[cube access] minutes from telecon (2013-07-03)

[Tim Jenness]

On Jul 22, 2013, at 00:52 , Markus Demleitner <msdemlei at ari.uni-heidelberg.de> wrote:

> 
> On Tue, Jul 16, 2013 at 12:15:32PM -0700, Patrick Dowler wrote:
>> 
> 
>> - define a reasonable subset of STC-S that everyone can support, for
>> prototypes we will be strict and only support that subset; STC-S with
>> additional phrases will fail (note: the decision on ignoring vs
>> rejecting unexpected STC-S phrases will be reviewed later during WG
>> review)
>> 
>> - restrictions: only allow FK4, FK5, GALACTIC, ICRS
> 
> Disclosure: I've never liked the notion of server-side coordinate
> transformations.  
> 

and doesn't FK4 need an epoch?

> What's the use cases for letting the client specify reference systems
> in its cutout queries?
> 
> For cutouts, allowing this is particularly insiduous, since cutouts
> along the coordinate axes are no longer rectagular after a
> transformation, so services would have to resample, at least provided
> the result is supposed to come in the coordinate system requested
> (otherwise: What's the point at all?).  Of course, image formats
> usually only support rectangles -- should the unwanted voxels be
> NULL?  What else?
> 

I assume that the cutout service returns a rectangular area that just encloses the requested area. Do we actually want to mask out the data if you specify a circular region? Or if you specify galactic and get back an ICRS image?

> 
> Conversely, server-side transformations need to touch all pixels,
> resample them, etc.  
> 

I think I would tend to agree that you don't really want the image to be resampled by the server in order for the FK5 image to be returned as a galactic image. Client viewers will be able to display the galactic coordinate system on that FK5 image. The main reason for wanting the resampling is that you get a smaller image returned.

-- 
Tim Jenness