation  Small specks of dust or nitrogen and oxygen molecules  The fact that the sky appears "blue" during the day is because of this phenomenon.  Rayleigh Scattering  1/λ4 RAYLEIGH SCATTERING
  68. 68. MIE SCATTERING • Mie scattering occurs when the particles are just about the same size as the wavelength of the radiation. e.g., Dust, pollen, smoke and water vapour • Mie Scattering  1/ λ to 1/λ2
  69. 69. NONSELECTIVE SCATTERING • This occurs when the particles are much larger than the wavelength of the radiation. Water droplets and large dust particles can cause this type of scattering. • Nonselective scattering gets its name from the fact that all wavelengths are scattered in all directions without following any law.
  70. 70. Raman Scatter • Any particle of any size • Elastic collision of energy with molecule resulting in loss or gain in energy • May have variable effect
  71. 71. RADIATION - TARGET INTERACTIONS • Radiation that is not absorbed or scattered in the atmosphere can reach and interact with the Earth's surface Three forms of interaction are Absorption (A) Transmission (T) Reflection (R).
  72. 72. Incident energy (I) from the source Absorption (A) occurs when radiation (energy) is absorbed into the target Transmission (T) occurs when radiation passes through a target Reflection (R) occurs when radiation "bounces" off the target and is redirected.
  73. 73. TWO TYPES OF REFLECTION
  74. 74. When a surface is smooth we get specular or mirror-like reflection where all (or almost all) of the energy is directed away from the surface in a single direction. When the surface is rough and the energy is reflected almost uniformly in all directions. SPECULAR REFLECTION DIFFUSE REFLECTION
  75. 75. • Because certain gases absorb electromagnetic energy in very specific regions of the spectrum, they influence the wavelengths, which reach the Earth available for remote sensing. • 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 WINDOWS
  76. 76. The transmission and absorption phenomenon varying with the wavelength
  77. 77. Thermal Infra Red Image (TIR )
  78. 78. True Color Thermal Infrared
  79. 79. CHARACTERISTIC OF IR IMAGES: ON MOST TIR IMAGES, BRIGHTEST TONE ( HIGHER DN VALUE ) REPRESENT THE WARMEST RADIANT TEMPERATURES AND THE DARKEST TONE ( LOWER DN VALUE ) REPRESENT THE COOLEST TEMPERATURES. AREAS OF APPLICATION: 1. PENETRATION OF SMOKE PLUMES AROUND STACKS IN INDUSTRIES 2. DETECTION OF DIFFERENTIAL VEGETATION 3. SOIL MOISTURE STUDIES 4. WEATHER RELATED STUDIES
  80. 80. RADAR WAVELENGTHS : WAVELENGTHS AND FREQUENCIES USED IN RS BAND DESIGNATION WAVELENGTHS FREQUENCY  ( CM ) GHZ KA 0.8 –1.1 40-26.5 K 1.1-1.7 26.5-18 KU 1.7-2.4 18-12.5 X 2.4-3.8 12.5-8 C 3.8-7.5 8.0-4 S 7.5-15 4-2 L 15-30 2-1 P 30-100 1-0.3
  81. 81. Radar • A Radar is an active remote sensing system operating in the microwave portion of the spectrum • Radar is an acronym for RAdio Detection and Ranging A radar performs 3 primary functions: 1. It transmits microwave pulses towards a target 2. It receives a return portion of the transmitted signal after it has interacted with the target 3. It observes the strength, temporal behavior, and the time delay of the returned signals
  82. 82. Some definitions: Target : Ground objects of interest in a radar image Backscatter : Returned signal from surface targets Range : The distance from the radar to the target Range direction : The direction in which the radar pulses are transmitted; generally perpendicular to the flight direction
  83. 83. Principles of Imaging Radars • A radar sensor operates by transmitting microwaves towards the earth's surface in a direction perpendicular to the flight path of the platform. • The sensor notes the time it takes for the signal to travel from the sensor to the target and back and uses this information to determine the relative distances of targets in the range direction. • A radar image is a record of the amount of backscatter received from a target.
  84. 84. The radar creates an electromagnetic energy pulse which is focused by an antenna and transmitted through the atmosphere. Objects in the path of this electromagnetic pulse, called targets, scatter the electromagnetic energy. Some of that energy is scattered back toward the The receiving antenna (which is normally also the transmitting antenna) gathers this back-scattered radiation and feeds it to a device called a receiver.
