How a GPS Device / System Works?
GPS can provide a very accurate digital map of the highway infrastructure. The technology operates on the principle of triangulation—if the difference from an observer to three known points can be measured, the position of the observer can be calculated. The system includes at least 24 satellites in orbit 19,320 kilometers (12,000 miles) above the earth and inclined at 55°.
These satellites continuously broadcast their position, a timing signal, and other information. By combining the measurements from four different satellites, users with receivers can determine their 3-dimensional position, currently within 4-20 meters (13-66 feet).
Putting it in Perspective
It takes many days to survey small sections of road using traditional techniques
Complete road inventories may take years.