1. BASIC PRINCIPLES OF REMOTE SENSING
ATMOSPHERE
OCEAN
LAND M E T O R L G Y

3. WHY MAKE MEASUREMENT FROM SPACE?
REPEAT OBSERVATIONS
750
SYNOPTIC
COVERAGE 4
600 3
450
300
150
800 km 2 1 14 13 12 11 10 9 8 7 6 00
Latitude
150
Orbit
Number
300 5
450
10 km
600
2820km
750
100 m
Swath = 70km
10 m
1.6 m
4.5 km
357 km
1956 km
11.3 km
35.7 km

4. Need for a Meteorological Satellite Observation System
Surface-based (in situ) meteorological observations are the most reliable
But they are confined to land
In situ observations are scanty over oceans which occupy two-thirds of the earth’s surface
It is difficult to set up observatories in inhospitable regions
Automatic weather stations cannot observe all parameters

5. Need for a Meteorological Satellite Observation System
Meteorological parameters inferred indirectly
Satellites can provide extensive coverage
Satellites can provide continuous monitoring
Problem is that a single satellite cannot perform both tasks simultaneously
Satellites are expensive

6. History of Remote Sensing
The history of remote sensing began with the invention of photography. The term "photography" is derived from two Greek words meaning "light" (phos) and "writing" (graphien).

7. First photograph in the world by Niepce
Niepce takes first picture of nature from a window view of the French countryside using a camera obscura and an emulsion using bitumen of Judea, a resinous substance, and oil of lavender (it took 8 hours in bright sunlight to produce the image)
French inventor, most noted as the inventor of photography

8. History of Remote Sensing
Gasper Felix Tournachon “Nadar" takes the first aerial photograph from a captive balloon from an altitude of 1,200 feet over Paris.
Gasper Felix Tournachon "Nadar" ( ) San Francisco, looking to the southwest. Published 1878, C. R. Parsons.
Balloons gave us the first real oppurtunity to view the earth from above, but before we could physically do this our artistic imaginations were capable of envisioning what this perspective (see above). With the development of a camera and image capturing mechanism it was possible to acquire remotely sensed imagery of urban areas for the first time.
. .
The cartoon above is from May 25, "What Nadar had really done was to change the level of art to the level of science and utility, from the artistic drawing to an instrument of work." - Daunier
Felix Tournachon, aka Nadar, captured the first aerial view of European cities, starting with Paris in 1868.
Boston from a captive balloon at 1,200 feet, October 13, 1860, James Wallace Black.
This is the oldest conserved aerial photograph (Nadar's first works were lost). This photograph is printed with Albumen (coal) and housed at the Boston Public Library.
Boston from a captive balloon at 1,200 feet,
October 13, 1860, James Wallace Black.
This is the oldest conserved aerial photograph

9. History of Remote Sensing
The Bavarian Pigeon Corps uses pigeons to transmit messages and take aerial photos.

10. History of Remote Sensing
1914 – WW I provided a boost in the use of aerial photography, but after the war, enthusiasm waned

11. History of Remote Sensing
First space photographs from V-2 rockets.
U-2 takes first flight.

12. Photograph from V-2 Rocket
Typical example of an oblique photograph,
looking across Arizona and Gulf of California

13. History of Remote Sensing
EXPLORER-7 launched in 1959
Carried Suomi radiometer
measuring solar &terrestrial radiation (ERB study)

14. History of Remote Sensing
TIROS-1, Launched 01 Apr 1960
Carried just an ordinary
TV camera. It was the
Beginning of Satellite
Meteorology.

