[Data Characterisation]: Spatial domain models comparison

[Doug Tody]

On Thu, 6 Nov 2003, Andreas Wicenec wrote:

> 1.) How will the astrometric accuracy of the spatial coverage be represented 
> in a single floating point value? A real WCS contains many different 
> parameters which all have their own error associated and they can be quite 
> different. Moreover the parameters for the spatial coverage have different 
> units (fill_factor and shape are dimensionless, fov is probably in degrees.

A key thing to keep in mind here is that the dataset characterization
metadata we are discussing here is summary metadata only, intended to be
used for data selection, for example following a DAL query, rather than
actual data analysis.  A single error value for spatial, energy, flux,
etc., measurements should be good enough at this level.  For actual data
analysis one would normally retrieve and use the dataset itself, which
would include the full WCS, flux calibration, etc.  (none of which have
yet been defined).   Doug



> 2.) What is a spatial sensitivity?? In my view the only way to represent 
> something like this is a sensitivity map as Alberto mentioned. The parameters 
> given in the table are certainly not representing anything like spatial 
> sensitivity, but global flux sensitivities deducted (how?) from the overall 
> FOV. The *how* is actually important here because if this is done differently 
> the values are not comparable. Note that I'm not against these parameters in 
> general I'm just saying that the name 'spatial sensitivity' should be 
> changed.
> 
> 3.) The concept name 'Photometric Accuracy' (first column) should also be 
> changed to flux uncertainity to be more consistent with the other concept 
> names in the same table.