International Federation of Digital Seismograph Networks

Thread: FDSNWS starttime/endtime

None
Started: July 28, 2015, noon
Last activity: July 28, 2015, noon
Tobias Megies
July 28, 2015, noon
Hi all,

during implementing fdsnws-station in a local database system, we
stumbled over some inconsistencies in the specifications of the behavior
for parameters "starttime" and "endtime".

The official specs state:

Table 4. Parameter descriptions for the fdsnws-station service.

"""
starttime Required
Limit to metadata epochs starting on or
after the specified start time.
"""

So, basically that would mean that a channel epoch starting before the
set "starttime", but recording data all the way through "starttime" and
later is supposed to not be included, because the epoch does not start
"on or after the specified time" but rather before it.

I think this is in collision with the intuitive interpretation of
"starttime" restriction in the search and it is also in collision with
the more general specification of time parameters on page 6:

"""
Time parameter interpretation

The starttime parameter should be interpreted as selecting any data or
information (time series samples, earthquake origins, metadata epochs)
at times on or later than the value specified.
Similarly, the endtime selects any data or information at times on or
prior to the value specified.
The selection shall include any metadata epochs
intersecting with the specified time range.
"""

Looking at real world implementations, e.g. at IRIS, the "starttime"
parameter is defined as one would expect intuitively and by reading the
general "time parameter interpretation":

"""
start[time]
Limit to metadata describing channels operating on or
after the specified start time.
"""


I suggest that the wording in the official FDSNWS specs should be
changed, probably to something like (endtime accordingly):

"""
starttime: Required
Limit to metadata epochs active on or
after the specified start time.
"""


best,
Tobias




--
Dipl.-Geophys. Tobias Megies

Geophysikalisches Observatorium
Ludwigshöhe 8
82256 Fürstenfeldbruck

Ludwig-Maximilians-Universität
Department für Geo- und Umweltwissenschaften
Sektion Geophysik
Theresienstrasse 41/IV
80333 München

Tel: +49 (0) 89 2180-73981
+49 (0) 89 2180-4326
Mail: tobias.megies<at>geophysik.uni-muenchen.de

  • Philip Crotwell
    July 28, 2015, 6:48 a.m.
    I agree. Another way of saying this reflects the actual test you would do
    in internally is:

    """
    starttime: Required
    Limit to metadata epochs ending
    after the specified start time.
    """

    Philip


    On Tue, Jul 28, 2015 at 6:02 AM, Tobias Megies <
    megies<at>geophysik.uni-muenchen.de> wrote:

    Hi all,

    during implementing fdsnws-station in a local database system, we
    stumbled over some inconsistencies in the specifications of the behavior
    for parameters "starttime" and "endtime".

    The official specs state:

    Table 4. Parameter descriptions for the fdsnws-station service.

    """
    starttime Required
    Limit to metadata epochs starting on or
    after the specified start time.
    """

    So, basically that would mean that a channel epoch starting before the
    set "starttime", but recording data all the way through "starttime" and
    later is supposed to not be included, because the epoch does not start
    "on or after the specified time" but rather before it.

    I think this is in collision with the intuitive interpretation of
    "starttime" restriction in the search and it is also in collision with
    the more general specification of time parameters on page 6:

    """
    Time parameter interpretation

    The starttime parameter should be interpreted as selecting any data or
    information (time series samples, earthquake origins, metadata epochs)
    at times on or later than the value specified.
    Similarly, the endtime selects any data or information at times on or
    prior to the value specified.
    The selection shall include any metadata epochs
    intersecting with the specified time range.
    """

    Looking at real world implementations, e.g. at IRIS, the "starttime"
    parameter is defined as one would expect intuitively and by reading the
    general "time parameter interpretation":

    """
    start[time]
    Limit to metadata describing channels operating on or
    after the specified start time.
    """


    I suggest that the wording in the official FDSNWS specs should be
    changed, probably to something like (endtime accordingly):

    """
    starttime: Required
    Limit to metadata epochs active on or
    after the specified start time.
    """


    best,
    Tobias




    --
    Dipl.-Geophys. Tobias Megies

    Geophysikalisches Observatorium
    Ludwigshöhe 8
    82256 Fürstenfeldbruck

    Ludwig-Maximilians-Universität
    Department für Geo- und Umweltwissenschaften
    Sektion Geophysik
    Theresienstrasse 41/IV
    80333 München

    Tel: +49 (0) 89 2180-73981
    +49 (0) 89 2180-4326
    Mail: tobias.megies<at>geophysik.uni-muenchen.de

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