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. Infinite Possibilities
What you get depends on
Sensor
Spectral window used
Response of the sensor
Field of view
Orbit
Satellite height
Inclination of the satellite orbit
Scan swath
Time of scan
Repeat cycle of the satellite visit

26. LOSS OF EM ENERGY Spherical Spreading Absorption Scattering
Amplitude dies off with distance
Absorption
Scattering
Spherical Spreading. This phenomena is simply the fact that the amplitude dies off with distance travelled (i.e., the further you are from the source, the weaker the signal). This obvious physical effect is no different than observing that as one gets farther and farther from a source of sound, a weaker and weaker sound is heard. Technically, as the wave travels, the wave-front is a sphere whose radius gets larger and larger. Since the area of a sphere is 4πR2, at some radius (distance travelled), the energy per unit area on the wave-front is equal to the original energy divided by 4πR2. Since the energy is proportional to the square of the amplitude, the amplitude is proportional to 1/R. Strictly speaking, the energy is not diminished by this effect, it is just spread over the surface of larger and larger spheres.
(b) Absorption. It is appropriate to think of absorption as the tendency for materials to simply soak up electromagnetic energy and convert it to heat. We can measure some of this energy as radiated (emitted) heat that is at a longer wavelength than the original energy.
(c) Scattering. In the interaction of electromagnetic waves with objects that are small relative to a wavelength of the incident radiation a dipole is induced within the scatterer. The induced dipole is in the same direction as the incident electrical vector, its moment proportional to the field and its phase same as that of the incident field.

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

28. 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. Windows and Absorption Bands

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

36. Atmospheric Gases - Selective Absorbers with reference to wavelength
Gamma and X-ray - completely absorbed in the upper atmosphere by Oxygen and Nitrogen
Ultraviolet (<0.2um) - absorbed by molecules of oxygen (O and O2 combine form ozone); ozone absorbs UV w/ wavelengths um in stratosphere
um - water vapor and carbon dioxide absorb in narrow bands
Thermal infrared
strong absorption by water vapor between 5-8um and 20um-1,000um (1cm)
carbon dioxide absorbs 14-20um
ozone 9-10um
Absorbed radiation heats the lower atmosphere
Microwave region - 3 relatively narrow absorption bands occur between cm (oxygen and water vapor)
beyond 0.6cm , atmospheric gases generally do not impede passage of microwave radiation

37. Atmospheric Windows

38. Infrared Windows in the Atmosphere
Wavelength Range
Band
Sky Transparency
Sky Brightness
microns J
high
low at night
microns H
very low
microns K
microns L
microns: fair microns: high
low
microns M
microns N
8 - 9 microns and microns: fair others: low
very high
microns
microns: Q microns: Z
microns

39. Atmospheric Windows Absorption Bands in MW
um 
um 
2.0 – 2.4um 
3.0 – 5.0um 
8.0 – 14.0um 
> 0.6 Cm
Absorption Bands in MW
Watervapour : 22.2 GHz and 183GHz
Oxygen : 60GHz(single line) and 118.7GHz(band)

40. Important Atmospheric Windows
µm       UV, visible, near infrared
µm        Mid infrared
µm        Mid infrared
µm        Mid infrared
µm      Thermal Infrared
  > 0.6cm           Microwave

41. 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

42. 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

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

44. 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.

45. 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.

46. Spectral Signatures

47. Spectral Signatures ♦ GL ■PW ♥ RS ● SW Percent Reflectance at 0.85µm
100 80
♦ GL 60
■PW
Percent Reflectance at 0.85µm
♥ RS 40 20
● SW 20 40 60 80
100
Percent Reflectance at 0.55µm

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

50. 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

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

52. Pixels and Bits
Using radio waves, data from Earth-orbiting satellites are transmitted on a regular basis to ground stations.
They are translated into a digital image that can be displayed on a computer screen. Just like the pictures on your television set, satellite imagery is made up of tiny squares
These squares are called pixels—short for picture elements—and represent the relative reflected light energy recorded for that part of the image.
Using radio waves, data from Earth-orbiting satellites are transmitted on a regular basis to ground stations.
They are translated into a digital image that can be displayed on a computer screen. Just like the pictures on your television set, satellite imagery is made up of tiny squares as shown in Fig.11, each of a different gray shade or color. These squares are called pixels—short for picture elements—and represent the relative reflected light energy recorded for that part of the image.

