Hi Tom,
Unfortunately the projection parameters returned from LambertConformal
do not contain N or the earth radius. Should they be there?
Regards,
Nate
*From:*Tom Kunicki [mailto:tkunicki@xxxxxxxx]
*Sent:* Friday, June 10, 2011 2:28 PM
*To:* Mittler, Nathan
*Cc:* netcdf-java@xxxxxxxxxxxxxxxx
*Subject:* Re: [netcdf-java] Bug/fix for processing grib v1 with
proper earth radius.
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 goodiesJ
*From:*Mittler, Nathan
*Sent:*Friday, June 10, 2011 10:39 AM
*To:*'John Caron'
*Cc:*netcdf-java@xxxxxxxxxxxxxxxx <mailto: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 <mailto: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
<mailto: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>[mailto:netcdf-java-bounces@xxxxxxxxxxxxxxxx]*On
Behalf Of*John Caron
*Sent:*Wednesday, June 08, 2011 6:39 AM
*To:*netcdf-java@xxxxxxxxxxxxxxxx <mailto: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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