Coordinate system of Nepal

Nepal uses Everest 1830 ellipsoid which is projected to UTM (cylindrical projection). While projecting the ellipsoid to UTM, Nepal’s system uses three different false datum for longitude - 81°, 84° and 87°. The X coordinate for each of  these longitudes is 500000 meters. To explain it further, the x-coordinate at 81° is 500000 meters. The x-coordinate keeps on increasing till 82° 30’. The longitude between 82° 30’ and 85° 30’ is the area of 84°, where 84°, similar to 81°, again corresponds to 500000 m. 82° 30’ is less than 500000 m and 85° 30’ is more than 500000m. Same is the case for 87°. We use the scale factor of 0.9999.  I don’t know what happens in the border line. Please be aware that 81°, 84°, 87° etc are not the same as that appears on google earth. The google earth uses WGS 1984 or WGS-84 coordinate system. The difference between Evererest 1830 ellipsoid and WGS-84 ellipsoid near Nepal  is around 2.5 seconds if not more. Many experts working with projects of Nepal don’t know this.

Nepal coordinate projections

Note that using UTM or Universal Transverse macater projection gives result like the one below. The area is not preserved.  You can change the aspect like the one shown below.

Projection using Transverse Mecator

Different aspects

Different ellipsoids suitable for different locations