To find address by specified coordinates, use the request get_locations. As an example, let's detect the address of the point with coordinates 27.516643322771575 EL and 53.91069937030936 NL.

<your_wialon_pro_address>/ajax.html?svc=gis/get_locations&
	params={
		"points":[{
			"x":27.516643322771575,
			"y":53.91069937030936
		}]
	}&ssid=<your_sid>	

Response:

{
    "locations": ["Skryganova st. 6, Minsk"]
}

Input data of this command is an array of coordinates, it gives us an opportunity to get location of many point in one request.