Re: [thredds] Thredds Opendap request

Relational constraint expressions do no work for grids in OpeNDAP.  You have to 
constrain based on the range of indices in the grid.  If you go to the OPeNDAP 
html page it will help guide you to perform a subset.  For example from one of 
the datasets my group serves:

http://oceanwatch.pfeg.noaa.gov/thredds/dodsC/satellite/BA/ssta/mday.html

to get the first time period, the first 30 lats and 50 lons the constraitn 
would be:

http://oceanwatch.pfeg.noaa.gov/thredds/dodsC/satellite/BA/ssta/mday?BAssta[0:1:0][0:1:0][0:1:29][0:1:49]

HTH,

-Roy 
On Jul 21, 2010, at 12:01 AM, Derrick.Wong@xxxxxxxx wrote:

> Hi all,
> 
> I have set up a TDS (Version 4.1.20100520.1554 - 20100520.1554) and I am 
> having some problem requesting for data using the built-in OPeNDAP service.
> 
> I am trying to subset the dataset based on a spatial extent (bbox), and in 
> the opendap documentation, it is mentioned that this is possible if you 
> specify a constraint in your request. 
> (http://opendap.org/user/guide-html/guide_34.html#id6)
> 
> I am getting the following error when I try to make a simple query 
> http://apacsrv6/thredds/dodsC/bom/mslp.2009043000.nc.ascii?mslp&lat>15.0 :
> 
> Error {
>    code = 2;
>    message = "The variable `15' was not found in the dataset.";
> };
> 
> 
> 
> My Dataset is as follows:
> 
> Dataset {
>    Float32 lat[lat = 480];
>    Float32 lon[lon = 600];
>    Int32 tm_step_size;
>    Int32 base_date;
>    Int32 base_time;
>    Int32 valid_date[time = 1];
>    Int32 valid_time[time = 1];
>    String seg_type[time = 1];
>    Float32 mslp[time = 1][lat = 480][lon = 600];
> } bom/mslp.2009043000.nc;
> ---------------------------------------------
> lat[480]
> -55.0, -54.875, -54.75, -54.625, .......
> 
> lon[600]
> 95.0, 95.125, 95.25, 95.375, 95.5, ......
> 
> tm_step_size, 240
> base_date, 20090430
> base_time, 0
> valid_date[1]
> 20090430
> 
> valid_time[1]
> 0
> 
> seg_type[1]
> "FORC"
> 
> mslp[1][480][600]
> 
> [0][0], 983.6426, 983.6654, 983.6847, 983.7006, ....
> [0][1], ....
> .....
> 
> 
> 
> I have noted that the syntax of the OPeNDAP request within thredds is a bit 
> different, could someone kindly assist?
> 
> Thank you for your time.
> 
> Regards,
> 
> 
> Derrick Wong 
> Software Engineer | ASRDC (Australian Spatial Research Data Commons) Project 
> | CSIRO
> 
> Phone: +61 8 6436 8945
> derrick.wong@xxxxxxxx | www.csiro.au
> Address: ARRC (Australian Resources Research Centre), 26 Dick Perry Avenue, 
> Kensington WA 6151, Australia
> 
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> 
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**********************
"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
1352 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."
"From those who have been given much, much will be expected" 



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