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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>
>
> ----------------
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> Product Manager
> Ocean Observatories Initiative Cyberinfrastructure Project: http://ci.oceanobservatories.org
> Marine Metadata Interoperability Project: http://marinemetadata.org
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Received on Mon Jan 14 2013 - 19:20:13 GMT
