One of the things I discovered a while back is that even fairly crude trig approximations don't put that much error into your position, over a small enough distance.

To calculate things like straight-line range from where you are now to where you need to put a unit for an emergency, you're probably not working over an area of more than a couple of hundred kilometres radius and the error will be within a few dozen metres. And once you get within about half a k, you're driving towards the column of smoke anyway ;-)