If you have a computer that can run Java and a GPS then this chart plotter program can show a map with a mark at your position.
It should work with all NMEA compatible GPS receivers.
The maps can be in JPEG format.
Translation between position and map co-ordinates is done with the help of 2-4 reference points that are read from a chart data file.
You may not use this software as your only means of navigation. In no way shall the creators of this software be responsible for any damage caused directly or indirectly by the use of this software.