To provide map data for rendering map images corresponding to a selected geographic region at a client device, a map server generates a set of base map tiles having vector descriptors, each of which indicates a geometry of a respective map element, in accordance with a non-raster format for rendering a first map image. The map server, at some point, provides the base map tiles to the client device. Upon receiving an indication that a specific map image for the selected geographic region is to be rendered at the client device, the map server further generates a set of difference map tiles that indicate changes to be made to the set of base map tiles and sends the difference map tiles to the client device for use, along with the set of base map tiles, in rendering the requested specific map image.