On 19/02/13 15:00, Mike Grant wrote:
To make replies easier and as some of us (normally me!) may be too lazy
And now for a reply (comments inline)..
First, did you coordinate with Aleksandar Jelenak's proposed new names?
They should be in the list archive for this list 19/Sept/2012 "New
Standard Names for Satellite Data" and for the main CF-metadata list on
7/Oct/2012 "New standard names for satellite obs data" and summarised at
http://wiki.esipfed.org/index.php?title=Standard_Names_For_Satellite_Observations,
before it got derailed by string-based time variables debate.
I think the platform ones fit well with your proposals (so perhaps you
already coordinated?) - perhaps by reincluding or referencing them in
your submission, you could rescue those parts from the time-string swamp.
Either way, it may be wise to split these proposals into multiple parts
to ensure that the whole set aren't hung up on a single argument.
Perhaps split into 3 parts by platform, sensor and toa names?
azimuth_angle
* degrees
* Azimuth angle is the angle measured towards the east, from north,
along the astronomical horizon to the intersection of the great circle
passing through the point and the astronomical zenith with the
astronomical horizon.
platform_latitude
* degrees_north
* Latitude of the satellite measured at the sub-satellite point
platform_longitude
* degrees_east
* Longitude of the satellite measured at the sub-satellite point
platform_altitude
* m
* Altitude of the satellite above mean sea level
If these are specifically about satellites, it may be worth renaming
them to satellite_XXX. I think it would be more useful to keep them as
platforms, in which case perhaps change the word "satellite" to
"platform" in the descriptions.
Either way, it would be nice to more clearly define what's meant by the
"sub-satellite point" for non-specialists (CF is used by all sorts of
people) or, better, rephrase it in generic "platform" language. Is this
the position on the surface/geoid/ellipsoid (intersection of the line
between the platform location and the centre of the Earth with the
geoid/ellipsoid)?
It might be worth stealing parts of the definition of the general term
"altitude" as it's nicely written:
"Altitude is the (geometric) height above the geoid, which is the
reference geopotential surface. The geoid is similar to mean sea level."
sensor_band_spectral_width
* cm-1
* Bandwidth of the satellite’s spectral channel
This also fits nicely with the sensor_band_ proposals Aleksandar made on
this list, but they didn't seem to go onto the CF list. Might be worth
rescuing too, unless Aleksander is reading and had another reason not to
submit?
Again, it would be good to replace "satellite" with "sensor". Unless
it's intentionally vague, perhaps define more clearly what's meant by
the bandwidth (e.g. full width half max?)
toa_spectral_irradiance
* mW m-2 (cm-1)-1
* "toa" means top of atmosphere; irradiance which is relevant for any
sensor measuring in the UV-VIS and NIR. This parameter is reported by
integrating over the whole sphere.
Might be worth stealing wording from other standard definitions
incorporating irradiance, e.g.
omnidirectional_spectral_spherical_irradiance_in_sea_water
- "spectral" means per unit wavelength or as a function of wavelength;
spectral quantities are sometimes called "monochromatic". Radiation
wavelength has standard name radiation_wavelength. Omnidirectional
spherical irradiance is the radiation incident on unit area of a
spherical (or "4-pi") collector. It is sometimes called "scalar
irradiance". Radiation incident on a 2-pi collector has standard names
of "spherical irradiance" which specify up/downwelling.
In fact, perhaps the name should be
toa_omnidirectional_spectral_spherical_irradiance ?
toa_spectral_reflectance
* 1 (dimensionless)
* Ratio of radiance to irradiance I/I0, reflection from a thick layer
where the layer, here the atmosphere, is part of the reflection's property.
Stealing a few bits from toa_bidirectional_reflectance, perhaps..
Reflectance is the ratio of the energy of the reflected to the incident
radiation. "spectral" means per unit wavelength or as a function of
wavelength; spectral quantities are sometimes called "monochromatic". A
coordinate variable of radiation_wavelength or radiation_frequency can
be used to specify the wavelength or frequency, respectively, of the
radiation. "toa" means top of atmosphere. toa_spectral_reflectance is
the ratio of radiance to irradiance I/I0, reflection from a thick layer
where the layer, here the atmosphere, is part of the reflection's property.
toa_outgoing_inband_radiance
* mW m-2 sr-1
* "toa" means top of atmosphere; "outgoing" means emitted toward outer
space; the radiance is integrated over a discrete band.
I think this one is quite new to CF (integrating over a band), so you're
probably setting a standard here. It may be worth saying that the band
can be specified by (e.g.) a coordinate variable or other ancillary data.
toa_reflectance
* Percent
* Ratio of the energy of reflected to incident light at the top of
atmosphere.
Steal most of the text from toa_bidirectional_reflectance?
Should this be unitless, like toa_bidirectional_reflectance and
toa_spectral_reflectance?
Ok, that was longer than I thought - hope it was helpful, but feel free
to take what you wish and reject what you don't. I think the splitting
idea may be worth it to avoid getting tied up in arguments though.
Cheers,
Mike.
Latest news: www.pml.ac.uk and @PlymouthMarine
Plymouth Marine Laboratory (PML) is a company limited by guarantee registered in England & Wales, company number 4178503. Registered Charity No. 1091222. Registered Office: Prospect Place, The Hoe, Plymouth PL1 3DH, UK.
This message is private and confidential. If you have received this message in
error, please notify the sender and remove it from your system. You are
reminded that e-mail communications are not secure and may contain viruses; PML
accepts no liability for any loss or damage which may be caused by viruses.
