[PROJ] Correcting metadata in GeoTIFF files

Fri Jan 28 04:08:34 PST 2022

Hi Even,

Thanks for the quick and clear reply. I now found the description for this use case at proj.org, which explicitly mentions the naptrans grid of the Netherlands as example (sorry for not RTFM). I have some remaining questions, though:

  *   Why is this use case not more common? This [1] was the standard way to get a transformation to a national compound CRS in PROJ4, right?
  *   Since the CRS of the GeoTIFF is the source-crs [2], does this mean that other software will would show the grid values at the latlon of the source-crs instead of at the latlon of the interpolation-crs?

Additional question on names and aliases:

  *   For EPSG:4289, the EPSG registry uses the name “Amersfoort”. However, we (the official authority of this CRS) never use this name. Since the name “Amersfoort” has been in EPSG for a long time, EPSG preferred not to correct this, but to add the official name “RD Bessel” as an alias in the EPSG registry. Can I use the official alias “RD Bessel” instead of the EPSG name “Amersfoort” for the WKT strings and/or the description in the metadata of the Geodetic TIFF Grids?

Regards, Jochem

[1] PROJ4-style transformation to national compound CRS of the Netherlands:

cs2cs +init=epsg:4937 +to +proj=sterea +lat_0=52.156160556 +lon_0=5.387638889 +k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel +nadgrids=rdtrans2018.gsb +units=m +geoidgrids=naptrans2018.gtx +vunits=m +no_defs

[2] Result of gdalinfo:

Driver: GTiff/GeoTIFF
Files: naptrans2018.tif
Size is 301, 481
Coordinate System is:
GEOGCRS["ETRF2000",
    DATUM["European Terrestrial Reference Frame 2000",
        ELLIPSOID["GRS 1980",6378137,298.257222101,
            LENGTHUNIT["metre",1]]],
    PRIMEM["Greenwich",0,
        ANGLEUNIT["degree",0.0174532925199433]],
    CS[ellipsoidal,3],
        AXIS["geodetic latitude (Lat)",north,
            ORDER[1],
            ANGLEUNIT["degree",0.0174532925199433]],
        AXIS["geodetic longitude (Lon)",east,
            ORDER[2],
            ANGLEUNIT["degree",0.0174532925199433]],
        AXIS["ellipsoidal height (h)",up,
            ORDER[3],
            LENGTHUNIT["metre",1]],
    USAGE[
        SCOPE["Geodesy."],
        AREA["Europe - onshore and offshore: Albania; Andorra; Austria; Belgium; Bosnia and Herzegovina; Bulgaria; Croatia; Cyprus; Czechia; Denmark; Estonia; Faroe Islands; Finland; France; Germany; Gibraltar; Greece; Hungary; Ireland; Italy; Kosovo; Latvia; Liechtenstein; Lithuania; Luxembourg; Malta; Moldova; Monaco; Montenegro; Netherlands; North Macedonia; Norway including Svalbard and Jan Mayen; Poland; Portugal; Romania; San Marino; Serbia; Slovakia; Slovenia; Spain; Sweden; Switzerland; United Kingdom (UK) including Channel Islands and Isle of Man; Vatican City State."],
        BBOX[32.88,-16.1,84.73,40.18]],
    ID["EPSG",7931]]
Data axis to CRS axis mapping: 2,1,3
Origin = (1.990000000000000,56.006250000000001)
Pixel Size = (0.020000000000000,-0.012500000000000)
Metadata:
  area_of_use=European Netherlands including EEZ of the North Sea
  AREA_OR_POINT=Point
  interpolation_crs_wkt=GEOGCRS[Amersfoort,DATUM[Amersfoort,ELLIPSOID[Bessel 1841,6377397.155,299.1528128,LENGTHUNIT[metre,1,ID[EPSG,9001]],ID[EPSG,7004]],ID[EPSG,6289]],CS[ellipsoidal,2,ID[EPSG,6422]],AXIS[latitude (Lat),north],AXIS[longitude (Lon),east],ANGLEUNIT[degree,0.0174532925199433,ID[EPSG,9102]],ID[EPSG,4289]]
  target_crs_epsg_code=5709
  TIFFTAG_COPYRIGHT=Nederlandse Samenwerking Geodetische Infrastructuur (NSGI). Creative Commons Attribution 4.0 International licence https://creativecommons/licenses/by/4.0/
  TIFFTAG_DATETIME=2022:01:28 00:00:00
  TIFFTAG_IMAGEDESCRIPTION=ETRF2000 (EPSG:7931) to NAP height (EPSG:5709). Converted from naptrans2018.gtx (last modified at 2019/03/22)
  TYPE=VERTICAL_OFFSET_GEOGRAPHIC_TO_VERTICAL
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (   1.9900000,  56.0062500) (  1d59'24.00"E, 56d 0'22.50"N)
Lower Left  (   1.9900000,  49.9937500) (  1d59'24.00"E, 49d59'37.50"N)
Upper Right (   8.0100000,  56.0062500) (  8d 0'36.00"E, 56d 0'22.50"N)
Lower Right (   8.0100000,  49.9937500) (  8d 0'36.00"E, 49d59'37.50"N)
Center      (   5.0000000,  53.0000000) (  5d 0' 0.00"E, 53d 0' 0.00"N)
Band 1 Block=301x6 Type=Float32, ColorInterp=Gray
  Description = geoid_undulation
  Unit Type: metre

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