⇐ ⇒

[CF-metadata] Platform Heave

From: Hamilton, Steve <sj.hamilton>
Date: Tue, 3 Jul 2018 08:12:02 +0000

Please can you advise if this standard name has now been accepted and when it will be included in the CF Standard Names

If there is something else to do please let me know

Thanks

Steve

From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> On Behalf Of Lowry, Roy K.
Sent: 04 June 2018 12:21
To: Jim Biard <jbiard at cicsnc.org>; cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] Platform Heave


I'm equally happy with this.



I have now retired but will continue to be active through an Emeritus Fellowship using this e-mail address.

________________________________
From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu<mailto:cf-metadata-bounces at cgd.ucar.edu>> on behalf of Jim Biard <jbiard at cicsnc.org<mailto:jbiard at cicsnc.org>>
Sent: 01 June 2018 22:56
To: cf-metadata at cgd.ucar.edu<mailto:cf-metadata at cgd.ucar.edu>
Subject: Re: [CF-metadata] Platform Heave


Nan,

Thanks for pulling things back in. I very much like the idea of keeping technology or specific methods out of the definition if at all possible, so I like your proposal. I expect we should include platform in the definition, as well as an indication that this is dynamic (over time). How about these definitions?

platform_heave (m) = upwards vertical displacement of a platform over a measurement time interval

platform_heave_rate (m s-1) = upwards rate of change in vertical displacement of a platform over a measurement time interval

They leave out some detail but capture the relative nature of the quantities.

(In my mind, the primary detail being left out is the 'net zero' nature of the quantities, which gets back to defining the 'moving-mean' sea level reference point.)
Grace and peace,

Jim
On 6/1/18 11:23 AM, Nan Galbraith wrote:
Hi all -

The latest version is confusing to me. The term 'a platform that is nominally at rest' does
not apply to many platforms for which heave is calculated; the original version of that,
'a moving object above the vertical level of that object when stationary' was maybe a little
more clear... if also a little wordy.

And, the term 'vertical displacement determined by integrating vertical accelerations' may
also not apply - I've been looking at the different ways heave is calculated, and there
are a few: 'Heave can be computed from GPS RTK height measurements and from
vertical accelerations measured by linear accelerometers'

Why not keep it simple: platform_heave (m) = upwards vertical displacement? Do we need
to be more specific than that?

Thanks - Nan

On 5/31/18 5:01 AM, Hamilton, Steve wrote:


Thanks for everyone's input, the below seems acceptable for now

Regards

Steve

From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu><mailto:cf-metadata-bounces at cgd.ucar.edu> On Behalf Of Lowry, Roy K.
Sent: 30 May 2018 21:37
To: Jim Biard <jbiard at cicsnc.org><mailto:jbiard at cicsnc.org>; cf-metadata at cgd.ucar.edu<mailto:cf-metadata at cgd.ucar.edu>
Subject: Re: [CF-metadata] Platform Heave

An afterthought. Heave is conventionally positive upwards so to make this clear I would add the word 'upwards' thus:

platform_heave (m) = upwards vertical displacement determined by integrating vertical accelerations of a platform that is nominally at rest.

platform_heave_rate (m s-1) = upwards vertical velocity determined by integrating vertical accelerations of a platform that is nominally at rest.

Cheers. Roy.

I have now retired but will continue to be active through an Emeritus Fellowship using this e-mail address.

------------------------------------------------------------------------

From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu<mailto:cf-metadata-bounces at cgd.ucar.edu> <mailto:cf-metadata-bounces at cgd.ucar.edu><mailto:cf-metadata-bounces at cgd.ucar.edu>> on behalf of Lowry, Roy K. <rkl at bodc.ac.uk<mailto:rkl at bodc.ac.uk> <mailto:rkl at bodc.ac.uk><mailto:rkl at bodc.ac.uk>>
Sent: 30 May 2018 21:02
To: Jim Biard; cf-metadata at cgd.ucar.edu<mailto:cf-metadata at cgd.ucar.edu> <mailto:cf-metadata at cgd.ucar.edu><mailto:cf-metadata at cgd.ucar.edu>
Subject: Re: [CF-metadata] Platform Heave

Thanks Jim,

That work for me.

Cheers, Roy.

