... Global positioning system - GPS - is a huge advance in navigation. ... The Global Positioning System is a network of satellites in different orbital paths. ... The unit takes measurements constantly and plots your path on a map (for mapping enabled GPS units), and also provides a digital display of relevant information. ... There are no fees or setup charges to use GPS. ... This type of unit is quick to lock onto satellites and will hold the lock in dense foliage or city streets with tall buildings and other obstructions. ... Twelve channel GPS devices are fairly standard. ... They hold the lock and are very accurate. ... Most handheld receivers weigh about 10 ounces. ... If you plan to use your GPS device outdoors or in a boat, you must get a waterproof model. ... Battery life is almost always shorter than the manufacturer’s advertised time. ... Make sure the GPS map can be updated with a simple download procedure. ... Check the price of the download. ... You should keep paper maps and navigation guides such as a compass to backup your GPS ...