[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 


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.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.maptools.org/pipermail/proj/attachments/20130102/9c1babbc/attachment.htm 

More information about the Proj mailing list