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I'm looking for a fairly simple way to append columns with WGS84 longitude and latitude to a table containing northings and eastings. The source data is Ordnance Survey's CodePoint Open, which I is I think OSBGB36. I want to use this with OpenStreetMap. I have the CodePoint data in a csv file and loaded into an MS Access database, from which I can load it into QGIS. From there I've tried exporting it with a transform operation into various file formats but this doesn't seem to do the trick. I do have access to PostGIS and SQL Server 08R2 but little experience of using sql spatial.

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up vote 14 down vote accepted

Try this:

  1. Load the .csv into QGIS using "Delimited Text Layer" plugin
  2. Define the projection OSBGB36 in layer properties
  3. In "Save layer as ..." set CRS to WGS84 (this will reproject your data) and chose an output format you like

To add columns to the attribute table containing long and lat in WGS84:

  1. Use "Export/Add Geometry Columns"
  2. If you need a .csv again: Chose "Comma Separated Value" format in "Save layer as ..."
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Thanks, that is very helpful. This projects the data correctly, but I wonder, is it possible to add columns to the source table with long and lat in WGS84, so that I can see these additional columns if I save the layer as a csv? Or to achieve this in some other way? – euki Dec 5 '10 at 11:52
I updated my answer. – underdark Dec 5 '10 at 13:11
Thanks, that's perfect. – euki Dec 5 '10 at 13:19
These instructions don't seem to work for me. I don't want to ask a new question for the same thing, but can someone provide extended step-by-step instructions for taking a CSV that contains OSGB36 eastings/northings and ending up with a CSV containing the same data, but also WGS84 latitude/longitudes and for both co-ordinates to point to (roughly) the same location on a map? I have QGIS and a Mac... – danherd Mar 6 '14 at 14:03
@danherd Nobody will see this comment. I only got notified because you commented my answer. Please open a new thread and include 3 or 4 lines of your original CSV for debug purposes. – underdark Mar 6 '14 at 17:37

There is a cache version of the OS OpenData site here:

The data has been already converted into WGS84 (lat/lng)

Just a time-saver.

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This is no longer true. – danherd Mar 6 '14 at 14:02

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