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Author Topic: NAD83 (2011) Prj fail in meta data  (Read 4610 times)

Phogi

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NAD83 (2011) Prj fail in meta data
« on: November 16, 2016, 06:10:40 AM »
Hi,

I'm trying to work my data on NAD83(2011) epsg: 6318, but then when I export the DEM, its metadata will give

GEOGCS["NAD83(2011)",
    DATUM["unknown",
        SPHEROID["GRS 1980",6378137,298.2572221010002,
            AUTHORITY["EPSG","7019"]],
        AUTHORITY["EPSG","1116"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","6318"]]

The prj is defined by PhotoScan. The same issue will happen if I define my prj with geoid definition in it, that the PROJ will be "unknown" in this case.

Is it a bug or I misunderstand the way it should work?

Thanks a lot for any help on this.

Alexey Pasumansky

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Re: NAD83 (2011) Prj fail in meta data
« Reply #1 on: November 16, 2016, 02:20:27 PM »
Hello Phogi,

PhotoScan is writing EPSG code to the file header, according to the GeoTIFF specification. There's no field for the coordinate system name, so recognition of the code is up to the application used for the file opening. If it "knows" the given code it would display the proper name.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Phogi

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Re: NAD83 (2011) Prj fail in meta data
« Reply #2 on: November 24, 2016, 01:08:23 AM »
Hi Alexey,

Thank you for the explain, however, I find this issue occurs only when it is NAD83 (2011). If I change the GCS to EPSG:4269 NAD83, then the DEM/Ortho TIF will be readable like:
   GEOGCS["NAD83",
    DATUM["North_American_Datum_1983",
        SPHEROID["GRS 1980",6378137,298.2572221010002,
            AUTHORITY["EPSG","7019"]],
        AUTHORITY["EPSG","6269"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","4269"]]

However, if I process the data in NAD83(2011) or with NAVD88, then it will return:
  GEOGCS["NAD83(2011)",
    DATUM["unknown",
        SPHEROID["GRS 1980",6378137,298.2572221010002,
            AUTHORITY["EPSG","7019"]],
        AUTHORITY["EPSG","1116"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","6318"]]

Would this be a problem only for NAD83 (2011)? Since if I use Compound PRJ it will return the header as Proj_CS as "noname", as well as DATUM "unknown".

Thanks a lot!

Phogi

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Re: NAD83 (2011) Prj fail in meta data
« Reply #3 on: December 06, 2016, 02:13:09 AM »
Does anyone find this is a problem? Any suggestions would be much appreciated!

Alexey Pasumansky

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Re: NAD83 (2011) Prj fail in meta data
« Reply #4 on: December 08, 2016, 04:01:07 PM »
Hello Phogi,

Do you have any file in EPSG::6318 system that is correctly interpreted in your application?

GeoTIFF exported from PhotoScan contains only the code, not the name of the coordinate system, so it looks like the application that you are using to read the TIFF header "knows" code 4269 and doesn't "know" 6318.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Phogi

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Re: NAD83 (2011) Prj fail in meta data
« Reply #5 on: December 13, 2016, 02:46:54 AM »
Hello Alexey,

Thank you very much, this solved my question! Thank you!

Best wishes,