[gdal-dev] [PATCH v2] Support Mercator_2SP in GeoTIFF

[Trent Piepho]

It looks like arcgis does not support Mercator_1SP in geotiff files.
It just ignores the scale factor and uses 1.0.  Which means in GDAL
and libgeotiff as they are now, there is no way to export Mercator
projections that don't have a scale of 1.0 to arcgis.

ArcGIS does support Mercator_2SP, but instead of placing the latitude
of true scale in ProjStdParallel1GeoKey, it uses
ProjNatOriginLatGeoKey.  Which seems to be plainly wrong, yet that's
what it does.

I wonder if ESRI used libgeotiff?  With unpatched libgeotiff, the only
way to get a latitude from a Mercator geotiff it to use one of the
origin latitude GeoKeys.  It's not correct, but it does allow one to
stick the number in the file and get it back out without having to
modify or understand any libgeotiff code.

It's possible that ArcGIS supports getting the latitude of true scale
from ProjStdParallel1GeoKey, even it it doesn't store it there.
Antii, could you test this file with ArcGIS?

https://drive.google.com/file/d/0BybuTedE9CLxak9iakZRTC00cHM/edit?usp=sharing

Pick file->download to get the geotiff file.

It should have projection information like this:
    PROJECTION["Mercator_2SP"],
    PARAMETER["standard_parallel_1",47.667],
    PARAMETER["central_meridian",0],
    PARAMETER["false_easting",0],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]]]
Origin = (-9278434.534151820465922,4143530.208984711207449)
Pixel Size = (240.003786961970206,-240.003786961970206)
Corner Coordinates:
Upper Left  (-9278434.534, 4143530.209) (123d32'26.22"W, 48d23'56.59"N)
Lower Left  (-9278434.534, 3984167.694) (123d32'26.22"W, 46d57'58.64"N)
Upper Right (-9165872.758, 4143530.209) (122d 2'30.76"W, 48d23'56.59"N)
Lower Right (-9165872.758, 3984167.694) (122d 2'30.76"W, 46d57'58.64"N)
Center      (-9222153.646, 4063848.952) (122d47'28.49"W, 47d41'15.43"N)