I've been contributing to OpenStreetMap for a while now, but I actually put OSM data to the test today.
A family member bought a new vehicle recently which has a built-in manufacturer-supplied GPS with proprietary mapping data on it. We decided to have a drive today to test it out. I brought along my Garmin eTrex 20 loaded up with OpenStreetMap-derived TalkyToaster maps. TalkyToaster's maps are routable and have a large number of points of interest.
We did a 35 mile drive down to Dungeness in Kent. While there, I did some site surveying in the freezing cold and have made a few updates to OSM.
The routing mostly worked. And the data was good. On the outward journey, I checked a lot of the side streets we passed by, and all those I checked had the correct name and There was only one problem I found with the data: there was a tiny little cul-de-sac I spotted that wasn't on the map. I added it as a waypoint on my Garmin and will add it to the map when I next transfer data off.
The routing had only one problem and that was on the return journey, while driving along Lower High Street, Wadhurst. Rather than continue on to the High Street, the Garmin device instead said that one should turn into Church Street. Church Street is a tiny single-width street that is only used for access and is tagged highway=residential. You wouldn't drive up it, especially in a larger vehicle like a van. It actually has a warning sign forbidding HGVs from entering. But the Garmin was quite insistent that one should drive up there. The manufacturer-installed GPS accurately stated to carry on along the High Street.
I shouldn't be surprised at how good OpenStreetMap data is (I've added plenty of it), but this slight routing mishap aside, certainly here in the south east of England, it is now pretty damn close to good enough that it can be used for in-car navigation. Having seen how much data upgrades are for some car GPS units (as much as £150 in some cases), the future really ought to belong to OpenStreetMap.
We've got open data, we've now got open source operating systems (Linux, Android), cheapish hardware, Kickstarter for funding: someone could build a completely open source satellite navigation system...