A GPS receiver determines your location by locking on to 3 or more GPS Satellites. By triangulating on these sources, it can determine your position to within a few feet. Since these satellites, in combination, cover the entire planet the GPS receiver can be used virtually anywhere in the world. Commercial GPS receivers can be used at altitudes less then 60,000 feet. Not only can they tell you where you are but what altitude you are at. Many units can also tell you how fast you are moving.

There are GPS units for different applications. There are marine and aviation units; receivers designed solely for mapping city streets, GPS units for determining how to get from point A to point B and combination units that are good for the backwoods and urban highways. The method of display and the kind of data it saves differs from receiver to receiver and is one of the details that separate units.

Some of the newest units like the Garmin eTrex Vista C have built in compasses and altimeters. These are in addition to the GPS functionality of the unit. The units also get their time from the satellite. Once synchronized the time displayed is very accurate.

For the purposes of our discussion we are looking at units that will help you get to that favorite spot in the woods while driving and keep you from getting lost once you’re on foot. These are the combination units we mentioned earlier.

Twelve-channel units are usually faster in acquiring satellite signals. We recommend this type of unit over the less expensive ones. Although you only need 4 satellites to get all the information of your position, being able to track multiple satellites increases the odds of keeping a good lock on your position as you move around.

These units allow for downloading maps from extra cost CDs provided by the manufacturers. When moving around the country you can upload the correct maps for your area into the receiver.

The following feature set is essential for any good deep woods receiver:

Small and lightweight

Map screen

Waterproof

Long battery life (20+ hours)

Mapping capability >22 meg memory

Route Capability >20

Waypoints >500

Bearing to next waypoint

Multiple Datum capability

Screen resolution

12 Channels

Topographical maps