Le 15/01/2013 20:23, John Graybeal a ?crit :
> Bruno,
>
> Given solar_azimuth_angle parallels this definition pretty closely, would you be OK with the originally proposed name if the definition is clear?
First, I apologize for not beeing able to answer yesterday.
It is true if you explain "platform_azimuth_angle" by giving the
analogue of "solar_azimuth_angle", things become clear.
But I whish to remind that there are contexts where the word
"azimuth" is defined as the quantity also named "yaw". Cf. my old
message
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2008/052686.html where
I explained that in some books, the angle between the platform axis and
a fixed direction is called Azimuth, and noted Psi, and it is
acknowledged that it is sometimes called the yaw angle.
For CF, I would propose to stick to one definition of azimuth, which
will be repeated every in all definition where it appears (as it is
commonly done in the cf-standard-name-table).
I propose : Azimuth is the angle between a reference direction
(usually the North) and the projection on a reference plane (usually the
local horizon) of a vector from an specific location to a point of interest.
Your opinion ?
Bruno.
>
> john
>
> On Jan 15, 2013, at 09:28, Bruno PIGUET wrote:
>
>> Aleksandar,
>>
>> Thank-you for the clarification. As John said, with the diagram,
>> everything becomes clear.
>>
>> But I fear I have no good suggestion on the way to name this
>> parameter. Spontaneously, I would say something like
>> "azimuth_of_sensor_seen_from_observed_point", but, clearly, this doesn't
>> follow the guidelines for construction of CF Standard Names.
>> At least, does this correctly reflect what you mean ?
>>
>> Bruno.
>>
>>
>> Le 15/01/2013 03:20, Aleksandar Jelenak - NOAA Affiliate a ?crit :
>>> Bruno, John:
>>>
>>> platform_azimuth_angle defines an angle where the observation point is
>>> at the vertex, one side of the angle points north, the other side
>>> points to the platform, and the angle is calculated clockwise from the
>>> north. The observation point is defined by an instrument on the
>>> platform.
>>>
>>> Here's one diagram explaining this angle:
>>> http://science-edu.larc.nasa.gov/SCOOL/images/azimuth.gif
>>>
>>> platform_azimuth_angle in the diagram is labelled "Satellite Azimuth
>>> from North". The observation target is labelled "Where You Are".
>>>
>>> I don't agree the definition is weak. It mentions that "platform"
>>> means the vehicle from which *observations* are made, and clearly
>>> indicates that *observation target* is at the vertex of this angle.
>>> Perhaps the confusion is arising from the term "azimuth" as it is
>>> widely used in ship and airplane navigation.
>>>
>>> I opted for "platform" in the name because I saw a standard name
>>> platform_zenith_angle which can be applied to satellite zenith angles
>>> and thought to complete the other two missing: satellite scan/look
>>> angle and satellite azimuth angle by replacing "satellite" with
>>> "platform".
>>>
>>> -Aleksandar
>>>
>>>
>>> On Mon, Jan 14, 2013 at 12:29 PM, John Graybeal <jgraybeal at ucsd.edu> wrote:
>>>> I agree with Bruno -- platform angle as it is defined in the request is the angle of the _platform_ with respect to a reference direction ("the horizontal angle between the line of sight from the observation point to the platform and a reference direction at the observation point, which is often due north"). The seems like platform orientation to me too.
>>>>
>>>> I wasn't excited about the name platform_azimuth_angle anyway, because it is ambiguous on this exact point -- is it the azimuth angle of the platform, or of the instrument on the platform? (the former, in this case). Platform_orientation seems to be the accepted name for the purpose.
>>>>
>>>> The definition is very weak though -- can we propose the substitution of this definition for that one?
>>>>
>>>> John
>>>>
>>>> On Jan 14, 2013, at 09:17, Bruno PIGUET wrote:
>>>>
>>>>> Le 14/01/2013 17:21, Aleksandar Jelenak - NOAA Affiliate a ?crit :
>>>>>> Dear Bruno,
>>>>>>
>>>>>> On Fri, Jan 11, 2013 at 11:52 AM, Bruno PIGUET <bruno.piguet at meteo.fr> wrote:
>>>>>>> I have one remark about "platform_azimuth_angle"
>>>>>>>
>>>>>>> I like this name and it correspond to usual navigation definition (as
>>>>>>> far as I can tell from my experience with airborne and shipborne
>>>>>>> measurements), but...
>>>>>>>
>>>>>>> There is already a standard name called "platform_orientation", whose
>>>>>>> definition seems to be the same, even if less precisely-worded : The
>>>>>>> platform orientation is the direction in which the "front" or
>>>>>>> longitudinal axis of the platform is pointing (not necessarily the same
>>>>>>> as the direction in which it is travelling, called platform_course).
>>>>>>
>>>>>> platform_orientation is not the same as platform_azimuth_angle. This
>>>>>> azimuth angle is related to measurements made by an instrument mounted
>>>>>> on a platform (satellite, ship, airplane, truck, etc.).
>>>>>
>>>>> Sorry for looking dumb, but I don't see the difference (except that
>>>>> "platform_orientation" is not precisely defined).
>>>>>
>>>>> I'm currently producing CF files containing airborne measurements,
>>>>> and the parameter which is usually called "heading", which is in fact
>>>>> exactly defined as "platform_azimuth_angle", is qualified with
>>>>> "standard_name = platform orientation".
>>>>>
>>>>> Bruno.
>>>>> --
>>>>> bruno.piguet at meteo.fr
>>>>> ?quipe GMEI/TRAMM
>>>>> CNRM-GAME : UMR Meteo-France/CNRS n?3589
>>>>> _______________________________________________
>>>>> CF-metadata mailing list
>>>>> CF-metadata at cgd.ucar.edu
>>>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>>>>>
>>>>
>>>>
>>>> ----------------
>>>> John Graybeal <mailto:jgraybeal at ucsd.edu> phone: 858-534-2162
>>>> Product Manager
>>>> Ocean Observatories Initiative Cyberinfrastructure Project: http://ci.oceanobservatories.org
>>>> Marine Metadata Interoperability Project: http://marinemetadata.org
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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>> --
>> bruno.piguet at meteo.fr
>> ?quipe GMEI/TRAMM
>> CNRM-GAME : UMR Meteo-France/CNRS n?3589
>> _______________________________________________
>> CF-metadata mailing list
>> CF-metadata at cgd.ucar.edu
>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
>
> ----------------
> John Graybeal <mailto:jgraybeal at ucsd.edu> phone: 858-534-2162
> Product Manager
> Ocean Observatories Initiative Cyberinfrastructure Project: http://ci.oceanobservatories.org
> Marine Metadata Interoperability Project: http://marinemetadata.org
>
>
>
>
>
>
>
>
Received on Thu Jan 17 2013 - 10:00:46 GMT