------------------------------------------------------------------------

From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu<mailto:cf-metadata-bounces at cgd.ucar.edu> <mailto:cf-metadata-bounces at cgd.ucar.edu><mailto:cf-metadata-bounces at cgd.ucar.edu>> on behalf of Jim Biard <jbiard at cicsnc.org<mailto:jbiard at cicsnc.org> <mailto:jbiard at cicsnc.org><mailto:jbiard at cicsnc.org>>
Sent: 30 May 2018 18:39
To: cf-metadata at cgd.ucar.edu<mailto:cf-metadata at cgd.ucar.edu> <mailto:cf-metadata at cgd.ucar.edu><mailto:cf-metadata at cgd.ucar.edu>
Subject: Re: [CF-metadata] Platform Heave

Roy,

So, heave is integrated vertical acceleration? How about

platform_heave (m) = vertical displacement determined by integrating vertical accelerations of a platform that is nominally at rest.

platform_heave_rate (m s-1) = vertical velocity determined by integrating vertical accelerations of a platform that is nominally at rest.

Jim

On 5/27/18 5:38 AM, Lowry, Roy K. wrote:

    Hi Jim,

    Does

         "Heave" is a term used to describe the vertical displacement
        of a moving object above the vertical level of that object
        when stationary.

    help by getting rid of the semantically-loaded word 'height'?
    If not, what would?

    I think the confusion is because you are thinking of heave in
    terms of position within a reference frame. To think of it as the
    vertical displacement between a real platform and a massless
    platform is misleading- such considerations are part of the
    derivation of wave height from high frequency heave measurements,
    which isn't relevant to a discussion of the raw measurement. It's
    also worth bearing in mind that whilst the debate has focused on
    platforms floating on the sea surface, the concept of heave could
    in theory be applied to objects in the atmosphere.

    In practice, heave is measured by accelerometers that are usually
    combined with tilt sensors that give pitch, roll and yaw. Hence,
    it is totally decoupled from any reference outside the platform.

    To answer your last muse, to get heave from a high frequency
    height relative to datum time series the method would need to
    determine the height of the object when 'stationary'. In the case
    of objects on the sea, 'stationary' is considered to be a flat
    calm sea (i.e. no waves), which can be approximated by averaging
    the raw time series. So, heave could be approximated by
    differencing the raw and averaged data. However, I can't think why
    anybody would want to do that.

    Cheers, Roy.

    ------------------------------------------------------------------------

    From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu><mailto:cf-metadata-bounces at cgd.ucar.edu>
    <mailto:cf-metadata-bounces at cgd.ucar.edu><mailto:cf-metadata-bounces at cgd.ucar.edu> on behalf of Jim Biard
    <jbiard at cicsnc.org><mailto:jbiard at cicsnc.org> <mailto:jbiard at cicsnc.org><mailto:jbiard at cicsnc.org>
    Sent: 26 May 2018 23:18
    To: cf-metadata at cgd.ucar.edu<mailto:cf-metadata at cgd.ucar.edu> <mailto:cf-metadata at cgd.ucar.edu><mailto:cf-metadata at cgd.ucar.edu>
    Subject: Re: [CF-metadata] Platform Heave

    My biggest concern is that the standard name definition makes it
    clear in some fashion or other that this is a measure of
    deviations from some lower frequency (or low-pass filtered)
    measure of vertical position. (As are sway and surge in relation
    to their corresponding horizontal coordinates.) As was pointed
    out, heave is used in certain communities, so it's reasonable to
    provide a standard name, but it seems rather imprecise as it has
    been described so far.

    If I have understood the explanations correctly, a time series of
    platform height relative to a fixed datum that has sufficient
    precision and frequency would fully represent the heave along with
    the more slowly varying effects of tide, waves, etc. So is heave,
    as usually used, the first-order instantaneous difference between
    the height of an actual platform and the height of a massless
    ideal platform that would maintain a fixed offset relative to the
    sea surface? And, just out of curiosity, how would a time series
    of instantaneous measures of height relative to a fixed datum be
    separated in practice into heave and "non-heave" height?

    Getting back on track, it seems to me that the definition ought to
    somehow assist the reader in understanding how heave relates to
    other measures of height.



