Concur with all. On Jan 17, 2013, at 09:00, Bruno PIGUET wrote:
> 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 <jgrayb...@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 écrit : >>>>>>> Dear Bruno, >>>>>>> >>>>>>> On Fri, Jan 11, 2013 at 11:52 AM, Bruno PIGUET <bruno.pig...@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.pig...@meteo.fr >>>>>> Équipe GMEI/TRAMM >>>>>> CNRM-GAME : UMR Meteo-France/CNRS n°3589 >>>>>> _______________________________________________ >>>>>> CF-metadata mailing list >>>>>> CF-metadata@cgd.ucar.edu >>>>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >>>>>> >>>>> >>>>> >>>>> ---------------- >>>>> John Graybeal <mailto:jgrayb...@ucsd.edu> 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 >>>>> CF-metadata@cgd.ucar.edu >>>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >>>> _______________________________________________ >>>> CF-metadata mailing list >>>> CF-metadata@cgd.ucar.edu >>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >>> -- >>> bruno.pig...@meteo.fr >>> Équipe GMEI/TRAMM >>> CNRM-GAME : UMR Meteo-France/CNRS n°3589 >>> _______________________________________________ >>> CF-metadata mailing list >>> CF-metadata@cgd.ucar.edu >>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >> >> >> ---------------- >> John Graybeal <mailto:jgrayb...@ucsd.edu> phone: 858-534-2162 >> Product Manager >> Ocean Observatories Initiative Cyberinfrastructure Project: >> http://ci.oceanobservatories.org >> Marine Metadata Interoperability Project: http://marinemetadata.org >> >> >> >> >> >> >> >> > ---------------- John Graybeal <mailto:jgrayb...@ucsd.edu> 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 CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
