Google Maps when used with GPS (and the built in compass of an iPhone 3GS) is a brilliant application, but it lacks an offline mode for times when you're in an area without a signal. If you're planning on going somewhere where you can't get 3G or EDGE then the application is pretty much useless. The only way it would be made more useful is if there was some way to cache a viewed map area at different zoom levels so you could peruse it at your own leisure - it is after all only a series of images that fit to specific geographical locations. This is where the application OffMaps comes in.
When I came across OffMaps it was purely by chance - I knew I'd need some mapping software that cached map images to use with GPS, but I thought it meant I'd have to write an application to do it. I chose to search the App Store for "offline map" and thankfully I found this application that fit the purpose. Rather than using Google Maps for providing the maps, they instead opted for OpenMaps but still has some familiar features such as being able to automatically locate where you are and to rotate as you turn round so that the map lines up with what you can see (iPhone 3GS only). If you use this feature then you can download a map of where you are automatically, and also download a "guide". These guides allow you to search the map whilst you are offline for various types of location such as restaurants or hotels. For example, if you download the guide for Sydney it contains 2347 points of interest, 69 restaurants, 197 bars, 137 hotels and fits into a 8.8Mb download. When you download the application you get to download two of these guides for free, after that you have to pay for them. It's not really that big a deal either as you can buy additional downloads at £0.59 for 3 of them which is nice and cheap and can be bought using in-app purchases.
The guides can also be accessed when not using the feature by tapping the same button on the tab bar and navigating through the places. I've found these guides to be quite useful as if for example you want to see the Sydney Opera House and you have already bought the guide then you can type it in the search and click on the entry, or click on the blue icon in the search box, switch to guides, navigate to the Sydney guide, and then find the Opera House under the list of sights. Once you've found it you see a small map showing where it is, a category in which it falls under (Theatre, Attraction) and then links to get from there to somewhere else, the route to there, or to add it to your favourites. I don't think the UX is the best in the world as it takes some getting use to in order to make the most of it (some of the features aren't obvious on how to find them).
When you want to download an area of map you click on the same icon as the guide, click on "Only Download Map" and then you drag out an area of the map you want. You then get the choice of how many zoom levels to obtain the map images for. If you've already downloaded the map at that zoom-level it does tell you at that point, but it would have been nice to have a way of browsing a list of what places you have cached (by giving the ability to name them).
The only problem I've really found with this application is that although you can see what filesize your cached maps have reached, there is no indication of what areas and zoom levels you have cached. Even if you've bookmarked several places you can't tell which of those are cached and that I think is it's biggest flaw.
Generally speaking it's a useful application and can save you money since you don't need to worry about getting data plans for abroad (it can stop you getting lost too!) and is certainly worth the download if you're going to a different country or somewhere without a signal.
