I’ve been in Oregon and Washington for about a week on hiking trails and lakes. I’ve been using the GPS on my iPhone as much as possible. I have read that the GPS uses cell phone towers as well as satellites to triangulate your position. It’s been a true test of the quality of the GPS chip because most of the time while on trails I haven’t had a cell phone signal. I’ve discovered a few things about the iPhone maps application and the GPS quality.
Pre-cache Map Tiles
The maps app will cache map tiles for areas that you visit while you have a data connection. When you are out of range the map will still be displayed. I imagine that there is a limit to how much storage the maps application can use for cached tiles. If you plan on taking advantage of cached map tiles you may want to consider viewing maps at more than one zoom level. I’ve discovered that one close up view and one far away view will usually suffice.
Latitude and Longitude
What if you know the coordinates of a location you wish to get to but you don’t know the path or you can’t find it on the map? We wanted to locate a few waterfalls on the map before visiting so that the maps would be cached. You can enter the latitude and longitude coordinates into the maps application to look up the location on the iPhone. An example would be “48.1188 N, 123.4278 W” (the Red Lion in Port Angeles, WA).
GPS Locator Depends on Speed
I discovered that it is usually unable to locate me when I’m traveling faster than about 5 MPH. While I can understand why this might be, it is still a real pain to have to stop the car just so that the GPS can find me on the map. Once it has initially located me it has no problem following me at 70 MPH. Seems inconsistent to me.
Altitude
The free application TrackThing available on the app store has been really cool as it has been able to provide fairly accurate latitude, longitude and altitude. It also graphs this information over time.
Thoughts
If you were planning on buying the iPhone 3G for the GPS functionality you might be better looking at a traditional GPS unit. While it’s really nice to have the GPS built in to your phone/camera/entertainment device, there has really only been one time this entire week when it was able to find us that was really helpful. It was cool to look up our altitude when we were sitting on top of Hurricane Ridge though.