oh.... so I was wrong and you've spotted the reason for what Greg
notices. So this is (was) a GDAL 3.3 specific bug (3.2 is fine).
GDAL should have passed HUGE_VAL when no explicit time is specified,
which would be interpreted by PROJ as ignoring the time-dependent parts
(or equivalently using the reference epoch of the transformation, which
nullifies the effect of those time-dependent parts), but it incorrectly
passes 0 currently
Transformation at epoch 0:
$ echo 100 -50 0 0 | gdaltransform -s_srs EPSG:6319 -t_srs EPSG:7912
100.000520678775 -49.9999650963593 1.20454746671021
==> ~ 100 m shift
Transformation at epoch 2010;
$ echo 100 -50 0 2010 | gdaltransform -s_srs EPSG:6319 -t_srs EPSG:7912
100.00001055598 -49.9999754213041 0.900845746509731
Current incorrect behavior is the same as at epoch 0
$ echo 100 -50 | gdaltransform -s_srs EPSG:6319 -t_srs EPSG:7912
100.000520678775 -49.9999650963593 1.20454746671021
With fix queued in https://github.com/OSGeo/gdal/pull/3738
we now get the same as epoch 2010
$ echo 100 -50 | gdaltransform -s_srs EPSG:6319 -t_srs EPSG:7912
100.00001055598 -49.9999754213041 0.900845746509731
Even
Le 24/04/2021 à 17:13, Javier Jimenez Shaw a écrit :
Just one idea: which time is setting GDAL (and/or PROJ understanding)
on the transformation if nothing is specified? Is it the same as in cs2cs?
That transformation is time dependent.
I read somewhere that the "default" value is not the same (but my
memory is not very reliable).
Cheers.
.___ ._ ..._ .. . ._. .___ .. __ . _. . __.. ... .... ._ .__
Entre dos pensamientos racionales
hay infinitos pensamientos irracionales.
On Sat, 24 Apr 2021 at 16:58, Even Rouault <[email protected]
<mailto:[email protected]>> wrote:
Greg,
There's a high chance for this to be completely PROJ behavior. GDAL
hardly knows about CRS those days :-)
Could you share your input and output files ?
Also set CPL_DEBUG=PROJ and PROJ_DEBUG=2 as environment variables
to see
which transformations PROJ pickup : look for lines starting with
"PROJ:
Using coordinate operation ..."
With latest PROJ master (and also 6.3.2), I see that
projinfo -s EPSG:6319 -t EPSG:7912 -o PROJ
Candidate operations found: 1
-------------------------------------
Operation No. 1:
unknown id, Conversion from NAD83(2011) (geog3D) to NAD83(2011)
(geocentric) + Inverse of ITRF2014 to NAD83(2011) (1) + Conversion
from
ITRF2014 (geocentric) to ITRF2014 (geog3D), 0 m, Puerto Rico -
onshore
and offshore. United States (USA) onshore and offshore - Alabama;
Alaska; Arizona; Arkansas; California; Colorado; Connecticut;
Delaware;
Florida; Georgia; Idaho; Illinois; Indiana; Iowa; Kansas; Kentucky;
Louisiana; Maine; Maryland; Massachusetts; Michigan; Minnesota;
Mississippi; Missouri; Montana; Nebraska; Nevada; New Hampshire; New
Jersey; New Mexico; New York; North Carolina; North Dakota; Ohio;
Oklahoma; Oregon; Pennsylvania; Rhode Island; South Carolina; South
Dakota; Tennessee; Texas; Utah; Vermont; Virginia; Washington; West
Virginia; Wisconsin; Wyoming. US Virgin Islands - onshore and
offshore.
PROJ string:
+proj=pipeline
+step +proj=axisswap +order=2,1
+step +proj=unitconvert +xy_in=deg +z_in=m +xy_out=rad +z_out=m
+step +proj=cart +ellps=GRS80
+step +inv +proj=helmert +x=1.0053 +y=-1.9092 +z=-0.5416
+rx=0.0267814
+ry=-0.0004203 +rz=0.0109321 +s=0.00037 +dx=0.0008
+dy=-0.0006
+dz=-0.0014 +drx=6.67e-05 +dry=-0.0007574 +drz=-5.13e-05
+ds=-7e-05
+t_epoch=2010 +convention=coordinate_frame
+step +inv +proj=cart +ellps=GRS80
+step +proj=unitconvert +xy_in=rad +z_in=m +xy_out=deg +z_out=m
+step +proj=axisswap +order=2,1
So it applies a time-dependent Helmert transformation, which has also
non-time dependent terms.
However trying a bit, the transformation seems to introduce a
shift of
about ~1 m or so, not 35 m
$ echo 50 -100 0 | cs2cs -d 8 EPSG:6319 EPSG:7912
50.00000754 -100.00001400 -0.68652183
$ echo 50 -100 50.00000754 -100.00001400 | geod -I +ellps=GRS80
-50d7'11.377" 129d52'48.584" 1.308
Even
Le 24/04/2021 à 16:39, Greg Troxel a écrit :
> Even Rouault <[email protected]
<mailto:[email protected]>> writes:
>
>> - http://download.osgeo.org/gdal/3.3.0/gdal-3.3.0beta1.tar.gz
<http://download.osgeo.org/gdal/3.3.0/gdal-3.3.0beta1.tar.gz>
> The tl;dr is:
>
> - I'm seeing bad transforms NAD83/ITRF with 3.3.0beta1 but I
do not
> have any basis to blame 3.3.0 because a lot of other things
are in
> flux.
>
> - If you are using 3.3.0beta1 and transforms I suggest
looking at your
> output data.
>
>
>
> I have noticed a problem but I have little idea where it is. I
will be
> looking into it myself but I wanted to mention it so that others
could
> be on the lookout.
>
> Besides updating to gdal, I'm doing a general software
freshening and
> rebuilding lots of things, but aside from the gdal beta my geo
packages
> haven't changed versions. I have proj 6.3.2 with installed
grids, which
> was just rebuilt.
>
> The background is that I'm mostly working in EPSG:6319 which is
> NAD83(2011).
>
> I transform to EPSG:7912 which is ITRF2014 to display the data on
> leaflet webmaps (as a proxy for WGS84 to avoid null transforms).
>
> I noticed that my points on the webmap were very far off,
displaced very
> roughly 35m ESE. I then put an NAD83 version in the webspace,
and that
> made things look ok (with the ~1 meter error from treating NAD83 and
> ITRF2014 as equal, surely).
>
> I'm extracting things from a geopackage in 6319 like
>
> ogr2ogr -f GeoJSON -t_srs "EPSG:7912" -s_srs "EPSG:6319"
FOO/issues.geojson foo.gpkg issues
> ogr2ogr -f GeoJSON -t_srs "EPSG:6319" -s_srs "EPSG:6319"
FOO/issues-nad83.geojson foo.gpkg issues
>
> which has previously been fine. I'm definitely getting very large
> offsets from two files extracted seconds apart from the very same
> geopackage.
>
> So this is not a request for help, but if you are using ogr2ogr to
> transform datums, and you are using gdal 3.3.0beta1 especially
with proj
> 6, I'd suggest a quick look at your output data to see if it
seems ok.
>
> I will be retesting after all the software rebuilds are done, and
> rolling back to released gdal. (Yes, I know proj 6.3 is old and
that I
> should update.)
>
> Thanks,
> Greg
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