[Proj] Add simple transformations to proj
Jan Hartmann
j.l.h.hartmann at uva.nl
Wed Jan 2 09:32:08 EST 2013
Hi Frank and all, happy new year!
Is the following possible with Proj? I am working with historical maps
that are rotated with respect to a well known epsg-projection, see for
example
http://mapserver.sara.nl/a1000/bladgrenzen.html
The blue squares are the sheets of the map 1:1000 of Amsterdam after
1940, in epsg:28992, the red squares are the same sheets before 1940 in
a local coordinate system. I know the conversion coefficients for the
two coordinate systems: a simple six-value transformation of the form:
xnew = a*xold + b*yold + c
ynew = d*xold + e*yold + f
I would like to access the second map via a proj-string. For that, I
would have to expand proj with a procedure that takes the six
coefficients (a-f) and generates the transformed coordinates after the
regular transformation.
Is this possible? Can anyone give me some pointers where to look in the
proj-code? Conceptually, it looks simple to me, but I don't know where
to start.
Jan
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