Well, a few days ago I wondered why some routes on my GPS are not being recognized or calculated. I went selecting some defined routes which I know by driving them. Then I checked all crossing for being connected and discovered that a few were not really connected. They were only placed near by or had some "zick-zack" back and forward lines or double placed lines for the same route more than once and with nearly the same definition.

Now knowing that I started checking a complete small town in e.g. Poland and discovered nearly 10% of those false connections. And, whow, the route descriptions on OSM Osmarender and Mapnik came up with the right and clearer renderings. I now started a heavy QA on connections by going in growing circles around that town I started with and ... I was nearly shocked how much of those double and false routes are in OSM. I keep up with discovering around 10%. :( One indicator is a route build along green GPS debug points. In nearly every second of those routes are doubled routes and/or missing connections. :(

It would be nice if everyone checks up "his or her OSM squares" on those things. And yes I found such things also in Cities like Hamburg in Germany.
(By the way, in the talk-de mailing list some people wrote that their routings had problems and discovered that the real best route hat errors based on this same problem.)

How to check? Simple with the on-line Flash Editor Potlatch! :)

Two main connections are available:

1. A 1-on-1-connection in a continuing route/road
Highlight a route/road/way by clicking once on the line. Moving the map around you will see where the endpoint of the highlighted part is. Is it somewhere in the middle of the route? Then highlight the potential connection point by clicking once on that visible endpoint of the highlighted route and highlight that connection-endpoint. Now you are able to move that point. And you should now move it once somewhere away from the placed location. - So far you leave the moved point highlighted/selected, nothing will be saved to the system. - If both ends of the moved point are fixed and stretched like elastic strap, everything is OK and you can undo your moving by clicking the undo button on the left lower corner of Potlatch (that one with the rounded arrow). If not, you know how to connect both ends. ;) And if you discover multiple zick-zack lines, clear up that disarrangement. ;)

2. A 3-and-more-crossing connection of multiple routes/roads
Similar like in 1. but you can direct move the crossing point and sometimes you will be surprised how much zick-zack you'll find below a crossing. ;)

Well, so far so much for this. Happy mapping and a soulfull weekend! :)