International Federation of Digital Seismograph Networks

Thread: station xml extension for obs

None
Started: July 11, 2014, 7:45 a.m.
Last activity: July 11, 2014, 9:54 a.m.
Sleeman, Reinoud (KNMI)
July 11, 2014, 7:45 a.m.


Dear all,

our colleagues from RESIF proposes an extension of Station.XML with the
new elements below, in particular to serve the needs for OBS deployments.
This proposal was presented already last year in an initial form but never
formally send around in this WG. Please consider this proposal and give
feedback within 4 weeks if needed. An image is attached to illustrate the
need and possibilities for having the 3 elements Depth. WaterDepth and
Elevation.

Best regards
Reinoud



Station level

+ Depth : element : distanceType: 0..1
indicates the wished depth of the station (relative to sea level). This information is required in the case of OBS station description

+ Levelling : LevellingType : 0..1
indicates the method used to level the equipment. This information is mandatory in the case of OBS station description

+ LevellingType : Type : attribute : string [MOTORIZED, GRAVITY]
Precision : attribute : double : 0..1
indicates the error factor of the levelling system
Unit : attribut : string [DEGREES]

_________________________________________________________________________

Channel level

+ WaterDepth : element : distanceType: 0..1
Water depth, mandatory for OBS position description

Motivation: both "depth" and "water depth" should be in the channel description as instruments
may be placed in bodies of water above sea level. It is important to know how far the instrument
is below the water surface, so that, among other things, surface reflections can be removed.
In the ocean, the "elev" and "depth" parameters are adequate for this: the "elev" is a negative number
giving the elevation of the sea floor relative to sea level, the depth specifies how far below or above
the seafloor the instrument is placed, and the water depth will simply be the inverse of the "elev".
In lakes, however, the water level is not necessarily sea level and so the water depth must be specified.

+ Clock : element : string : 0..*
Clock type

+ Vault: element : string : 0..*

Motivation: The element <Vault> is presently defined at the 'Station level'. But the <Vault> element
should also be present at the Channel Level, because the vault can differ from sensor to sensor in the
case of a complex antenna.

+ Geology: element : string : 0..*

Motivation: The element <geology> is presently defined at the 'Station level'. But the <geology> element
should also be present at the Channel Level (in the case of a complex antenna).

_________________________________________________________________________
END



Attachments
  • Florian Haslinger
    July 11, 2014, 9:37 a.m.
    Dear Reinoud and all,

    I couldn't resist reading - and now I can't resist commenting. Please see comments embedded



    Station level

    + Depth : element : distanceType: 0..1
    indicates the wished depth of the station (relative to sea level). This information is required in the case of OBS station description


    - why 'wished' - and not measured? (and if whished, by whom and when? :-)

    - according to the drawing 'depth' is relative to sea floor level (not sea level)
    (following the argumentation that 'elevation' is the height of 'solid ground' relative to sea level - question on that - how well can in this sense the sea floor elevation be determined?)

    - why at Station level? following logic for land-based sensors Depth should be at the Channel level? (text after WaterDepth also requests Depth at Channel level)
    (see also below question re. Elevation (elev))

    + Levelling : LevellingType : 0..1
    indicates the method used to level the equipment. This information is mandatory in the case of OBS station description


    - given the argumentation below about 'complex antennas' I would assume that Levelling and LevellingType may be instrument specific and thus should rather be on the Channel (Location?) level than the Station level?


    + LevellingType : Type : attribute : string [MOTORIZED, GRAVITY]
    Precision : attribute : double : 0..1
    indicates the error factor of the levelling system
    Unit : attribut : string [DEGREES]

    _________________________________________________________________________

    Channel level

    + WaterDepth : element : distanceType: 0..1
    Water depth, mandatory for OBS position description

    Motivation: both "depth" and "water depth" should be in the channel description as instruments
    may be placed in bodies of water above sea level. It is important to know how far the instrument
    is below the water surface, so that, among other things, surface reflections can be removed.
    In the ocean, the "elev" and "depth" parameters are adequate for this: the "elev" is a negative number
    giving the elevation of the sea floor relative to sea level, the depth specifies how far below or above
    the seafloor the instrument is placed, and the water depth will simply be the inverse of the "elev".
    In lakes, however, the water level is not necessarily sea level and so the water depth must be specified.


    question to 'elevation': in the current description of stationXML1.0 at http://www.fdsn.org/xml/station/fdsn-station-1.0.xsd the channel.elevation is described as 'elevation of the sensor' (rather than topographic elevation of the earth surface at the sensor location). If this description is correct then 'elevation' at the channel level for OBS channels (in oceans) should be the distance of the sensor from sea level. (is 'elevation' at the station level different than 'elevation' at the channel level?)


    + Clock : element : string : 0..*
    Clock type

    + Vault: element : string : 0..*

    Motivation: The element <Vault> is presently defined at the 'Station level'. But the <Vault> element
    should also be present at the Channel Level, because the vault can differ from sensor to sensor in the
    case of a complex antenna.

