A handheld Global Positioning System (GPS) device works by using signals from satellites and reference stations on Earth to triangulate a person's location anywhere on Earth. GPS receivers use signals from satellites and provide information on the user's latitude, longitude and altitude.
GPS technology uses U.S. satellites orbiting the Earth to pinpoint any location on land or sea. According to outdoor gear store REI, a GPS device uses signals from three or more satellites to triangulate your position on Earth.
Wide Area Augmentation System (WAAS)
WAAS is a network of ground-based stations that monitor the variations in satellite signals and improve its accuracy and availability. According to REI, a WAAS-enabled GPS receiver can obtain greater accuracy than a satellite-only unit.
A handheld GPS unit will tell you your location in every type of condition and any day of the year.
A GPS receiver requires satellite reception to triangulate your location so high canyon walls or thick forest can block reception. Also, GPS is an electronic device and can run out of batteries or malfunction.
A GPS should not be relied on as a sole navigational device. You should still always carry a map and compass and know how to use them.