I've been playing around with GPS mapping software in preparation for a backpacking trip I'm taking. So far I've settled on using Maemo Mapper because it has the ability to download the topographical maps. Of course, while downloading the maps I've found myself caught with deciding how much detail versus how much coverage I want.

To that end, I was wondering how exactly does Maemo mapper store the downloaded tiles. Are they stored as gifs, jpegs, some other format? Would it be possible for setting a compression level to the tiles as they are downloaded and saved? I understand there would be a loss in the quality of the tiles by doing this but if it saves me some space I could download the lower quality tiles for areas I "might" need in the future if I happened to travel to that part of a state or something.