By leaving your GPS unit on constantly your unit will record your path. The route tracking feature makes backtracking extremely easy. However, GPS units use a lot of battery power so if you are going on an extended trip and plan on leaving your GPS unit on constantly, you will be switching your batteries multiple times, increasing weight and cost.
Many GPS units permit you to save routes for future reference.
Waypoints allow you to mark positions on your GPS. Waypoints are convenient because you can leave your GPS unit off the majority of the time and then turn it on when you need to mark an important position (trail intersection, major feature, parking lot etc.).
GPS units can be used to find your exact position on a map (presuming latitude and longitude are shown on the map). This is nice when there are long distances between distinct features or when there aren't trails.
Loading GPS Topo Maps Regional topographic maps are available for most GPS units. This is an excellent addition for any outdoor use. Topographical maps show the terrain, roads, summits, lakes and other major features.
Due to memory limitations (on your GPS unit) you will need to select which maps you want to load.
Deciding if you want to use Topo Maps on your GPS unit is an important decision prior to purchasing the device because the software is very expensive if purchased separately. Package deals or GPS units that come with Topo Maps already loaded are considerably cheaper.