Automatic generation of a road map of a site can be performed. Data records collected by vehicles with a GNSS-positioning system while driving are provided, each data record having a position information representing a two-dimensional or three-dimensional position of the vehicle, an identification reference specific to a corresponding vehicle, a time tag, and a heading information. The data records are assigned to corresponding trips based on the time tag and the identification reference. The trips are mapped within an area and the area is divided into a plurality of uniform tiles. For each tile, a heading information variance of the data records covered by the respective tile is determined. A tile is defined as junction tile, if the tile has a heading information variance higher than a computed threshold variance. An area of interest (AoI) having a perimeter is determined by which a plurality of junction tiles is surrounded.