[webservices] requesting full day using ws_bulkdataselect

[Doug Neuhauser]

One suggestion (which unfortunately changes the IRIS web service
time specification) is for time intervals to be half-open invervals,
represented in math notation as
	[time1, time2)
This means the time interval where time t >= time1 and t < time2.

I believe that all IRIS services currently defined a closed interval
[time1, time2] which means the time interval where
time t  >= time1 and <= time2.

Closed intervals make it very hard to request a series of
requests whose results can be concatenated to generate a
contiguous timeseries with no overlap.  For day requests,
2 request for:
	2007-03-03T00:00:00.0000 to 2007-03-04T00:00:00.0000
	2007-03-04T00:00:00.0000 to 2007-03-05T00:00:00.0000
will contains 2 copies of a sample whose timestamp is 2007-03-04T00:00:00.0000
However, if the requests are open intervals, you will never miss a sample or
get a duplicate sample at a request boundary.

If you are missing 1 sample at a day boundary, it could be that you are missing a
sample timestamped between 59.999 and 00.000 seconds.  If you are missing
more than one sample, there is either a timetear (or gap) in the timeseries,
or there is a problem with the IRIS web service.

- Doug N

On 1/25/12 10:24 PM, John D. West wrote:
> Hi.
>
> I'm retrieving continuous data using bulkdataselect, one day at a time. A typical request line might look like "TA X16A -- BHZ 2007-03-30T00:00:00 2007-03-30T23:59:59.999"
>
> Using this method, I occasionally miss one or two samples at the day boundaries. I'm under the impression that the DMC internals make it more efficient to request on day boundaries. How do you recommend I do this to keep the data continuous and not miss samples at the day boundaries?
>
> Thanks!
>
>       -- John
>
>
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-- 
Doug Neuhauser                  University of California, Berkeley
doug at seismo.berkeley.edu        Berkeley Seismological Laboratory
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