I'd like to add turn by turn instructions for my hiking-app. I already know how to retrieve the turn-by-turn steps the user has to take, but now I am wondering about strategies on how to figure out what step to display to the user.
So I have my GPS running and the user want's to navigate to a point. If the user starts at the beginning and really follows each step provided, then it's quite easy I guess. I display the information the user has to do in his next step and once he arrives at that location, just display the next step after that. Sure... that's easy...
But in reality that will not always be like that. Users will take shortcuts, GPS signal will be inaccurate, ect.
So I was wondering if anybody could point me to good literature on how to do that. How to determine the proper next step for the user? How to figure out he left the track he should follow? How to detect a shortcut and skip some steps?
I am developing an iOS app, but I guess the same would be true for any platform. Would be great if somebody could point me in the right direction.