[Proj] Help with a custom projection that is Transverse Mercator with Affine post-process

[James Cox]

Hi Mikael,

Thanks very much for the answer.
At least the question of whether or not the Affine process is
supported has been resolved. :)

Cheers,
James

On Tue, Jan 29, 2013 at 5:02 PM, Mikael Rittri
<Mikael.Rittri at carmenta.com> wrote:
> Hello James.
>
> Just a partial answer, I am afraid:
>
>
>
> I don’t think you can add an affine post-processing to a Proj.4 CRS
> definition.
>
>
>
> For your example, the interpretation of the MapInfo CoordSys clause should
> be
>
>
>
> “CoordSys Earth Projection”, // Just a name (probably the wrong one in this
> case)
>
> 8,                   // The projection type, in this case Transverse
> Mercator
>
> 33,                 // The geodetic datum, in this case GRS80 (treat it like
> WGS84)
>
> 7,                   // length unit, in this case meter
>
> 117,                // central longitude
>
> 0,                   // central latitude
>
> 0.9996,           // scale factor
>
> 500000,          // false easting
>
> 10000000,       // false northing
>
> 7,                   // length unit for affine transformation, also meters,
>
> 0.890953, -0.455062, 2903977.24, 0.455063, 0.890954, -6919253.68,         //
> affine parameters A, B, C, D, E, F
>
> -100000, -100000, 100000, 100000               // bounds
>
>
>
> I think the basic CRS in this example can be expressed in Proj.4 as
>
>
>
> +init=epsg:28350
>
>
>
> which gives GDA94 / MGA zone 50, but I think you must implement the affine
> transformation yourself.
>
>
>
> I got the information from
> http://www.sgsi.com/dnld/MapInfoPro_UserGuide_Current.pdf
>
> but I didn’t understand the meaning of the affine parameters.
>
>
>
> And I think the 8 ought to have been 3008, maybe…
>
>
>
> Best regards,
>
>
>
> Mikael Rittri
>
> Carmenta
>
> Sweden
>
> http://www.carmenta.com