1. A method of distributing map data from a map server to a wireless communications device, the method comprising steps of: obtaining vector map data in response to a request for map data received at the map server from the wireless communications device; generating a bitmap array representative of the vector map data for a particular location specified in the request; computing attributes of the bitmap array to determine which map features are to be retained and which map features are to be omitted; and transmitting to the wireless communications device only the map data for the map features to be retained.