    + Geology: element : string : 0..*

    Motivation: The element <geology> is presently defined at the 'Station level'. But the <geology> element
    should also be present at the Channel Level (in the case of a complex antenna).

    is it realistic that for oone station (i.e. one station code) the geology changes that drastically over the location of sensors? (shouldn't that almost require separate station codes then?)

    if vault & Geology are to be defined at channel level then I would not also define them at station level

    (I would in general try to avoid having parameters with the same name (and potentially different meanings) at various levels.)


    Kind regards
    florian




    _________________________________________________________________________
    END


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    • Philip Crotwell
      July 11, 2014, 9:54 a.m.
      Hi

      I agree with everything Florian said, but wanted to add that there is
      no need to add a "clock" element as that can be accommodated within
      the existing <Equipment> element of channel.

      My understanding is station elevation is at free surface, so the
      elevation of the lake surface, channel elevation is the sensor,
      channel depth is emplacement depth into solid earth. Thus water depth
      would be "station elevation" - "channel elevation" - "channel depth".
      So a OBS drilled 10 m into the bottom of a 30m deep lake with water
      surface at 100m elevation would have:
      station elevation = 100m
      channel elevation = 60m
      channel depth = 10m
      That said I am not opposed to having an explicit spot to put water
      depth as that is something that is directly measured and so is useful
      to keep in original form.

      Also, this does bring up the point that both <vault> and <geology>
      probably should have been declared on the channel in the first place
      since even on land it is legitamate to have multiple "vaults" that
      contain different instruments all contained within the same "station".
      For example a borehole seismometer that also has a surface strong
      motion instrument. A channel <geology> field would be useful to
      describe the rock type that the borehole is emplaced in, while the
      surface geology might be very different.

      It is a bit late in the game, but I wish there had been a containing
      element in between station and channel, perhaps a "site" or "location"
      or "substation" that would collect all channels that were together to
      avoid repeating much of the channel information that is shared by all
      three components of a seismometer for example. The horse has left the
      barn, so I will just file that under "what could have been".

      thanks
      Philip


      On Fri, Jul 11, 2014 at 5:37 AM, Haslinger Florian
      <florian.haslinger<at>sed.ethz.ch> wrote:
      Dear Reinoud and all,

      I couldn't resist reading - and now I can't resist commenting. Please see comments embedded



      Station level

      + Depth : element : distanceType: 0..1
      indicates the wished depth of the station (relative to sea level). This information is required in the case of OBS station description


      - why 'wished' - and not measured? (and if whished, by whom and when? :-)

      - according to the drawing 'depth' is relative to sea floor level (not sea level)
      (following the argumentation that 'elevation' is the height of 'solid ground' relative to sea level - question on that - how well can in this sense the sea floor elevation be determined?)

      - why at Station level? following logic for land-based sensors Depth should be at the Channel level? (text after WaterDepth also requests Depth at Channel level)
      (see also below question re. Elevation (elev))

      + Levelling : LevellingType : 0..1
      indicates the method used to level the equipment. This information is mandatory in the case of OBS station description


      - given the argumentation below about 'complex antennas' I would assume that Levelling and LevellingType may be instrument specific and thus should rather be on the Channel (Location?) level than the Station level?


      + LevellingType : Type : attribute : string [MOTORIZED, GRAVITY]
      Precision : attribute : double : 0..1
      indicates the error factor of the levelling system
      Unit : attribut : string [DEGREES]

      _________________________________________________________________________

      Channel level

      + WaterDepth : element : distanceType: 0..1
      Water depth, mandatory for OBS position description

      Motivation: both "depth" and "water depth" should be in the channel description as instruments
      may be placed in bodies of water above sea level. It is important to know how far the instrument
      is below the water surface, so that, among other things, surface reflections can be removed.
      In the ocean, the "elev" and "depth" parameters are adequate for this: the "elev" is a negative number
      giving the elevation of the sea floor relative to sea level, the depth specifies how far below or above
      the seafloor the instrument is placed, and the water depth will simply be the inverse of the "elev".
      In lakes, however, the water level is not necessarily sea level and so the water depth must be specified.


      question to 'elevation': in the current description of stationXML1.0 at http://www.fdsn.org/xml/station/fdsn-station-1.0.xsd the channel.elevation is described as 'elevation of the sensor' (rather than topographic elevation of the earth surface at the sensor location). If this description is correct then 'elevation' at the channel level for OBS channels (in oceans) should be the distance of the sensor from sea level. (is 'elevation' at the station level different than 'elevation' at the channel level?)


      + Clock : element : string : 0..*
      Clock type

      + Vault: element : string : 0..*

      Motivation: The element <Vault> is presently defined at the 'Station level'. But the <Vault> element
      should also be present at the Channel Level, because the vault can differ from sensor to sensor in the
      case of a complex antenna.

      + Geology: element : string : 0..*

      Motivation: The element <geology> is presently defined at the 'Station level'. But the <geology> element
      should also be present at the Channel Level (in the case of a complex antenna).

      is it realistic that for oone station (i.e. one station code) the geology changes that drastically over the location of sensors? (shouldn't that almost require separate station codes then?)

      if vault & Geology are to be defined at channel level then I would not also define them at station level

      (I would in general try to avoid having parameters with the same name (and potentially different meanings) at various levels.)


      Kind regards
      florian




      _________________________________________________________________________
      END


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