[Proj] Datum shifts in PROJ's EPSG table (The Netherlands and Belgium)

Frank Warmerdam warmerdam at pobox.com
Thu Nov 2 10:01:56 EST 2006

Roger Oberholtzer wrote:
> On Thu, 2006-10-26 at 16:17 +0200, Oscar van Vlijmen wrote:
>> I suppose the "confirmed" transformation:
>> <quote>
>> a more accurate definition for the Dutch system is:
>> +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,-1.87
>> 03473836068,4.0812 
>> +no_defs +to +proj=latlong +datum=WGS84
>> </quote>
> OK. Given these values, how would one do this using the C API, and the
> pj_transform() function. Starting with WGS84 lat/long values as provided
> by a GPS receiver set to provide WGS84 values?
> I know that I am asking numerous similar C-API question on this list,
> but I do not really feel I have it sorted out in my mind. 
> Would it be:
> fromProj = pj_init_plus(+proj=latlong +ellps=bessel)
> toProj   = pj_init_plus(
> 		"+proj=sterea +lat_0=52.15616055555555 
> 		"+lon_0=5.38763888888889 
> 		"+k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel
> 		"+towgs84=565.2369,50.0087,465.658,-0.406857330322398,0.350732676542563,-1.87
> 		+units=m +no_defs)
> pj_transform(fromProj, toProj, 1, 0, &lng, &lat, &alt)


There are several missing double quotes in the above example.

I think the fromProj should also be "+proj=latlong +datum=WGS84".
As you have expressed it now, pj_transform() will see no need for a
datum or ellipsoid conversion since the source and destination are
both on the bessel ellipsoid and no datum info was provided for the

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    | President OSGeo, http://osgeo.org

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