On Tuesday 15 February 2005 12:42 pm, Gilles DUVERT wrote:
> If 'Quantity' is, or will be, able to deal with such things as flux
> conversions from/to air wavelength vs. humidity and frequency,etc.. and
> Janskys from/to Cousins/Johnson magnitudes, at least to a large extent
> and great accuracy, all the best. In that case all units or combinaisons
> thereof supported by Quantity should be authorized in, e.g., the SED DM.
> But at the same time one could use the Quantity DM to convert the data
> beforehand to specific quantities that would be the only ones referred
> to in the SED DM, such as basic MKSA units. And make the DM simpler.
The issue is ensuring that the model includes all the necessary meta-data needed to convert *from* MKSA units to other more esoteric systems. For instance, if all flux density-like data is required to be stored in W/m^2/Hz (or do I mean W/m^2/Angstrom?) within the DM but the end user wants to see antenna temperature, then the DM needs to include all the necessary efficiency factors, etc, needed to do this conversion. Likewise, converting to/from magnitudes.
Then what if the meta data needed to convert from your estoteric system to the standard DM system are only poorly known? It is surely possible that useful science could be done in the esoteric system, without ever converting to the standard system. But if the DM *insists* that all data is converted to a standard system, then you are immediately introducing errors which need not be there.
So what system should the DM use for flux density-like data?
David Received on 2005-02-16Z09:18:16