Derrick,
The documentation you're referencing shows how to make constraint
expressions to both 'sequence' containers, and 'arrays and grids'.
The selection operation you're using is only applicable to 'sequences'
and not 'arrays and grids' (at least not currently though value-based
array selection is often a requested capability for the DAP).
To accomplish your goal you would need to retrieve the 'lat'
variable first to determine the indices in the value range you're
looking for (.i.e., lat > 15)
then you could constrain the 'mslp' variable accordingly, like so:
http://www.apacsrv6/thredds/dodsC/bom/mslp.2009043000.nc.asc?
mslp[0][355:479][0:599]
the above assumes that 'lat' values greater than '15' reside in
the indices [355 to 479] (the top of the lat dimension), and you want
all the 'lon' coverage.
Dan
On Jul 21, 2010, at 3:01 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://apacsrv
6/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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