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Geography SRIDs in a Geometry column? RRS feed

  • Question

  • I've recently used ArcCatalog to load a shapefile into SQL Server Express 2012.  The shapefile data was in NAD83, a geographic coordinate system with SRID 4269 in SQL Server.  I forgot to set the data type in the import wizard though, and the data was imported into SQL Server as a "Geometry" column.  The weird thing is that every record was imported with an SRID of 4269.  How is it possible to have a Geographic SRID stored in a Geometry column?  I think this one is for Alistair :)

    Thanks,

    Spatial Cowboy

    Wednesday, October 9, 2013 9:03 PM

Answers

  • In SQL geometry, the SRID doesn't mean very much and you can use any integer for it. It is used to check that two coordinate systems are the same when doing spatial operations between geometries but the value of the SRID has no other effect on these operations since it is all planar geometry.

    In geography, the SRID is used to account for the datum when doing spatial operations (for example distances between points). Supported geography SRIDs are stored in the table sys.spatial_reference_systems and, indeed, 4269 is in there.

    If you want accurate distance and area calculations on your imported shapefile, then you should use geography with the appropriate SRID, otherwise you will end up with distance and area calculations in (inaccurate and relatively meaningless) decimal degrees. Converting to geography from geometry is easy to do in SQL Server.

    • Marked as answer by SpatialCowboy Thursday, November 9, 2017 8:08 PM
    Tuesday, October 15, 2013 10:12 AM

All replies

  • Hi,

    Thanks for posting question here.
    I am trying to involve someone more familiar with this topic for a further look at this issue. Sometime delay might be expected from the job transferring.Your patience is greatly appreciated.
    Thank you for your understanding and support.

    Thanks
    Candy Zhou


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    Friday, October 11, 2013 7:34 AM
  • Hi,

    Possible set by ArcCatalog itself?

    You can also modify it by yourself, http://technet.microsoft.com/en-us/library/bb933851.aspx


    Regards,
    Christian HL
    Microsoft Online Community Support


    Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

    Friday, October 11, 2013 8:17 AM
  • Hello

    why shouldn't it be possible? The storage of spatial data bound to a plane coordinate system like UTM (e. g. SRID = 25832), Gauss-Krueger (e. g. SRID = 31467) etc. requires the usage of datatype GEOMETRY.

    Regards,

    Klaus

    Monday, October 14, 2013 9:30 AM
  • In SQL geometry, the SRID doesn't mean very much and you can use any integer for it. It is used to check that two coordinate systems are the same when doing spatial operations between geometries but the value of the SRID has no other effect on these operations since it is all planar geometry.

    In geography, the SRID is used to account for the datum when doing spatial operations (for example distances between points). Supported geography SRIDs are stored in the table sys.spatial_reference_systems and, indeed, 4269 is in there.

    If you want accurate distance and area calculations on your imported shapefile, then you should use geography with the appropriate SRID, otherwise you will end up with distance and area calculations in (inaccurate and relatively meaningless) decimal degrees. Converting to geography from geometry is easy to do in SQL Server.

    • Marked as answer by SpatialCowboy Thursday, November 9, 2017 8:08 PM
    Tuesday, October 15, 2013 10:12 AM