Thanks Even,
looks like a good workaround for the moment. Hopefully, the USGS will update
their files accordingly.
Thanks Kirk for kicking this up. I'm sure it is not trivial to fix such an
issue for a national dataset.
Have a great day,Conrad
On Friday, March 22, 2024 at 04:57:03 AM EDT, Even Rouault
<even.roua...@spatialys.com> wrote:
Hi,
having looked at the file, I believe GDAL behaves correctly given the metadata
in the file. This is clearly a unit type attached to the Band, and it should be
corrected by the data producer to reflect what is really used in it
One way to correct it on your side is for example this little Python snippet
from osgeo import gdal
ds = gdal.Open('test.tif')
ds.GetRasterBand(1).SetUnitType('metre')
As the file is used in read-only mode, this will generate an auxiliary .aux.xml
side car file overriding the unit.
You can also directly override the wrong metadata inside the TIFF with
ds = gdal.OpenEx('test.tif', open_options=['IGNORE_COG_LAYOUT_BREAK=YES'])
ds.GetRasterBand(1).SetUnitType('metre')
The IGNORE_COG_LAYOUT_BREAK=YES open option is because modifying TIFF metadata
causes it to be rewritten at the end of the file, which "breaks" the COG
convention. But that's still a perfectly valid GeoTIFF file, and will not
change anything for local use of such file. You could reprocess that to a fully
compliant COG with gdal_translate -of COG
Regarding how that is used by gdalwarp, the doc enhancement at
https://github.com/OSGeo/gdal/pull/9527 captures my initial attempt at
answering your questions.
Even
Le 22/03/2024 à 01:16, Conrad Bielski a écrit :
Just realised I should have put you also in CC
Here is my response message again.
Thanks Even,
you are correct about the tag number (I sent the incorrrect one).
I have provided a sample tif and some other descriptions of the issue here:
bad_geotiff - Google Drive
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bad_geotiff - Google Drive
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The three files there are the following: 1. A bad tiff (this is slightly
smaller; they are all pretty big). 2. A GDAL info dump (survey feet is almost
at the bottom) 3. A PDF with an explanation of the issue
thanks for your help. Conrad
On Thursday, March 21, 2024 at 04:49:57 PM EDT, Even Rouault
<even.roua...@spatialys.com> wrote:
Le 21/03/2024 à 21:45, Conrad Bielski via gdal-dev a écrit :
Hello GDALers,
I have a question about reading USGS 3DEP (3D Elevation Program) data. Inside
of this data, a GEOTIFF tag 42114 is provided which is causing problems with
datum shifts.
There's no such thing as a GEOTIFF tag 42114.
The closest tags are:
#define TIFFTAG_GDAL_METADATA 42112
#define TIFFTAG_GDAL_NODATA 42113
It would be helpuful if you could provide the file, or the result of a
"tiffdump -m 1000 the.tif" and "listgeo the.tif" on it.
And was the .tif.aux.xml provided with the TIFF, or computed by GDAL. Because
the information might come from it too.
So when I use GDAL to compute the datum shifts, the tag is read and interprets
that the DEM is showing elevation in 'feet' while the DEM is actually in
metres. The DEMs are in fact in meter elevations and meter UTM horizontal
coordinates. This is obviously erroneously integrated into the tag.
So my question is whether anyone has come across this issue and found a
solution? Is there a way to edit the offending tag so that it is correctly
interpreted as metres instead of feet? Other potential solutions so that GDAL
interprets the elevation correctly?
Thanks in advance for your help. I provide below the output of gdalinfo which
I hope could help with the offending info in bold.
Have a great day,
Conrad
Driver: GTiff/GeoTIFF
Files:I:\v3_us_3dep\asheville\ashevilleUSGS_1M_17_x34y392_NC_Phase5_2018_A18.tif
I:\v3_us_3dep\asheville\ashevilleUSGS_1M_17_x34y392_NC_Phase5_2018_A18.tif.aux.xml
Size is 10012, 10012
Coordinate System is:
PROJCRS["NAD83 / UTM zone 17N",
BASEGEOGCRS["NAD83",
DATUM["North American Datum 1983",
ELLIPSOID["GRS 1980",6378137,298.257222101,
LENGTHUNIT["metre",1]]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433]],
ID["EPSG",4269]],
CONVERSION["UTM zone 17N",
METHOD["Transverse Mercator",
ID["EPSG",9807]],
PARAMETER["Latitude of natural origin",0,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8801]],
PARAMETER["Longitude of natural origin",-81,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8802]],
PARAMETER["Scale factor at natural origin",0.9996,
SCALEUNIT["unity",1],
ID["EPSG",8805]],
PARAMETER["False easting",500000,
LENGTHUNIT["metre",1],
ID["EPSG",8806]],
PARAMETER["False northing",0,
LENGTHUNIT["metre",1],
ID["EPSG",8807]]],
CS[Cartesian,2],
AXIS["(E)",east,
ORDER[1],
LENGTHUNIT["metre",1]],
AXIS["(N)",north,
ORDER[2],
LENGTHUNIT["metre",1]],
USAGE[
SCOPE["Engineering survey, topographic mapping."],
AREA["North America - between 84°W and 78°W - onshore and offshore.
Canada - Nunavut; Ontario; Quebec. United States (USA) - Florida; Georgia;
Kentucky; Maryland; Michigan; New York; North Carolina; Ohio; Pennsylvania;
South Carolina; Tennessee; Virginia; West Virginia."],
BBOX[23.81,-84,84,-78]],
ID["EPSG",26917]]
Data axis to CRS axis mapping: 1,2
Origin = (339993.999958705157042,3920005.999981591943651)
Pixel Size = (1.000000000000000,-1.000000000000000)
Metadata:
AREA_OR_POINT=Area
Image Structure Metadata:
COMPRESSION=LZW
INTERLEAVE=BAND
LAYOUT=COG
PREDICTOR=3
Corner Coordinates:
Upper Left ( 339994.000, 3920006.000) ( 82d45'43.98"W, 35d24'38.21"N)
Lower Left ( 339994.000, 3909994.000) ( 82d45'36.92"W, 35d19'13.36"N)
Upper Right ( 350006.000, 3920006.000) ( 82d39' 7.17"W, 35d24'43.82"N)
Lower Right ( 350006.000, 3909994.000) ( 82d39' 0.55"W, 35d19'18.95"N)
Center ( 345000.000, 3915000.000) ( 82d42'22.15"W, 35d21'58.63"N)
Band 1 Block=512x512 Type=Float32, ColorInterp=Gray
Min=669.509 Max=1604.949
Minimum=669.509, Maximum=1604.949, Mean=988.295, StdDev=159.804
NoData Value=-999999
Overviews: 5006x5006, 2503x2503, 1251x1251, 625x625, 312x312
Unit Type: US survey foot
Metadata:
STATISTICS_APPROXIMATE=YES
STATISTICS_MAXIMUM=1604.9490966797
STATISTICS_MEAN=988.29463693706
STATISTICS_MINIMUM=669.50915527344
STATISTICS_STDDEV=159.80361228109
STATISTICS_VALID_PERCENT=100
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