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
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>>
>>
>> ----------------
>> 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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Received on Tue Jan 15 2013 - 10:28:27 GMT
