<div dir="ltr"><div><div>I have updated to 4.9.3. My rdnap file is identical to yours:<br><br># RDNAP with NTv2 and VDatum<br><rdnap> +proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889<br>+k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel<br>+nadgrids=rdtrans2008.gsb +geoidgrids=naptrans2008.gtx +units=m +no_defs<br><><br><br></div>If I run this:<br>cs2cs -r +init=epsg:4258 +to +init=rdnap:rdnap -f %.4f<br><br></div>And provide these locations:<br><br><div>50.792584908 5.773795547 174.9478<br><br></div><div>I get this:<br><br></div><div>182225.9086 311388.1617 128.9976<br><br></div><div>Not the values you listed:<br><br>182260.4500 311480.6701 129.0000<br><br><br></div><div>I'm confused.<br><br><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Nov 1, 2016 at 3:28 PM, Bas Couwenberg <span dir="ltr"><<a href="mailto:sebastic@xs4all.nl" target="_blank">sebastic@xs4all.nl</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="HOEnZb"><div class="h5">On 2016-11-01 15:05, Roger Oberholtzer wrote:<br>
> I downloaded the grid shift file from<br>
> <a href="http://www.kadaster.nl/transformatie-van-coordinaten" rel="noreferrer" target="_blank">http://www.kadaster.nl/<wbr>transformatie-van-coordinaten</a><br>
><br>
> I am not using it yet. I took one of the sample points from the Use doc<br>
> that came with it to see what I got compared to the expected. For<br>
> example:<br>
><br>
> Zuid-Limburg:<br>
> Ref: Latitude: 50.7925849160 Longitude: 5.<a href="tel:7737955480" value="+17737955480">7737955480</a> Altitude:<br>
> 245.948<br>
> Ref: Easting: 182260.450 Northing: 311480.670 Altitude:<br>
> 200.000<br>
> Proj4: Easting: 182225.909 Northing: 311388.163 Altitude:<br>
> 245.948<br>
> 98.746 meters from Ref<br>
><br>
> The reference values are ETRS89. But I cannot think that accounts to<br>
> 100<br>
> meters of difference. My proj spec is:<br>
><br>
> +proj=sterea<br>
> +lat_0=52.15616055555555<br>
> +lon_0=5.38763888888889<br>
> +k=0.9999079<br>
> +x_0=155000<br>
> +y_0=463000<br>
> +ellps=bessel<br>
><br>
> +towgs84=565.4174,50.3319,465.<wbr>5542,-0.398957388243134,0.<wbr>343987817378283,-1.<wbr>87740163998045,4.0725<br>
> +units=m<br>
> +no_defs<br>
><br>
> Doing this via the C API as I do for many other projections. These are<br>
> passed to pj_init_plus.<br>
><br>
> Would the grid shift make such a large correction?<br>
<br>
</div></div> From the proj-rdnap test script (using PROJ.4 4.9.3):<br>
<br>
Test: 05 Zuid-Limburg<br>
Exec: cs2cs -r +init=epsg:4258 +to +init=rdnap:rdnap -f %.4f<br>
Input: 50.792584908 5.773795547 174.9478<br>
Output: 182260.4500 311480.6701 129.0000<br>
Expect: 182260.4500 311480.6700 129.000<br>
Test OK: From ETRS89 to RD/NAP - 05 Zuid-Limburg (Not identical, but<br>
within margin)<br>
<br>
The above uses the test values from "Use of RDTRANS2008 and<br>
NAPTRANS2008.pdf" included in the NTv2.zip, your values are different,<br>
not sure where you got those.<br>
<br>
The rdnap configuration for the above test contains:<br>
<br>
# RDNAP with NTv2 and VDatum<br>
<rdnap> +proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889<br>
+k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel<br>
+nadgrids=rdtrans2008.gsb +geoidgrids=naptrans2008.gtx +units=m +no_defs<br>
<><br>
<br>
Try using the grid shift files for your test, it should be more accurate<br>
(at ground level) than using +towgs84 values.<br>
<div class="HOEnZb"><div class="h5"><br>
Kind Regards,<br>
<br>
Bas<br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br><div class="gmail_signature" data-smartmail="gmail_signature">Roger Oberholtzer</div>
</div>