The below picture is of an inexpensive (100$) GPS hooked up to an inexpensive (200$) laptop that is equipped with free GPS mapping software from www.sping.com What you get, for 250 dollars. is an electronic map with your boat appearing on the display as a little circle or flashing dot. All of your travels are also plotted on the display, and the right hand side has a status window containing all the usual GPS information. The laptop does not have to be a Pentium 4 supercomputer. Any laptop will work, because they all have the (required) serial input port as a standard item.

The maps themselves can be downloaded from a goverment site listed in www.sping.com

The Sea-Clear software is excellent but does take a little learning (especially the map calibration) But it ain't bad, since I did it!