Re: netCDF and other things

• To: dmurray@xxxxxxxxxxxxxxxx
• Subject: Re: netCDF and other things
• From: "Kevin Manross" <kevin.manross@xxxxxxxx>
• Date: Tue, 19 Aug 2003 12:58:11 -0500

Thank you all very much for your responses!

Please read below for a follow-up qustion.


Don Murray wrote:
 >
> Kevin Manross wrote:
 >
>> I would like to obtain the following:
>>
>> latitude = corner_lat - lat_index*LatGridSpacing
>> longitude = corner_lon + lon_index*LonGridSpacing
>> elevation = DEM
>>
>> I have all the data I need in the netCDF file, specifically,
>> (lat_index = Lat, corner_lat = Latitude, LatGridSpacing
>> LatGridSpacing):
>>
>> netcdf kiwaTerrain {
>> dimensions:
>>         Lat = 1079 ;
>>         Lon = 1298 ;
>> variables:
>>         float DEM(Lat, Lon) ;
>>                 DEM:Units = "Meters" ;
>>
>> // global attributes:
>>                 :TypeName = "DEM" ;
>>                 :DataType = "LatLonGrid" ;
>>                 :Latitude = 37.7833333333342 ;
>>                 :Longitude = -117.358333333342 ;
>>                 :Height = -9.09494701772928e-10 ;
>>                 :Time = 0 ;
>>                 :FractionalTime = 0. ;
>>                 :attributes = "" ;
>>                 :LatGridSpacing = 0.00833333333333 ;
>>                 :LonGridSpacing = 0.00833333333333 ;
>>                 :MissingData = -99900.f ;
>>                 :RangeFolded = -99901.f ;
>> data:
>>
>>  DEM

>>     1648, 1643, 1639, 1637, 1638, 1645, 1648, 1660, 1676, 1688, 1695,
>> 1702,
>>     1727, 1757, 1826, 1878, 1805, 1812, 1822, 1751, 1715, 1690, 1666,
>> 1655,
>>
>>
>> but would like to know how to extract the desired information from the
>> netCDF file so I can complete the equations above.  Does VisAD have
>> the capability to extract such values?
>
>
> The VisAD netCDF adapter does not do anything with global attributes.
> You could use the netCDF classes in the VisAD distribution to get
> a list of attributes:
>
>      NetcdfFile ncFile = new NetcdfFile(filename, true);
>      Attribute latSpace = ncFile.getAttribute("LatGridSpacing");
>      float latS = latSpace.getNumericValue().floatValue();
>      ...
>

I've thought about modifying Plain to create a Tuple from the
global attributes, but sometimes there are more attributes than
data in a netCDF file.  And, netCDF best practices would have
you use coordinate variables instead of global attributes to define
the lat/lon values at each point. ;-)

Thanks, Don.  This worked to extract the data that I was wanting.

Taking the data that I have extracted can I "force" a ScalarMap with
the extracted values?  I.e. after calculating the actual Lat/Lon,
create a ScalarMap with those calculated ranges and then (hopefully) the

-------

    ScalarMap.setOverrideUnit(km);

I have also tried

    xMap.setOverrideUnit(km);
    yMap.setOverrideUnit(km);


but still get the previous behavior (xxx.xxxx 1000.0 m)


Thanks again!

-kevin.


--
+------------------------------------------------------------+
Kevin L. Manross        [KD5MYD]               (405)-366-0557
CIMMS Research Associate               kevin.manross@xxxxxxxx
[NSSL-WRDD/SWATN]           http://www.cimms.ou.edu/~kmanross

"My opinions are my own and not representative of CIMMS, NSSL,
  NOAA or any affiliates"
+------------------------------------------------------------+

• Follow-Ups:
  • Re: netCDF and other things
    • From: Don Murray

• References:
  • netCDF and other things
    • From: Kevin Manross
  • Re: netCDF and other things
    • From: Don Murray