53. Satellite Image of Hurricane Floyd
Pixels
Using radio waves, data from Earth-orbiting satellites are transmitted on a regular basis to properly equipped ground stations. As the data are received they are translated into a digital image that can be displayed on a computer screen. Just like the pictures on your television set, satellite imagery is made up of tiny squares as shown in Fig.11, each of a different gray shade or color. These squares are called pixels—short for picture elements—and represent the relative reflected light energy recorded for that part of the image. This weather satellite image of hurricane Floyd from September 15, 1999, has been magnified to show the individual picture elements (pixels) that form most remote sensing images. (Image derived from NOAA GOES DATA). Each pixel represents a square area on an image that is a measure of the sensor's ability to resolve (see) objects of different sizes. For example, the Enhanced Thematic Mapper (ETM+) on the Landsat 7 satellite has a maximum resolution of 15 meters; therefore, each pixel represents an area 15 m x 15 m, or 225 m2. Higher resolution (smaller pixel area) means that the sensor is able to discern smaller objects. By adding up the number of pixels in an image, you can calculate the area of a scene. For example, if you count the number of green pixels in a false color image, you can calculate the total area covered with vegetation.
Satellite Image of Hurricane Floyd
15 Sep 99

54. Pixels
Each pixel represents a square area on an image that is a measure of the sensor's ability to resolve (see) objects of different sizes.
For example, the Enhanced Thematic Mapper (ETM+) on the Landsat 7 satellite has a maximum resolution of 15 meters;
Therefore, each pixel represents an area 15 m x 15 m, or 225 m2.
Higher resolution (smaller pixel area) means that the sensor is able to discern smaller objects. By adding up the number of pixels in an image, you can calculate the area of a scene.
For example, if you count the number of green pixels in a false color image, you can calculate the total area covered with vegetation.

55. Bits
How does the computer know which parts of the image should be dark and which one should be bright?
Computers understand the numeric language of binary numbers, which are sets of numbers consisting of 0s and 1s that act as an "on-off" switch. Converting from our decimal system to binary numbers,
Darkest point is assigned the binary number 00,
Dark gray as 01,
Light gray as 10 and the Brightest part the binary number 11.
How does the computer know which parts of the image should be dark and which one should be bright? Computers understand the numeric language of binary numbers, which are sets of numbers consisting of 0s and 1s that act as an "on-off" switch. Converting from our decimal system to binary numbers,
00 = 0, 01 = 1, 10 = 2, 11 = 3.
Note that we cannot use decimal numbers since all computers are fussy—they only like "on" and "off." For example, consider an image shown below that is made up of 8 columns by 5 rows of pixels. In this figure, four shades are present: black, dark gray, light gray and white. The darkest point is assigned the binary number 00, dark gray as 01, light gray as 10, and the brightest part the binary number 11. We therefore have four pixels (B5, C4, D7 and E2) that the spacecraft says are 00. There are three dark gray pixels (B3, C2, C6 and E6) assigned the binary number 01, three light gray pixels (D3, D6 and E5) that are binary number 10, and 29 white pixels are assigned the binary number 11.

56. Bits
Four shades between white and black would produce images with too much contrast.
So instead of using binary numbers between 00 and 11, spacecraft use a string of 8 binary numbers (called "8-bit data"), which can range from to
These numbers correspond from 0 to 255 in the decimal system.
With 8-bit data, we can assign the darkest point in an image to the number , and the brightest point in the image to
This produces 256 shades of gray between black and white.
It is these binary numbers between 0 and 255 that the spacecraft sends back for each pixel in every row and column—and it takes a computer to keep track of every number for every pixel!

57. Color Images
Another essential ingredient in most remote sensing images is color.
Variations in black and white imagery can be very informative.
The number of different gray tones that the eye can separate is limited to about 20 to 30 steps (out of a maximum of about 200) on a contrast scale.
On the other hand, the eye can distinguish 20,000 or more color tints, enabling small but often important variations within the target materials or classes to be discerned.
How does the computer know which parts of the image should be dark and which one should be bright? Computers understand the numeric language of binary numbers, which are sets of numbers consisting of 0s and 1s that act as an "on-off" switch. Converting from our decimal system to binary numbers,
00 = 0, 01 = 1, 10 = 2, 11 = 3.
Note that we cannot use decimal numbers since all computers are fussy—they only like "on" and "off." For example, consider an image shown below that is made up of 8 columns by 5 rows of pixels. In this figure, four shades are present: black, dark gray, light gray and white. The darkest point is assigned the binary number 00, dark gray as 01, light gray as 10, and the brightest part the binary number 11. We therefore have four pixels (B5, C4, D7 and E2) that the spacecraft says are 00. There are three dark gray pixels (B3, C2, C6 and E6) assigned the binary number 01, three light gray pixels (D3, D6 and E5) that are binary number 10, and 29 white pixels are assigned the binary number 11.