15. Remote Sensing: Definitions
Remote Sensing is the art, science and technology of obtaining reliable information about physical objects and the environment, through a process of recording, measuring and interpreting imagery and digital representations of energy patterns derived from non-contact sensor systems" (Colwell, 1997).
Photogrammetry and Remote Sensing are the art, science and technology of obtaining reliable information about physical objects and the environment, through a process of recording, measuring and interpreting imagery and digital representations of energy patterns derived from non-contact sensor systems" (Colwell, 1997).
"Remote sensing may be broadly defined as the collection of information about an object without being in physical contact with the object. Aircraft and satellites are the common platforms from which remote sensing observations are made. The term remote sensing is restricted to methods that employ electromagnetic energy as the means of detecting and measuring target characteristics" (Sabins, 1978).
"Remote sensing is the art and science of obtaining information from a distance, i.e. obtaining information about objects or phenomena without being in physical contact with them. The science of remote sensing provides the instruments and theory to understand how objects and phenomena can be detected. The art of remote sensing is in the development and use analysis techniques to generate useful information"(Aronoff, 1995).

16. History of Remote Sensing
"Remote sensing may be broadly defined as the collection of information about an object without being in physical contact with the object. The term remote sensing is restricted to methods that employ electromagnetic energy as the means of detecting and measuring target characteristics" (Sabins, 1978).

17. History of Remote Sensing
"Remote sensing is the art and science of obtaining information from a distance, i.e. obtaining information about objects or phenomena without being in physical contact with them. (Aronoff, 1995).
The science of remote sensing provides the instruments and theory to understand how objects and phenomena can be detected.
The art of remote sensing is in the development and use analysis techniques to generate useful information"
techniques involve amassing knowledge pertinent to the sensed scene (target) by utilizing electromagnetic radiation, force fields, or acoustic energy sensed by recording cameras, radiometers and scanners, lasers, radio frequency receivers, radar systems, sonar, thermal devices, sound detectors, seismographs, magnetometers, gravimeters, scintillometers, and other instruments.
Remote Sensing in the most generally accepted meaning refers to instrument-based techniques employed in the acquisition and measurement of spatially organized data/information on some property(ies) (spectral; spatial; physical) of an array of target points (pixels) within the sensed scene that correspond to features, objects, and materials, doing this by applying one or more recording devices not in physical, intimate contact with the item(s) under surveillance); techniques involve amassing knowledge pertinent to the sensed scene (target) by utilizing electromagnetic radiation, force fields, or acoustic energy sensed by recording cameras, radiometers and scanners, lasers, radio frequency receivers, radar systems, sonar, thermal devices, sound detectors, seismographs, magnetometers, gravimeters, scintillometers, and other instruments.

18. Basic Principles of EM Wave Propagation
Black body radiation at different temperatures
( 300, 950, and 2500 Kelvin).

19. Electromagnetic Waves

20. Period, Amplitude and Wavelength

21. Electromagnetic Spectrum
0.4
0.5
0.6
0.7

22. Infinite Possibilities
The electromagnetic spectrum stretches across x-rays to radio waves
Theoretically speaking, it can be broken into an infinite number of parts

23. Infinite Possibilities
Depending on which spectral region is scanned we will get different information

24. Infinite Possibilities
Depending upon where we place a satellite, we will get different information

25. What Happens When EMR Strikes Matter?
Transmission
Reflection
Absorption

26. Transmission
It is a process by which incident radiation passes through matter w/o measurable attenuation
1> 2
1= 3
Medium 1 1 3 2
Medium 2

27. Reflection and Scattering
Reflection process whereby incident radiation "bounces off" the surface of substance in a single, predictable direction; caused by surfaces smooth relative to wavelengths of incident radiation; no change in velocity or wavelength
1= 2 1 2
Medium 1
Medium 2
Reflection

28. Reflection and Scattering
Scattering (Diffused reflection) occurs when incident radiation is dispersed or spread out unpredictably in many different directions; occurs when surfaces rough relative to wave-lengths of incident radiation; no change in velocity or wavelength
Medium 1
Medium 2
Scattering

