Convert eastings/northings to latitude/longitude using NetTopologySuite

Question

I have a bunch of Eastings/Northings coordinates, using the UTM convention as far as I can tell - so basically, they are cartesian coordinates - that I would like to convert to Latitude and Longitude.

Presumably NetTopologySuite can help me with this, but I can't find much documentation on it.

Anyone got some pointers to get me started?

Edit: The Eastings and Northings turned out to be, specifically, OS Grid Reference Eastings and Northings, the issues and conventions around which are discussed here.

Answer 1

This is more likely a simpler tools for your needs.

http://www.codeplex.com/ProjNET

You need to project from UTM (if it really is UTM - there A LOT of cartersian systems out there) to Geographic coordinate system. You will most likely need to find out the datum of your data as well. If you have have your data in a shapefile then look at the .prj file in a text editor - it will contain the projection information. Otherwise you need to go back to the data producer and ask them about the projection.

Answer 2

To answer my own question, the Eastings and Northings turned out to be Ordinance Survey (OS) ones, for which the conversion to Latitude and Longitude is quite well defined.

This very good page by Chris Veness discusses the main algorithm and common pitfalls. He presents a Javascript algorithm but I found a C# equivalent in this forum.

As Chris Veness points out, that algorithm gets you to Latitude and Longitude, but on the OSGB36 datum. Usually, you will then want to convert that to the WGS84/GRS80 datum more commonly used (otherwise you'll be up to 120m out, for UK locations). For that you need a Helmert transformation, as described by Chris here.

edit: Chris Veness's code is licensed under the GNU LGPL license.