Andreas Behm


Using the techniques of this disclosure, a system can efficiently and accurately select digital maps from a large number candidate available maps related to a specified geographic area. As discussed in more detail below, for each map, the system identifies a set of tiles (equalsized units into which maps are divided) fully covering the map and obtains a quality metric for the map. The tiles are organized into a hierarchical data structure such as a quadtree, where each layer corresponds to a certain level of magnification. The system then generates inverted indices for the set of tiles, such that a tile is a key and the {map, quality metric} is the corresponding value. The system updates the nodes of the data structure using the indices, so that the maps subsequently can be quickly retrieved accurately and efficiently.