I have some recent data that is at the Lower Super Output Area (LSOA) level for Greater Manchester. I wrongly assumed that the data was for the latest LSOA boundaries, i.e. for the 2011 boundaries.
Once I realised that my data did not fit this LSOA version, I tried to do the same with the 2001 ONS data. This was less successful. Even retaining 2.5% of discardable vertices still leaves a lot of holes in the map, as you can see here:
I used the following command to do the simplification and conversion before using a simple ruby script to select just the Greater Manchester features:
mapshaper -i LSOA_2001_EW_BFC_V2.shp encoding=utf8 -simplify 1% keep-shapes -o uk-2001-lsoa-boundaries-1pc.geojson format=geojson
- The encoding parameter in the command above is a guess. Both sets of data required an explicit encoding and utf8 worked fine on 2011 data.
- I think I used the same command for the 2011 data (there are not a lot of parameters to play with) but I may be wrong.
- The results that I get with the full, clipped 2001 data look like the results I got when I unknowingly used the 20m generalised 2011 data. In fact, the first thing I did when I saw the results was to check that I had not used 20m generalised data.