We did it long before GPS existed.

Keep in mind that some rented cars have GPS trackers.

keep in mind that your GPS might not be functional (ie: gps has dead batteries, you forgot to bring it, dropped it, EMP, hackers, etc )

If your GPS isn't working for whatever reason,as long as you have the numbers, just plot the location on a decent topo map. You may need to convert the numbers to the relevant vase line, and it won't be as accurate, but it will get you in the ball park and you will have a reasonable chance.