Re: Lake GPS ???
Just to add to what others said, all GPS' work the same in that they communicate with multiple satellites all at once in order to determine its own position - on water, on land, in the air, no matter where it is. With that said, some brands do a better job than other at performing this task. For the GPS to relay its own position in a way that you can understand, such as using a display screen with a map vs looking at a bunch of numbers (which is the way they used to be), the GPS nowadays are loaded with basemaps. For your car gps, you have a basemap containing city streets, highways, and other features that would be important to someone on land. For a boat, you want a chartplotter, which is a water resistant GPS with waterway features built in to its maps with things like marinas, channels, depths, etc. The GPS doesn't determine your depth other than knowing where it is on the map and then using the location on the map to tell you what the depth is according to the maker of the map. A car GPS isn't exactly "wrong" for a boat, its just that you will just see your position marked with a picture of a car in most cases in the middle of a blue area, that being the lake or ocean. It still works on the water because it technically knows where it is its just that the car GPS is not loaded with a marine basemap which you'd need to know where the heck you are.
To make you even more confused, many hand held GPS brands, such as the Magellan Sportrak Marine/Pro, come with BOTH maps so you can use it anywhere. Additionally, if you have the pro version for example, you can later purchase the marine map pack and then using a computer, load the marine maps on your GPS. Same thing goes for other brands as well.
Good luck!
