Good value for declaring "Position reached" in geo coords

Question

Hi Guys, I've written a kind of navigation system for pedestrians. The only thing is, that I need a criterion to finish the navigation.

My values are gives as lat/long pairs.

What would you assume would be a good value to say, both positions are equal/near enough to tell the user that he has reached the goal?

Please keep also in mind, that it's idfficult to say "directly equal", because GPS modules may have variances...

greetz from europe,

poeschlorn

Answer 1

if you compare the distance to 0.0001 (Around 10 meters) you should be set.

To do this

distance = sqrt( pow ( lat1 - lat2 , 2 ) + pow ( long1 - long2 , 2 ) )
if ( distance < 0.0001 ) {
   //Grats! you got there
}