[Proj] Amersfoort / RD New

Thu Nov 3 03:15:07 EST 2016

It could be that the old epsg file was still being used. The old
(non-working) definition of 4258 was:

     <4258> +proj=longlat +ellps=GRS80 +no_defs  <>

and the new (working) is:

     <4258> +proj=longlat +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +no_defs  <>

I think the problem was the missing +towgs84=0,0,0,0,0,0,0. Without that,
the grid shift file was not used. And probably other things as well.

I want to continue this without reference to files as they are too variable
to be reliable. Instead, I have moved everything to the command line so
there is no confusion about what is in each system's files.

The command:

     echo "50.792584908 5.773795547 174.9478" | \
         cs2cs -r +proj=longlat +ellps=GRS80 +towgs84=0,0,0,0,0,0,0
+no_defs \
              +to +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 -f %.4f

Now correctly provides:

182260.4500     311480.6701 129.0000

I have 'translated' this to the C API and all is working great. I have been
testing with the reference points that came with the grid file.

Texel:
        Ref:    Latitude:   53.1607530420 Longitude:    4.8247619120
Altitude:     42.861
        Ref:    Easting:       117380.120 Northing:       575040.340
Altitude:      1.000
        Calc:   Easting:       117380.120 Northing:       575040.340
Altitude:      1.000    0.000 meters from Ref
        Inv:    Latitude:   53.1607530431 Longitude:    4.8247619081
Altitude:   2455.773

Noord-Groningen:
        Ref:    Latitude:   53.4194820500 Longitude:    6.7767266740
Altitude:     42.359
        Ref:    Easting:       247380.560 Northing:       604580.780
Altitude:      2.000
        Calc:   Easting:       247380.560 Northing:       604580.780
Altitude:      2.000    0.000 meters from Ref
        Inv:    Latitude:   53.4194820513 Longitude:    6.7767266740
Altitude:   2426.971

Amersfoort:
        Ref:    Latitude:   52.1551728970 Longitude:    5.3872036570
Altitude:     43.255
        Ref:    Easting:       155000.000 Northing:       463000.000
Altitude:      0.000
        Calc:   Easting:       155000.000 Northing:       463000.000
Altitude:      0.000    0.000 meters from Ref
        Inv:    Latitude:   52.1551728982 Longitude:    5.3872036577
Altitude:   2478.331

Amersfoort 100m:
        Ref:    Latitude:   52.1551729100 Longitude:    5.3872036580
Altitude:    143.255
        Ref:    Easting:       155000.000 Northing:       463000.000
Altitude:    100.000
        Calc:   Easting:       155000.000 Northing:       463000.001
Altitude:    100.000    0.001 meters from Ref
        Inv:    Latitude:   52.1551728982 Longitude:    5.3872036577
Altitude:   8207.909

Zeeuws-Vlaanderen:
        Ref:    Latitude:   51.3686071520 Longitude:    3.3975885950
Altitude:     47.402
        Ref:    Easting:        16460.910 Northing:       377380.230
Altitude:      3.000
        Calc:   Easting:        16460.910 Northing:       377380.230
Altitude:      3.000    0.000 meters from Ref
        Inv:    Latitude:   51.3686071526 Longitude:    3.3975885974
Altitude:   2715.954

Zuid-Limburg:
        Ref:    Latitude:   50.7925849160 Longitude:    5.7737955480
Altitude:    245.948
        Ref:    Easting:       182260.450 Northing:       311480.670
Altitude:    200.000
        Calc:   Easting:       182260.450 Northing:       311480.671
Altitude:    200.000    0.001 meters from Ref
        Inv:    Latitude:   50.7925849065 Longitude:    5.7737955467
Altitude:  14091.766

Maasvlakte:
        Ref:    Latitude:   51.9473938980 Longitude:    4.0728871010
Altitude:     47.597
        Ref:    Easting:        64640.890 Northing:       440700.010
Altitude:      4.000
        Calc:   Easting:        64640.890 Northing:       440700.010
Altitude:      4.000    0.000 meters from Ref
        Inv:    Latitude:   51.9473938985 Longitude:    4.0728871025
Altitude:   2727.102

The Ref values are the sample points. The Calc is what I now get from proj
(yeah!). The Inv is what I get when I do an inverse projection of my
projected point. It is rather close to the original Ref. Except the
Altitude. I am using the shift file for that as well. Maybe it does not
allow an inverse on the Altitude? It is probably not a big issue for me.
More of a curiosity.

I am also curious about some additional sample points that came with the
grid shift data.

outside:
        Ref:    Latitude:   48.8430302100 Longitude:    8.7232602350
Altitude:     52.029
        Ref:    Easting:       400000.230 Northing:       100000.450
Altitude:      5.000

no_rd&geoid:
        Ref:    Latitude:   50.6874203920 Longitude:    4.6089718130
Altitude:     51.611
        Ref:    Easting:       100000.670 Northing:       300000.890
Altitude:      6.000

no_geoid:
        Ref:    Latitude:   51.1368251970 Longitude:    4.6013753610
Altitude:     50.967
        Ref:    Easting:       100000.670 Northing:       350000.890
Altitude:      6.000

no_rd:
        Ref:    Latitude:   52.4824408390 Longitude:    4.2684038890
Altitude:     49.944
        Ref:    Easting:        79000.010 Northing:       500000.230
Altitude:      7.000

edge_rd:
        Ref:    Latitude:   51.0039765320 Longitude:    3.8912478300
Altitude:     52.743
        Ref:    Easting:        50000.450 Northing:       335999.670
Altitude:      8.000

All of these fail. Since I expect our data to be within the area of the
grid shift file, I guess I do not need to worry about these. Out of
curiosity, how do others deal with such points?

-- 
Roger Oberholtzer
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