I use depth maps but they only show the depths of water. I look for structures that represent shoals or underwater islands. With all the dams up this way alot of lakes have the under water islands that very from 10 - 25 feet. These are great for icefishing and in the summer I look for under water points that may be down 70 feet or so. It all depends on what you are fishing for when it comes to depth as well as what time of year you are fishing. Salmon and trout will be on top when the water is cold and closer to the bottom as it warms up.