... Having paper maps available (and knowing your current location on them) will give you peace of mind when traveling or hiking. ... Global positioning system - GPS - is a huge advance in navigation. Highly accurate map capable units can be purchased at reasonable prices and are readily available just about everywhere. The Global Positioning System is a network of satellites in different orbital paths. A GPS unit establishes contact with at least three of these satellites and uses the information received to determine altitude, longitude, and latitude. 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. In order to calculate altitude, the unit must have access to at least four satellites. There are no fees or setup charges to use GPS. GPS receivers are extremely accurate due to their parallel multi-channel operation. 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. Most portable GPS receivers are accurate to within 10 feet. Twelve channel GPS devices are fairly standard. These receivers can lock onto more than one satellite at the same time. They hold the lock and are very accurate. This is important if you plan to use the unit while hiking or camping. Most handheld receivers weigh about 10 ounces. This is an important consideration if you want to carry the GPS device in your pocket. If you plan to use your GPS device outdoors or in a boat, you must get a waterproof model. Salt water can ruin an ordinary GPS receiver, so look for a marine rated unit if it will be operated in a boat ...