[Talk-GB] OS Boundaries

Chris Hill osm at raggedred.net
Mon Apr 19 17:18:42 BST 2010

I've been taking a look at the boundary data released as part of the OS 
bundle. I've put together a little script that will extract a named 
boundary as an OSM file ready for loading into JOSM. OS data uses the OS 
projection and we use the WGS84 projection. I used ogr2ogr to transform 
the data from one to the other, but there seems to be a bug with its 
handling of the OS data projection. The resulting OSM way is the correct 
size and shape, but is not in quite the right place. The discrepancy in 
location varies across the UK, so a fixed correction will not work. The 
variation between individual nodes will be too small to matter in a 
parish boundary, but might be a problem for the biggest counties.

Does anyone have a different projection translator not based on GDAL 
(where it seems the error lies)? Does a working version of ogr2ogr exist?

When this little problem is solved I then have to work on how to use the 
resulting ways. I've been looking at the civil parish boundaries, which 
only exist in England and Wales (communities in Wales). There seem to be 
about 14,000, so dealing with them individually is an ideal 
crowd-sourced project. :-)  The only other source of these data is NPE, 
which are badly out-of-date in some areas.

Each boundary needs to share nodes with adjacent ones. County and 
district boundaries will also need to share nodes, so the process of 
loading them individually might be quite tedious, and would involve 
dealing with any existing boundaries. Working on improving county 
boundaries might be a good place to start.

Any suggestions or comments?

Cheers, Chris

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