[GRASS-dev] v.transform: what is zrot supposed to do ?

[Moritz Lennert]

I have the feeling I'm missing something, here, and I prefer asking the 
question here before posting a possible bug report.

What is the exact meaning of zrot in v.transform ? I would have thought 
that with no scaling and no shift, zrot would create a simple rotation.

I create a square as such:

v.in.lines in=- out=testline sep=, --o << EOF
610000,200000
680000,200000
Nan,Nan
680000,200000
680000,270000
Nan,Nan
680000,270000
610000,270000
Nan,Nan
610000,270000
610000,200000
EOF

I then try to rotate that squate by 45 degrees:

v.transform input=testline output=testline45 zrotation=45

The result is shown the attached image: The rotation works, but I get a 
shift of about 445km NW. Is this expected ?

Moritz
-------------- next part --------------
A non-text attachment was scrubbed...
Name: v_transform_rotation.png
Type: image/png
Size: 3678 bytes
Desc: not available
URL: <http://lists.osgeo.org/pipermail/grass-dev/attachments/20150619/11b2786e/attachment.png>