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<div class="moz-cite-prefix">On 01/02/2013 04:51 PM, Andre Joost
wrote:<br>
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<blockquote cite="mid:kc1l1r$72i$1@ger.gmane.org" type="cite">
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</pre>
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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.
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<font face="Times New Roman, Times, serif">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). <br>
<br>
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?<br>
<br>
Jan </font><br>
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