[GRASS-dev] .g.proj datum_trans (5514)

[Markus Neteler]

On Sat, Mar 26, 2016 at 9:26 AM, Martin Landa <landa.martin at gmail.com> wrote:
> Hi,
>
> I tested recently committed changes regarding S-JTSK. I discovered
> strange behaviour of g.proj:
>
> 1) list transformation parameters
>
> g.proj epsg=5514 datum_trans=-1
> ERROR: No output format specified, define one of flags -p, -g, -j, or -w
>
> I needed to specify -t flag:
>
> .proj epsg=5514 datum_trans=-1 -t
> ---
> 1
> Used in whole S_JTSK region
> towgs84=589.000,76.000,480.000
> Default 3-Parameter Transformation (May not be optimum for older
> datums; use this only if no more appropriate options are available.)
> ---


Yes, this is a know and old issue. The -t flag should not be needed to
be specified since

" datum_trans=index
     Index number of datum transform parameters "0" for unspecified or
"-1" to list and exit
"



> Moreover in GRASS 7.0 I DO NOT need to specify -t flag. Why this
> change happen in trunk? At least it's not documented in the parameter
> description.

I guess it is simply a bug.


> 2) specify transformation parameters
>
> g.proj epsg=5514 datum_trans=2 -p
> -PROJ_INFO-------------------------------------------------
> name       : S-JTSK / Krovak East North
> ...
> towgs84    : 589,76,480,0,0,0,0
>
> Still uses first transformation option even I asked for second.

ouch

> Is there anything I am doing wrong or it's a bug? Thanks, Martin

This part is still buggy.
See also

https://trac.osgeo.org/grass/ticket/2456

Markus