[OSM-dev] Code for OSTN02?

[John McKerrell]

On 19 Oct 2009, at 23:19, TimSC wrote:

> Thomas Wood wrote:
>> Good luck, this is the one projection that the OS actually sell for
>> professional uses.
>>
>> I thought that OSTN02 wouldn't actually be needed unless for the very
>> high precision stuff. The standard OSGB36 transform should be good
>> enough otherwise?
> I don't think they are that restrictive. They seem to have a freeware
> library and API for windows (closed source) here
> http://www.ordnancesurvey.co.uk/oswebsite/gps/osnetfreeservices/furtherinfo/questdeveloper.html
>
> On accuracy, converting NR730100 to ETRS89,
>
> OSTN02: 55.33149630, -5.58040715
> Helmert (based on OS spreadsheet[1], ported to C++): 55.331258,  
> -5.580440849
> Nearby.org.uk:  55.331495, -5.580444
> http://www.rutter.uklinux.net/ostowiki.html: 55.33149480 -5.58044426
> Streetmap.co.uk: 55.331967, -5.579682
> ganzc (by Chuck Gantz): 55.3314950512,-5.58040512526
>
> [1]
> http://www.ordnancesurvey.co.uk/oswebsite/gps/docs/ProjectionandTransformationCalculations.xls
>
> First observation: there is a range of accuracies from various  
> sources!
> ganzc was better than I remember. I will investigate that one further.

Not sure it'll be any use but Multimap have (or at least had) a REST  
API that I think does this conversion. A while since I've had anything  
to do with it but you might want to take a look and see if it helps:

http://blog.multimap.com/2008/06/20/new-open-api-features-in-time-for-mashed-08/

John