A Personal Digital Location Apparatus for displaying a geographical location as an icon on a map. The apparatus includes a GPS Smart Antenna for determining the geographical location, a personal computing device including a display, a processing system including a standard software operating system such as DOS, Windows, Macintosh, or Geoworks, and a map application program capable of running in the operating system. The GPS Smart Antenna includes an internal battery and a power sensor for sensing the connection of an external power source. The GPS Smart Antenna receives power from the external power source when the power sensor senses that the external power source is connected and receives power from the internal battery when the power sensor senses that the external power source is not connected. An input select switch controlled by a Request to Send signal from the personal computing device enables the GPS Smart Antenna to use a single UART chip for receiving a command/control signal from the personal computing device and a differential GPS (DGPS) signal from a DGPS radiowave receiver.