So, the mp3Car folks tell me that there's likely to be great interest among mp3Car users in OpenStreetMap.

What is OpenStreetMap?

It's a free and open map of the world. Free? Yes, completely free. Free as in zero cost, and free as in freedom. Open as in open to contributions from its users. And World as in we are targetting the entire world. We're getting there: catching up where other map vendors had a head start, and in some places, we're way ahead where they never mapped at all.

We abbreviate it OSM, and we recently had http://osm.org donated to us.

What's wrong with (insert map name here)

Nothing, as long as you don't mind paying too much money for too little data with too few rights. One problem with existing maps is that they're all expensive. They're produced the old-fashioned way: by paying people to drive around and record the location of map features. People are expensive to hire. Volunteers are cheap, but volunteers won't let you copyright their data.

Another problem with existing maps is that they're all copyrighted, and your rights to do interesting things (like put maps into your car computer) are limited by the license. They enforce their copyright because they make money by restricting distribution. In the OSM world, all the map editors are volunteers, and they insist that the map data be free, and stay free.

Another problem with existing maps is that they're wrong, and you can't fix them. They update their maps by sending people around, which goes back to the first paragraph where these people are expensive. The maps don't get updated as often as anyone would like, so they are always out of date. OSM data can be edited in real time, and if you're working off a compressed and/or edited data dump, it's as accurate as the last time you chose to create it.

How do I use OSM in my mp3Car?

As a consequence of the data being free to get, use, and share, there are a number of programs which use OSM data. Some are web services and some use downloaded data. Some are open source, and some are not. The OSM wiki has a category for routing software. Too many choices? Pick a package, try it out, and post a review.

If it's free, how can be it any good

Good question! If it was merely free data that somebody was giving away, you might wonder and worry about why they're giving it away. But not OSM. OSM is being actively improved by volunteers who are using the map, see flaws in it, and don't want to tolerate those flaws. It's produced by people like you, who care about place, and who care about their place.

In Germany, the data is very good. There are many German users of OSM, so there are many German editors of OSM. The data is very usable for routing there. Germany arguably has the best OSM data.

Because OSM was founded in the UK, the UK and other European countries are further ahead than anywhere else. In some countries, such as the Netherlands, the data is also usable for routing.

In the United States, the street data largely came from the Census Bureau's TIGER data. This has street names and locations, but has a few structural flaws which cause it to route badly. Since it was imported on a county-by-county basis, the roads are disconnected at county boundaries. Since it has no bridges, every road that crosses is considered to be an intersection, but that's not the case for Interstates and other limited-access highways. It needs improvement before it will route correctly.

I love it! How do I contribute?

Just by using the data, you're contributing! Volunteers get paid in love, respect, and attention. When you use OSM data, you're paying them something that money can't buy.

No, I mean, how do I edit?

OpenStreetMap is like a wiki in that anybody can edit, but because it's positional, and locational, you need to use a graphical editor. We do require that you register with the site before you start editing, but that just requires email confirmation. Once you have your username, go to http://openstreetmap.org. Login, and move the map to the place that needs editing. Click on the Edit tab, and you're in the Potlatch editor. There's a full set of documentation on Potlatch on the OSM website; no need to reproduce it here.

Another widely used editor is called "JOSM". It's written in Java and has the obvious derivation from Java OSM editor. It has some advantages over Potlatch, and some disadvantages. There's a comparison of editor so you can see what other people have to say about the two editors. The Germans largely prefer JOSM, and they've been very successful.