Re: Problem with Albers and Spherical Earth

Sorry, we only have the spherical case for Albers Equal Area. the 
closed-form elliptical looks pretty hairy. There are often good 
numerical solutions that are much faster, but i dont know of any java 
implementations.

Roland Viger wrote:
> Hi Rich,
>
> Glad to see that something/anything comes up at this early point.
>
> It would be nice to figure out the georeferencing issue. I suppose I 
> could reproject all this stuff into something that is more readily 
> handled (like geographic coordinates? not sure that ArcInfo will go to 
> albers on a sphere...) and then convert again to netcdf. Probably good 
> to think a few minutes before undertaking that.
>
> Roland
>
>
> From:   Rich Signell <address@hidden>
> To:     Roland Viger <address@hidden>
> Cc:     John Caron <address@hidden>
> Date:   10/08/2009 03:29 PM
> Subject:        Problem with Albers and Spherical Earth
> Sent by:        address@hidden
>
>
> ------------------------------------------------------------------------
>
>
>
> Roland,
>
> Attached is the NcML for your uniformly spaced Albers Equal Area
> Delaware grid, and while NetCDF-Java figured out the geospatial
> coordinates,  it didn't plot in exactly the right place (see
> attached).
>
> Do you think folks will mind?  ;-)
>
> I figured that this was probably an ellipsoid issue, realizing that I
> hadn't specified a datum or ellipsoid.
>
> But then I discovered (remembered?) that it isn't possible to specify
> anything -- the Unidata Common Data Model assumes a spherical earth
> for Albers
>
> http://www.unidata.ucar.edu/software/netcdf-java/reference/StandardCoordinateTransforms.html
>
> and of course this data uses the GRS80 Spheroid.  ;-(
>
> I tried adding an inverse_flattening, hopefully, but nothing happened,
> so I guess the Albers Equal Area routine would have to be improved for
> this to work correctly.
>
> John, please correct me if I'm wrong.
>
> -Rich
> --
> Dr. Richard P. Signell   (508) 457-2229
> USGS, 384 Woods Hole Rd.
> Woods Hole, MA 02543-1598
> [attachment "2009-10-08_1650.png" deleted by Roland 
> Viger/WRD/USGS/DOI] [attachment "de.ncml" deleted by Roland 
> Viger/WRD/USGS/DOI]