Le 15/01/2013 20:23, John Graybeal a écrit : > 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 écrit : >>> 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 <[email protected]> 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 écrit : >>>>>> Dear Bruno, >>>>>> >>>>>> On Fri, Jan 11, 2013 at 11:52 AM, Bruno PIGUET <[email protected]> >>>>>> 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. >>>>> -- >>>>> [email protected] >>>>> Équipe GMEI/TRAMM >>>>> CNRM-GAME : UMR Meteo-France/CNRS n°3589 >>>>> _______________________________________________ >>>>> CF-metadata mailing list >>>>> [email protected] >>>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >>>>> >>>> >>>> >>>> ---------------- >>>> John Graybeal <mailto:[email protected]> phone: 858-534-2162 >>>> Product Manager >>>> Ocean Observatories Initiative Cyberinfrastructure Project: >>>> http://ci.oceanobservatories.org >>>> Marine Metadata Interoperability Project: http://marinemetadata.org >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> _______________________________________________ >>>> CF-metadata mailing list >>>> [email protected] >>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >>> _______________________________________________ >>> CF-metadata mailing list >>> [email protected] >>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >> -- >> [email protected] >> Équipe GMEI/TRAMM >> CNRM-GAME : UMR Meteo-France/CNRS n°3589 >> _______________________________________________ >> CF-metadata mailing list >> [email protected] >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > > ---------------- > John Graybeal <mailto:[email protected]> phone: 858-534-2162 > Product Manager > Ocean Observatories Initiative Cyberinfrastructure Project: > http://ci.oceanobservatories.org > Marine Metadata Interoperability Project: http://marinemetadata.org > > > > > > > > _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
