Satellite System
Originally intended for the U.S. military, the GPS satellite system, according to Scientific American, consists of a network of 24 satellites. A handheld GPS unit must receive a signal from three or more satellites to calculate the user's location.
WAAS
Some handheld GPS units are enabled with a Wide Area Augmentation System and can obtain better accuracy than standard units. WAAS uses ground-based stations in the United States to monitor the accuracy of satellite signals.
Accuracy
GPS is the most accurate navigational technology. According to REI, basic GPS units typically have accuracy levels of four to 20 meters of the actual position.
Improving Accuracy
The accuracy of your GPS handheld unit depends on the quality of its reception. Choose a GPS receiver with a high-sensitivity processor chip and a high-quality antenna.
Limitations
Since a handheld GPS unit requires a good satellite signal to get an accurate reading, overhead obstacles, such as high canyon walls and thick forests, can block signal reception. Also, a GPS unit is no substitute for a good map and compass.
