[OSM-talk] Coordinate transforms

Laurence Penney lists at lorp.org
Thu Apr 27 01:03:01 BST 2006


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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