Dear All,
Do we need to include any reference to instrument, platform or
satellite? It seems to me that the complexity arises because the
reference lines from which the angle is defined are different in
different applications. Wouldn't it be better to use zenith_angle and
scan_angle with respect to fixed reference lines and include an
attribute that accounts for any offset with respect to that?
For instance, scan_angle would be referenced against the nadir of the
object. If the instrument is tilted with respect to that line and you
want to represent the angle with respect to the reference instrument
line of sight, then the offset will be /=0.
Cheers,
Alejandro
> -----Original Message-----
> From: cf-metadata-bounces at cgd.ucar.edu
> [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Lowry, Roy K
> Sent: Wednesday, October 20, 2010 8:46 AM
> To: Aleksandar Jelenak; cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] New standard names for satellite obs data
>
> Dear All,
>
> I'd just like to reinforce John's last point that the
> semantics of 'instrument' and 'platform' are becoming blurred
> in these discussions. From my perspective as one who has to
> map to CF datasets I would prefer it if the semantics of
> terms used in Standard Names had a universally understood meaning.
>
> Another point that struck me from John's response is that
> when we do have multiple data streams sharing a single
> Standard Name, we need to ensure that there are objective
> criteria (i.e. not plaintext in the longname) that enable
> each stream to be uniquely identified. Otherwise, even
> 'common concepts' (which incidentally will be worked during a
> workshop in November) won't deliver interoperability.
>
> Cheers, Roy.
>
> -----Original Message-----
> From: cf-metadata-bounces at cgd.ucar.edu
> [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of
> Aleksandar Jelenak
> Sent: 20 October 2010 01:33
> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] New standard names for satellite obs data
>
> Dear Evan,
>
> Thanks for your suggestions.
>
> Evan Manning wrote on 10/18/10 11:30 PM:
> > The names below mix "satellite" and "instrument"
> differently than I'm
> > used to.
>
> I started with "satellite_*" names but then wanted to
> generalize since remote sensing instruments are not only
> carried on satellites. But you brought up an important
> distinction that the observation geometry of an instrument
> can be different from the generic one associated with the
> entire spacecraft.
>
> > I recommend changing:
> > instrument_zenith_angle -> satellite_zenith_angle
> > instrument_azimuth_angle -> satellite_azimuth_angle
> > satellite_scan_angle -> satellite_view_angle
>
> I think the "instrument_*" names are more applicable as they
> allow for either instrument-specific or spacecraft-generic
> geometries. I also think being able to distinguish between
> the two observation geometries is important and would like to
> have sets of standard names for both. So a data provider can
> clearly signal what is given, even for data from the same instrument.
>
> To summarize:
>
> 1) Use "instrument_zenith_angle", "instrument_azimuth_angle",
> and "instrument_scan_angle" for precise, instrument-specific
> observation geometry.
>
> 2) Use "platform_zenith_angle", "platform_azimuth_angle", and
> "platform_view_angle" for generic satellite (here generalized to
> "platform") observation geometry.
>
> 3) Mixing names from these two sets is allowed, whatever is
> more applicable for the zenith, azimuth, and scan/view angle data.
>
> Too complicated?
>
> > And add:
> > instrument_scan_angle
> > The angle between the line of sight from an instrument and its
> > reference scan position.
>
> Agree.
>
> -Aleksandar
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Received on Wed Oct 20 2010 - 02:24:19 BST