    On Sat, May 26, 2018 at 3:11 AM, Lowry, Roy K. <rkl at bodc.ac.uk<mailto:rkl at bodc.ac.uk>
    <mailto:rkl at bodc.ac.uk><mailto:rkl at bodc.ac.uk>> wrote:

        Dear Jim and John,

        Heave is indeed a height relative to a datum, that datum being
        the calm sea surface, which is a local short interval mean sea
        level that isn't linked into any global reference system.
        Indeed the 'datum' moves relative to the rest of the world -
        but not the platform - as tide rises and falls so many would
        prefer to call it an 'instrument zero' rather than a 'datum'.

        Heave is therefore a very different measurement to any sea
        level parameter and is the raw measurement recorded at high
        (Hz to kHz) frequency as a time series by floating wave
        instruments such as waveriders and shipborne wave recorders.
        It therefore cannot be sensibly described by the same or
        similar Standard Name as a measurement of height above a
        globally referenced datum like long-term mean sea level or
        geoid. Whilst the Standard Name could be
        'platform_height_above_calm_sea_surface' or
        'platform_height_above_stationary_position' I would argue that
        'heave' is a term from the same domain vocabulary as 'pitch',
        'roll' and 'yaw' and therefore should be used.

        John is right to point out that the heave measurement is
        affected by the nature of the platform with a 250,000 tonne
        supertanker moving up and down much less than a rowing boat in
        a given wave climate, especially a wind sea. That was what was
        behind the SBWR corrections based on platform dimensions set
        up by Laurie Draper and Tom Tucker back in the 1980s.

        Cheers, Roy.

        ------------------------------------------------------------------------

        From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu<mailto:cf-metadata-bounces at cgd.ucar.edu>
        <mailto:cf-metadata-bounces at cgd.ucar.edu><mailto:cf-metadata-bounces at cgd.ucar.edu>> on behalf of John
        Helly <hellyj at ucsd.edu<mailto:hellyj at ucsd.edu> <mailto:hellyj at ucsd.edu><mailto:hellyj at ucsd.edu>>
        Sent: 26 May 2018 04:48
        To: Jim Biard; cf-metadata at cgd.ucar.edu<mailto:cf-metadata at cgd.ucar.edu>
        <mailto:cf-metadata at cgd.ucar.edu><mailto:cf-metadata at cgd.ucar.edu>
        Subject: Re: [CF-metadata] Platform Heave

        Can't let go of this yet.

        If you think about the inverse problem of deriving the sea
        surface elevation from the heave you would have to account for
        the latency of ship motion relative to the sea-surface. A
        wave passing under a ship induces motions that are not
        instantaneous either in attack or decay.

        J.

        On 5/25/18 20:42, John Helly wrote:

            I believe it's a synonym within the oceanographic
            community for the vertical motion of an ocean-going platform.

            https://en.wikipedia.org/wiki/Ship_motions

            Ship motions - Wikipedia
            <https://en.wikipedia.org/wiki/Ship_motions><https://en.wikipedia.org/wiki/Ship_motions>

            en.wikipedia.org <http://en.wikipedia.org><http://en.wikipedia.org>

            Ship motions are defined by the six degrees of freedom
            that a ship, boat or any other craft can experience.

            Could just be jargon but it strike me as more complex:
            nonetheless a vertical position relative to a datum, but
            the buoyancy, stability and momentum of the platform are
            implied as part of the dynamics. It seems that the datum
            is not a geophysical one alone but confounded with the
            'normal' waterline for a platform so it may be relative to
            the water level in which the platform is embedded. That's
            a tough one. Two different platforms on the same sea
            surface would have different 'heave', for example.

            J.

            On 5/25/18 19:54, Jim Biard wrote:

                Hi.

                I get and endorse the need for pitch, roll, and yaw,
                but I remain perplexed about heave. How is a time
                series of 'heave' different from a time series of
                height relative to some vertical datum? I've yet to
                see a proposed definition that convinces me that this
                is a uniquely different quantity.

                Grace and peace,

                Jim



                On Fri, May 25, 2018 at 7:28 AM, Lowry, Roy K.
                <rkl at bodc.ac.uk<mailto:rkl at bodc.ac.uk> <mailto:rkl at bodc.ac.uk><mailto:rkl at bodc.ac.uk>> wrote:

                    Dear All,

                    I agree with Nan that definitions of pitch roll
                    and yaw would improve the existing Standard Name
                    definitions. I also agree with using the existing
                    orientation Standard Names for ADCPs and that the
                    'platform' definition wording could make this
                    clearer. However, such an enhancements should be
                    submitted as a separate proposal and not be
                    considered as part of Steve's proposal.

