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I have adapted someone else's VB code to convert lat long to OSGB for UK locations. In essence my code converts a Google API location returned from a text search, into Eastings and Northings that can then be checked against the OS using (e.g.) StreetMap.

My conversions are only ball park correct, and I think I need to incorporate the Helmert Conversion, to get more accurate transformation.

Is there a VB savvy person out there who might be able to help me, if I posted up existing VB code?

  • Have you considered using the GDAL/OGR libraries rather than roll your own? This will eliminate your problems in reprojecting data between SRS. Although GDAL has VB bindings, I don't think they are complete, but GDAL also had C# bindings which you can use through the .NET framework with with VB.NET. – MappaGnosis Jul 16 '15 at 13:23
  • Thanks for reply. As the code is running from within an Access database, no I hadn't considered trying to bolt anything more in..I guess this is a different library that would have to referenced in? – baffle Jul 17 '15 at 16:10
  • If you would like a more accurate conversion you will need to use OSTN02 transformation rather than Helmert. Not sure if this exists in VB though but you can download the info from the OS website - ordnancesurvey.co.uk/business-and-government/help-and-support/… – tjmgis Jul 17 '15 at 17:24

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