[Proj] Add simple transformations to proj
j.l.h.hartmann at uva.nl
Wed Jan 2 12:03:00 EST 2013
On 01/02/2013 04:51 PM, Andre Joost wrote:
> Simpliest way would be to play with the +towgs84 parameters of the
> current EPSG definition.
> The first three are shifts of the center of the earth in all three
> dimensions, the next three rotations around these axes, and the last a
> scale factor.
> So I would change the values four to six one after the other and look
> for the result. Quantum GIS can handle self-defined proj strings,
> create vector grids in all projections, and show them togehter with
> other grids.
Thanks Andre, it's in the right direction, but it is a bit more complex.
The towgs84 parameters are around the center of the earth. The rotations
of the historical maps, and the coefficients I computed, are around the
center of the projection of epsg:28992 (church tower of Amersfoort).
However, I can compute wgs84 latlon values for every point on the
historical map, by first converting the point to epsg:28992 and then to
epsg:4326 (wgs84). Do you know of any software that can compute the
towgs84 parameters based on a set of input coordinates and the
corresponding wgs84 coordinates?
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