title: How to test if a geographic location has been visited in the "real world"?
body: <p>OK, so I already have the answer to this question but it took me a long time to reach it so I thought I would share it, particularly since <a href="https://stackoverflow.com/users/975457/fusion27">someone</a> asked me but under an <a href="https://stackoverflow.com/questions/16735449/beep-not-working-when-phonegap-app-is-in-background-on-ios?answertab=active#tab-top">unrelated question</a></p>
  
  <p>I created a Phonegap-based navigation app for guided walks that tracks the user's location around a predefined route using GPS. My routes have triggers placed at specific geo-locations around the route which give instructions to the user based on their current location. The problem is that GPS is not super accurate or reliable, so even though I allowed a "visiting radius" around those locations of around 20 metres, real-world testing resulted in those triggers sometimes being missed because a GPS position update would occur slightly before the user entered the visiting radius and slightly afterwards. I tried increasing the radius but this meant that the trigger fired too early to be relevant to the user's current position. </p>
  
  <p>So how do I solve this in a way that works using “real-world” GPS data?</p>