[Proj] Amersfoort / RD New

[Roger Oberholtzer]

I downloaded the grid shift file from
http://www.kadaster.nl/transformatie-van-coordinaten

I am not using it yet. I took one of the sample points from the Use doc
that came with it to see what I got compared to the expected. For example:

Zuid-Limburg:
        Ref:    Latitude:   50.7925849160 Longitude:    5.7737955480
Altitude:    245.948
        Ref:    Easting:       182260.450 Northing:       311480.670
Altitude:    200.000
        Proj4:  Easting:       182225.909 Northing:       311388.163
Altitude:    245.948    98.746 meters from Ref

The reference values are ETRS89. But I cannot think that accounts to 100
meters of difference. My proj spec is:

     +proj=sterea
     +lat_0=52.15616055555555
     +lon_0=5.38763888888889
     +k=0.9999079
     +x_0=155000
     +y_0=463000
     +ellps=bessel

+towgs84=565.4174,50.3319,465.5542,-0.398957388243134,0.343987817378283,-1.87740163998045,4.0725
     +units=m
     +no_defs

Doing this via the C API as I do for many other projections. These are
passed to pj_init_plus.

Would the grid shift make such a large correction?

On Tue, Nov 1, 2016 at 12:51 PM, Bas Couwenberg <sebastic at xs4all.nl> wrote:

> On 2016-11-01 12:33, Roger Oberholtzer wrote:
> > I am trying to get the Amersfoort / RD New projection working with
> > proj4. The users (a road authority in the Netherlands) claim to use
> > this definition with ESRI:
> >
> > PROJCS["RD_New",GEOGCS["GCS_Amersfoort",DATUM["D_Amersfoort",
> > SPHEROID["Bessel_1841",6377397.155,299.1528128]],
> > PRIMEM["Greenwich",0.0],
> > UNIT["Degree",0.0174532925199433]],
> > PROJECTION["Double_Stereographic"],
> > PARAMETER["False_Easting",155000.0],
> > PARAMETER["False_Northing",463000.0],
> > PARAMETER["Central_Meridian",5.38763888888889],
> > PARAMETER["Scale_Factor",0.9999079],
> > PARAMETER["Latitude_Of_Origin",52.15616055555555],UNIT["Meter",1.0]]
> >
> > I have started with the definition at
> > http://spatialreference.org/ref/epsg/amersfoort-rd-new/proj4/. The
> > projections from that are 100 meters from where they should be. I have
> > seen claims that the Spatial Reference definition is incorrect, and
> > that a better one is (it adds the +towgs84):
> >
> > “+proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889
> > +k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel
> > +towgs84=565.4174,50.3319,465.5542,-0.398957388243134,0.
> 343987817378283,-1.87740163998045,4.0725
> > +units=m +no_defs”
> >
> > Still no joy. My source values are WGS84 lat/long from a GPS receiver.
> >
> > Anyone have the correct proj4 definition for this?
>
> The +towgs84 parameters as published by the Dutch Kadaster are:
>
>   +towgs84=565.4171,50.3319,465.5524,-0.398957,0.343988,-1.877402,4.0725
>
> These are used in the epsg file from PROJ.4 4.9.3, see:
>
>   https://github.com/osgeonl/rdprojectie/blob/master/doc/ntv2grid.md
>
> Alternatively you can use the RDNAP grid shift files also published by
> Kadaster. If you're on Debian/Ubuntu you can install the proj-rdnap
> package (available in jessie-backports/non-free and Ubuntu wily and
> later), otherwise you can find the download link in the PROJ.4
> documentation at:
>
>   http://proj4.org/grids.html#netherlands
>   http://www.kadaster.nl/transformatie-van-coordinaten
>
> Use the link in the "Benadering transformatieprocedure" section to go to
> the request package and fill in the form. You'll be sent a download link
> by email.
>
> We've recently had a mini-seminar about the correct usage of RD in open
> source software, and started collecting reference information resulting
> from that in a git repository:
>
>   https://github.com/osgeonl/rdprojectie
>
> You'll find more information in the linked posts on the Dutch
> mailinglist.
>
> Kind Regards,
>
> Bas
> _______________________________________________
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-- 
Roger Oberholtzer
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