1. A computer implemented method, comprising: identifying one or more spans across an overpass in an overpasses model, the overpasses model including information for one or more overpasses and respective locations and widths of the spans; associating one or more terrain elevation values with the one or more identified spans, the terrain elevation values included in an elevation model corresponding to the overpasses model; interpolating terrain elevation values for one or more points across the identified spans; and updating the elevation model with the interpolated terrain elevation values, wherein the identifying, the associating, the interpolating and the updating are performed using one or more processors.