This takes me back to one of my first hacker projects. We were going on a family road trip and I had found an old marine GPS receiver. The manual it came with showed a special cable for RS232, but I didn't have it and so drilled a hole in the side to solder wires to the back of the connector. Then there was some desktop program where you could plot your position on top of downloaded openstreetmaps maps. This was around the time where smartphones with maps existed, but nobody I knew had one. I think you could also get GPS receivers from Sparkfun, but they were expensive and I was a kid with no money. Good times.