The short and oversimplified answer to how a GPS receiver works out where you are is:
- It calculates how long it takes the signal from each satellite it can see to arrive.
- It multiplies that time by the speed of light to calculate the distance to each satellite.
- It then calculates its position relative to no fewer than three satellites using trilateration.
- Because the receiver knows the precise position of each satellite when the signal was sent, it can translate its own relative position into an Earth-based co-ordinate system.
Of course, this explanation causes an explosion of questions in most minds. How can a receiver calculate the travel time of the signal unless it knows when it was sent—and how could it possibly know that? What is trilateration? How does the receiver know where a satellite was when it sent the signal? And that’s just the beginning.
The good news is you don’t need to understand any of this in order to use GPS. However, there’s no such thing as too much information, so if you’re curious to understand a little more about how it works (which might help you when you’re collecting measurements for work), carry on reading our related articles: