I think the killer feature of Gaia GPS is the ability to download iPhone offline maps. Some of the other GPS apps out there cache tiles a little bit, but Gaia GPS is the only one, as far as I know, that provides the ability to select an area of the map to pre-download. There are other iPhone apps that have this feature, but no one besides us has integrated it with a GPS recorder and other releated geo-features.
Downloading a map is simple – here’s a screenshot of the map download feature in Gaia GPS. To create a map, you just bring up the map download screen, and drag a rectangle with your finger. If you choose High Detail (the button at the top of the screen), then the map will include deep zoom levels, but if you do not, the map will be about 1/4 the size. I rarely find it necessary to use High Detail.
What makes these offline maps even better is that you can download MyTopo maps – another feature only available on Gaia GPS. For my money, MyTopo maps are by far the best way to navigate outdoors in the U.S. or Canada. MyTopo maps are not international, but we have also included OpenCycle maps in v1.2, which will come out very soon. Gaia GPS also has road maps from OpenStreetMap/CloudMade.