[Proj] Custom projection wildly inaccurate
martin.vermeer at hut.fi
Tue Nov 21 02:13:48 EST 2006
On Mon, 2006-11-20 at 08:36 -0500, Greg Troxel wrote:
> > There seem to be several approximations. Most straight (read:
> > what you can do per proj/cs2cs command line alone) projective
> > approximations are bad.
> > There is really only one way to do it correctly: use the
> > official polynomial solution.
> Yes, but that's not easily translatable for use in Proj-based
> applications like GDAL and MapServer (as far I know, at least).
> We will most likely have to convert the data manually, but in
> the meantime it would be nice to have a bad-and-fast projection
> for demonstration and testing purposes.
> One thing that would work, but perhaps set a bad precedent, is to
> define a new projection in the proj source, that knows the
> polynomials. This would be a particular transform, rather than a
> generic projection with parameters. Alternatively, there could be a
> polynomial transform with vast numbers of parameters.
Alternatively, generate a shift grid containing the shifts produced by
the polynomial. This is the approach I am considering for the Finnish
kkj, which is officially represented by a multi-triangle (Delaunay)
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Size: 189 bytes
Desc: This is a digitally signed message part
Url : http://lists.maptools.org/pipermail/proj/attachments/20061121/47145760/attachment.bin
More information about the Proj