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

[Anna Petrášová]

On Fri, Jun 19, 2015 at 7:48 AM, Moritz Lennert <
mlennert at club.worldonline.be> wrote:

> 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 ?


I think the rotation axis is in (0, 0), I would say that is expected
behavior, although should be better documented.

Anna

>
>
> Moritz
>
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