Try the following if you're having trouble with inaccurate tags of your parked car or low GPS reception:
- wait 10-15 seconds for acceptable accuracy (see our GPS testing and why GPS takes so long below)
- set a timer or make a note while waiting for the GPS
- go to a spot where there is clear sight to the sky above you
- if you’re in a building or parking structure, go near the sides where your phone has clearer sight to the sky
We know some of you would like to open the app, tag and close quickly. We do too. Unfortunately GPS technology needs a bit more time than that and it's not something the app has control over. Apple has added a feature to use local wifi hotspots, if available, to assist location update. For now, the best thing you can do is open Mission: Park! app a couple of minutes before you're going to tag giving GPS the time it needs.
Our GPS Testing
In our testing, we found the GPS on the iPhone 4 and iPhone 4S to be faster and a little more accurate than the 3G/3GS models. In good areas, we were able to tag our car to within 5 m (15 ft) and it typically took 30-40 seconds.
We also learned that in 10-15 seconds, we got an acceptable accuracy of 20-50 m. This was sufficiently close to the car that we were able to spot it.
Why GPS takes so long?
For a good location accuracy, the GPS in your phone, or any navigation device, needs to connect to 3-4 GPS satellites that are orbiting the earth 12,000 miles above us. The more satellites your GPS device can connect to, the better the location accuracy will be.
Your GPS device goes through several steps to figure out your location. However, most of the time is spent listening to the signal from the satellites - at least 30 seconds - before it can be used for location calculations. If it looses the connection with the satellite or you changed location/altitude significantly, then it will have to start over. In the mean time, your smartphone uses other methods of finding your location, like wifi hotspots (a little less accurate) or cell towers (a lot less accurate).
We did 3 things in our app to help reduce the chance of inaccurate tagging:
- the most important thing was to start the GPS as soon as the app launches
- we created a nice GPS reception meter in the maps screen to display the current accuracy
- and last, we made the app notify you if the GPS accuracy is low when tagging your parked car. (Map Alerts in Settings must to be set to ON.)