Re: [netcdf-java] Bug/fix for processing grib v1 with proper earth radius.

  • To: "Tom Kunicki" <tkunicki@xxxxxxxx>
  • Subject: Re: [netcdf-java] Bug/fix for processing grib v1 with proper earth radius.
  • From: "Mittler, Nathan" <nathan.mittler@xxxxxxxxxx>
  • Date: Fri, 10 Jun 2011 15:33:39 -0700
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 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

 


This message is intended only for the addressee and may contain
information that is company confidential or privileged. Any technical
data in this message may be exported only in accordance with the U.S.
International Traffic in Arms Regulations (22 CFR Parts 120-130) or the
Export Administration Regulations (15 CFR Parts 730-774). Unauthorized
use is strictly prohibited and may be unlawful. If you are not the
intended recipient, or the person responsible for delivering to the
intended recipient, you should not read, copy, disclose or otherwise use
this message. If you have received this email in error, please delete
it, and advise the sender immediately.

 


This message is intended only for the addressee and may contain
information that is company confidential or privileged. Any technical
data in this message may be exported only in accordance with the U.S.
International Traffic in Arms Regulations (22 CFR Parts 120-130) or the
Export Administration Regulations (15 CFR Parts 730-774). Unauthorized
use is strictly prohibited and may be unlawful. If you are not the
intended recipient, or the person responsible for delivering to the
intended recipient, you should not read, copy, disclose or otherwise use
this message. If you have received this email in error, please delete
it, and advise the sender
immediately._______________________________________________
netcdf-java mailing list
netcdf-java@xxxxxxxxxxxxxxxx
For list information or to unsubscribe, visit:
http://www.unidata.ucar.edu/mailing_lists/

 

 

 

 

 

-
This message is intended only for the addressee and may contain information 
that is company confidential or privileged.  Any technical data in this message 
may be exported only in accordance with the U.S. International Traffic in Arms 
Regulations (22 CFR Parts 120-130) or the Export Administration Regulations (15 
CFR Parts 730-774). Unauthorized use is strictly prohibited and may be 
unlawful. If you are not the intended recipient, or the person responsible for 
delivering to the intended recipient, you should not read, copy, disclose or 
otherwise use this message. If you have received this email in error, please 
delete it, and advise the sender immediately. 
-                                                                               
                                                                                
                                                                                
        
  • 2011 messages navigation, sorted by:
    1. Thread
    2. Subject
    3. Author
    4. Date
    5. ↑ Table Of Contents
  • Search the netcdf-java archives: