Map Tile Caching for Offline Viewing

Question

I'm trying to build an application that will use open source maps from Open Street Maps (though the concept should be applicable to any map provider). The application will enable the user to specify a number of waypoints along a route prior to departure.

Because I don't have a data plan for my cell phone (and because rambling in the countryside rarely gives you a good connection), I want to be able to pre-load the relevant map tiles for the waypoints and/or route before departure so that maps can continue to be used without a data connection.

My initial thoughts are to download the required tiles from the map provider and store them in isolated storage. However, the Bing Maps control implementation, which uses the TileSource class relies on returning an absolute URI that it can download the tile(s) from, which clearly won't work with data stored in isolated storage.

The question has already been asked: Windows Phone 7 Map Control with custom layer in offline mode, but wasn't answered and I'm wondering if since then anyone has cracked the problem.

Answer 1

I've seen this done with a custom layer placed over the map. Tiles are then loaded from anywhere you like (IsolatedStorage, online, somehwere else?) into the custom layer.

Sorry, I don't have any code I can share which demonstrates this at the moment but am currently doing something very similar.