[Proj] Custom projection wildly inaccurate
Oscar van Vlijmen
ovv at hetnet.nl
Sat Nov 18 11:18:07 EST 2006
> From: "Thy, Kristian"
> Date: Sat, 18 Nov 2006 01:17:16 +0100
> Subject: [Proj] Custom projection wildly inaccurate
> I'm trying to reproject data in an obsolete Danish orthogonal projection
> called System34 in MapServer. To this end, I've found a .prj file for ArcMap
> distributed by the Danish National Survey & Cadastre, which defines the
> following parameters:
> Problem is that this transposes the data many kilometres north and slightly
> west (and perhaps also distorts it slightly, I'm not sure). The effect can be
> seen in these three maps:
Another problem is that System 34 is not coupled to any projection. I have
heard of a transverse mercator approximation, but an orthographic?
The Danish use a 11th (13th?) degree polynomial to convert System 34
coordinates to UTM. I haven't seen this polynomial roaming on the internet,
so I cannot comment on the accuracy of approximations.
There are 3 zones in System 34 and the coordinate system is west-oriented.
Kort & Matrikelstyrelsen - Mere om System 34
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