  85. 85. TRANSMITTER DUPLEXER OBJECT CONTROL ANTENNA RECEIVER Basic Structure of Radar System CRT MONITOR Film Data Tapes Data Processing & Storage
  86. 86. DEPRESSION ANGLE Pulse length RANGE DIRECTION TARGET A B RANGE RESOLUTION( RR) OF RADAR : RANGE RESOLUTION OR RESOLUTION IN THE RANGE DIRECTION IS DETERMINED BY THE DEPRESSION ANGLE AND BY THE PULSE LENGTH. IT IS THEORETICALLY EQUAL TO ONE HALF THE PULSE LENGTH.
  87. 87. How Radar Works A typical radar system consists of the following components: (1) a pulse generator that discharges timed pulses of microwave/radio energy (2) a transmitter (3) a duplexer (4) a directional antenna that shapes and focuses each pulse into a stream (5) Returned pulses that the receive antenna picks up and sends to a receiver that converts (and amplifies) them into video signals (6) A recording device which stores them digitally for later processing and/or produces a real time analog display on a cathode ray tube (CRT) or drives a moving light spot to record on film.
  88. 88. RADAR CHARACTERISTICS : RADAR RECORDS MAY BE DIVIDED INTO FEATURES CHARACTERISTIC OF AN RADAR IMAGE . THESE ARE : 1.HIGHLIGHTS : CAUSED BY STRONG RADAR RETURNS. 2.SHADOW : NO ENERGY FROM TRANSMITTED PULSES REACH THESE AREAS 3.DIFFUSED : SIGNATURES WITH INTERMEDIATE GRAY TONES DENOTING IRREGULAR SURFACE. 4.CORNER REFLECTORS : FORMED BY INTERSECTING PLANAR STRUCTURES. 5.SPECULAR SIGNATURES : NO TRANSMITTED ENERGY RETURNS TO THE ANTENNA AND A DARK SIGNATURE FORMS. LightSpecular CORNER REFLECTION HIGHLIGHT Diffused SHADOW DARK GRAY SCALE
  89. 89. Elements of Interpretation  Tone  Size  Shape  Pattern  Shadow  Texture  Location / Site  Association  Resolution  Slope & Aspect
  90. 90. Red, Green Blue Display R G B R G B R G B
  91. 91. 1.Tone •Relative Brightness or Color of the Objects •On Panchromatic imagery - Shades of Gray •On True / False Color Imagery - RGB/IHS •For Vegetation Depends upon Aspect & Slope, soil changes, Season/Time etc. •Depends upon Properties of the objects
  92. 92. 2.Size •Spatial dimension of the object 3.Shape •General form, Configuration of the object 4.Pattern •Spatial arrangement of the surface features •Linear, Regular or Irregular – Manmade /Natural forest 5.Shadows •Due to Sun’s illumination angle, size and shape of the object 6.Texture •Frequency of tonal changes •Product of size, shape, tone, pattern shadow •Fine, Medium, Coarse, Rough •Grass lands - Fine, Homogeneous young Forest - Medium to Coarse, Degraded Forest - Coarse
  93. 93. FINE MEDIUM TEXTURE COARSE
  94. 94. 7. Association •Occurrence of certain features in relation to other • Building and shadow 8.Location/Site •Geographic or Topographic location •Altitudinal variation 9.Resolution •Spatial, Spectral, Radiometric, Temporal 10.Aspect •Direction in which slope is facing
  95. 95. 1.Data Selection & Screening •Quality & Contrast •Cloud, Fog etc free or minimal % 2.Mapping Scale •For Country - 1:1Million •For State - 1:250,000 •For District / Division - 1:50000 •For Watersheds - 1:25000 •For Micro-plans - 1:12500 or larger
  96. 96. Ground Truthing •Process of establishing correlation between spectral signatures and ground information •Scene dependant High contrast images - Less amount If tonal & textural variations are high - More amount •Utilized for calibrating the radiometers, Spectrometers etc. •Probability Proportionate Stratified Random sampling •Field visit and collection of ground information, ancillary information and reference material for inaccessible areas •Collection of spectral signatures for various representative objects •Feeding the details to computer and Refinement of classification
  97. 97. • REAL TIME • SPATIAL LOCATIONS AND EXTENTS OF FEATURES CAN BE COLLECTED ACURATELY • CHEAPER • FASTER • DIFFERENT SCALES • EASY UPDATION • MORE ANALYTICAL THEMES ADVANTAGES OF REMOTE SENSING
