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NCDF_COORD

NCDF_COORD

Name


      NDCF_COORD

Purpose



      The purpose of this function is to translate map projection and grid information
      in a netCDF file into a map coordinate object (MAPCOORD) that can be used to
      georeference images found in a netCDF file. Both the Coyote and Catalyst Libraries
      are required to be on your IDL PATH.

Author



        FANNING SOFTWARE CONSULTING
        1645 Sheely Drive
        Fort Collins
        CO 80526 USA
        Phone: 970-221-0438
        E-mail: davidf@dfanning.com

Category



      Image display and map projection.

Calling Sequence



      mapCoord = NCDF_Coord( netCDF_Filename )
             

Arguments


 
    netCDF_Filename: The name of a netCDF file from which map projection and grid
                        information can be obtained.
                       

Input Keywords


 
    GRID_COLOR: The name of a color the map grid should be displayed with. The default
                          is "indian red". Color names are those supported by cgColor.
                         
    MAP_GRID: If a MapCoord object is made successfully, then setting this keyword
                          will add a Map_Grid object to the MapCoord object.
    MAP_OUTLINE: If a MapCoord object is made successfully, then setting this keyword
                          will add a Map_Outline object to the MapCoord object.
                       
    OUTLINE_COLOR: The name of a color the map outline should be displayed with. The default
                          is "indian red". Color names are those supported by cgColor.
                       
    SILENT: IDL cannot map every GeoTiff image to a supported map projection or datum.
                          Normally, if the GeoTIFF image is unsupported, an error message is issued.
                          Setting this keyword will suppress such error messages. If you do this, you
                          MUST check the SUCCESS keyword to see if the program ran successfully. (Of
                          course, it is a good idea to check it in any case!)
                         
  USE_LATLON: If this keyword is set, the boundary ranges will be forced to be determined
                          from the latitude and longitude arrays in the file.
                         

Output Keywords


                   
    SUCCESS: An output variable that will contain a 1 if the map coordinate object was
                          created successfully. Or to a 0 if it was not created successfully.
                         
    XRANGE: An output variable containing the X range (outside boundaries) of the
                          map projection grid in the file, if it can find them.
                         
    YRANGE: An output variable containing the Y range (outside boundaries) of the
                          map projection grid in the file, if it can find them.
                         

Return Value


 
    mapCoord A MAPCOORD object that can be used as the data coordinate object for
                          an image. Creation of this object requires that the Catalyst Library
                          be on your IDL path.
                         

Notes


 
    It is not possible to have a one-to-one mapping between every netCDF file and a map projection
    in IDL, since IDL has a limited number of map projections and datums available. And, even at that,
    I have not implemented all of IDL's map projections or datums, only those that I thought were most
    likely to be encountered in my own work. If you run into a netCDF file that does not work in this
    code (either because of an error in the code or because it is not supported), please contact me.
    I am interested in supporting as many netCDF files as possible and I will take pains to do so if
    I know they are needed.
   

Restrictions


 
    Programs from both the Coyote and Catalyst Libraries are required to run this code.
   
      http://www.dfanning.com/catalyst/howtoinstall.html

Modification History



      Written by: David W. Fanning, 20 Feb 2010, DWF.
      Added XRANGE and YRANGE keywords to return the map projection grid boundaries, if
          they can be found in the netCDF file. 21 Feb 2010. DWF.
      Found a problem when navigating Polar Stereograpic images and TRUE_SCALE_LATITUDE.
          22 Mar 2010. DWF
      Added USE_LATLON keyword. 31 Mar 2010. DWF.
      Bug resulted in "half-pixel" being "full-pixel". Fixed. Borders now conform to
          NSIDC-supplied borders. 6 April 2010. DWF
      Typo in code that computes boundary when reading latitude and longitude arrays.
          Fixed so that semi-minor axes is used correctly. 15 April 2010. DWF
      Fixed a leaking memory problem from failing to delete the file object
          created in the program when finished with it. 19 July 2010. DWF.



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