<html><head></head><body><div class="yahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;"><div dir="ltr" data-setdir="false"><div>Hello GDALers,<br><br>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.<br><br>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.<br><br>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?<br><br>Thanks in advance for your help. I provide below the output of gdalinfo which I hope could help with the offending info in bold.<br><br>Have a great day,<br>Conrad<br><br></div><br></div><div><br></div><div><br></div><div dir="ltr" data-setdir="false"><div>Driver: GTiff/GeoTIFF<br>Files: I:\v3_us_3dep\asheville\ashevilleUSGS_1M_17_x34y392_NC_Phase5_2018_A18.tif<br> I:\v3_us_3dep\asheville\ashevilleUSGS_1M_17_x34y392_NC_Phase5_2018_A18.tif.aux.xml<br>Size is 10012, 10012<br>Coordinate System is:<br>PROJCRS["NAD83 / UTM zone 17N",<br> BASEGEOGCRS["NAD83",<br> DATUM["North American Datum 1983",<br> ELLIPSOID["GRS 1980",6378137,298.257222101,<br> LENGTHUNIT["metre",1]]],<br> PRIMEM["Greenwich",0,<br> ANGLEUNIT["degree",0.0174532925199433]],<br> ID["EPSG",4269]],<br> CONVERSION["UTM zone 17N",<br> METHOD["Transverse Mercator",<br> ID["EPSG",9807]],<br> PARAMETER["Latitude of natural origin",0,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8801]],<br> PARAMETER["Longitude of natural origin",-81,<br> ANGLEUNIT["degree",0.0174532925199433],<br> ID["EPSG",8802]],<br> PARAMETER["Scale factor at natural origin",0.9996,<br> SCALEUNIT["unity",1],<br> ID["EPSG",8805]],<br> PARAMETER["False easting",500000,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8806]],<br> PARAMETER["False northing",0,<br> LENGTHUNIT["metre",1],<br> ID["EPSG",8807]]],<br> CS[Cartesian,2],<br> AXIS["(E)",east,<br> ORDER[1],<br> LENGTHUNIT["metre",1]],<br> AXIS["(N)",north,<br> ORDER[2],<br> LENGTHUNIT["metre",1]],<br> USAGE[<br> SCOPE["Engineering survey, topographic mapping."],<br>
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."],<br> BBOX[23.81,-84,84,-78]],<br> ID["EPSG",26917]]<br>Data axis to CRS axis mapping: 1,2<br>Origin = (339993.999958705157042,3920005.999981591943651)<br>Pixel Size = (1.000000000000000,-1.000000000000000)<br>Metadata:<br> AREA_OR_POINT=Area<br>Image Structure Metadata:<br> COMPRESSION=LZW<br> INTERLEAVE=BAND<br> LAYOUT=COG<br> PREDICTOR=3<br>Corner Coordinates:<br>Upper Left ( 339994.000, 3920006.000) ( 82d45'43.98"W, 35d24'38.21"N)<br>Lower Left ( 339994.000, 3909994.000) ( 82d45'36.92"W, 35d19'13.36"N)<br>Upper Right ( 350006.000, 3920006.000) ( 82d39' 7.17"W, 35d24'43.82"N)<br>Lower Right ( 350006.000, 3909994.000) ( 82d39' 0.55"W, 35d19'18.95"N)<br>Center ( 345000.000, 3915000.000) ( 82d42'22.15"W, 35d21'58.63"N)<br>Band 1 Block=512x512 Type=Float32, ColorInterp=Gray<br> Min=669.509 Max=1604.949 <br> Minimum=669.509, Maximum=1604.949, Mean=988.295, StdDev=159.804<br> NoData Value=-999999<br> Overviews: 5006x5006, 2503x2503, 1251x1251, 625x625, 312x312<br> <b>Unit Type: US survey foot</b><br> Metadata:<br> STATISTICS_APPROXIMATE=YES<br> STATISTICS_MAXIMUM=1604.9490966797<br> STATISTICS_MEAN=988.29463693706<br> STATISTICS_MINIMUM=669.50915527344<br> STATISTICS_STDDEV=159.80361228109<br> STATISTICS_VALID_PERCENT=100</div></div><div dir="ltr" data-setdir="false"><br></div></div></body></html>