Gis (Geographic Information System) is a system of hardware and software used for storage, retrieval, mapping and analysis of geographic data. Where as remote sensing is the science of obtaining information from a remote platform. Thus gis remote sensing is integrated. To understand gis remote sensing integration, first we should know what is gis. Gis differs from other computer application program in the sense that it can only produce geo-referenced map with reliable spatial data as well as attribute data. in gis softwares we can produce ‘topology’ which depicts the interrelation between spatial objects. Most well known softwares used in gis are –
• map information
• arc view gis
• cad overlay
• autocad
From raw raster data or map we produce vector data which is represented in the form of various forms of maps and diagrams. there are three fundamental concepts that a gis have. These are –
• point (for showing point features like post office, fire stations etc)
• polygon (for showing area features)
• line (for showing linear features like road, railways etc)
The most common source for collecting gis data includes –
• aerial photography – photographs are taken from aerial platforms with automatically shuttered camera after a specific time interval.
• satellite imagery – Imageries are taken from satellites. after processing they are used in remote sensing.
• ground survey – it includes GPS survey as well as other methods of survey.
• scanned images – soft copy images are scanned as input to use in gis.
In the first two sources gis remote sensing relation lies. As aerial photography and satellite images are two major sources of remote sensing data. In todays topic gis remote sensing, our work is to emphasize on gis remote sensing integration in the context of satellite imagery. Or it can be said gis remote sensing relation on the basis of satellite imagery. Remote sensing data need to be rectified before it can be used in gis. As those data contains some error due to –
• atmospheric disturbances
• undulating plane
• unconformity in camera angle
• camera resolution
• ground surface condition and many other reasons
The correction procedure includes –
• Pre-processing – it removes the geometric as well as radiometric errors fro image.
• Image enhancement – it includes the improvement of image quality for a better visual representation.
• Image classification – classification of features shown in image.
• Analysis – it includes the generation of spatial and attribute information on the area of interest.
After those all aforesaid techniques a remote sensing data can directly be used in gis. Thus gis remote sensing relationship becomes possible. Some fields where gis remote sensing are used vigorously are –
• environmental monitoring
• coastal disaster management
• slope degradation monitoring
• ground engineering
• geoscientific study
• vegetation monitoring
• ocean floor study
• ocean color study and also many other many fields
Some most common satellite that are used for remote sensing to use in gis to sustain a gis remote sensing relation are –
• LANSAT
• NDVI (Normalized Differential Vegetation Index)
• AVHRR (Advanced Very High Resolution Radiometer)
• IKONOS
• Cartosat
After all these taken techniques remote sensing data is used in gis for producing maps. Thus we may say that gis remote sensing integration becomes possible. Some vectorized data using remote sensing softwares also used in gis. With new technical era gis remote sensing integration becomes a obvious part of todays study.
Map Digitization