<div dir="ltr"><div><br>Just to make sure I am doing this correctly...<br><br>If I have a known channel start time, say 1995-03-21T17:16:00, then to limit the returned xml to be just the response for that single channel I should use endafter and endtime like this:<br>
<a href="http://service.iris.edu/fdsnws/station/1/query?network=IU&sta=ANMO&loc=--&cha=BHZ&endafter=1995-03-21T17:16:00&endtime=1995-03-21T17:16:00&level=response&nodata=404">http://service.iris.edu/fdsnws/station/1/query?network=IU&sta=ANMO&loc=--&cha=BHZ&endafter=1995-03-21T17:16:00&endtime=1995-03-21T17:16:00&level=response&nodata=404</a><br>
<br>In contrast, if I use starttime andendtime like this:<br><a href="http://service.iris.edu/fdsnws/station/1/query?network=IU&sta=ANMO&loc=--&cha=BHZ&starttime=1995-03-21T17:16:00&endtime=1995-03-21T17:16:00&level=response&nodata=404">http://service.iris.edu/fdsnws/station/1/query?network=IU&sta=ANMO&loc=--&cha=BHZ&starttime=1995-03-21T17:16:00&endtime=1995-03-21T17:16:00&level=response&nodata=404</a><br>
<br>then I get both the channel I want, as well as the one that was operational immediately before the time I am interested in.<br><br>But the docs are confusing as they say that:<br><br> startbefore, endbefore, startafter, endafter<br>
<br> These criteria are applied at the station level, regardless of which level is requested or which channel, network, location, <br> station filters are used.<br><br>Which I think means that my above query should not work, even though it does seem to, as the time restriction I am trying for is on the channel times and there was one station operating over this time that had 5 channels, but both of my above queries return fewer (one or two).<br>
<br>The fdsn ws specification doesn't make the way time params are interpreted very clear as it only says that these 4 times "Limit to metadata epochs...", but does not say they are limited to the station or in fact what they are applied to. I am guessing that the iris docs are wrong, but the fdsn spec also seems incomplete.<br>
</div><div><br>The other confusing thing to me is that the iris docs talk about how the time criteria apply based on whether there is a channel or location or station parameter and ignores the level parameter, but i dont' see any similar idea in the fdsn spec. Is this an iris implementation detail, or is the spec incomplete? I feel like the most natural way is to have the time criteria apply to the level asked for, but maybe I am missing something. Some experimentation seems to show that the level param is actually what controls the time aspect, but not totally sure.<br>
<br>IMHO, this whole starttime, endtime, startsbefore, endbefore, startsafter, endafter system seems really confusing. All the other systems of querying this type of data in the past have used a simple start/end window, and the "effective times" of the channel-like objects were "half open intervals" that included their begin, but not their end. In math notation, [start, end), meaning if you asked for an interval where the start/end were the same, you got the single channel that you likely wanted. I am not sure the added complexity and non-intuitiveness of these 6 time query parameters is really worth it.<br>
<br>Can someone clarify how all this is supposed to work?<br><br>thanks,<br>Philip</div></div>