[ncl-talk] convert grd to nc
Mary Haley
haley at ucar.edu
Tue Jun 5 09:17:26 MDT 2018
FYI, I have renamed the "nasa_ndvi" color map to NOC_ndvi:
http://www.ncl.ucar.edu/Document/Graphics/ColorTables/NOC_ndvi.shtml
We have added 29 color maps for V6.5.0, see:
http://www.ncl.ucar.edu/future_release.shtml#NewColorTables6.5.0
On Wed, May 23, 2018 at 4:11 PM, Dennis Shea <shea at ucar.edu> wrote:
> Forgot to mention. NCL has an 'NDVI' page:
>
> https://www.ncl.ucar.edu/Applications/
>
> Under '*Datasets*', Click
>
>
>
> *NDVIhttps://www.ncl.ucar.edu/Applications/ndvi.shtml
> <https://www.ncl.ucar.edu/Applications/ndvi.shtml>*===
> Further, there will be some
>
> *NDVI related colormaps in the next NCL release: 6.5.0*See:
> https://www.ncl.ucar.edu*/future_release*.shtm
>
> *l*
> Click "*New Color Tables*"
>
> For example:
>
> The nasa_ndvi color map
> <https://www.ncl.ucar.edu/Document/Graphics/ColorTables/nasa_ndvi.shtml>
> comes from NASA's Ocean Color <https://oceancolor.gsfc.nasa.gov/>
> website.
>
> The vegetation_ClarkU color map
> <https://www.ncl.ucar.edu/Document/Graphics/ColorTables/vegetation_ClarkU.shtml>
> was contributed by Clark Labs <https://clarklabs.org> / Clark University
> <http://www.clarku.edu>.
>
>
>
>
> On Wed, May 23, 2018 at 3:22 PM, Dennis Shea <shea at ucar.edu> wrote:
>
>> Hi Amy,
>>
>> The Climate Data Operators (CDO) can be used to convert a binary file to
>> netCDF. The command is described at:
>>
>> https://www.ncl.ucar.edu/Applications/grads.shtml
>>
>> %> cdo -f nc import_binary ndvip.ctl NDVI.polar_82-17.nc
>>
>> cdo import_binary: Processed 1 variable ( 1.27s )
>> ----------------------------------------------------------------------
>> This has a 'minor' problem.
>>
>> The file contains the following which looks good!
>>
>> float ndvi(time, lat, lon) ;
>> ndvi:long_name = "normalized difference vegetation index"
>> ;
>> ndvi:*_FillValue = -999.f *;
>> ndvi:*missing_value = -999.f *;
>>
>> However, if we observe *the golden rule of data processing: Look at your
>> data*
>>
>> %> ncdump -v ndvi NDVI.polar_82-17.nc | less
>>
>> You will see the the actual _FillValue and missing_value should be
>>
>> *-0.0999**ndvi *=
>> *-0.0999*, -0.0999, -0.0999, -0.0999, -0.0999, -0.0999, -0.0999,
>> -0.0999,
>> [SNIP]
>>
>> From and NCL perspective, this is readily addressed:
>>
>> f = addfile("NDVI.polar_82-17.nc", "r")
>> ndvi = f->ndvi
>> ndvi at _FillValue = -0.0999 ; change to correct _FillValue
>> printVarSummary(ndvi)
>>
>> You could also use the netCDF Operator's attribute editor:
>> ncatted <https://linux.die.net/man/1/ncatted>
>> to change the values on the file.
>> -----------------------------------------------------------------------
>> The files [~ 291 MB] created by the CDO [ NDVI.polar_82-17.nc ] and NCL
>> [ polar_82-17_MaxNDVI3g.grd.NCL.nc ] are at:
>>
>> ftp ftp.cgd.ucar.edu
>> anonymous
>> your_email
>> cd pub/shea
>> get NDVI.polar_82-17.nc
>> get polar_82-17_MaxNDVI3g.grd.NCL.nc
>> quit
>> ===========================================
>>
>> They are functionally equivalent
>> &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
>> ============================================
>> The NCL script you sent had an error or two. The .ctl file had:
>>
>> [1] the .ctl pointed to
>>
>> DSET ^polar82-*16*_maxndvi_dat.grd
>>
>> The file you sent was named: polar_82-17_MaxNDVI3g.grd
>> The .ctl should point to:
>>
>> DSET ^polar_82-*17*_MaxNDVI3g.grd
>>
>> ====
>> The file you sent has size:
>>
>> 299220480 May 22 22:25 polar_82-17_MaxNDVI3g.grd
>>
>> nlat(=481)*mlon(=4320)*ntim(=36)*nbyte(=4) = 299220480
>>
>> This means the the file has no 'extra' embedded bytes.
>> Fortran's sequential binary files have record boundaries. They add to the
>> size of the file.
>>
>> This means that you should be using NCL's 'fbindirread' function.
>>
>> https://www.ncl.ucar.edu/Document/Functions/Built-in/fbindirread.shtml
>>
>> and not 'fbinrecread' function.
>>
>> See attached.
>>
>> Good Luck
>>
>>
>>
>>
>> On Tue, May 22, 2018 at 7:05 PM, Amy Hendricks <ashendricks at alaska.edu>
>> wrote:
>>
>>> Hell NCL heroes,
>>>
>>> I am trying to read in ndvi data in .grd format and convert to netcdf.
>>> The problem occurs when I go to read in the ndvi data. This script is
>>> modified from grads_2.ncl (https://www.ncl.ucar.edu/Appl
>>> ications/Scripts/grads_2.ncl). Please find attached the script, data,
>>> and ctl file. The ctl file is an example from my advisor, only the DSET and
>>> # of years are different.
>>>
>>> Thanks!
>>>
>>> Amy
>>> ndvip.ctl
>>> <https://drive.google.com/a/alaska.edu/file/d/1gfTy4cedHoVucV-YEan0Ph7NES9FfsMM/view?usp=drive_web>
>>>
>>> polar_82-17_MaxNDVI3g.grd
>>> <https://drive.google.com/a/alaska.edu/file/d/1DNzWno-3WmFqINZBY-ENH7nnMn0lsGvf/view?usp=drive_web>
>>>
>>>
>>> --
>>> Amy Hendricks
>>> Graduate Research Assistant
>>> Department of Atmospheric Sciences
>>> University of Alaska Fairbanks
>>> IARC 343-R
>>> 907-388-9893
>>> ashendricks at alaska.edu
>>>
>>> _______________________________________________
>>> ncl-talk mailing list
>>> ncl-talk at ucar.edu
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>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>
>>>
>>
>
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