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GPS Facts

How many GPS satellites are there? Minimum of 24 plus some spares. Currently there are 28 operational satellites. The number varies - see http://tycho.usno.navy.mil/gpscurr.html for up-to-date status.
What is the orbital distance of the satellites? 20,200 km (10,900 miles)
How many satellites are required to allow 3 dimensional positioning? At least 4. The system is designed so that there are always at least 4 satellites visible at every location on earth.
What are the 3 dimensions for a position? Latitude, Longitude, and Altitude.
How long does each satellite take to complete one orbit? 12 hours
When was the first GPS satellite launched? 1978
Created by: wths-scioly