Hi all,
I would appreciate any hints as to how I can compare 2
WKT/OGRSpatialReference objects.
My goal is to make sure that a more detailed WKT (with authority codes
and explicit datum) corresponds (numerically) to a simpler one, such
as in the following examples.
I understand that the oSRSGDAL.exportToPrettyWkt() function can remove
AXIS, AUTHORITY and EXTENSION nodes, but how can I guarantee that the
PARAMETER nodes are in the same order? Does FixupOrdering() solve that
problem?
Furthermore, How could I compare the datums?
CF=[PROJCS["unnamed",
GEOGCS["unknown",
DATUM["unknown",
SPHEROID["Spheroid",6378137,298.2572221010002]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433]],
PROJECTION["Lambert_Conformal_Conic_2SP"],
PARAMETER["standard_parallel_1",-18],
PARAMETER["standard_parallel_2",-36],
PARAMETER["latitude_of_origin",0],
PARAMETER["central_meridian",134],
PARAMETER["false_easting",0],
PARAMETER["false_northing",0]]]
GDAL=[PROJCS["GDA94 / Geoscience Australia Lambert",
GEOGCS["GDA94",
DATUM["Geocentric_Datum_of_Australia_1994",
SPHEROID["GRS 1980",6378137,298.2572221010002,
AUTHORITY["EPSG","7019"]],
TOWGS84[0,0,0,0,0,0,0],
AUTHORITY["EPSG","6283"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4283"]],
PROJECTION["Lambert_Conformal_Conic_2SP"],
PARAMETER["standard_parallel_1",-18],
PARAMETER["standard_parallel_2",-36],
PARAMETER["latitude_of_origin",0],
PARAMETER["central_meridian",134],
PARAMETER["false_easting",0],
PARAMETER["false_northing",0],
UNIT["metre",1,
AUTHORITY["EPSG","9001"]],
AUTHORITY["EPSG","3112"]]]
Another option is exporting to PROJ.4 strings, but there are the
+towgs84 that shows up , plus some differences in +datum vs. +ellps.
e.g.
CF=[+proj=utm +zone=55 +ellps=WGS84 +units=m +no_defs ]
GDAL=[+proj=utm +zone=55 +datum=WGS84 +units=m +no_defs ]
or
CF=[+proj=lcc +lat_1=-18 +lat_2=-36 +lat_0=0 +lon_0=134 +x_0=0 +y_0=0
+ellps=GRS80 +units=m +no_defs ]
GDAL=[+proj=lcc +lat_1=-18 +lat_2=-36 +lat_0=0 +lon_0=134 +x_0=0
+y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs ]
many thanks,
Etienne
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