I am working with the SQL Spatial Tools from http://sqlspatialtools.codeplex.com/
And a variety of data sets, primarily from LINZ and Google.
These involve working with projections for 4326 (WGS84?) 3785 / 3857 (WGS84 Mercator / Web Projection?) 4167 (NZGD2000?) 2193 (NZGD Transverse Mercator?)
After looking at what's available, I'm wanting primarily to map 2193 <-> 4167 <-> 4326 And I'm going to store 2193 and 4326 to work with.
But I'm unclear on how to go about converting between the different projections.
I'm guessing that one of the following is correct for going from 2193 to 4326
Either 1. Generate a Transverse Mercator Projection with appropriate settings 2. Call Unproject on it to get a 4167 projection 3. Generate a "Something" Projection with the 4167 settings 4. Call Unproject to get to a unit sphere co-ordinate set 5. Generate a "Something" projection with the 4326 settings 6. Call "Project" with the unit sphere co-ordinate set to get the 4326 co-ordinate set
Or 1. Generate a "Something" projection to get directly from 2193 to the unit sphere 2. Generate a "Something" projection to get from the unit sphere to 4326