                    Cheers, Roy.

                    ------------------------------------------------------------------------

                    From: CF-metadata
                    <cf-metadata-bounces at cgd.ucar.edu<mailto:cf-metadata-bounces at cgd.ucar.edu>
                    <mailto:cf-metadata-bounces at cgd.ucar.edu><mailto:cf-metadata-bounces at cgd.ucar.edu>> on
                    behalf of Nan Galbraith <ngalbraith at whoi.edu<mailto:ngalbraith at whoi.edu>
                    <mailto:ngalbraith at whoi.edu><mailto:ngalbraith at whoi.edu>>
                    Sent: 25 May 2018 14:46
                    To: cf-metadata at cgd.ucar.edu<mailto:cf-metadata at cgd.ucar.edu>
                    <mailto:cf-metadata at cgd.ucar.edu><mailto:cf-metadata at cgd.ucar.edu>
                    Subject: Re: [CF-metadata] Platform Heave

                    I'd really like to see pitch, roll and yaw defined
                    in the CF standard
                    name table; currently
                    the definitions only say 'Standard names for
                    platform describe the
                    motion and orientation
                    of the vehicle from which observations are made
                    e.g. aeroplane, ship or
                    satellite.'

                    Also, not to get too far into the weeds, but many
                    of the platform terms
                    are important
                    for instruments like ADCPs, so I'd just like to
                    confirm that these
                    definitions - and
                    the names themselves - can be used to describe
                    instruments, not just
                    vehicles
                    'e.g. aeroplane, ship or satellite'. We already
                    use pitch roll and
                    yaw for these
                    instruments on surface moorings, and I hope (and
                    assume) this is legal.

