If you get the seperate GPS with the appropriate chip for where your fishing, it'll show the contours and drop-offs very clearly. You can also track and save your movements plus leave markers on your screen to come back to an exact spot if you want.
A perfect example...couple years back we were trolling a deeper weedflat on Stoney and I was explaining to my daughter how the GPS works. It showed a 7' hump off to the right and I told Sheri how a musky will often sit on top of them.
We changed course, went over the hump and sure enuff, we hooked a musky.
Their an excellent tool for sure.