I am using developer.here API.
My endpoint is discover.search.hereapi.com/v1/discover?apiKey=###&q=delhi&at=13.08362,80.28252&limit=5
it's returning the distance. but there is no identification of the distance calculated by road or air? is there any way to send the param specifically by road, or by air?
It is by air. You can get the road distance if you use the routing API and supply your initial position and the position of the result.