Re: Web service for Total Precipitation

Hi Ernest:

Ernest To wrote:
> John,
>
> My name is Ernest To and I am a student of Dr.
> Maidment's.  Tim Whiteaker and I are trying to write a
> webservice that would download total precipitation
> data for the continental US at resolution of 20km from
> unidata website for a given time and place.  We have
> so far been experimenting with the following link:
>
> http://motherlode.ucar.edu:8080/thredds/dodsC/model/NCEP/NAM/CONUS_20km/surface/NAM_CONUS_20km_surface_20060324_1800.grib1.html
>
> Can we ask you the following questions?
> 1.  What is a .grib1 or a .grib2 file?  Is it in
> netcdf format?

no, grib1 and grib2 are WMO formats for gridded data


> 2.  We noticed that in the link above (OPENDAP ) there
> are options for getting a binary file or an ASCII
> file.  Are those files in netcdf and cdl formats
> respectively?

no, they are in opendap specific formats. normally you would use the opendap 
client library (C++ or Java) to access data through opendap, rather than 
downloading files.


> 3.  Our webservice requires the creation of a URL
> query based on user inputs (such as coordinates of
> bounding rectangle, time period of interest and
> parameter of interest) which will then be used to
> request data from the website.  Could you provide
> information on how to convert geographical coordinates
> (in decimal degrees) and time values (MM/DD/YYYY
> hh:mm) into the array indices shown in the website
> above? e.g. time[0:1:0] y[0:1:0] x[0:1:0] 

this is not trivial, as it depends on the specific file. there are routines in 
the netcdf-java 2.2 library that can do it. Are you using java?

what file formats can you handle? what does your web service do?


>   Thank you for your kind attention.  Please let me
> know if anything is unclear.  I can be reached either
> by e-mail: address@hidden or by phone:
> 512-508-4834.
>
>   Thanks.
>
> Ernest To
> PhD student
> Center for Research in Water Resources
> University of Texas at Austin
> 512-508-4834
>
>  
>
>
> --- John Caron <address@hidden> wrote:
>
>
> > Hi David, Ernest:
> >
> > Have a look at the motherlode catalog:
> >
> >  http://motherlode.ucar.edu:8080/thredds/
> >
> > we were guessing you will want the NAM 21-km
> > dataset?
> >
> > If you want to use WCS protocol, you can get back
> > geotiff or netcdf-CF. Otherwise you could use
> > Opendap.
> >
> > There's a few other wrinkles concerning time
> > dimension, we can go over.
> >
> > David Maidment wrote:
> >
> > > Ernest:
> > >
> > > Please see the message below from Mohan Ramamurthy
> >
> > at Unidata.  Can you
> >
> > > please work with John Caron
> > > to see how we can ingest a field using web
> >
> > services.  I'd like to stick
> >
> > > to something 2D on the land 
> > > surface like precipitation, evaporation or soil
> >
> > moisture.  I believe
> >
> > > those are all in the eta model
> > > output.   Likely what we want to do is to give a
> >
> > lat-long box, a time
> >
> > > point and a variable, and ask
> > > for a field over the region of the lat-long box
> >
> > for that variable and
> >
> > > time point, and it might occur
> > > that the field actually covers several forecast
> >
> > intervals, eg. 3 hour
> >
> > > forecast times for a day.  I'm
> > > not sure in that case if we should treat each time
> >
> > slice as one field in
> >
> > > the web services ingest, but
> > > lets look into what is involved and then figure
> >
> > out what is best.
> >
> > > John -- I'd like to see what can be done with a
> >
> > WCS service if possible.
> >
> > > Thanks for your help.
> > >
> > > David
> > >
> > >
> > > -----Original Message-----
> > > From: Mohan Ramamurthy [mailto:address@hidden] 
> > > Sent: Friday, March 10, 2006 5:40 PM
> > > To: David Maidment
> > > Cc: John Caron; Mohan Ramamurthy
> > > Subject: Web service to Operational Eta model
> >
> > output
> >
> > > David,
> > >
> > > I just spoke to John Caron
> >
> > (address@hidden), our lead developer
> >
> > > on THREDDS, re. our conversation this afternoon to
> >
> > create a web service
> >
> > > to access fields from the operational model output
> >
> > in the IDD stream.
> >
> > > John will be happy to work the person on your to
> >
> > make it happen.  It
> >
> > > looks like many of the pieces are already in place
> >
> > to enable a web
> >
> > > service for accessing, subsetting, and moving
> >
> > individual fields, because
> >
> > > the data is served via OPeNDAP.  For example, here
> >
> > is the OPeNDAP URL
> >
> > > for today's Eta output:
> http://motherlode.ucar.edu:8080/thredds/dodsC/model/NCEP/NAM/Alaska_22km
>
> > > /NAM_Alaska_22km_20060310_1200.grib1
> > >
> > > By the way, John also has an experimental WCS
> >
> > server that provides the
> >
> > > same data via the WCS interface.
> > >
> > > I will let John and your technical developer to
> >
> > work out the details on
> >
> > > how to make this happen, but it looks
> >
> > straightforward and doable based
> >
> > > on my discussions with John.
> > >
> > > Mohan
>
>
>
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