This past weekend, we went geocaching for the first time in a few years. We assumed, with each of us having an iPhone 3G, that we had everything we needed to find some caches.

Yeah… No.

We tried two different methods. First, we browsed to a cache page in Safari and clicked the Google Maps link to see the location in the Maps app. This all worked as it should — eventually. We were on a very slow Edge connection, so it took minutes to load the page, and more minutes whenever the map needed more tiles. The iPhone would find the location just fine. The problem was, the map app doesn’t have a high enough resolution to lead you to a specific set of coordinates.

We next tried MotionX GPS Lite. Downloading a 7MB app over Edge is a special experience I wouldn’t wish on anyone. MotionX works pretty well — put in your coordinates and the on-screen compass leads you to the location. This would work for geocaching, but the app depends on the iPhone being in motion for it to calculate a heading. In motion at a speed of at least 3 MPH, in fact. So to use this app I had to run back and forth in the woods, trying not to step on a cactus or slam into a tree. Ultimately, I gave up, as each heading update just made me more lost.

This was all very dissappointing. One of the reasons I bought an iPhone 3G was for geocaching and other GPS-related activities. But since it failed to achieve in the modest task that was its charge, I’m left wondering if I need to buy a separate GPS device.

Some people claim the iPhone GPS chip isn’t accurate enough for geocaching or turn-by-turn directions. I don’t buy that. The first commercial GPS devices were accurate to within 3-5 meters, same as most new devices. No reason the iPhone would be any different. A GPS receiver picks up signals from a minimum number of satellites then tringulates its location. The device itself has very little influence over the accuracy that comes from that process. It may be that the iPhone uses a small receiver that has more trouble detecting satellites. But the GPS-A chip is supposed to help compensate for that.

My gut tells me the real problem here is Core Location, the API apps use to access the GPS data. I know it provides speed, heading, and coordinates, but what an application really needs for geocaching is a continuous stream of updated coordinates. I’d be willing to bet Core Location can not provide those updates fast enough. If someone more familiar with the API could shed some light on that, I’d love to hear about it.

So am I giving up on my iPhone as a GPS device? Not necessarily. It’s possible that a future update to the OS will improve the situation. In fact, that may be what GPS software companies like TomTom are waiting for before they release their apps — a better API. Or perhaps there’s a better GPS app in the iTunes store that I haven’t tried yet. If anybody’s had success with a particular app, let me know in the comments.

In the mean time, though, I probably won’t be doing much geocaching.