Andrew,
This posting exactly reflects the thoughts I was having. Your proposal (which I'm assuming is for a single profile) assumes that the CTD is a 3-D trajectory feature rather than a profile feature (which assumes x, y and t co-ordinates to be a single value for each CTD).
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<mailto: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
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