[gradsusr] NETCDF4 problem

[Ricardo Hallak]

Conrado,

please, try open the data with a control file similar to this one below:

dset  ndvi3g_geo_v1_1981_0712.nc4
UNDEF -5000
dtype netcdf
*
XDEF      4320 LINEAR    -180.0     0.083333333
YDEF      2160  LINEAR       -90.0     0.083333333
*
TDEF       12  LINEAR  01212jul1981        15DY
*
ZDEF 1 LEVELS     1000

VARS 1
ndvictl=>ndvi     1 t,z,y,x   NDVI GRIDDED DATA   [[  units  ]]
ENDVARS

-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-

Save this as a control file, for example: ndvi1981.ctl, and open it in
grads.

In LINUX:

grads -pc 'open ndvi1981.ctl'
and
d ndvictl

to see if it works.

This .ctl  was built accordingly to the necdump above. As, obviously, I
haven't tested this .ctl with your data, it is possible that it is missing
something or it needs a few corrections to work with your data file.

Note that the choice of using the varname "ndvictl" is arbitrary. It could
be another varname, or even ndvi, as I know.

Let me now if there is yet some problem with this.

Regards,


-- 
Prof. Ricardo Hallak
Laboratório de Meteorologia de Mesoescala - LMM
Departamento de Ciências Atmosféricas
Instituto de Astronomia, Geofísica e Ciências Atmosféricas
Universidade de São Paulo

Phone: +55(11)3091-4698

2018-03-09 10:26 GMT-03:00 <jorge.conrado at cptec.inpe.br>:

>
>
> Hi,
>
>
> I have some NDI data in netcdf4 format, here is the result of the ncdfdump
> for my data:
>
>
>  ncdump -h ndvi3g_geo_v1_1981_0712.nc4
> netcdf ndvi3g_geo_v1_1981_0712 {
> dimensions:
>         lon = 4320 ;
>         lat = 2160 ;
>         time = 12 ;
> variables:
>         double lon(lon) ;
>         double lat(lat) ;
>         double time(time) ;
>         short satellites(time) ;
>         short ndvi(time, lat, lon) ;
>                 ndvi:units = "1" ;
>                 ndvi:scale = "x 10000" ;
>                 ndvi:missing_value = -5000. ;
>                 ndvi:valid_range = -0.3, 1. ;
>         short percentile(time, lat, lon) ;
>                 percentile:units = "%" ;
>                 percentile:scale = "x 10" ;
>                 percentile:flags = "flag 0: from data                flag
> 1: spline interpolation     flag 2: possible snow/cloud cover" ;
>                 percentile:valid_range = "flag*2000 + [0 1000]" ;
>
> // global attributes:
>                 :FileName = "ndvi3g_geo_v1_1981_0712.nc4" ;
>                 :Institution = "NASA/GSFC GIMMS" ;
>                 :Data = "NDVI3g version 1" ;
>                 :Reference = "1. Pinzon, J.E.; Tucker, C.J.
>                          A Non-Stationary 1981-2012 AVHRR NDVI3g Time
> Series.                Remote Sens. 2014, 6, 6929-6960.
>               2. Pinzon, J.E.; Tucker, C.J.
>          A Non-Stationary 1981-2015 AVHRR NDVI3g.v1 Time Series: an
> update.  Remote Sens. 2016, in preparation
>  " ;
>                 :CommentsVersion1 = "version1 includes two major fixes (a
> and b), and three minor (c-g):     (a) Reprocessed Level 2 entire SeaWIFS
> mission for the land products       to reduce artifacts in the data,
> particularly changes in calibration    after 2006 that generates drops in
> ndvi lower values.                   OB.DAAC / Ocean Biology Processing
> group NASA/GSFC 616  (april 2016) (b) Recovered ndvi negative values of
> snow-covered regions in winter       Northern latitudes.  In Version0, we
> masked them with zero values,      creating artifacts in phenology
> parameters.                          (c) Arranged data in ncd format,
> compiled it in two nc4 files a year.       Each nc4 file includes 6 months
> of ndvi data (jan-jun and jul-dec),     with a total of 12 (15-day)
> composites each semester.               (d) Rescaled ndvi values and
> splitted the flag values from them.        (e) Added a new variable,
> percentile, to represent the distribution of      ndvi values in the time
> series. Range 10*[0, 100]                   (f) Flag values are (simpler):
>                                             flag 0: ndvi without apparent
> issues (good value)                       flag 1: ndvi retrieved from
> spline interpolation                        flag 2: ndvi retrieved from
> seasonal profile (possible snow/cloud)  (g) Flag values are embeded on the
> percentile variable:                     2000*flag + percentile. Thus, the
> actual percentile three ranges        [0 1000], [2000 3000] and [4000 5000]
> could provide direct              information of how interpolation is
> affecting the time series.      " ;
>                 :Temporalrange = "1981-07-01 -> 2015-12-31" ;
>                 :Year = 1981. ;
>                 :RangeSemester = "Jul 1 - Dec 31 (7:0.5:12.5)" ;
>                 :SpatialResolution = "1/12 x 1/12 degrees" ;
>                 :TemporalResolution = "1/24 a year" ;
>                 :_fill_val = -32768. ;
>                 :NorthernmostLatitude = "90" ;
>                 :SouthernmostLatitude = "-90" ;
>                 :WesternmostLongitude = "-180" ;
>                 :EasternmostLongitude = "180" ;
> }
>
>
> Then I did:  grads -p
>
> sdfopen ndvi3g_geo_v1_1981_0712.nc4
>
> and I had:
>
> Scanning self-describing file:  ndvi3g_geo_v1_1981_0712.nc4
> gadsdf: SDF file has no discernable X coordinate.
>
>
> Please, what can I do to solve this.
>
>
>
> Thanks,
>
>
> Conrado
>
>
>
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