@Conan - Don't stress about it too much. Are you planning a Bun Burner 1500 ride?
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What you're really asking about are called Satellite tracking devices, not GPS per se. Most people sign up for Spotwalla and create a trip there, linking their Spot or Delorme/Gamin satellite tracker, or even a cell phone app to the Spotwalla account. This gives them a link to share, which is a lot easier than trying to print a route.
You need to get an extra corner receipt if there is a short cut that could be taken. And generally speaking, it would need to be faster too to make any sense. You don't need to document every direction change, or document at the exact point you have the corner. You DO need to be able to show the path you took with your receipts so it's clear and obvious that you rode the route you said you did.
You can test your route and receipt choices ahead of time by plugging in the gas stations or other receipt location, (the dated business receipt, (DBR), does not have to be for gas, that's just a super easy one to use when you're getting gas anyway), into a mapping program like Google Maps.
If you plug in your receipt locations and it comes up with the same route you plan to ride, you're golden! If it finds a route shorter than what you intend to ride, then you're going to need another receipt to show your intended route. Figure out where it makes sense to do that, add that to the Google Maps route and see if it then shows your intended route. Yes, awesome, you figured it out. No, try a different receipt location or add an additional one until it maps the route you plan to take.
Hope that helps. You've got plenty of time for the Bun Burner 1500 ride. Enough to get some sleep in the middle of it. Don't be afraid to do that if you want or need to.