Place your three GPS towers (the purple ones) then place the beacon (the green one). Then while you could already tell where you are, and Scratch itself. We're pretending you don't. Also the part that finds you isn't possible to do irl, computers just have more opportunity.
How a GPS works is it has three points. Whenever you need to find your location, a GPS sends a signal to those 3 points. Each point knows how far away you are from it. So, they make a circle of how far away you are. So say you're 3 miles away, it only knows that you could be anywhere that's exactly 3 miles away. Now when you have 3 of these points, you can do this for each point and get only one place along each circle. That's where the beacon is.
