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

[Conrad Bielski]

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.

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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