1. A computer-implemented method for fusing three-dimensional (3D) ground and airborne models for a geographical information system, comprising: (a) aligning a ground model and an airborne model relative to one another, wherein each of the ground model and the airborne model includes a respective plurality of facades, and wherein the aligning includes extracting edges of the facades from both the airborne model and the ground model and moving at least some of the extracted edges to optimize congruence between the extracted edges; (b) modifying three-dimensional mesh information in the ground and airborne models after the aligning to obtain modified ground and airborne models; (c) merging the modified ground and airborne models to obtained a fused 3D model; and (d) storing the fused 3D model in memory for subsequent access by the geographical information system.