What is Global Positioning?

What is global positioning and how does a global positioning satellite work? Global positioning satellites orbit the earth, transmitting signals to receivers on the ground – the global positioning systems and portable GPS receivers you buy in or for your car.

A GPS system does not transmit a signal. It is only a receiver. The older systems do not work well in certain areas, e.g., cities with very tall skyscrapers and heavily forested areas with tall trees, though newer global positioning systems have improved considerably.   

Above the earth, the global positioning satellites synchronize signals by maintaining the same time and transmitting location. The satellites in the U.S. are carefully managed. Their location is tracked every day to determine issues with orbit or function.  

Back on earth, the portable or built-in GPS receiver receives the satellite signal and note location based on the location of the satellite above the earth and the exact distance and time it takes to process the signal. Because the satellites process location in three dimensions, the portable GPS unit can calculate the user’s location with great accuracy.

These units were originally used by the United States military. Today, the GPS technology is used by military and civilians alike. Some GPS units use differential GPS or DGPS. This technology is even more accurate but requires a stationery receiver in a fixed location. The fixed location receiver compares and corrects GPS signal variance to provide more accurate location reports. 

If your GPS receiver loses the signal from the satellite, it must start the positioning process again to determine your location. If you stop your vehicle to determine position and program your directions you are less likely to lose your signal.  

Twenty-four global positioning satellites form the original constellation but these satellites only last ten years. In order to keep up with demand, the U.S. must launch replacement satellites frequently.  

Though we are less impressed with global positioning system technology today, the reality of GPS results is still a wonder. Imagine never having to stop and ask for directions again. Your great grandfather would consider this technology a true miracle!