[webservices] requesting full day using ws_bulkdataselect

[John D. West]

Thanks, Doug.

That's exactly correct, in one case I'm missing a sample which should have
been at 23:59.999998. I was trying to avoid crossing day boundaries because
I understood that was more intensive processing on the DMC end. My process
for stitching together traces can handle overlap, so the brute force method
would be to just request to 00:00:01 the next day. I'd like to know if
there is a more efficient way.

     -- John


On Thu, Jan 26, 2012 at 5:19 PM, Doug Neuhauser <doug at seismo.berkeley.edu>wrote:

> 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
> Office: 510-642-0931            215 McCone Hall # 4760
> Fax:    510-643-5811            Berkeley, CA  94720-4760
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>
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