Projecting "rotated pole" coordinate system (from netCDF)

Discussion created by nelliott13 on Nov 21, 2011
Latest reply on Oct 25, 2019 by KatyAppletonUEA

Neither ArcGIS 9.3x or 10 seem to handle the importation of a netCDF file with a "rotated pole" coordinate system, listing the coordinate system as "unknown" in the data source tab.  Barring an automatic fix allowing the program to correctly read these data, how would I go about manually defining a projection so that they display properly?

The projection metadata provided in the netCDF file are as follows:
   char rotated_pole;
     :grid_mapping_name = "rotated_latitude_longitude";
     :grid_north_pole_latitude = 42.5; // double
     :grid_north_pole_longitude = 83.0; // double
     :_CoordinateTransformType = "Projection";
     :_CoordinateAxisTypes = "GeoX GeoY";

This is not enough information, in and of itself, to define a specific projection, which is probably why ArcGIS is having the problem.  Looking at the CF Metadata convention (specifically Appendix F), it appears that a third parameter of north_pole_grid_longitude defaults to 0 if not specified. 

I think these three parameters should be enough to manually define the projection, but I'm unsure of how to do so.  In the 'Define Projection' tool, what projected coordinate system should I select as a base?  There are no "rotated_pole" or "rotated_latitude_longitude" or "arctic somethingorother"...

Oh, and the purpose of defining the coordinate system is more so that I can project other things into the same coordinate system (for example a polygon representing the extent of the studyarea so that I can clip the netCDF data).

I apologize if this question has been asked/answered elsewhere, and thanks for your time!

Nathan Elliott