[gdal-dev] Bug in coordinate system library? unknown elliptical parameter for BNG coordinate system

[Andreas Joisten]

Hi Jean-Claude,

many thanks for your answer.

As you can see I did not specifiy the ellipsoid parameter:

gdalwarp -s_srs EPSG:27700 -t_srs EPSG:4326 input_geotiff_in_BNG.tiff  output_geotiff.tiff


the gdal error message was:
ERROR 6: Failed to initialize PROJ.4 with `+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.
9996012717 +x_0=400000 +y_0=-100000 +ellps=airy +datum=OSGB36 +units=m +no_defs'.
unknown elliptical parameter name


Is that a bug in GDAL?


Many thanks

----- Original Message -----
From: jrepetto at free.fr
Date: 23.03.2010 19:06:33
Subject: Re: [gdal-dev] Problem with +ellps=airy which is used for BNG


> Andreas Joisten a écrit :
> > Hi all,
> > 
> > The BNG (British Natial Grid) based on the airy Ellipsoid but GDAL did not know this parameter.
> > 
> > 
> > +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +ellps=airy +datum=OSGB36 +units=m +no_defs 
> > 
> > Probably, gdal does not know this parameter:  +ellps=airy
> 
> Hello,
> 
> You don't need to specify the ellipsoid, because it is already contained 
> in the datum definition :
> 
> proj -v +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 
> +y_0=-100000 +datum=OSGB36 +units=m +no_defs
> #Transverse Mercator
> #	 Cyl, Sph&Ell
> # +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000
> # +datum=OSGB36 +units=m +no_defs +ellps=airy
> # +towgs84=446.448,-125.157,542.060,0.1502,0.2470,0.8421,-20.4894
> 
> Jean-Claude
>