I've been messing around, on and off, for the past couple years with the idea of building my very own carputer.

Originally, it was to be merely an mp3 server/player so I could listen to all my music when out on the road - especially on roadtrips, where there is often a fair distance between decent radio stations.

Well, recently the bug bit me again and I went out to re-evaluate the options available to people like me.

Oh my, look at all the stuff that's available. GPS mapping, music, video, cell phone interface, vehicle diagnostics, backup and side-view cams, control of power windows(!)... Oh, the possibilities.

Well, my possibilities are limited a bit. I don't have an OBD-II vehicle, so I can't control stuff like power windows and whatnot, but I can read OBD-I codes.

During this search, I stumble across someone offering a GPS moving-map display in their carputer software, but of course it's rather costly and Windows-only. I had already made the decision to go Linux, due to its low overhead. OS cost wasn't really a factor, because I can readily pick up a used computer with Windows pre-installed. But I can run the mp3 stuff under Linux with considerably less memory and processing power. That gives me that much more to play with.

So, off to find a Linux moving map.

A couple of solutions come my way, including both commercial and OSS software. I'm leaving the commercial software out of this for now, as I'd really like to see if I can make the whole thing for free.

The first GPL'd thing that I run across is GPSdrive, which despite its name, isn't up to par with the mobile GPS units you can get. Two major things hold it back. First, it doesn't do turn-by-turn routing. Second, you have to be connected online in order to see where you are on a map - it uses map tiles from an online source.

Well, that's no good, surely. It sure looks nice, though.

After a bit of digging, I found one that's closer to what I'm looking for. Roadnav is an open source cross-platform mapping application that does turn-by-turn routing. The map data needs to be pre-fetched from the 'net before you go, but it keeps all the data in a cache on disk for later use.

It has a few unfortunate traits, but all-in-all, I think this is the one to use.