  98. 98. 1. Readily available at range of scales 2. Cheaper and more accurate than field surveys 3. Gives Synoptic view 4. Remote sensing data is a record of earth surface at one point in time 5. The radiation outside the human sensitivity range i.e.,UV, IR, MW etc., can be sensed through remote sensing 6. Stereoscopic view can be created and measured horizontally and vertically 7. Inaccessible areas can be mapped easily Rationale for use of Remote Sensing data
  99. 99. Photogrammetry • Photogrammetry is defined as the technique of obtaining reliable measurements of objects from photographs • To make accurate measurements it is necessary to determine, as accurately as possible, photographic scale Photographic Scale • Scale defines the relationship between a linear distance on a vertical photograph and the corresponding actual distance on the ground • Photographic scale indicates proportional distance • Scale expressed as a representative fraction (RF) between the linear distance on the photo (numerator) and the corresponding distance on the ground (denominator) • Example: 1/25,000 or 1:25,000 means that a length of 1 unit of measurement on the photo represents 25,000 units of measurement on the ground
  100. 100. Principles of Photogrammetry
  101. 101. Principal Point
  102. 102. The amount of the relief displacement, d, is: directly proportional to the difference in elevation, h, between the top of the object whose image is displaced and the local datum, i.e., the greater the height of the object above the local datum, the greater its displacement. directly proportional to the radial distance, r, between the top of the displaced image and the principal point, the greater the displacement. inversely proportional to the altitude ,H, of the camera of the local datum Therefore, a reduction in relief displacement of object can be achieved by increasing the flying height.
  103. 103. RESOURCESAT SPECIFICATIONS
  104. 104. IRS-P6 (RESOURCESAT-1) is the most advanced remote sensing satellite built by ISRO. The tenth satellite of ISRO in IRS series, IRS-P6 , launched on Oct. 17, 2003 PSLV-C5 Sun Synchronous Orbit Three cameras RESOURCESAT (IRS-P6) sensors viz., LISS-3, LISS-4 and AWiFS are designed to provide monoscopic and stereoscopic data of varying resolutions. The geometric and spectral characteristics of the sensors are given. The payloads will greatly aid crop/vegetation and integrated land and water resources related applications.
  105. 105. Senso r Spatia l Resn m Steera blity Swat h Km Spectral Bands Radiom etric Resn LISS-3 23.5 No 140 B2, B3, B4 & B5 7 bits LISS-4 5.8 Yes 70 B3 (Mono chromatic) 7 bits 5.8 23 B2, B3 & B4 AWiFS - A - B 70 No 370 B2, B3 & B4 10 bits 70 370 ---Do---
  106. 106. Salient Features : • Orbit : Circular Polar Sun Synchronous • Orbit height : 817 km • Orbit inclination : 98.7 deg • Orbit period : 101.35 min • Number of Orbits per day : 14 • Local Time of Equator crossing : 10.30 a.m. • Repetivity (LISS-3) : 24 days • Revisit (LISS-4) : 5 days • Lift-off Mass : 1360 kg • Attitude and Orbit Control : 3-axis body stabilised using Reaction Wheels, Magnetic Torquers and Hydrazine Thrusters • Power : Solar Array generating 1250 W, Two 24 Ah Ni-Cd batteries • Mission Life : 5 years
  107. 107. IRS 1C/1D RESOURCESAT OCEANSAT LISS III PAN WiFS LISS III LISS IV AWifs OCM (Ocean Colour Monitor) No of Spectral bands 4 1 2 4 3 3 8 Spectral Bands (microns) B2 0.52-0.59 B3 0.62-0.68 B4 0.77-0.86 B5 1.55-1.70 0.50 -0.75 B3 0.62-0.68 B4 0.77-0.86 0.52-0.59 0.62-0.68 0.77-0.86 0.52-0.59 0.62-0.68 0.77-0.86 1.55-1.70 0.52-0.59 0.62-0.68 0.77-0.86 1.55-1.70 0.402-0.422 0.433-0.453 0.480-0.500 0.500-0.520 0.545-0.565 0.660-0.680 0.745-0.785 0.845-0.885 Spatial Resolution (m) 23.5 for B2,B3,B4 and 70.5 for B5 Better than 10 188 23.5 5.8 56 360 Swath 142 km for B2, B3,B4 and 148 km for B5 70 km, nadir Steering Range 26 774 km 141km 23.9 (MX mode) 70.3 (PAN mode) 740 km 1420 km Radiometri c levels 128 64 128 7 bits 7 bits 10 bits
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