[Proj] EPSG:28992 to EPSG:23031 conversion

[OvV_HN]

----- Original Message ----- 
From: <bartvde at osgis.nl>
To: <proj at lists.maptools.org>
Sent: Wednesday, October 08, 2008 4:24 PM
Subject: [Proj] EPSG:28992 to EPSG:23031 conversion


> Hi list,
>
> when I use PROJ.4 to do a conversion between EPSG:28992 (the Dutch
> national grid) and UTM zone 31 ED50 I get:
>
> cs2cs -f %.9f +proj=sterea +lat_0=52.15616055555555
> +lon_0=5.38763888888889 +k=0.999908 +x_0=155000 +y_0=463000 +ellps=bessel
> +units=m
> +towgs84=565.2369,50.0087,465.658,-0.406857330322398,0.350732676542563,-1.8703473836068,4.0812
> +no_defs +to +proj=utm +zone=31 +ellps=intl +units=m +no_defs
> 19465 394814
> 530108.861080788        5708613.329898705 -150.818087836
>
> If I use the coordinate calculator (Windows only sorry,
> http://www.rdnap.nl/download/setup%20cc41.exe) which is an official tool
> in The Netherlands, I get:
>
> Northing 5708615,754
> Easting 530199,479
>
> so especially the difference in easting is too large.
>
> Is there a logical explanation for this difference? TIA.
>
> Best regards,
> Bart



If there is a difference of some tens to around one hundred meters and 
everything else (such as the command line instruction) seems to be ok, then 
there are two usual suspects:
* The rotation model is wrong - coordinate frame vs. position vector; try 
changing the signs.
* The units of the rotation angles are wrong - microradians vs. arcseconds.

Oscar van Vlijmen