[Proj] Parsing Lambert Conformal Conic in GDAL

Kyle Shannon kyle at pobox.com
Thu Jan 2 22:00:23 EST 2014


I've come across a proj.4 projection (lcc) that may not be parsed
correctly by GDAL/OGR.  If I roundtrip EPSG:3979 through gdalsrsinfo,
I lose a standard parallel (forgive the clutter):

kyle at kyle-hp-laptop:gdal$ gdalsrsinfo -o proj4 EPSG:3979
'+proj=lcc +lat_1=49 +lat_2=77 +lat_0=49 +lon_0=-95 +x_0=0 +y_0=0
+ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs '

kyle at kyle-hp-laptop:gdal$ gdalsrsinfo -o wkt '+proj=lcc +lat_1=49
+lat_2=77 +lat_0=49 +lon_0=-95 +x_0=0 +y_0=0 +ellps=GRS80
+towgs84=0,0,0,0,0,0,0 +units=m +no_defs '
PROJCS["unnamed",GEOGCS["GRS 1980(IUGG,

So, is:

+proj=lcc +lat_1=49 +lat_2=77 +lat_0=49 +lon_0=-95 +x_0=0 +y_0=0
+ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs

a completely valid proj.4 string?  Is it okay to set a lat_1=lat_0,
and also specify lat_2.  I suspect it is, but I haven't found any
concrete definition on limits (and I don't really think there are,
within reason).

Thought I'd consult the pros on the list to be sure.

There is a ticket on gdal trac at: http://trac.osgeo.org/gdal/ticket/5191



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