I'm currently using building data from the Ordnance Survey Vectormap District and I've noticed that a lot of building polygons are split in 2 because of the way the OS split up the shapefile.
This is what I'm seeing in QGIS – I've highlighted some of the buildings split at the tile boundary (I can't post images so here's a link): http://i.stack.imgur.com/9FJZM.png
I can't manually merge the buildings as there are way too many of them that have been split at the boundaries (this is just a zoomed in example). I'm looking for an automated way to solve this.
Unfortunately, each side of the split buildings has a different id so I can't easily dissolve them.
How would you suggest I can automatically merge the building tiles?
I'm now using PostGIS to merge the polygons split at the tile boundaries. Here is the SQL statement that does this for me – it's many, many times faster than doing it with QGIS:
DROP TABLE merged; CREATE TABLE merged AS SELECT -- Merge polygons that are within 0.01 metres of each other (ST_Dump(ST_Union(ST_Buffer(the_geom, 0.01)))).geom AS the_geom FROM unmerged; -- Update the geometry_columns table SELECT Populate_Geometry_Columns();