1. A computer-implemented method for determining a salient region of a geographic map, the method comprising: obtaining, by one or more processors, a plurality of geographic areas corresponding to a plurality of viewports associated with a geographic map, the plurality of viewports having been previously used by a plurality of users to view a portion of the geographic map; overlaying, by one or more processors, a plurality of grid points arranged in a fixed grid on the portion of the geographic map; overlaying the plurality of geographic areas corresponding to the plurality of viewports with the portion of the geographic map, each of the plurality of geographic areas overlaying zero or more of the plurality of grid points; scoring, by one or more processors, each of the plurality of grid points based on a number of the plurality of geographic areas that overlay each of the grid points; determining, by one or more processors, a polygon enclosed by a set of the plurality of grid points based on the scores of the grid points; identifying, by one or more processors, the polygon as defining a salient region of the geographic map; comparing, by one or more processors, a feature of the geographic map to the salient region; and determining, by one or more processors, whether the feature has changed based on the comparison.