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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 @PlymouthMarinePlymouth 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.
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