This enables a number of new possibilities.
But first a demonstration
More interesting location data in the simulator
Testing a Core Location app in the simulator is really boring. Apple might eventually wire the simulator up to Snow Leopard’s Core Location implementation, but that would just move your app from Apple’s headquarters to yours. Trail Location lets you send your own test data, which your app receives just as from Core Location.
Trail Location includes a sample app for your device that can send locations to the simulator as you pan around the map. It should also be easy to make an app that plays back recorded location patterns.
Send real GPS data to an iPod touch during development
This one’s a bit more complicated, but worth mentioning. The first two iPod touch models (hopefully NOT the third, but we’ll see) don’t have GPS chips and rely exclusively on Skyhook positioning, which is based on visible wireless networks. With Trail Location, you can use a laptop and a GPS receiver for better results in rural areas. (I bought an Amod ABG 108 Bluetooth GPS mouse for about $20! Unfortunately, you can’t use a Bluetooth GPS directly even with a second-generation iPod touch, because it would degrade the core experience or something.)
Trail Location includes a sample Mac app that can pass locations from gpsd to a listening iPhone app via WiFi.
Better Core Location on the desktop?
Snow Leopard adds the Core Location API to Mac OS X. This is interesting, because while on current hardware the Core Location framework itself is still limited to Skyhook positioning, the rest of the Mac platform is much, much more developer friendly. Trail Location could serve as the glue that connects third-party apps to third-party GPS receivers using the same well-designed API that Core Location provides. Just like you can use your device to send data to Trail Location on the simulator, you could use an iPhone as a GPS mouse for a desktop app.
Eventually, I hope Trail Location can grow mature enough to be left in code that ships to end-users, giving more people the benefits of an open location platform. Currently, you should consider it as an alpha release, NOT ready for anything but debug builds. Right now the code is overbuilt (debatably) but under-implemented (definitely). We’ve released it now so that it can help other developers test their Core Location apps, and so that any progress towards the long-term goals can be influenced by other developers. Get the source at Google code; it’s shared under a non-viral license but your patches are welcome.