Road height values for a road network area are generated based on locations of junctions and stacking orders of roads in junctions in which at least one road passes over another road. A cost function can be optimized to obtain height values for each road of each junction. The cost function can be constrained such that roads of the grade separated crossings satisfy the stacking order designated for the roads and to have a minimum distance between roads having consecutive stacking order values. The obtained height values can be used for rendering a three-dimensional map of a part of the road network area.