Re: [thredds] applying functions (filtering, seasonal signal removal) to served time series

  • To: Benno Blumenthal <benno@xxxxxxxxxxxxxxxx>
  • Subject: Re: [thredds] applying functions (filtering, seasonal signal removal) to served time series
  • From: Christian Ward-Garrison <cwardgar@xxxxxxxx>
  • Date: Fri, 12 Sep 2014 01:48:28 -0600
The NetCDF Subset Service (part of THREDDS) allows filtering based on time
and space parameters, but not arbitrary functions. Here is an example:

http://thredds-test.unidata.ucar.edu/thredds/ncss/pointData/cf_doc_dsg/example/H.2.1.1.nc/dataset.html

Cheers,
Christian Ward-Garrison

On Thu, Sep 11, 2014 at 12:48 PM, Benno Blumenthal <benno@xxxxxxxxxxxxxxxx>
wrote:

> Despite all the good reasons that Roy provided not to do it, we provide
> server-side services.
>
> You could look at
>
>
> http://iridl.ldeo.columbia.edu/SOURCES/.NOAA/.NCEP/.EMC/.CMB/.GODAS/.monthly/.surface/.SSHG/
>
> as a sample sea surface height dataset -- many of our functions are
> documented at
>
> http://iridl.ldeo.columbia.edu/dochelp/Documentation/funcindex.html
>
>  and it includes a number of time-aware operators as well as spatial
> selection.  Perhaps off-line we can work out an example that might be of
> interest.
>
> On Thu, Sep 11, 2014 at 2:39 PM, Dallas Masters <
> Dallas.Masters@xxxxxxxxxxxx> wrote:
>
>> Thanks. I wasn't going to advertise this service on our ERDDAP server. It
>> was going to be used to fulfill backdoor requests generated by our own web
>> pages (albeit possible for someone to view the source and see how to make
>> the request).
>>
>> --
>> Dallas Masters
>> Sea Level Research Group
>> University of Colorado
>>
>>
>> On Thu, Sep 11, 2014 at 12:22 PM, Roy Mendelssohn <
>> roy.mendelssohn@xxxxxxxx> wrote:
>>
>>> ERDDAP can serve the time series.  At the moment it does not have the
>>> type of server-side function you are describing.  I believe GDS and F-TDS
>>> have such capabilities.
>>>
>>> We have been holding back on doing this in ERDDAP  for some simple
>>> reasons:
>>>
>>> 1.  There is no agreed upon syntax for such requests.
>>>
>>> 2.  It could open up your server to quite large amounts of data
>>> processing
>>>
>>> 3.  The processing requests could take long enough that it would require
>>> an asynchronous response.
>>>
>>> All of these things imply not insignificant changes in the service.
>>>
>>> -Roy
>>>
>>> On Sep 11, 2014, at 10:50 AM, Dallas Masters <Dallas.Masters@xxxxxxxxxxxx>
>>> wrote:
>>>
>>> > Here's what I'm trying to do, but I'm unsure of the simplest method:
>>> >
>>> > I have a netCDF file of gridded sea surface heights over time. I'd
>>> like Ramadda (or ERDDAP or THREDDS) to serve time series from that file at
>>> specific lat,lon requests. But I'd like to apply some filters to the time
>>> series before sending on as JSON data to the client. Is there a method to
>>> apply intermediate processing or internal server functions to data prior to
>>> sending the data, perhaps specifying the function call in the URL? I guess
>>> this is like server-side processing in GRADS or F-TDS? I've seen some
>>> discussions about doing NCO ncwa or perhaps applying IDV functions to data
>>> in Ramadda, but I'm not sure if this is documented and how to implement
>>> something similar. Any advice is appreciated.
>>> > _______________________________________________
>>> > thredds mailing list
>>> > thredds@xxxxxxxxxxxxxxxx
>>> > For list information or to unsubscribe,  visit:
>>> 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/NMFS
>>> Environmental Research Division
>>> Southwest Fisheries Science Center
>>> ***Note new address and phone***
>>> 110 Shaffer Road
>>> Santa Cruz, CA 95060
>>> Phone: (831)-420-3666
>>> Fax: (831) 420-3980
>>> e-mail: Roy.Mendelssohn@xxxxxxxx www: http://www.pfeg.noaa.gov/
>>>
>>> "Old age and treachery will overcome youth and skill."
>>> "From those who have been given much, much will be expected"
>>> "the arc of the moral universe is long, but it bends toward justice"
>>> -MLK Jr.
>>>
>>>
>>
>> _______________________________________________
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>> thredds@xxxxxxxxxxxxxxxx
>> For list information or to unsubscribe,  visit:
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>>
>
>
>
> --
> Dr. M. Benno Blumenthal          benno@xxxxxxxxxxxxxxxx
> International Research Institute for climate and society
> The Earth Institute at Columbia University
> Lamont Campus, Palisades NY 10964-8000   (845) 680-4450
>
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> thredds mailing list
> thredds@xxxxxxxxxxxxxxxx
> For list information or to unsubscribe,  visit:
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>
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