[Proj] proj and Dutch RD

[tvijlbrief]

No, it is not the same.

 "+proj=latlong +ellps=WGS84" will give incorrect results because there is
no conversion
from the Bessel to the WGS84 spheroid!

You can compare the results by trying both:

tom at giant:~$ cs2cs +init=epsg:4326 +to +init=epsg:28992
6 53
196139.44       557179.10 -41.78
tom at giant:~$ cs2cs +init=epsg:4326 +to +proj=sterea +lat_0=52.15616055555555
+lon_0=5.38763888888889+k=0.9999079 +x_0=155000 +y_0=463000 +ellps=WGS84
+units=m +nodefs
6 53
196114.10       557077.21 0.00

The error is about 25 meters!!

Tom



Roger Oberholtzer wrote:
> 
> 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
> Fax: Int +46 8-31 42 23
> 
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