Hi Nate,
Have you looked at using the values returned from
Projection.getProjectionParameters? Here's some snippets from our code base...
====
Projection projection = ...
// put in form that's a little easier to interrogate...
Map<String, Parameter> parameterMap = new HashMap<String, Parameter>();
for (Parameter p : projection.getProjectionParameters()) {
parameterMap.put(p.getName(), p);
}
// check projection type
Parameter p = parameterMap.get("grid_mapping_name");
String gridMappingName = p == null ?
"LatLon" : // or "latitude_longitude"
p.getStringValue();
if ("lambert_conformal_conic".equals(gridMappingName)) {
Parameter p = parameterMap.get("earth_radius");
double earthRadius = p == null ? Double.NaN : p.getNumericValue();
// repeat for desired parameters:
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.5/apf.html#id2731485
}
===
Tom Kunicki
Center for Integrated Data Analytics
U.S. Geological Survey
8505 Research Way
Middleton, WI 53562
On Jun 10, 2011, at 1:01 PM, Mittler, Nathan wrote:
> Strike that John, I need access to N in order to do the rotation … so I’ll
> need a getN() added to LambertConformal instead. Honestly, we might as well
> add accessors for all the goodies J
>
> From: Mittler, Nathan
> Sent: Friday, June 10, 2011 10:39 AM
> To: 'John Caron'
> Cc: netcdf-java@xxxxxxxxxxxxxxxx
> Subject: RE: [netcdf-java] Bug/fix for processing grib v1 with proper earth
> radius.
>
> Hi John,
> Next week would be great! Also would we be able to add that getEarthRadius()
> method to LambertConformal? I can send you an updated file if that will be
> easier. The reason is that we need this value to help us properly rotate the
> wind vectors in our RUC files.
>
> As far as a data set goes … I’m reading a GRIB1 file (so it assumes a radius
> of 6367.47km). We have some legacy code that uses JGrib with this radius.
> I’ve been writing a new version of our library using NetCDF and was comparing
> projections at various points to get a warm fuzzy that the new code is
> working. When NetCDF was incorrectly using a radius of 6371.229km, the
> projections differed in some cases by 3 km. After making my fixes, the
> projections were within 4-5 decimal places of our JGrib version.
>
> Does that answer your question?
>
> Thanks again,
> Nate
>
> From: John Caron [mailto:caron@xxxxxxxxxxxxxxxx]
> Sent: Friday, June 10, 2011 10:08 AM
> To: Mittler, Nathan
> Cc: netcdf-java@xxxxxxxxxxxxxxxx
> Subject: Re: [netcdf-java] Bug/fix for processing grib v1 with proper earth
> radius.
>
> Hi Nathan:
>
> Sorry, ive been hoping I could just tell you it was done, but we have a delay
> for another reason, so 4.2.28 will probably be out next week and will have
> your fixes in it.
>
> the question I have is whether you have a dataset where theres any noticeable
> difference between earth radius 6371.229km and 6367.47km ?
>
> thanks for contributing your fix.
>
> John
>
> On 6/10/2011 10:56 AM, Mittler, Nathan wrote:
> Hi John,
> It’s been a couple of days, so I figured I should repost …. Any idea when the
> next release of netcdf-java will be? And whether or not my changes can make
> it in?
>
> Also, I was wondering if we could add a getEarthRadius() method to the
> LambertConformal projection?
>
> Thanks,
> Nate
>
> From: Mittler, Nathan
> Sent: Wednesday, June 08, 2011 8:06 AM
> To: 'John Caron'; netcdf-java@xxxxxxxxxxxxxxxx
> Subject: RE: [netcdf-java] Bug/fix for processing grib v1 with proper earth
> radius.
>
> Hi John,
> Glad I could help! I’m not quite sure I understand your question … are you
> asking whether these changes would somehow affect projections that use the
> standard Earth radius? I don’t have a test dataset that uses the standard
> radius at the moment, but I would assume there would be no issue.
>
> Also, do you have a feel for when the next release of netcdf-java will be?
> And whether or not these changes could make it in?
>
> Thanks,
> Nate
>
>
> From: netcdf-java-bounces@xxxxxxxxxxxxxxxx
> [mailto:netcdf-java-bounces@xxxxxxxxxxxxxxxx] On Behalf OfJohn Caron
> Sent: Wednesday, June 08, 2011 6:39 AM
> To: netcdf-java@xxxxxxxxxxxxxxxx
> Subject: Re: [netcdf-java] Bug/fix for processing grib v1 with proper earth
> radius.
>
> Hi Nathan:
>
> These changes look good, thanks very much. It looks like the two bugs
> cancelled each other out in use.
>
> BTW, are there any noticeable effects of the change of standard radius?
>
> John
>
>
>
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