[Talk-GB] building shapes from OS Street View, with code

[TimSC]

Hi mappers,

Thanks for the comments on automatic tracing. I have finished an 
implementation and it is ready for testing. It runs really slowly (30 
minutes a tile). Be careful if you try it and don't remove any existing 
OSM information (and try not to annoy other mappers). The OS open data 
license is also a concern, so keep the source tags where appropriate. 
Please limit yourself to areas you are prepared to manually check and 
fix. (The LWG are aware of this issue, but don't anticipate problems.) 
The python code is here (with a readme file): 
http://timsc.dev.openstreetmap.org/dev/mapseg0.1.tar.gz

Let me know if there are any major bugs or possible improvements. I am 
not sure I can put in much time in the short term but I will fix any 
major problems. I will do a wiki page eventually for further updates.

http://wiki.openstreetmap.org/wiki/Mapseg

As Ed Avis suggested, I flag suspected errors during the conversion. I 
don't use the surrounding pixel colours but there are plenty of other 
heuristics that indicate problems. I assume all buildings have at least 
4 sides which are orthogonal. Any non orthogonal buildings will be 
flagged for checking.

I automatically add a source tag "auto_os_street_view". This should be 
changed to a different source tag when it has been verified. I suggest 
"source=os_street_view" for verified buildings.

The fuzzer plugin for JOSM is nicely integrated but it operates on the 
rectified tiles which have lower quality images. My approach uses the 
original opendata tiles.

TimSC