                    Thanks - Nan Galbraith


                    On 5/25/18 8:53 AM, Lowry, Roy K. wrote:
>
>
> Dear Steve,
>
>
> One of the reasons I was interested in your
                    definitions was your
> perspective on the datum (i.e. zero value) for
                    heave. The datum
> 'mean_sea_level' is well used in CF, but with
                    the definition 'time
> mean of sea surface elevation at a given
                    location over an arbitrary
> period sufficient to eliminate the tidal
                    signals.' This is obviously
> not appropriate for platform heave which doesn't
                    take any account of
> the state of the tide and so I would exclude
                    'mean_sea_level' from the
> Standard Name.
>
>
> I think my preference would be to keep the term
                    'heave' as we already
> have 'pitch', 'yaw' and 'roll', giving:
>
>
> platform_heave (m)
>
>
> Standard names for platform describe the motion
                    and orientation of the
> vehicle from which observations are made e.g.
                    aeroplane, ship or
> satellite. "Heave" is a term used to describe
                    the vertical
> displacement of the platform above its position
                    when not moving.
>
>
> tendency_of_platform_heave (m s-1)
>
>
> Standard names for platform describe the motion
                    and orientation of the
> vehicle from which observations are made e.g.
                    aeroplane, ship or
> satellite. "Tendency_of_X" means derivative of X
                    with respect to time.
> "Heave" is a term used to describe the vertical
                    displacement of the
> platform above its position when not moving.
>
>
> What do you think?
>
>
> Cheers, Roy.
>
>
> I am retiring on 31/05/2018 but will continue to
                    be active through an
> Emeritus Fellowship using this e-mail address.
>
>
>
>
                    ------------------------------------------------------------------------
> *From:* CF-metadata
                    <cf-metadata-bounces at cgd.ucar.edu<mailto:cf-metadata-bounces at cgd.ucar.edu>
                    <mailto:cf-metadata-bounces at cgd.ucar.edu><mailto:cf-metadata-bounces at cgd.ucar.edu>> on
                    behalf of
> Hamilton, Steve <sj.hamilton at fugro.com<mailto:sj.hamilton at fugro.com>
                    <mailto:sj.hamilton at fugro.com><mailto:sj.hamilton at fugro.com>>
> *Sent:* 25 May 2018 08:51
> *Subject:* Re: [CF-metadata] Platform Heave
>
> All,
>
> Thanks for all the comments, I have tried to
                    capture as below -
>
> *Parameter Name***
>
>
>
> *Standard Name*
>
>
>
> *Definition*
>
>
>
> *Canonical Units*
>
> Platform Heave
>
>
>
> Platform_Height_above_mean_sea_Level
>
>
>
> Standard names for platform describe the motion and
> orientation of the vehicle from which
                    observations are made e.g.
> aeroplane, ship or satellite. Height above mean
                    sea Level is the
> linear vertical (up/down) distance of the
                    platform in respect to the
> mean sea level.
>
>
>
> m
>
> Platform Heave Rate
>
>
>
> Tendency_of_Platform_Height_above_mean_sea_Level
>
>
>
> Standard names for platform describe the motion and
> orientation of the vehicle from which
                    observations are made e.g.
> aeroplane, ship or satellite. "tendency_of_X"
                    means derivative of X
> with respect to time. Height above mean sea
                    Level is the linear
> vertical (up/down) distance of the platform in
                    respect to the mean sea
> level.
>
>
>
> m s-1
>
> Please let me know if you have further comments
>
> Thanks
>
> Steve
>
> *From:*Steven Emmerson <emmerson at ucar.edu<mailto:emmerson at ucar.edu>
                    <mailto:emmerson at ucar.edu><mailto:emmerson at ucar.edu>>
> *Sent:* 21 May 2018 19:18
> *Subject:* Re: [CF-metadata] Platform Heave
>
> Whatever name you come up with, the canonical
                    unit of the heave rate
> shouldn't be "ms-1", but rather one of the
                    following:
>
> m s-1
>
> m/s
>
> m.s-1
>
> I favor "m/s".
>
>
> Regards,
>
> Steve Emmerson
>
> On Mon, May 21, 2018 at 6:32 AM, Hamilton, Steve
> <sj.hamilton at fugro.com<mailto:sj.hamilton at fugro.com>
                    <mailto:sj.hamilton at fugro.com><mailto:sj.hamilton at fugro.com>
                    <mailto:sj.hamilton at fugro.com><mailto:sj.hamilton at fugro.com>> wrote:
>
> Hi
>
> I am trying to find the CF name for heave of
                    a vessel or
> platform. platform_roll_angle and
                    platform_pitch_angle already
> exist but nothing on heave
>
> Would be the following be acceptable
>
> Platform_heave (m)
>
> Platform_heave_rate (ms-1)
>
> Standard names for platform describe the motion
                    and orientation of
> the vehicle from which observations are made
                    e.g. aeroplane, ship
> or satellite.
>
> Kind Regards,
>
> Steve


--
[CICS-NC]<http://www.cicsnc.org/>Visit us on
Facebook <http://www.facebook.com/cicsnc>
Jim Biard
Research Scholar
Cooperative Institute for Climate and Satellites NC <http://cicsnc.org/>
North Carolina State University <http://ncsu.edu/>
NOAA National Centers for Environmental Information <http://ncdc.noaa.gov/>
formerly NOAA's National Climatic Data Center
151 Patton Ave, Asheville, NC 28801
e: jbiard at cicsnc.org<mailto:jbiard at cicsnc.org>
o: +1 828 271 4900
Connect with us on Facebook for climate<https://www.facebook.com/NOAANCEIclimate> and ocean and geophysics<https://www.facebook.com/NOAANCEIoceangeo> information, and follow us on Twitter at _at_NOAANCEIclimate<https://twitter.com/NOAANCEIclimate> and @NOAANCEIocngeo<https://twitter.com/NOAANCEIocngeo>.
________________________________
This message (and any attachments) is for the recipient only. NERC is subject to the Freedom of Information Act 2000 and the contents of this email and any reply you make may be disclosed by NERC unless it is exempt from release under the Act. Any material supplied to NERC may be stored in an electronic records management system.
________________________________
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.cgd.ucar.edu/pipermail/cf-metadata/attachments/20180703/04408bd0/attachment-0001.html>
Received on Tue Jul 03 2018 - 02:12:02 BST

This archive was generated by hypermail 2.3.0 : Tue Sep 13 2022 - 23:02:43 BST

⇐ ⇒