[Proj] Amersfoort / RD New

[Roger Oberholtzer]

I have updated to 4.9.3. My rdnap file is identical to yours:

# RDNAP with NTv2 and VDatum
<rdnap> +proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889
+k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel
+nadgrids=rdtrans2008.gsb +geoidgrids=naptrans2008.gtx +units=m +no_defs
<>

If I run this:
cs2cs  -r +init=epsg:4258 +to +init=rdnap:rdnap -f %.4f

And provide these locations:

50.792584908 5.773795547 174.9478

I get this:

182225.9086     311388.1617 128.9976

Not the values you listed:

182260.4500     311480.6701 129.0000


I'm confused.



On Tue, Nov 1, 2016 at 3:28 PM, Bas Couwenberg <sebastic at xs4all.nl> wrote:

> On 2016-11-01 15:05, Roger Oberholtzer wrote:
> > 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?
>
>  From the proj-rdnap test script (using PROJ.4 4.9.3):
>
>   Test:   05 Zuid-Limburg
>   Exec:   cs2cs -r +init=epsg:4258 +to +init=rdnap:rdnap -f %.4f
>   Input:  50.792584908 5.773795547 174.9478
>   Output: 182260.4500     311480.6701 129.0000
>   Expect: 182260.4500     311480.6700 129.000
>   Test OK: From ETRS89 to RD/NAP - 05 Zuid-Limburg (Not identical, but
> within margin)
>
> The above uses the test values from "Use of RDTRANS2008 and
> NAPTRANS2008.pdf" included in the NTv2.zip, your values are different,
> not sure where you got those.
>
> The rdnap configuration for the above test contains:
>
>   # RDNAP with NTv2 and VDatum
>   <rdnap> +proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889
> +k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel
> +nadgrids=rdtrans2008.gsb +geoidgrids=naptrans2008.gtx +units=m +no_defs
> <>
>
> Try using the grid shift files for your test, it should be more accurate
> (at ground level) than using +towgs84 values.
>
> Kind Regards,
>
> Bas
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>



-- 
Roger Oberholtzer
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