Hi Jeff,
My motives for 'looking down' rather than 'looking up' were that we already had a 'sea_floor_depth_below_mean_sea_level' and established practice with CF name development has been to be as consistent as possible with name structure. Jonathan Gregory has led this development in the past - let's see what his take is on the best name syntax.
The issue of encoding sea level measurements relative to reference datums other than MSL has been discussed on the list at length previously and I don't recall our ever reaching a satisfactory resolution. It might be worth your having a trawl around the archives or waiting for somebody with a better memory than me to summarise where the discussion had reached.
Incidentally, I have seen the 'datum' for streams without a datum described as 'tide gauge zero', which often has a physical manifestation such as a metal peg driven into a wall.
Cheers, Roy.
-----Original Message-----
From: Jeff deLaBeaujardiere [mailto:Jeff.deLaBeaujardiere at noaa.gov]
Sent: 28 January 2010 14:06
To: Lowry, Roy K
Cc: John Graybeal; cf-metadata at cgd.ucar.edu; Mike Garcia
Subject: Re: [CF-metadata] seeking CF name for total water column height
I should mention that there are other types of water level measurements for which we will want names. These are instruments such as tide gauges that measure water relative to a reference datum (such as mean lower low water, or highest astronomical tide), or stream gauges that measure relative to the station itself but not a formal datum.
I spoke about this yesterday afternoon with some water-level experts at NOAA CO-OPS, and we felt that three new CF names like the following might suffice:
sea_floor_depth_below_sea_surface[*]
water_level_with_reference datum (or "above" instead of "with")
water_level_without_reference datum
[*] Looking at this one again, I wonder whether sea_surface_height_above_sea_floor would be more appropriate. NDBC had suggested total_water_column_height.
-Jeff DLB
Lowry, Roy K wrote:
> Hi John,
>
> Ah, I thought you were objecting to having different names for different averaging intervals. Let's see if I can improve the definition.
>
> There are three varieties of water depth (sea_floor_depth_below_sea_surface) that I've encountered.
>
> 1 Instantaneous measurements collected at high frequency over a short time interval designed to quantify waves. These are normally reduced to a raft of wave statistics by processing on board the instrument and I've certainly never seen them as a stream and so didn't see any point in setting up a separate standard name.
>
> 2 Measurements averaged over a sampling interval (an hour or shorter) to filter out variance caused by normal waves but not tide (or unusually long period waves). This is Jeff's stream, and also pretty much what is measured by an echosounder mounted on all but the smallest ship.
>
> 3 Long-term averages or nominal calculations by models that filter out (or ignore in the case of models) the variances caused by waves and tide - which are covered by the existing Standard Name 'sea_floor_depth_below_mean_sea_level'.
>
> How about 'The vertical distance between the sea surface and the seabed as measured at a given point in space including the variance caused by tides and possibly waves'? Or can you do better?
>
> Cheers, Roy.
>
> -----Original Message-----
> From: John Graybeal [mailto:jbgraybeal at mindspring.com]
> Sent: 27 January 2010 23:01
> To: Lowry, Roy K
> Cc: cf-metadata at cgd.ucar.edu; Mike Garcia
> Subject: Re: [CF-metadata] seeking CF name for total water column height
>
> I have no concern about whether this stream needs labeling. My concern
> is whether you are defining something in the definition which is in no
> way described by the label, and which will prevent that label being
> used for other variables in other streams.
>
> Put another way, what should the models that calculate the nominal
> sea_floor_depth_below_sea_surface -- or an averaged value longer than
> 1 hour -- call their values?
>
> John
>
>
> On Jan 27, 2010, at 12:54, Lowry, Roy K wrote:
>
>> Hi John,
>>
>> Simple pragmatism. It's what a BPR data stream tends to contain and
>> so it needs labelling.
>>
>> Cheers, Roy.
>>
>> ________________________________________
>> From: John Graybeal [jbgraybeal at mindspring.com]
>> Sent: 27 January 2010 16:41
>> To: Lowry, Roy K
>> Cc: Jeff deLaBeaujardiere; cf-metadata at cgd.ucar.edu; Mike Garcia
>> Subject: Re: [CF-metadata] seeking CF name for total water column
>> height
>>
>> Any particular reason that you are biased for this name representing
>> only a short-term value? Seems to me there is equally the need for a
>> (measured or modeled) value that would be defined exactly the same
>> way, but without the time qualifiers.
>>
>> In general, when CF has a measured observable, the name makes no
>> statement about whether the variable has been measured
>> instantaneously, or for 1 hour, or for one month. It's time-neutral.
>> This has several advantages.
