1. A method for generating road height values for a road network area that includes a plurality of junctions, the method comprising: receiving, by a computing device, a data set for each junction in the road network area, wherein each data set includes a road designation, a first coordinate, a second coordinate, and a stacking order for each road of a respective junction, wherein the plurality of junctions include a plurality of grade separated crossings, a grade separated crossing including at least two roads having a different stacking order signifying that the at least two roads have different heights; determining, by the computing device, height variables that provide on optimal value for a cost function based on the road data set for each junction, wherein height values of roads of a grade separated crossing are constrained: to satisfy the stacking order of each road in the junction, and to have a minimum distance between roads having consecutive stacking order values; and transmitting, from the computing device to a controller, the height values to the controller for rendering a three-dimensional map of a part of the road network area.