[Proj] proj and Dutch RD

[Roger Oberholtzer]

On Tue, 2006-10-17 at 02:35 -0700, tvijlbrief wrote:
> Much confusion, but the following definition will work! I submitted this
> as a patch for the epsg file to the libproj maintainers.
> 
> <28992> +proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889 
> +k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel 
> +towgs84=565.040,49.910,465.840,-0.40939,0.35971,-1.86849,4.0772 +units=m 
> +no_defs  <>

Is the
"+towgs84=565.040,49.910,465.840,-0.40939,0.35971,-1.86849,4.0772" the
same as "+proj=latlong +ellps=WGS84" ?

I have an RD conversion and all mine is the same except for this.

> 
> For some reason Oscar van Vlijmen's conversion:
> 
> Transformation from Bessel 1841 to WGS84:
> dx=565.040; dy=49.910; dz=465.840; rx=0.40939; ry=-0.35971; rz=1.86849;
> ds=4.0772;
> 
> had the sign of rx,ry and rz reversed!
> 
> Tom
> 
> ====================
> 
> Roger Oberholtzer wrote:
> > 
> > On Thu, 2006-01-12 at 00:17 +0200, Martin Vermeer wrote:
> >> On Wed, Jan 11, 2006 at 12:43:13PM -0800, Eric Miller wrote:
> >> > I think Martin's comment is a little to brief.
> >> > 
> >> > Your source coordinate system is geodetic coordinates using the WGS84
> >> Datum (implies WGS84 ellipsoid)
> >> > In cs2cs terms:  +proj=latlong +datum=WGS84
> >> > 
> >> > Your destination coordinate system is RD (new)
> >> > In cs2cs terms: +proj=sterea +lat_0=52.15616055555555
> >> +lon_0=5.38763888888889 +k=0.9999079 +x_0=155000 +y_0=463000
> >> +ellps=bessel +units=m +towgs84=593,26,478
> >> > 
> >> > I'm not sure about the signs for the towgs84 parameters (dx,dy,dz),
> >> maybe they're supposed to be negative.  Anyway, the +towgs84 tells cs2cs
> >> how to transform the WGS84 coordinates (in XYZ space) to whatever the
> >> output datum for RD is.  The +towgs84 or +datum for a different target
> >> coordinate systems will likely be different.  But, your source definition
> >> would stay the same.  If you have some reference coordinates, you can
> >> probably work out whether the towgs84 numbers are supposed to be positive
> >> or negative (provided those are good values).
> >> > 
> >> > Clear as mud?
> >> 
> >> This is precisely what I meant. Thanks!
> > 
> > But the 'fix' was to change the description of the source lat/longs from
> > 
> > 	+proj=latlong +ellps=WGS84
> > to
> > 	+proj=latlong +ellps=bessel
> > 
> > After the '+to' I always had +ellps=bessel to describe the desired
> > result. That was not changed.
> > 
> > Confusion here continues...
> > 
> >> 
> >> So play around with those +towgs84 parms, until you can reproduce your
> >> reference values. There must be decimetre precision shift values
> >> somewhere too, as I know the triangulation to be that precise. They must
> >> know at the cadastral survey in Apeldoorn. Here is their on-line
> >> transformer:
> >> 
> >> https://RDinfo.kadaster.nl/rd/transformator.html
> > 
> > I have looked at that. In summary, the conversion that does the best
> > (almost identical values) is:
> > 
> > +proj=latlong +ellps=bessel +to
> > +proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889
> > +k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel +units=m +no_defs
> > 
> > The one that was off by at least 60 meters was:
> > 
> > +proj=latlong +ellps=wgs84 +to
> > +proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889
> > +k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel +units=m +no_defs
> > 
> > -- 
> > Roger Oberholtzer
> > OPQ Systems AB
> > 
> > 
> > _______________________________________________
> > Proj mailing list
> > Proj at lists.maptools.org
> > http://lists.maptools.org/mailman/listinfo/proj
> > 
> > 
> 
-- 
Roger Oberholtzer

OPQ Systems AB
Ramböll Sverige AB
Kapellgränd 7
P.O. Box 4205
SE-102 65 Stockholm, Sweden

Tel: Int +46 8-615 60 20
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