>>
>> I suggest either the same principle be applied here, or that the
>> possibility of the longer-time-frame name be accommodated by adding a
>> qualifier to the name associated with this definition.
>>
>> John
>>
>>
>> On Jan 27, 2010, at 00:58, Lowry, Roy K wrote:
>>
>>> Dear All,
>>>
>>> I think a new Standard Name 'sea_floor_depth_below_sea_surface' is
>>> what's needed here. My definition for this would be 'The vertical
>>> distance between the sea surface and the seabed at a given point in
>>> space and at a given instant in time or averaged over a time
>>> interval that is significantly less than a tidal cycle (1 hour or
>>> less).' This may seem complicated, but is needed to cover BPRs which
>>> do some averaging to smooth out waves. My take on
>>> 'height_above_sea_floor' would be as the z co-ordinate for something
>>> inside a water body.
>>>
>>> May be worth pointing out to Jeff that there is already
>>> 'sea_water_pressure_at_sea_floor' for BPR data that haven't been
>>> converted to depth.
>>>
>>> I've expressed this as a depth rather than as a height to be
>>> consistent with 'sea_floor_depth_below_sea_level' and so we don't
>>> end up with different terms for the same quantity depending upon
>>> whether one is looking upwards or downwards.
>>>
>>> Cheers, Roy.
>>>
>>> -----Original Message-----
>>> From: cf-metadata-bounces at cgd.ucar.edu [mailto:cf-metadata-bounces at cgd.ucar.edu
>>> ] On Behalf Of Jeff deLaBeaujardiere
>>> Sent: 26 January 2010 22:22
>>> To: cf-metadata at cgd.ucar.edu
>>> Cc: Mike Garcia
>>> Subject: [CF-metadata] seeking CF name for total water column height
>>>
>>> Hello-
>>>
>>> I am a new subscriber. We are hoping to adopt CF names wherever
>>> possible in the context of the Integrated Ocean Observing System
>>> (IOOS) Sensor Observation Services (SOS). Not all phenomena we
>>> measure have immediately apparent CF names, however. We are using
>>> this URL as a reference:
>>> http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/current/cf-standard-name-table.html
>>>
>>> The first example is total water column height as derived from a
>>> bottom pressure recorder associated with a tsunami warning buoy.
>>> This is not sea_surface_height_above_reference_ellipsoid or
>>> _above_sea_level. It might be height_above_sea_floor but we're not
>>> really sure what that refers to (height of what?).
>>>
>>> Is there a standard name present or planned that is equivalent to
>>> total_water_column_height?
>>>
>>> Thanks for any information,
>>> Jeff DLB
>>>
>>> --
>>> Jeff de La Beaujardi?re, PhD
>>> Senior Systems Architect, Data Integration Framework
>>> Integrated Ocean Observing System (IOOS) Program Office
>>> National Oceanic and Atmospheric Administration
>>> 1100 Wayne Ave #1225, Silver Spring MD 20910 USA
>>> +1 301 427 2427
>>> Jeff.deLaBeaujardiere at noaa.gov
>>> _______________________________________________
>>> CF-metadata mailing list
>>> CF-metadata at cgd.ucar.edu
>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>>>
>>> --
>>> 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.
>>>
>>> _______________________________________________
>>> CF-metadata mailing list
>>> CF-metadata at cgd.ucar.edu
>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>>
>> --------------
>> I have my new work email address: jgraybeal at ucsd.edu
>> --------------
>>
>> John Graybeal <mailto:jgraybeal at ucsd.edu>
>> phone: 858-534-2162
>> System Development Manager
>> Ocean Observatories Initiative Cyberinfrastructure Project: http://ci.oceanobservatories.org
>> Marine Metadata Interoperability Project: http://marinemetadata.org
>> --
>> 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.
>>
>> _______________________________________________
>> CF-metadata mailing list
>> CF-metadata at cgd.ucar.edu
>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
>
> --------------
> I have my new work email address: jgraybeal at ucsd.edu
> --------------
>
> John Graybeal <mailto:jgraybeal at ucsd.edu>
> phone: 858-534-2162
> System Development Manager
> Ocean Observatories Initiative Cyberinfrastructure Project: http://ci.oceanobservatories.org
> Marine Metadata Interoperability Project: http://marinemetadata.org
>
>
--
Jeff de La Beaujardi?re, PhD
Senior Systems Architect, Data Integration Framework
Integrated Ocean Observing System (IOOS) Program Office
National Oceanic and Atmospheric Administration
1100 Wayne Ave #1225, Silver Spring MD 20910 USA
+1 301 427 2427
Jeff.deLaBeaujardiere at noaa.gov
--
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.
Received on Thu Jan 28 2010 - 08:12:25 GMT
