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