Explain · analogy
How GPS works in terms of a game of Marco Polo
GPS is essentially playing a game of Marco Polo where the four people shouting "Marco" from the heavens are actually expensive metal boxes, and you are the idiot standing in a muddy field trying to triangulate your existence.
In this cosmic game, each satellite broadcasts its precise location and a timestamp, which is basically the equivalent of the satellite yelling "I am at latitude 52, longitude 0, and it is exactly 12.00pm" into the void. Your phone sits there with its metaphorical blindfold on, listening to these broadcasts like a contestant on a very high-stakes version of University Challenge. It measures the tiny delay between the signal leaving the satellite and hitting your receiver, effectively calculating how far away each shouter is based on the speed of light.
Crucially, you are not shouting back. Your phone is a purely passive participant in this game, refusing to engage with the satellites even if you are feeling quite lonely in a multi-storey car park in Swindon. By receiving signals from at least four of these orbiting loudmouths, your phone uses basic geometry to cross-reference the distances and pinpoint your location to within a few metres. It is the ultimate feat of navigation, requiring only the constant, polite endurance of celestial shouting and a device that can do sums faster than a nervous accountant.
Where the analogy breaks downThe satellites do not actually care where you are and they do not wait for you to find them.