[gdal-dev] Motion: adopt RFC 81: support for coordinate epochs in geospatial formats

jratike80 jukka.rahkonen at maanmittauslaitos.fi
Fri May 28 01:08:48 PDT 2021


I guess that by "data" you mean datasets like GeoJSON file or GeoTIFF image. 
For individual coordinates folks in the Finnish Geospatial Institute (FGI)
do conversions like in this cs2cs example 

echo 2258573.56109 1010806.43899 5859099.49087 2021.26 | cs2cs -d 4 --area
finland EPSG:7789 EPSG:4936

where "2021.26" after the x, y, and z coordinates is the epoch and it gets
used with this operation:

projinfo -s EPSG:7789 -t EPSG:4936 -o PROJ --area Finland
Operation No. 1:
NKG:ITRF2014_TO_FI, ITRF2014 to ETRS89 (EUREF-FIN), 0.01 m, Finland -
onshore and offshore.
PROJ string:
+step +proj=helmert +x=0 +y=0 +z=0 +rx=0 +ry=0 +rz=0 +s=0 +dx=0 +dy=0 +dz=0
+drx=8.5e-05 +dry=0.000531 +drz=-0.00077 +ds=0 +t_epoch=1989
+step +inv +proj=deformation +t_epoch=2000.0 +grids=eur_nkg_nkgrf17vel.tif
+step +proj=helmert +x=0.15651 +y=-0.10993 +z=-0.10935 +rx=-0.00312861
+ry=-0.00378935 +rz=0.00403512 +s=0.00529 +convention=position_vector +step
+proj=deformation +dt=-3 +grids=eur_nkg_nkgrf17vel.tif

The same thing with Python:

    transformer = pyproj.Transformer.from_pipeline("""
            +step +proj=helmert +x=0 +y=0 +z=0 +rx=0 +ry=0 +rz=0 +s=0 +dx=0
                +dy=0 +dz=0 +drx=8.5e-05 +dry=0.000531 +drz=-0.00077 +ds=0
                +t_epoch=1989 +convention=position_vector
            +step +inv +proj=deformation +t_epoch=2000.0
            +step +proj=helmert +x=0.15651 +y=-0.10993 +z=-0.10935
                +rx=-0.00312861 +ry=-0.00378935 +rz=0.00403512 +s=0.00529
            +step +proj=deformation +dt=-3 +grids=eur_nkg_nkgrf17vel.tif""")
    coord = transformer.transform(x_wgs84, y_wgs84, z_wgs84, year)

-Jukka Rahkonen-

Nyall Dawson wrote
> On Thu, 27 May 2021 at 23:40, Even Rouault <

> even.rouault@

> > wrote:
>> Hi,
>> - merging the underlying API without any format support is I believe of
>> little interest.
> Well.. it would give users the command line tools to do static <->
> dynamic transformation of data with the epoch specified in the command
> line arguments. That's a quite compelling feature on its own, as it
> could be used to transform data if the user has knowledge of the epoch
> from other sources (e.g. in some pdf doc provided with the data, or if
> they collected it themselves and know the correct epoch). I'm unaware
> of any other tool (commercial or open source) which currently allows
> this type of transformation.
> Nyall
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> gdal-dev at .osgeo

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