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Hi Eric,OCAPI uses the OPeNDAP protocol (more information at http://www.opendap.org/). The THREDDS NetCDF Subsetting Service (NCSS) is not related to OPeNDAP. The NCSS will require additional conventions so that requests can be made in lat/lon instead of index space. OPeNDAP, on the other hand, is limited to index space so doesn't need further conventions.
You might be able to get NCSS working by changing the appropriate "units" attributes to "degrees_east" and "degrees_north". There might be some other details I'm missing. So, here's the link for the netCDF page on conventions: http://www.unidata.ucar.edu/software/netcdf/conventions.html. CF is probably the one you want to follow.
As for OPeNDAP, I don't know OCAPI but it should have a way to include an Constrained Expression (CE) when you request data. For the dataset you list below a CE might be something like
"POTENTIAL_TEMPERATURE__MEAN_[0:1:65][0:1:240][0:1:480]"Which would return all the data for that variable? You can get subsets by changing the starting index, stride and ending index for each dimension in the CE (the form is [start:stride:stop] with stride being optional).
A CE of the above form should also return the depth, lat, and lon variables (appropriately subset) since they appear to be proper netCDF coordinate variables which OPeNDAP servers recognize.
Hope that helps, Ethan Eric Davies wrote:
Hi Roy,I'm written a C application using the OCAPI. The application produces the url, sends it to the server, and accepts binary results.I want the server to do the subsetitng, and pass the subsetted results to my application. Presumably thiswould be more efficient than asking the application to do it.The server is stuck behind our firewall I'm afraid. Presumably there is some configuration magic I still need to do to get ncss to work, if there is a way for me to use ncss effectively.Eric. At 04:12 PM 1/7/2008, Roy Mendelssohn wrote:Hi Eric:It is unclear if what you are asking is that you only want the TDS to display a subset of the data to the user, or if you want to know how a user can subset the data that is being served by the TDS. If the latter, what applications do you use or do you just want to use the hrml page.Either way, is the TDS publicly accessible? Thanks, -Roy M. On Jan 7, 2008, at 4:04 PM, Eric Davies wrote:I've got the Thredds Data Server installed and I'm trying to use it to subset a 3D grid (depth, latitude, longitude) large netcdf file. The netcdf file was generated by a third parties software, and is probably not compliant with anything. As subset of its schema is shown below.If I rename some coordinate variables, I should be able to make it compliant with some convention. My question is how do I most efficiently extract a 3D subset? I want to extract a subset of depth as well as a subset of longitude and latitude.Any ideas would be most appreciated. Thank you. Eric. netcdf d7110.subvol { dimensions: TIMESTEP = 1 ; LONGITUDE_T = 481 ; LATITUDE_T = 241 ; LONGITUDE_U = 481 ; LATITUDE_U = 241 ; DEPTH = 66 ; DEPTH_EDGES = 67 ; variables: int TIMESTEP(TIMESTEP) ; TIMESTEP:long_name = "Timestep" ; float LONGITUDE_T(LONGITUDE_T) ; LONGITUDE_T:long_name = "Longitude" ; LONGITUDE_T:units = "degrees" ; LONGITUDE_T:Format = "F10.4" ; float LATITUDE_T(LATITUDE_T) ; LATITUDE_T:long_name = "Latitude" ; LATITUDE_T:units = "degrees" ; LATITUDE_T:Format = "F10.4" ; float DEPTH(DEPTH) ; DEPTH:long_name = "Depth" ; DEPTH:units = "cm" ; DEPTH:Format = "F5.2" ; DEPTH:positive = "down" ; DEPTH:edges = "DEPTH_EDGES" ;float POTENTIAL_TEMPERATURE__MEAN_(DEPTH, LATITUDE_T, LONGITUDE_T) ; POTENTIAL_TEMPERATURE__MEAN_:long_name = "potential temperature(mean)" ; POTENTIAL_TEMPERATURE__MEAN_:units = "C" ; POTENTIAL_TEMPERATURE__MEAN_:_FillValue = 0.f ; POTENTIAL_TEMPERATURE__MEAN_:LEVEL = 0 ; POTENTIAL_TEMPERATURE__MEAN_:T_GRID = -1 ; .... } ********************************************** Eric Davies, M.Sc. Barrodale Computing Services Ltd. Tel: (250) 472-4372 Fax: (250) 472-4373 Web: http://www.barrodale.com <http://www.barrodale.com/> Email: eric@xxxxxxxxxxxxx ********************************************** Mailing Address: P.O. Box 3075 STN CSC Victoria BC Canada V8W 3W2 Shipping Address: Hut R, McKenzie Avenue University of Victoria Victoria BC Canada V8W 3W2 ********************************************** _______________________________________________ thredds mailing list thredds@xxxxxxxxxxxxxxxxFor list information or to unsubscribe, visit: http:// <http:///> www.unidata.ucar.edu/mailing_lists/ <http://www.unidata.ucar.edu/mailing_lists/>**********************"The contents of this message do not reflect any position of the U.S. Government or NOAA."********************** Roy Mendelssohn Supervisory Operations Research Analyst NOAA/NMFSEnvironmental Research Division Southwest Fisheries Science Center1352 Lighthouse Avenue Pacific Grove, CA 93950-2097 e-mail: Roy.Mendelssohn@xxxxxxxx (Note new e-mail address) voice: (831)-648-9029 fax: (831)-648-8440 www: http://www.pfeg.noaa.gov/ "Old age and treachery will overcome youth and skill."********************************************** Eric Davies, M.Sc. Barrodale Computing Services Ltd. Tel: (250) 472-4372 Fax: (250) 472-4373 Web: _http://www.barrodale.com_ <http://www.barrodale.com/> Email: eric@xxxxxxxxxxxxx ********************************************** Mailing Address: P.O. Box 3075 STN CSC Victoria BC Canada V8W 3W2 Shipping Address: Hut R, McKenzie Avenue University of Victoria Victoria BC Canada V8W 3W2 ********************************************** ------------------------------------------------------------------------ _______________________________________________ thredds mailing list thredds@xxxxxxxxxxxxxxxxFor list information or to unsubscribe, visit: http://www.unidata.ucar.edu/mailing_lists/
-- Ethan R. Davis Telephone: (303) 497-8155 Software Engineer Fax: (303) 497-8690 UCAR Unidata Program Center E-mail: edavis@xxxxxxxx P.O. Box 3000 Boulder, CO 80307-3000 http://www.unidata.ucar.edu/ ---------------------------------------------------------------------------
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