Objective:- To do Geo-referencing and Projections on toposheet no. NE 44-14 (Vijayawada) by QGIS.
Survey of India produces the topographic maps of India. These maps are produced at different scales. In order to identify a map of a particular area, a numbering system has been adopted by the Survey of India. The area grid numbered numerically(1-136) in the international map of scale 1:1000000 is divided into 16 area grids of scale 1:250000 arranged alphabetically(A-P) column wise form north-west corner of grid. These alphabetically numbered grids are further individually subdivided into 16 area grids of scale 1:50000 arranged numerically(1-16) column wise from north west corner.
Geo-referencing means that the internal coordinate system of a map or aerial photo image can be related to a ground system of geographic coordinates.
The toposheet is added in QGIS by layer toolbar in QGIS database as raster data set and then with the help of geo-referencer tool available in raster menu the image is added for geo-referencing. Control points are added by providing longitudes and latitudes of points as X and Y values respectively, Ground control points table is viewed and error is noted down.
In transformation settings transformation type is selected as “Thin Plate Spline” and Target SRS is set as geographic coordinate system GCS_WGS 1984. Geo-referencing is started and geo-referenced image is obtained as rectified.
Rectified image is saved for projection in WGS 1984 UTM Zone 44N as projected image
Inference: from this lab we have seen new software that is QGIS which is similar to ARCGIS in this software it is more easier compared to arcgis. First we have downloaded toposheet of Vijayawada and then we georefernced it and then by projected it.
Prepared by:
A. Jaya Prakash
Research scholar,
IIT Khargpur
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