[Gdal-dev] bessel to wgs84?

[Kees Krikke]

Frank,

Thanks for your reply. cs2cs seems to give the correct result. If i 
understand correctly i should use:

gdalwarp -s_srs "+proj=stere +lat_0=52.15616055555555 
+lon_0=5.38763888888889 +k=0.999908 +x_0=155000 +y_0=463000 +ellps=bessel 
+units=m +towgs=565.04,49.91,465.84,-0.409394387,0.35970519561,-1.868491 
+no_defs" -t_srs  "proj=utm +zone=31 +datum=wgs84" input.tif output.tif.

..to get the same result as cs2cs gives. My first impression is that the 
gdalwarp output is not wgs84. I will test this tomorrow and let you know.



Regards,

Kees




----- Original Message ----- 
From: "Frank Warmerdam" <fwarmerdam at gmail.com>
To: "Kees Krikke" <kees.krikke at wanadoo.nl>
Cc: "gdal-dev" <gdal-dev at remotesensing.org>
Sent: Monday, May 23, 2005 10:33 PM
Subject: Re: [Gdal-dev] bessel to wgs84?


On 5/23/05, Kees Krikke <c.krikke at hccnet.nl> wrote:
>
> Hello,
>
> I'm trying to reproject some images from the Dutch RD coordinate system
> (epsg:28992) that is defined as:
>
> +proj=stere +lat_0=52.15616055555555 +lon_0=5.38763888888889 +k=0.999908
> +x_0=155000 +y_0=463000 +ellps=bessel +units=m  +no_defs
>
> to utm zone 31N /wgs84
> +proj=utm +zone=31 +datum=wgs84
>
> For the datum shift i guess i need to specify the +towgs argument also 
> with
> the source coordinate system.
> (+towgs=565.04,49.91,465.84,-0.409394387,0.35970519561,-1.868491)
>
> I verified these values by running proj.exe and the results are ok.

Kees,

Note that proj.exe ignores the +towgs84 specification.  If you want 
something
analygous to what gdalwarp will do, then you should use cs2cs.

eg.

cs2cs    +proj=stere +lat_0=52.15616055555555 +lon_0=5.38763888888889
+k=0.999908 +x_0=155000 +y_0=463000 +ellps=bessel +units=m 
+towgs=565.04,49.91,465.84,-0.409394387,0.35970519561,-1.868491 +no_defs 
+to +proj=utm +zone=31 +datum=wgs84


If gdalwarp isn't agreeing with the result of the cs2cs then we can talk
about that.  If you think the cs2cs result is wrong, then that is another
ball of wax.

Best regards,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, 
warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent