Two issues that should be pointed out this this change. The first is
that a "leap second occurs IN this record" is required in either case,
and positive/negative direction is needed. A record that overlaps a
leap second is different from a record where the start time is IN a
leap second. Consider a 1sps record containing 11 samples with a start
time of 23:59:50 on 31 Dec. The starttime is not a leap second in
either case, but the last sample could occur either at 00:00:00 on 1
Jan or at 23:59:60 on 31 Dec. Allowing the seconds field to be 60 is
insufficient in this case and so some extra information beyond the
start time is needed even in the case of the BTime structure.
The second comment is that users do not interact directly with
miniseed currently, and will not do so in the future. There will be
software libraries in each of the popular languages that do this for
them, and those libraries will convert times into the languages
default representation. A BTime might be a little less confusing for
the developer, but the user is going to use a value in software that
looks a lot like the IEEE format when they initiate any processing.
Having the file format doesn't make this problem go away or really
even make it less likely. What would help is if libraries were created
with functions such as getTimeOfSample(27) or
timeDifferenceBetweenSamples(sample1, sample2) so that the library
does the math correctly taking into account the leap seconds.
I was originally somewhat against the IEEE format, but the more I
think about it, the less I think it matters. Math with time is hard
and the file format is not the right place to protect users against
doing wrong subtraction across leap seconds. The software that uses
the file format is the right place for that.
On Thu, Aug 11, 2016 at 3:49 PM, Chad Trabant <chad<at>iris.washington.edu> wrote:
Change proposal #7 to the 2016-3-30 straw man (iteration 1) is attached:
Change start time to custom structure.
Please use this thread to provide your feedback on this proposal by
Wednesday August 24th.
Posted to multiple topics:
FDSN Working Group II
FDSN Working Group III
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