Hi.
A colleague of mine has told me that if you use size-1 array for a
variable, then data servers such as THREDDS can aggregate the variable over
multiple files and deliver a single file in which the variables will be
arrays of size > 1. He said that if a variable is a scalar, THREDDS won't
do this. (I don't mess with THREDDS, so I am just parroting what he said.)
If this is correct, then you might want to consider this point when
deciding which way to represent coordinates.
Grace and peace,
Jim
On Tue, Apr 3, 2012 at 1:02 PM, Upendra Dadi <upendra.dadi at noaa.gov> wrote:
> Andrew,
>
> However I have another small concern about all of this. Given there is
> more than
> 1 way to treat dimensions does the netCDF plotting and visualising sofware
> out
> there understand both approaches. That is can we expect something like
> ncBrowse, IDV or ODV? give me a plot of say salinity vs. pressure
> and work OK with BOTH approaches to coding the netCDF?
>
> Software like ncBrowse do not understand CF conventions. They can read
> netCDF files, but wouldn't know how to interpret the attributes like
> "coordinates". So if you want to plot the profile location on a map, for
> example, it wouldn't be able to do it by itself. It would need to be told
> how to interpret the coordinates. A CF based software wouldn't have to be
> supplied with the additional semantics since it can read from the file by
> itself. But if you want to plot salinity vs pressure, software like
> ncBrowse can already do it since lot of these software make it easy to make
> plots based on a shared dimension. And here salinity and pressure share
> the same dimension. So I guess, the correct answer to your question is -
> it depends on what kind of plot or task you want to do and if the software
> can understand CF conventions.
>
> Upendra
>
>
>
>
> Thanks and Regards All,
>
> Andrew Walsh
>
> ----- Original Message -----
> *From:* Lowry, Roy K. <rkl at bodc.ac.uk>
> *To:* Upendra Dadi <upendra.dadi at noaa.gov> ; andrew walsh<awalsh at metoc.gov.au>
> *Cc:* Luke Callcut <luke at metoc.gov.au> ; cf-metadata at cgd.ucar.edu ;
> sdn2-tech at seadatanet.org
> *Sent:* Tuesday, April 03, 2012 9:31 AM
> *Subject:* RE: [CF-metadata] Ocean CTD data following CF Conventions v1.6
>
> Hi Upendra,
>
> I like the idea of a station dimension. It goes a long way to resolving
> the issue raised in my response to Jim which was based on the tunnel vision
> of having pressure/depth as a dimension. I have yet to look at the
> recently published NODC NetCDF templates. Is this CTD encoding included in
> them? If so, I'll bump up looking at them on my 'todo' list. I'd also
> recommend that Andrew and my colleagues in SeaDataNet take a look.
>
> Cheers, Roy.
>
> ------------------------------
> *From:* cf-metadata-bounces at cgd.ucar.edu [cf-metadata-bounces at cgd.ucar.edu]
> On Behalf Of Upendra Dadi [upendra.dadi at noaa.gov]
> *Sent:* 02 April 2012 17:21
> *To:* andrew walsh
> *Cc:* Luke Callcut; cf-metadata at cgd.ucar.edu
> *Subject:* Re: [CF-metadata] Ocean CTD data following CF Conventions v1.6
>
> Hi Andrew,
> Either way it should be okay as far as CF compliance is concerned. But
> the dimensions - latitude, longitude and time are not really required. If
> it is required to indicate that there is only one station(profile) in the
> file, there could be a dimension for number of stations instead, with a
> value of 1. Also, using a station dimension is the way to go if storing a
> collection of profiles in a single file. Here at NODC, we took the approach
> that we would use the same consistent representation whether there is a
> single instance or a collection in a file.
>
> Upendra
>
>
>
>
> On Mon, Apr 2, 2012 at 2:51 AM, andrew walsh <awalsh at metoc.gov.au> wrote:
>
>> Hi CF lis
>> We are working on coding up some 1000's netCDF files off CTD
>> instruments and want to make usre we are following the
>> latest netCDF conventions (v1.6) OK. As background the CTD records
>> a profile pressure, temperature and salinity.
>>
>> Here is a summarised CDL version (not all attributes+variables+qc flags
>> there, just majors for now)
>> of what we propose:
>>
>> dimensions:
>> TIME=1
>> PRESSURE=729
>> LATITUDE=1
>> LONGITUDE=1
>>
>> variables:
>> double TIME(TIME) ;
>> TIME:standard_name = "time" ;
>> TIME:units = "days since 1950-01-01 00:00:00Z" ;
>> TIME:axis = "T" ;
>> TIME:valid_min = 0. ;
>> TIME:valid_max = 999999. ;
>>
>> double LATITUDE(LATITUDE) ;
>> LATITUDE:standard_name = "latitude" ;
>> LATITUDE:units = "degrees_north" ;
>> LATITUDE:axis = "Y" ;
>> LATITUDE:valid_min = -90. ;
>> LATITUDE:valid_max = 90. ;
>>
>> double LONGITUDE(LONGITUDE) ;
>> LONGITUDE:standard_name = "longitude" ;
>> LONGITUDE:units = "degrees_east" ;
>> LONGITUDE:axis = "X" ;
>> LONGITUDE:valid_min = -180. ;
>> LONGITUDE:valid_max = 180. ;
>>
>> double PRESSURE(PRESSURE) ;
>> PRESSURE:standard_name = "sea_water_pressure" ;
>> PRESSURE:units = "decibars" ;
>> PRESSURE:axis = "Z" ;
>> PRESSURE:valid_min = 0. ;
>> PRESSURE:valid_max = 12000. ;
>> PRESSURE:positive = "down" ;
>>
>> double TEMPERATURE(PRESSURE) ;
>> TEMPERATURE:standard_name = "sea_water_temperature" ;
>> TEMPERATURE:units = "degrees_C" ;
>> TEMPERATURE:_FillValue = -99.99 ;
>> TEMPERATURE:valid_min = -2. ;
>> TEMPERATURE:valid_max = 40. ;
>> TEMPERATURE:coordinates="TIME LATITUDE LONGITUDE PRESSURE"
>>
>> double SALINITY(PRESSURE) ;
>> SALINITY:standard_name = "sea_water_salinity" ;
>> SALINITY:units = "psu" ;
>> SALINITY:_FillValue = -99.99 ;
>> SALINITY:valid_min = 0. ;
>> SALINITY:valid_max = 40. ;
>> SALINITY:coordinates="TIME LATITUDE LONGITUDE PRESSURE"
>>
>> // global attributes:
>> :conventions = "CF-1.6" ;
>> :featureType = "profile"
>> :cdm_data_type = "profile"
>> + several other attributes later for ISO19115 metadata generation
>>
>> I am not sure if I should have TEMPERATURE and SALINITY arrays with 4
>> dimensions
>> like TEMPERATURE(TIME,LATITUDE,LONGITUDE,PRESSURE) or just 1 dimension
>> like I have above i.e. TEMPERATURE(PRESSURE). ?
>>
>> Any feedback on the above is greatly appreciated.
>>
>> Andrew Walsh
>> _______________________________________________
>> CF-metadata mailing list
>> CF-metadata at cgd.ucar.edu
>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>>
>
>
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--
Jim Biard
Research Scholar
Cooperative Institute for Climate and Satellites
Remote Sensing and Applications Division
National Climatic Data Center
151 Patton Ave, Asheville, NC 28801-5001
jim.biard at noaa.gov
828-271-4900
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