BNG to WGS84 Lat and Long

Topics: Algorithms
Jan 11, 2008 at 1:28 PM
I have written some code to use SharMap to transform ESRI shape file data to GPS latitudes and longitudes. I have read that a further transform is required, the Ordance Survey OSTN02 transform, as I am converting from British National Grid eastings and northings. Without this my GPS points are out by a few tens of metres.

Does anyone know if SharpMap can do this, or if the functionality is proposed?
Developer
Jan 11, 2008 at 6:26 PM
You should be able to create the transform, but a word of warning. On the OS web site their exists the formula for the transformation, but this is not very accurate, its only fro rough workings and erros of up to 200 meters can be possible. If you search around the site, will be able to find a correction table file which is ascci based. Use this with the instrcutions on how to apply the corrections to give accurracies better than sub meter.

If am able to find the bits I will post you the links via the messsage board
Developer
Jan 11, 2008 at 6:46 PM


I've found the link,

http://www.ordnancesurvey.co.uk/oswebsite/gps/osnetfreeservices/furtherinfo/questdeveloper.html

download the zip file and go on from their. Have fun!
Jan 16, 2008 at 11:46 AM

Many thanks, I'll give it a try and let you know how I get on


Cairn wrote:


I've found the link,

http://www.ordnancesurvey.co.uk/oswebsite/gps/osnetfreeservices/furtherinfo/questdeveloper.html

download the zip file and go on from their. Have fun!

Jan 16, 2008 at 1:38 PM
Well I got the dll and the associated dat file for the transform by installing InQuest. (rather than using the msm file download, which my computer refused to recognise). Using the document download too it was an easy matter to get the code working and then do the transform to a very good accuracy. I am using C# in Visual Studio 2005.

Thanks again for the help.