Re: [netcdf-java] ncWMS and ellipsoid-support in CF-1.2

• To: netcdf-java@xxxxxxxxxxxxxxxx
• Subject: Re: [netcdf-java] ncWMS and ellipsoid-support in CF-1.2
• From: Heiko Klein <Heiko.Klein@xxxxxx>
• Date: Wed, 24 Mar 2010 14:00:43 +0100

Hi Jon,

I just found some time to look at the source of netcdf-java 4.1. As far
as I can see, only some projections (LambertConformalConicEllipse,
AlbersEqualAreaEllipse, UTM) support ellipsoids, while the others use a
constant spherical earth with EARTH_RADIUS = 6371.229km

In particular, Stereographic projection doesn't support ellipsoids, so
this explains the offset in my maps.

Would be nice to have this assured by one of the unidata-developpers. I
mainly checked the ucar/unidata/geoloc/projection sources.

Best regards,

Heiko

On 2010-03-10 14:38, Jonathan Blower wrote:
> Hi Heiko,
> 
> This is a good question.  ncWMS relies on netcdf-java for converting coords 
> to wgs84 lat lon, so I'm copying this to the mailing list in the hope that 
> someone can enlighten me about ellipsoid support in the library.
> 
> Cheers, Jon
> 
> -----Original Message-----
> From: Heiko Klein <Heiko.Klein@xxxxxx>
> Sent: 09 March 2010 08:54
> To: Jonathan Blower <j.d.blower@xxxxxxxxxxxxx>
> Subject: ncWMS and ellipsoid-support in CF-1.2
> 
> Hi Jon,
> 
> I currently try to visualize some satellite ice-maps over the north-pole
> with ncWMS, but the data seems to be displaced by some 10-30km compared
> with the land-maps (generated by mapserver).
> 
> While geo-tools and therefore ncWMS support lots of coordinate reference
> systems for the presented maps, the support for ellipsoids was only
> added to CF-1.2. Do you know if ncWMS already supports the CF-1.2
> features like semi_major_axis/semi_minor_axis for input-files, or does
> it assume the CF-1.0 spherical earth with 6371km radius?
> 
> Best regards,
> 
> Heiko
> 

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  • Re: [netcdf-java] ncWMS and ellipsoid-support in CF-1.2
    • From: Jonathan Blower