[GRASS-user] Warning regarding Datum unknown not recognised by GRASS

[Kim Besson]

Hello Markus
Thanks for the reply
To do what you suggest, I would have to retrieve LOCATION's CRS EPSG code
and I'm not able to get it automatically. I only can get that PROJ4 string
by using g.proj. Is there a way to automatically get a LOCATIONS's EPSG
code?
Best regards,
Kim

2010/6/29 Markus Neteler <neteler at osgeo.org>

> On Tue, Jun 29, 2010 at 11:20 AM, Kim Besson <kimbesson1981 at gmail.com>
> wrote:
> > Greetings
> > A couple of days ago I have exchanged a few messages with Paul Kelly and
> > Micha Silver regarding this issue. But now I have a new example and I
> want
> > to know if I'm doing anything wrong and better understand what is  GRASS
> > behaviour.
> > I'm trying to have an aumatic procedure to reproject images using
> gdalwarp.
> > First it checks image CRS (g.proj input=IMAGE -jf) and compares with
> > Location's CRS (g.proj -jf).
> > As target_CRS I'm using the output from g.proj -j -f .
> > In this case, g.proj -jf give me the Location«s CRS:
> > +proj=utm +south +no_defs +zone=24 +a=6378137 +rf=298.257223563
> > +towgs84=0.000,0.000,0.000 +to_meter=1
> > (Sidenote. This Location was created based on an EPSG)
> > I use this expression to warp the image:
> > gdalwarp -t_srs "+proj=utm +south +no_defs +zone=24 +a=6378137
> > +rf=298.257223563 +towgs84=0.000,0.000,0.000 +to_meter=1" input.tif
> > proj4.tif
> > But if I check proj4.tif CRS I get this:
> > +proj=utm +south +no_defs +zone=24 +a=6378137 +rf=298.257223563
> +to_meter=1
> > Trying to open with OGR...
> > Trying to open with GDAL...
> > ...succeeded.
> > Datum <unknown> not recognised by GRASS and no parameters found
> > Why towgs84 is not kept in the image?
>
> To my knowledge the GeoTIFF format is not able to keep the towgs84 string.
> Did you try with different formats?
>
> But in general, it may be better to assign proj metadata via EPSG code.
>
> Markus
>
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