GIS Mapping is the mapping technique in which we show the graphical representation of the earth surface using GIS technique. Before depicting the Concept of GIS Mapping , there must be a idea about GIS Mapping. GIS is the technology where spatial objects are represented graphically and map is the graphical representation of the earth surface. In Geographical Information System (GIS) mapping objects are the objects of the ground. These objects are represented in the form of three elements. These are –
- point – it shows point features or nodal features like post office, fire stations, water pumping stations etc.
- polygon – in GIS Mapping polygon features show the vast area. it is used for showing area features like building, moutaneous region, large grassland etc .
- Line – it is for showing linear features like road, railways, river, stream etc.
There are some well known softwares which are used for GIS Mapping . These include –
- MapInfor
- arc view gis
- cad overlay
- auto cad
The major source of data for GIS mapping include –
- 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.
Cad overlay and auto cad are the two softwares which can create “topology” in GIS Mapping .
Mapping with GIS include some operations while producing the map. These are –
- Preprocessing of raw data to remove both geometric and radiometric errors.
- Enhancement of image for better visual representation which is not present in raw image due to photo quality.
- Classification of data to categories the object into different categories.
- Analysis of data for interpretation of the produced map.
In GIS Mapping , it stores the information about the world in some themed layers. As for example polygon features in one layer, point features in one and line features in another layer irrespective of the object. But layers should be geographically referenced ie. each layer should contain latitude and longitude irrespective of their position. Generally GIS Mapping provides two types of map –
- Digital map
- Paper printed map or hard copy map.
For producing all types of map there are mainly two method. These are –
Map Projection :
This the method of projecting the two dimensional earth surface onto a flat plane. These maps are geographically referenced. But all maps distort the mapped area into some degree. They are not perfect. The degree of distortion effects the shape, size, direction and direction of the mapped area. The distortion is negligible for projecting small ares. But it is very higher in projecting the world. That is why in “mercator’s projection” the area of Greenland is much higher than Australia while the case is opposite in real case. The type of map projection should be considered on the basis of the area to be projected.
Coordinate System :
In GIS Mapping it is very important to locate features in two dimensional form with a point of origin to remove distortion that are created from transforming 3D data in 2D format. Though GIS Mapping provide this facility to make the data auto correct.
Using Attribute data in GIS Mapping , the last task is to put attribute data ie. The textual information of the associated feature.
So GIS and map are the two sides of one coin. It the most useful and scientific technique for generating map.