Skip to main content
Warning This document has not been updated for a while now. It may be out of date.
Last updated: 2 Mar 2021

mapit: About datasets

ONSI Datasets

OSNI releases can be found via their Spatial NI site at Note that they don't have a single download and you have to fetch each dataset we want individually. We're looking for the latest releases from the OSNI Open Data Largescale Boundaries of the following:

Note: the package of OSNI data that is mirrored on mysociety's cache is currently a .tar.gz that contains all the all 5 shapefile downloads and a metadata.json file describing the source, release date, SRID and type. You should check that any new package has the same structure and if not, update import-uk-onspd accordingly. If you have to download your own copies of the OSNI data you should check the shapefiles have the correct SRID because they may change from the defaults. If they are incorrect the point lookup can fail (finding parents) or give incorrect results (postcodes).

Use ogrinfo to get the SRID of a shapefile:

$ ogrinfo OSNI_Open_Data_Largescale_Boundaries__Parliamentary_Constituencies_2008.shp OSNI_Open_Data_Largescale_Boundaries__Parliamentary_Constituencies_2008 -so

Look up the GEOGCS field on this coordinate systems page to find the SRID. Most likely SRIDs are 29902 (the NI projection), 29900 (the UK projection), 4326 (the web mercator projection used by google earth among others).