1. GS 5102: Introduction to Remote Sensing
Time: – on Saturdays

2. Course Outline Introduction
The history and development of remote sensing, basic definitions, the remote sensing system, aerial photography, satellite remote sensing and their applications.
Basic Principles of Electromagnetic Energy
The electromagnetic spectrum, electromagnetic sources, the role of electromagnetic energy in remote sensing
Remote Sensors
Aerial sensors, satellites and their characteristics, land oriented systems and meteorological satellites, satellite sensors and their characteristics, pixels and pixel properties, spatial, spectral, radiometric and temporal resolutions.

3. Course Outline Digital Image Processing
Image file formats, colour composites, band mathematical operations, contrast stretching, radiometric and geometric correction, image enhancement.
Image Interpretation
Interpretation of aerial photographs and satellite images, visual and digital interpretation, supervised and unsupervised classification.
Laboratory Sessions
Visual and digital analysis of remote sensing images and the applications.

4. What is Remote Sensing?
The science and art of obtaining information of an object, area or phenomenon at a distance
Aerial Photography
Satellite Remote Sensing
Optical
Microwave

5. Remote Sensing – Data Acquisition
Sensor
Energy Source
Atmosphere
Earth Surface

6. The History Remote sensing with kites, balloons and pigeons
Development of Aerial Photography
During World War I& II – Military reconnaissance tool
Between World Wars – Non military applications
After 2nd world war – development of photogrammetry
Spatial Era
1957 – Spoutnik
1960 – First image from meteorological satellite TIROS
July, 1972 – ERTS I (Renamed Landsat I)

7. Electro-magnetic Radiation
The EM spectrum

8. Electro-magnetic Radiation
Atmospheric Effects
Refraction
Absorption
Atmospheric Transparency – Windows
Absorption by other environments crossed by the EM radiation
Diffusion

9. Atmospheric Windows Atmospheric Transparency
The wave length ranges in which the atmosphere is particularly transmissive of energy.
Atmospheric windows correspond to spectral bands for which transmission is relatively high.
Dry atmospheres are more transparent than wet atmospheres.

10. Atmospheric Windows

11. EM Radiation – Object Interactions
Reflectance gives an idea about the characteristics of the natural surfaces.
Spectral response measured over objects permits an assessment of the type and condition of them.
These responses are called ‘ Spectral Signatures”
These responses are not absolute or unique.
Spectral response patterns can be changed due to spatial and temporal effects.

12. Remote sensors record electromagnetic radiation emitted or reflected from the Earth’s surface. Different types of vegetation, soils and other features emit and reflect energy differently. This characteristic makes it possible to identify different cover types on the surface. Using multi-temporal images it is possible to monitor the changes.

13. EM Radiation – Object Interactions
Vegetation
In visible spectrum
Radiation is absorbed by leaf pigments for photosynthesis (chlorophyll)
Main pigments are Chlorophyll a & b with two absorption bands in blue and red
In NIR
Leaf pigments and the cellulose containing walls are transparent.
High levels of reflectance from vegetation
In MIR
Reflectance is affected by the water content

14. EM Radiation – Object Interactions

15. EM Radiation – Object Interactions
Soil
Reflectance increases regularly from visible to NIR
Absorption bands due to water (1.4mm & 1.9mm)
Water
Reflectance regularly decreases from visible to NIR
Complete absorption in NIR
When the water is loaded with particles, the curve shows a similar form but the reflectance is higher.

16. EM Radiation – Object Interactions

17. EM Radiation – Object Interactions

18. Aerial Photography First Method of Remote Sensing
Low altitude analog/ digital pictures
High information content
Important as historical documents

19. Important Components of an Aerial Photograph
Clock
Level
Altimeter
Fiducial marks
Principle point – photo center
Camera constant

20. Comparison of Aerial Photographs with Maps
Air Photos

21. Flight planning
Aerial photographs are normally taken with % overlap and 20-30% sidelap

22. Vertical Aerial Photographyd D
Principal point
Optical axis
Projection center
Ground
Film Plane
Focal length – Camera constant
Flying height

23. Vertical Aerial Photography
Terminology
Center of Projection
All rays of light reflected from the ground must pass this point
Optical Axis
The line through the projection center, perpendicular to the film plane. This shows the photo direction
Principal Point
Point where the optical axis hits the film plane. The approximate principal point is the photo center
Focal Length
The distance between the principal point and the center of projection.
* Camera constant

24. Scale Calculations in Aerial Photography
Scale of a map
Relative distance between two points on the map compared to the true horizontal distance between the same points in the terrain.
This relation is called the representative fraction – 1:S or 1/S
S = Scale Factor

25. d c H D
1/s = d/D = c/H
S = D/d = H/c

26. Practical Procedure for Scale Correction
Identify two points in the air photos, situated on level ground
Measure the distance between two points in the field (D)
If maps are available, use them to find D
In individual photos, indicate the center point of each photo. For measurements, always choose the photo where the area of interest is as close as possible to the photo center
Measure the photo distance between the points selected (d)
The Scale Factor (S)
S = D/d

27. Examples
Aerial photographs have no definite scale.

28. A photo survey has been carried out at a height of 4560 m above the mean altitude of the area. The camera used has a focal length of mm.
What is the mean scale of the photo?
What is the scale at a hilltop situated approximately 380 m above the mean altitude of the terrain?
What is the scale at a valley floor approximately 228 m below the mean altitude of the terrain?

29. Focal length of camera is 150 mm
Flying height is 3000 m above the mean altitude A B
2450 msl Mean Altitude
2750 msl
1850 msl C

30. Applications of Aerial Photography
Land use mapping
Soil mapping
Geological applications
Soil erosion and landslide studies
Topographical analysis
Urban planning

31. Aerial Photography
play an important role in the execution of cartographic mapping on various scales and in evaluation of natural resources of a region.
involves qualitative examination of the terrain, the correct correlation of the observed data and finally the quantitative evaluation of data.
offers possibility of detailed study of the terrain
full use of immense wealth of information recorded on an aerial photograph, which not only economize and expedite the investigation but offer more reliable results.

32. Satellite Remote Sensing
Acquire images from space
Earth observation satellites – earth surface monitoring
Weather satellites – meteorological applications
Digital multi-spectral information – easy to interpret using computers
Earth Observation Satellites
Landsat
SPOT
IRS
IKONOS
NOAA
ASTOR

33. Satellites and their Sensor Properties
Satellite Orbits
Geostationary & Polar Orbiting

34. Satellites and their Sensor Properties
Spatial Resolution
The area covered by a single pixel on the ground (Pixel is the smallest homogenous area of a recorded image)
Small pixels – High spatial Resolution
Large pixels – Low spatial resolution
Spectral Resolution
Spectral resolution describes the ability of a sensor to define fine wavelength intervals.
Temporal Resolution
Frequency of obtaining data over a given area
Radiometric Resolution
The radiometric resolution of an imaging system describes its ability to discriminate very slight differences in energy.

35. Scale Diversity of Remote Sensing Data
Global to Local
OCM
WiFS
LISS-III
NOAA AVHRR
PAN
IKONOS