How Does a Handheld GPS Work?

How Does a Handheld GPS Work?The handheld GPS has become a fixture in many rucksacks for its navigational assistance in remote country. The technology hinges on communications between the portable unit and a satellite system.

The GPS System

A squadron of 24 satellites orbiting 12,000 miles above Earth comprises the heart of the GPS. Each satellite, powered mainly by solar energy, completes its orbit every 12 hours.

The Signal

Each GPS satellite broadcasts radio signals that code the exact time of the pulse and information about the satellite's course and status.

The Receiver

If the handheld GPS receives signals from at least four satellites, it can attempt to calculate its position, based on factors like the time differential between the radio pulse's emission and reception, the satellite's orbit and the speed of light. Four satellites are required to calculate position in three dimensions: latitude, longitude, and elevation.

Warning

Potential errors in the communication between satellite and receiver include satellite/handheld unit clock discrepancies, signal bounce off buildings and topography (the multipath effect) and atmospheric signal delay.

History

The first GPS satellite achieved orbit in 1978, and the entire arsenal of 24 was in place by 1994.

Article Written By Ethan Schowalter-Hay

Ethan Schowalter-Hay is a writer and naturalist living in Oregon. He has written for the "Observer," the Bureau of Land Management and various online publishers. He holds a Bachelor of Science in wildlife ecology and a graduate certificate in geographic information systems from the University of Wisconsin.

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