[Talk-GB] building shapes from OS Street View

TimSC mapping at sheerman-chase.org.uk
Mon Apr 5 17:57:16 BST 2010


Hi all,

I was looking at the available OS data and one of the things they have 
but is not really in the current OSM database is building shapes. 
Individual buildings appear in the Street View data. The VectorMap 
District data seems to focus on land use and only has "important" 
buildings. The Street View data is much more complete in terms of 
individual buildings. I guess the questions we have to address are: "is 
this data worth having in OSM?" and "are there any better sources of 
building outline?" I think it would be a valuable addition for highly 
detailed mapping of urban areas, campuses, etc.

The other sources of building outlines I know of are the 1st edition OS 
sheets (which are rather old), Yahoo imagery (which takes work to 
trace), and manual surveying (which is a major hassle since buildings 
tend to throw off GPS positions). Another source would be preferable to 
these.

If we do want this data, it seems to be only available as a raster 
layer. (Does anyone know if this will be available as a vector layer?) 
Converting raster map data to vector data is non trivial but I think it 
is achievable. The building colour in the raster map seems to be unique. 
The raster maps could be selected by colour, vectorised and simplified 
(to remove redundant nodes). Since we have a significant number of 
buildings mapped in the UK, we could presume that we don't want to 
overwrite or duplicate what is already there. Buildings could be 
imported if it would not overlap with an existing building in OSM. One 
problem is some buildings are marked as leisure=stadium without a 
building=*. We might end up with duplicates of stadiums, leisure 
centres, churches and so on. Would we want the import to be more 
cautious to prevent this? I won't be importing anything until the 
rectification of Street View is complete (and I get a feel for the 
consensus on the mailing list) but I have demoed most of the method in 
python using the shapely module to do some geometry transforms.

Any general thoughts on buildings and imports? Will this data be 
officially available in vector form at some point?

We don't seem to have much comment on the legal issues and the 
implications of ODbL yet. Do we have a view as to if our attribution is 
sufficient?

Regards,

TimSC





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