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.
>
>
> 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> on behalf of
> Jim Biard <jbiard at cicsnc.org>
> *Sent:* 26 May 2018 23:18
> *To:* 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.
>
> CICS-NC <http://www.cicsnc.org/>Visit us on
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>
>
> On Sat, May 26, 2018 at 3:11 AM, Lowry, Roy K. <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.
>
>
> 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>> on behalf of John Helly
> <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>
> *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
>> <https://en.wikipedia.org/wiki/Ship_motions>
>>
>> Ship motions - Wikipedia <https://en.wikipedia.org/wiki/Ship_motions>
>> 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
>>>
>>> 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
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>>>
>>> e: jbiard at cicsnc.org <mailto:jbiard at cicsnc.org>
>>> o: +1 828 271 4900
>>>
>>> /Connect with us on Facebook for climate
>>> <http://www.facebook.com/NOAANCEIclimate>?and ocean and
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>>>
>>> /
>>>
>>>
>>> On Fri, May 25, 2018 at 7:28 AM, Lowry, Roy K. <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.
>>>
>>>
>>> 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>> on behalf of Nan
>>> Galbraith <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>
>>> *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>> on behalf of
>>> > Hamilton, Steve <sj.hamilton at fugro.com
>>> <mailto:sj.hamilton at fugro.com>>
>>> > *Sent:* 25 May 2018 08:51
>>> > *To:* cf-metadata at cgd.ucar.edu
>>> <mailto:cf-metadata at cgd.ucar.edu>
>>> > *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>>
>>> > *Sent:* 21 May 2018 19:18
>>> > *To:* Hamilton, Steve <sj.hamilton at fugro.com
>>> <mailto:sj.hamilton at fugro.com>>
>>> > *Cc:* cf-metadata at cgd.ucar.edu
>>> <mailto:cf-metadata at cgd.ucar.edu>
>>> > *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>> 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
>>> >
>>> >
>>>
>>>
>>> --
>>> *******************************************************
>>> * Nan Galbraith Information Systems Specialist *
>>> * Upper Ocean Processes Group Mail Stop 29 *
>>> * Woods Hole Oceanographic Institution??????????????? *
>>> * Woods Hole, MA 02543 (508) 289-2444 *
>>> *******************************************************
>>>
>>>
>>> _______________________________________________
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>>
>> --
>> John Helly, University of California, San Diego / San Diego Supercomputer Center / Scripps Institution of Oceanography / 760 840 8660 mobile /http://www.sdsc.edu/~hellyj <http://www.sdsc.edu/%7Ehellyj>
>> ORCID ID:orcid.org/0000-0002-3779-0603 <http://orcid.org/0000-0002-3779-0603>
>
> --
> John Helly, University of California, San Diego / San Diego Supercomputer Center / Scripps Institution of Oceanography / 760 840 8660 mobile /http://www.sdsc.edu/~hellyj <http://www.sdsc.edu/%7Ehellyj>
> ORCID ID:orcid.org/0000-0002-3779-0603 <http://orcid.org/0000-0002-3779-0603>
>
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> 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
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>
>
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