58. Color Images
Since different bands have a different contrast, computers can be used to produce a color image from a black and white remote sensing data set.
Similar to the screen on a color television set, computer screens can display three different images using blue light, green light and red light. The combination of these three wavelengths of light will generate the color image that our eyes can see.
This is accomplished by displaying black and white satellite images corresponding to various bands in either blue, green, or red light to achieve the relative contrast between the bands.
Finally, when these three colors are combined, a color image—called a "false color image"—is produced

59. Colour Images Thermal IR NIR Red Green VIS Blue Colour
Another essential ingredient in most remote sensing images is color. While variations in black and white imagery can be very informative, the number of different gray tones that the eye can separate is limited to about 20 to 30 steps (out of a maximum of about 200) on a contrast scale. On the other hand, the eye can distinguish 20,000 or more color tints, enabling small but often important variations within the target materials or classes to be discerned.
Fig.12. Images at different bands and false colour image
Since different bands (or wavelengths) have a different contrast, computers can be used to produce a color image from a black and white remote sensing data set. Remember, satellites record the reflected and emitted brightness in the different parts of the spectrum, as is demonstrated in the figure above. Similar to the screen on a color television set, computer screens can display three different images using blue light, green light and red light. The combination of these three wavelengths of light will generate the color image that our eyes can see. This is accomplished by displaying black and white satellite images corresponding to various bands in either blue, green, or red light to achieve the relative contrast between the bands as shown in Figure.14. Finally, when these three colors are combined, a color image—called a "false color image"—is produced (it's called "false color" because colors are assigned that we can see and easily interpret with our eyes). In order to understand what the colors mean in the satellite image, we must know which band (or wavelength) is used for each of the blue, green and red parts of the computer display. Without detailed knowledge of how each band has been changed for contrast and brightness, we cannot be sure why the colors are what they are.
Blue
Colour

60. … close-up view over the Alps
Color Images
MSG-1, 24 Feb 2004, 11:00 UTC, VIS 0.6
… close-up view over the Alps
SEVIRI VIS 0.6

61. Color Images MSG-1 24 Feb 2003 11:00 UTC Channel 03 (NIR1.6)
1= low-level fog or stratus
2= Snow
3= Thin mid-level cloud with
water droplets
(supercooled cloud)
4= Lakes

62. Recommended RGBs for Monitoring of Day-time Fog1 2 3
MSG-1
24 Feb 2003
11:00 UTC
RGB Composite
R = NIR1.6
G = VIS0.8
B = VIS0.6
1= low-level fog
or stratus
2= snow
3= thin mid-level
cloud with
water droplets
(supercooled
cloud)

63. RGB VIS 0.6, IR 10.8-IR 8.7, IR 12.0-IR 8.7 Fire sulphur plant
Dust storms

64. Scanning microwave Radiometer (MSMR)
Remote Sensors
Passive
Active
Optical IR (OIR)
Microwaves
Active instruments provide their own energy (electromagnetic radiation) to illuminate the object or scene they observe. They send a pulse of energy from the sensor to the object and then receive the radiation that is reflected or backscattered from that object. Scientists use many different types of active remote sensors.
(a) Radar (Radio Detection and Ranging). A Radar uses a transmitter operating at either radio or microwave frequencies to emit electromagnetic radiation and a directional antenna or receiver to measure the time of arrival of reflected or backscattered pulses of radiation from distant objects. Distance to the object can be determined since electromagnetic radiation propagates at the speed of light.
(b) Scatterometer. A scatterometer is high frequency microwave radar designed specifically to measure backscattered radiation. Over ocean surfaces, measurements of backscattered radiation in the microwave spectral region can be used to derive maps of surface wind speed and direction.
(c) Lidar (Light Detection and Ranging). A lidar uses a laser (light amplification by stimulated emission of radiation) to transmit a light pulse and a receiver with sensitive detectors to measure the backscattered or reflected light. Distance to the object is determined by recording the time between the transmitted and backscattered pulses and using the speed of light to calculate the distance travelled. Lidars can determine atmospheric profiles of aerosols, clouds, and other constituents of the atmosphere.
(d) Laser Altimeter A laser altimeter uses a lidar (see above) to measure the height of the instrument platform above the surface. By independently knowing the height of the platform with respect to the mean Earth's surface, the topography of the underlying surface can be determined.
Photographic camera, Opto-mechanical Scanner(MSS),
Push-broom Scanner (IRS-LISS)
Scanning microwave Radiometer (MSMR)
LIDAR
Scatterometer, SAR

65. DIFF STAGES OF REMOTE SENSING SYSTEM

66. Questions if any ?

67. Thank you