[gdal-dev] false easting and northing units

[Kirk Waters - NOAA Federal]

Hi,
I've run across an odd issue with GeoTIFFS using custom projections written
by GDAL and their interpretation in ArcPro. The specific case is doing a
projection for Michigan State Plane North using U.S. survey feet. [insert
embarrassing tale of another US agency wanting to always use survey feet
regardless of state legislation or that the federal government has been
officially metric for a long time]. For a file that should land in the
Michigan upper peninsula, ArcPro puts it in New Zealand. It appears the
issue is that Arc is interpreting the false easting as meters instead of
survey feet. If I do a define projection in ArcPro and make a custom
projection, it lands in the right place.

I used an old listgeo from the geotiff library to look at the tags both in
the original file and a copy that had define projection applied to see what
was different. They looked essentially the same, including having the same
value for the false easting. However, the Arc version had an extra tag
(3059) that wasn't in the GDAL produced one. An internet search turned up this
13-year old GDAL issue <https://trac.osgeo.org/gdal/ticket/3901>. If I
understand it correctly, a bug in GDAL was found that always used meters
for the false easting and northing. In addition to fixing that, a tag
(3059) was added to indicate this was fixed so software could differentiate
broken GDAL output from new output. It looks like Arc is looking for this
tag and if it's not there, false easting is assumed to be meters.

A few questions, assuming I interpreted that issue correctly:
1) Why is gdal not adding that 3059 tag? (GDAL command used is below)
2) If it's only supposed to be relevant to GDAL written files, why is Arc
writing it?
3) How do I get GDAL to add the tag?

Command used in file creation:
gdal_translate -a_srs 'COMPD_CS[PROJCS["NAD83 / Michigan
North",GEOGCS["NAD83",DATUM["North_American_Datum_1983",SPHEROID["GRS
1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],TOWGS84[0,0,0,0,0,0,0],AUTHORITY["EPSG","6269"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4269"]],PROJECTION["Lambert_Conformal_Conic_2SP"],PARAMETER["standard_parallel_1",47.08333333333334],PARAMETER["standard_parallel_2",45.48333333333333],PARAMETER["latitude_of_origin",44.78333333333333],PARAMETER["central_meridian",-87],PARAMETER["false_easting",26246666.6666667],PARAMETER["false_northing",0],UNIT["US
survey
foot",0.304800609601219],AXIS["X",EAST],AXIS["Y",NORTH]],VERTCRS["NAVD88
height (ftUS)",  VDATUM["North American Vertical Datum 1988"],
 CS[vertical,1],  AXIS["gravity-related height (H)",up],  LENGTHUNIT["US
survey foot",0.304800609601], ID["EPSG",6360]]]' -co TILED=YES -co
COMPRESS=DEFLATE -co PREDICTOR=3 -co BIGTIFF=IF_SAFER input.tif output.tif

Kirk Waters, PhD
NOAA Office for Coastal Management
Applied Sciences Program
coast.noaa.gov/digitalcoast
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