29. Absorption
It is a process by which incident radiation is taken in by the medium (e.g., surface, atmospheric particulates, atmospheric layer); medium opaque to incident radiation
It is the tendency for materials to simply soak up electromagnetic energy and convert it to heat.
Some of this energy can be measured as radiated (emitted) heat that is at a longer wavelength than the original energy.
Emission
Absorption
Emission

30. EMR - Atmosphere Interactions
EMR travels through space w/o modification
Diversion and depletion occurs as solar and terrestrial radiation interact with earth's atmosphere
Interference is wavelength selective - meaning at certain wavelengths EMR passes freely through atmosphere, whereas restricted at other wavelengths

31. Windows and Absorption Bands
Atmospheric Windows (transmision bands) - areas of EMS where specific wavelengths pass relatively unimpeded through atmosphere
Absorption Bands - areas where specific wavelengths are totally or partially blocked

32. Windows and Absorption Bands

33. Important Atmospheric Windows
um       UV, visible, near infrared
um       SWIR
um       Mid infrared
um       Mid infrared
um      Thermal Infrared
  > 0.6cm           Microwave

34. IMAGING AND SOUNDING
Objective to study earth's surface - different remote sensing instruments designed to operate in windows where cloudless atmosphere will transmit sufficient radiation for detection
Objective to study atmosphere constituents - operate in atmospheric absorption bands

35. SATELLITE OBSERVATIONAL SYSTEM FOR METEOROLOGY
SURFACE SENSING (IMAGING)
( VHRR, SSMI, SCATTEROMETERS, MADRAS)
SOUNDERS
(TOVS, TRMM-RADAR,SAPHIR)
T, P, RH PROFILE
MINOR CONSTITUENTS
PRECIPITATION PROFILE
LAND COVER
SEA SURFACE TEMPERATURE
CLOUD MOTION VECTOR
OCEAN SURFACE WIND VECTOR
SNOW COVER
CLOUD STRUCTURE
CYCLONE MOVEMENT

36. Atmospheric Absorption and Transmission
Most significant absorbers of EMR:
Ozone
Carbon dioxide
Water vapor
Oxygen
Nitrogen

37. Spectral Signatures
A primary use of remote sensing data is in classifying the myriad features in a scene into meaningful categories
The image then becomes a thematic map (the theme is selectable e.g., land use, geology, vegetation types, rainfall).
A farmer may use to monitor the health of his crops without going out to the field
A geologist may use the images to study the types of minerals or rock structure
A biologist may want to study the variety of plants in a certain location.

38. Spectral Signatures
At certain wavelengths, sand reflects more energy than green vegetation while at other wavelengths it absorbs more (reflects less) energy.
Therefore, in principle, various kinds of surface materials can be distinguished from each other by these differences in reflectance.
When more than two wavelengths are used, the resulting images tend to show more separation among the objects.
The improved ability of multispectral sensors provides a basic remote sensing data resource for quantitative thematic information, such as the type of land cover.
These data provide unique identification characteristics leading to a quantitative assessment of the Earth's features.

39. Spectral Signatures

40. PRINCIPLE OF LAND COVER DISCRIMINATION
FRESH SNOW
GREEN VEGETATION
DARK TONED SOIL
LIGHT TONED SOIL
CLEAR WATER
TURBID WATER

41. TYPICAL SPECTRAL REFLECTANCE CURVE OF SNOW.
Snow reflectance depends on:-
Wavelength
Grain size (hence age)
Snow pack thickness
Liquid water content
Contaminant present
Solar zenith angle
Reflectance relative to BaSO4
TYPICAL SPECTRAL REFLECTANCE CURVE OF SNOW.
Snow condition cold, sifted, `sugar’ consistency. Snow density g/cm3
Wavelength in micrometer

42. SNOW
(a)
(b)
IRS LISS-3 image over part of Himalayas. (a) is in band-2 (Green) and (b) in band-5 (SWIR).

43. DIFF STAGES OF REMOTE SENSING SYSTEM

44. Questions if any ?

45. Thank you