[gdal-dev] USGS 3DEP (3D Elevation Program) - feet should be metres, how can I fix this?

Fri Mar 22 06:02:57 PDT 2024

 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.rouault at 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.rouault at 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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