What does a GPS satellite do?
GPS satellites carry atomic clocks that provide extremely accurate time. The time information is placed in the codes broadcast by the satellite so that a receiver can continuously determine the time the signal was broadcast. Thus, the receiver uses four satellites to compute latitude, longitude, altitude, and time.
Where are GPS satellites?
GPS satellites fly in medium Earth orbit (MEO) at an altitude of approximately 20,200 km (12,550 miles). Each satellite circles the Earth twice a day.
Why do you need 3 satellites for GPS?
The GPS receiver gets a signal from each GPS satellite. The satellites transmit the exact time the signals are sent. So given the travel time of the GPS signals from three satellites and their exact position in the sky, the GPS receiver can determine your position in three dimensions – east, north and altitude.
Do GPS satellites orbit the earth?
GPS satellites fly in medium Earth orbit at an altitude of approximately 12,550 miles . Each satellite circles the Earth twice a day.
How many satellites are required for GPS position?
four satellites
Why do GPS satellites lose time?
Calculation of time dilation That is, the satellites’ clocks lose 7,214 nanoseconds a day due to special relativity effects. This is because Earth’s equipotential makes net time dilation equal across its geodesic surface.
How much time do satellites lose?
Einstein’s general relativity theory says that gravity curves space and time, resulting in a tendency for the orbiting clocks to tick slightly faster, by about 45 microseconds per day. The net result is that time on a GPS satellite clock advances faster than a clock on the ground by about 38 microseconds per day.
Does GPS really need relativity?
A calculation using General Relativity predicts that the clocks in each GPS satellite should get ahead of ground-based clocks by 45 microseconds per day. Relativity is not just some abstract mathematical theory: understanding it is absolutely essential for our global navigation system to work properly!
What causes GPS error?
The major sources of GPS positional error are: Atmospheric Interference. Calculation and rounding errors. Ephemeris (orbital path) data errors.