This tool will provide the approximate top elevation Above Mean Sea Level(AMSL) of the proposed structure at your size/Plot/Location.
 
Site coordinates in WGS 84 and site Elevation in metres AMSL are required to get approximate Top Elevation.
Alternatively you can choose your site on the map and get Approximate Top Elevation. This will not be a NOC, but only the indication of the approximate Top Elevation. For NOC, you shall apply online.