Dear Bruno, John:
Here are revised definitions for the standard names
platform_azimuth_angle and sensor_azimuth_angle. I have tried to
address the issues you two raised with my initial proposals.
Standard name: platform_azimuth_angle
Definition:
"platform" refers to the vehicle on which the sensor making
observations is mounted on, e.g. airplane, ship, or satellite.
Platform azimuth angle is the horizontal angle where the observation
target is at the vertex, one side of the angle points to the reference
direction (typically due north) and the other side points to the
platform. The angle is measured clockwise starting from the reference
direction. The observation target is a location on the Earth defined
by the sensor performing the observations.
Units: degrees
Standard name: sensor_azimuth_angle
Definition:
The horizontal angle with the observation target at its vertex, one
side of the angle points to the reference direction (typically due
north) and the other side points to the sensor. The angle is measured
clockwise starting from the reference direction. The observation
target is a location on the Earth defined by the sensor performing the
observations.
Units: degrees
-Aleksandar
On Tue, Jan 15, 2013 at 2:23 PM, John Graybeal <jgraybeal at ucsd.edu> wrote:
> Bruno,
>
> Given solar_azimuth_angle parallels this definition pretty closely, would you be OK with the originally proposed name if the definition is clear?
>
> 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.
Received on Tue Mar 19 2013 - 11:02:23 GMT
