On the OpenStreetMap talk list today, a community member by the name of Jochen Topf unveiled a cool experimental map comparing service. It allows you to browse Google and OSM maps side-by-side, and automatically keeps their position and zoom level matched for accurate comparison.
This is more than just a novelty tool – it is a great way to show how many mistakes there are in Google’s maps. Within about 2 hours someone had emailed a link to the map of Delmeny (near Edinburgh in the UK), claiming there were at least 4 errors visible on the Google map. Twenty minutes later, someone had identified 7 incorrect features on the Google map!
A little closer to home is this section of Canberra. Although the OSM rendering (particularly street names) could be more nicely proportioned, it is apparent that the community-built map is simply more detailed and more accurate. Note especially the connection between North Road and Sullivan’s Creek Road on the left of the map frame.
Of course, there are still a great many places where the OSM map coverage is poor compared to commercial maps (even to the point of being non-existent). This problem, however, is gradually diminishing. Where OSM mappers have been, it is clear that Linus’s old adage holds true: many eyes do make bugs shallow.