[gdal-dev] Validating a projection

[Doug McCorkle]

> On Jun 7, 2015, at 1:22 PM, Doug McCorkle <doug.mccorkle at gmail.com> wrote:
> 
>> 

[snip]

>> If you run gdalsrsinfo on this proj.4 string, you get the following WKT output:
>> 
>> PROJCS["unnamed",
>>   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","9108"]],
>>       AUTHORITY["EPSG","4269"]],
>>   PROJECTION["Albers_Conic_Equal_Area"],
>>   PARAMETER["standard_parallel_1",29.5],
>>   PARAMETER["standard_parallel_2",45.5],
>>   PARAMETER["latitude_of_center",23],
>>   PARAMETER["longitude_of_center",-96],
>>   PARAMETER["false_easting",0],
>>   PARAMETER["false_northing",0],
>>   UNIT["Meter",1]]
>> 
>> So it is really a matter of naming the same parameter. Using longitude_of_center will make all GDAL-dependent software happy, while the Central_Meridian might be invoked by ESRI.
>> 
>> See also http://www.remotesensing.org/geotiff/proj_list/albers_equal_area_conic.html for the official OGC WKT parameter names.
> 
> Andre,
> 
> Perfect! Thanks for the quick response and tip. 
> 
> Doug
> 

Andre,

I have updated the projection information with the recommended names. When I process GeoTIFF files with this projection everything works fine while all of the data is in memory and none of the Datasets in question are written to disk. If I write the data to disk in a GeoTIFF file and then try to reload the data and acquire the EPSG with the AutoIdentifyEPSG method I get the unsupported srs error. This is the output from gdalsrsinfo for the GeoTIFF file:

OGC WKT :
PROJCS["USA_Contiguous_Albers_Equal_Area_Conic_USGS_version",
    GEOGCS["NAD83",
        DATUM["North_American_Datum_1983",
            SPHEROID["GRS 1980",6378137,298.2572221010002,
                AUTHORITY["EPSG","7019"]],
            TOWGS84[0,0,0,0,0,0,0],
            AUTHORITY["EPSG","6269"]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433],
        AUTHORITY["EPSG","4269"]],
    PROJECTION["Albers_Conic_Equal_Area"],
    PARAMETER["standard_parallel_1",29.5],
    PARAMETER["standard_parallel_2",45.5],
    PARAMETER["latitude_of_center",23],
    PARAMETER["longitude_of_center",-96],
    PARAMETER["false_easting",0],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]]]

It appears that the projection EPSG code is dropped during the write process to geotiff. I do notice with other projections like EPSG:3857 that this is not the case with GeoTIFF files:

OGC WKT :
PROJCS["WGS 84 / Pseudo-Mercator",
    GEOGCS["WGS 84",
        DATUM["WGS_1984",
            SPHEROID["WGS 84",6378137,298.257223563,
                AUTHORITY["EPSG","7030"]],
            AUTHORITY["EPSG","6326"]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433],
        AUTHORITY["EPSG","4326"]],
    PROJECTION["Mercator_1SP"],
    PARAMETER["central_meridian",0],
    PARAMETER["scale_factor",1],
    PARAMETER["false_easting",0],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    EXTENSION["PROJ4","+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs"],
    AUTHORITY["EPSG","3857”]]

Is there a method for enabling the EPSG code to be passed through to the GeoTIFF file in a consistent manner? Thanks again.

Doug