I searched all over, the closest thing I came to was a chart drawing program, using a downloaded bathy chart from noaa, then you overlay coordinates. At least that's what I think I was doing. I couldn't make it work and the computer that I had it on accidentally got smashed so i gave up anyway. Way over my head but it was worth a try.
SeaClear II is the program that you can import high res bath charts to and "calibrate" to work in the program. It works pretty well, and if you have some of your own charts you really like to use, is a nice (free) choice. SeaClear GPS Navigation Software