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Geographic information systems(GIS)
Geographic information systems(GIS)
DEFINITION
An organised collection of computer hardware, software, geographical data and personnel designed to efficiently capture, store, update, manipulate, analyze & display all forms of geographically referenced information.
GIS• Gives spatial information• Two types of data:Spatial dataNon spatial data
GIS mapSpatial data• Depicted as point, line or a polygon featureNon spatial data Attributes stored in a table as numbers or characters
Storing data• Vector formats- linear feature• Raster formats- stored as image- looks real. Line, polygon
and point features• GIS takes care of features, attributes and layers.
Applications of GIS• Agrl development• Vegetative cover• Crop acreage and production estimation• Wasteland mapping• Forest area mapping• soil resources mapping• Ground water potential mapping etc…
Trends in GISoNRM• Watershed Delineation• Waste land demarcation• Ground water resources• Identifying water bodies• Disaster areas
Modern tools for planning watersheds• DEM map( Digital Elevation Model)
to represent continually varying surface by isolines or contours.
Global system – WGS 84
In India - LCC
Web portals – Google earth, Bhuvan(ISRO)
Co ordinates taken in UTM plane
India falls in 43, 44, 45,46 planes
DEM
DEM
Images on GIS
REMOTE SENSING
Remote sensing• Technique of obtaining information about an object
through analysis of data collected without coming in touch with the object.
Stages in RS• Emission of EMR• Transmission, absorption and scattering of energy from
source to earth’s surface• Interaction of EMR with earth surface• Transmission of energy from surface to remote sensor• Data output transmission, processing and analysis
Basic hypothesis• Any object on earth is having a unique spectral signature
This helps to distinguish one object from another
The Electromagnetic Spectrum
What is Light?
What is Colour?
Why Do We See Colour?
after Campbell, J.B., 1987. Introduction to Remote Sensing. New York: Guildford.
near IRblue green red
Spectral Bands
A fundamental premise in remote sensing is that we can identify and learn about objects and features on the Earth's surface by studying the spectral characteristics of the radiation reflected (and/or emitted) by these features.
Colour Composite Displays
• We typically create multispectral image displays or colour composite images by showing different image bands in varying display combinations.
True Colour Composites
Standard False Colour Composites
Colour Composite Images
Colour Composite Images
Feature True Colour False Colour
trees and bushes olive green red
crops medium to light green pink to red
wetland vegetation dark green to black dark red
water shades of blue & green blue to black
urban areas white to light blue blue to grey
bare soil white to light grey blue to grey
Source: U.S. Department of Defense, 1995. Multispectral Users Guide.
General Appearance of Surface Features on Colour Composite
Images
What is Spatial Resolution?
• The fineness of spatial detail visible in an image
• Most affected by contrast• Determined by the sensor’s
Instantaneous Field of View (IFOV)• “Resolution”
Low Spatial Resolution
Spatial Resolution: 80 mFile Size: 0.5 Mb
Ground Dimensions: 33 x 33 kmImage Dimensions: 418 x 418
Landsat Multispectral Scanner Image
A
Medium Spatial Resolution
Spatial Resolution: 30 mFile Size: 0.5 Mb
Ground Dimensions: 12.5 x 12.5 kmImage Dimensions: 418 x 418
Image size required to cover area in A:1.2 Mb (1100 x 1100 )
Landsat Thematic Mapper Image
B
High Spatial Resolution
Spatial Resolution: 1.5 mFile Size: 0.5 Mb
Ground Dimensions: 625 x 625 mImage Dimensions: 418 x 418
Image size required to cover area in A:500 Mb (22,300 x 22,300 ) SPIN-2 Panchromatic Image
C
Spatial Resolution: 500 m
Terra MODIS August 24, 2002 NASA Earth Observatory
Spatial Resolution: 30 m
Landsat 7 ETM August 27, 2000
Spatial Resolution: 30 m
Landsat 7 ETM August 27, 2000
Spatial Resolution: 2.4 m
QuickBird 1 September 11, 2002
Spatial Resolution: 0.62 m
QuickBird 1 September 11, 2002
Instantaneous Field of View
Satellites• Geo stationary satellites
Orbit in synchrony with earth’s rotation
Altitude of 35000km
Mainly for communication and meterology
GEOS,METOSAT, INTELSAT,INSAT• Sun synchronous satellites
All remote sensing resource satellites
LANDSAT,IRS,CARTOSAT
GLOBAL POSTIONING SYSTEM(GPS)
• GPS is a satellite based radio-navigation system established by US dept of Defence for military purposes.
• 24 satellites and their ground stations involved.• Provides information on latitude, longitude,elevation and
direction
GPS position
• Unique position corresponding to a reference system
• WGS 84 (global)• NAD 83 (US)• LCC (India)• NARSTAR satellites are involved
System• Handle device• Satellite• Ground station• Processing station
2D position – 3 satellites are involved
3D position – 4 satellites are involved