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.
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On Sat, May 26, 2018 at 3:11 AM, Lowry, Roy K. <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> on behalf of John
> Helly <hellyj at ucsd.edu>
> *Sent:* 26 May 2018 04:48
> *To:* Jim Biard; 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>
> 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
>
> [image: 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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>
>
> On Fri, May 25, 2018 at 7:28 AM, Lowry, Roy K. <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> on behalf of Nan
> Galbraith <ngalbraith at whoi.edu>
> *Sent:* 25 May 2018 14:46
> *To:* 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> on behalf of
> > Hamilton, Steve <sj.hamilton at fugro.com>
> > *Sent:* 25 May 2018 08:51
> > *To:* 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>
> > *Sent:* 21 May 2018 19:18
> > *To:* Hamilton, Steve <sj.hamilton at fugro.com>
> > *Cc:* 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
> <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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> subject to the Freedom of Information Act 2000 and the contents of this
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> _______________________________________________
> CF-metadata mailing listCF-metadata at cgd.ucar.eduhttp://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
>
> --
> John Helly, University of California, San Diego / San Diego Supercomputer Center / Scripps Institution of Oceanography / 760 840 8660 mobile / http://www.sdsc.edu/~hellyj
> ORCID ID: 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
> ORCID ID: orcid.org/0000-0002-3779-0603
>
> ------------------------------
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> subject to the Freedom of Information Act 2000 and the contents of this
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