To efficiently transmit image map data to a client device, a map server selects map data for rendering a digital map of a certain geographic area at the client device and generates multiple map image layers using the selected map data, each covering the geographic area. In particular, the map server generates (i) a first map image layer including a first type of geographic data and having a first resolution, and (ii) a second map image layer including a second type of geographic data and having a second resolution. The map server then transmits the multiple map image layers to the client device via a communication network for generating a single digital map of the geographic area.