[OSM-talk] Coordinate transforms

Barry Hunter barry at barryhunter.co.uk
Thu Apr 27 18:52:54 BST 2006

There is links to various PHP/Perl/JS code here:
nearly all converted from the gps.gov.uk information.
These use the Hermert Transformation, with a typical accuracy of about 7m I 
believe for most of GB. Irish gets better at about 2m.

For an online batch converter checkout
uses the definitive OSTN02 transformation.
Or the one at www.gps.gov.uk (no longer requires you to login)

I don't think there are any issues of IP after conversion. However 
technically any coordinates in OSGB36 could be an issue as there is some 
debate if the BNG is itself copyrighted, but as its just a means of 
specifying a position its a real world fact. (A database of points could be 
copywrited as that is a 'work', as such its the database of postcodes that 
copywrited not the individual postcodes)

Hope that helps

- www.nearby.org.uk - www.geograph.org.uk - www.trigtools.co.uk -

----- Original Message ----- 
From: "Laurence Penney" <lists at lorp.org>
To: <talk at openstreetmap.org>
Sent: Thursday, April 27, 2006 1:03 AM
Subject: [OSM-talk] Coordinate transforms

> Richard's posting of the IoW outline makes me wonder about we can all do 
> similar things for data sources we have access to.
> Is there a page on the wiki (or elsewhere) on methods for transforming 
> coordinates between OSGB and WGS84 lat-long? It would be very helpful to 
> have such a guide and for people to share experiences, for both the 
> technical and legal aspects, so people can decide how to build this stuff 
> into their projects.
> It would also be super to offer a web-based transformation service, i.e. 
> text files of coordinate lists uploaded, and transformed coordinates 
> generated, ideally with an indication of the algorithm (and any accuracy 
> parameters) used.
> Right now I'd like to have a version in PHP to use in my web projects. I 
> already implemented the algorithms in [1] in C, although without the datum 
> shift. It looks like using the whole of [2] is the way to go. Is this the 
> only realistic method? Is it free of IP consequences in the resulting 
> data?
> If anyone has any tips on using the OS methods below or something else I 
> would be pleased to hear, along with any accuracy warnings for their use. 
> Thanks!
> [1] "OS: A guide to coordinate systems in Great Britain", Appendix C
> http://www.ordnancesurvey.co.uk/oswebsite/gps/docs/A_Guide_to_Coordinate_Systems_in_Great_Britain.pdf
> [2] OS "Quest Developer" Coorindate Transformer (includes [1])
> http://www.ordnancesurvey.co.uk/oswebsite/gps/osnetfreeservices/furtherinfo/questdeveloper.html
> -- Laurence
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