Absolutely set your waypoints. Crappies hold and move between some pretty insignificant structural markers, as often as not little more than where currents (and natural lakes have them, too) coming together concentrate forage and/or comfort levels. GPS has become one of the best tools for locating and relocating the mobile schools ever added to a fisherman's arsenal. When added to lake maps and depth finders, you have a nearly unbeatable combination of tools that will enable a fisherman to avoid skunks nearly everytime, provided you learn how to use them and then do it.