Multi-dimensional Data Access minimal requirements

[Tom McGlynn]

Douglas Tody wrote:
> On Tue, 11 Mar 2014, Robert J. Hanisch wrote:
>
>> On 3/11/14 3:49 PM, "Douglas Tody" <dtody at nrao.edu> wrote:
...
>> But either way,
>> I still think "circle" is not what one wants for a cutout.  It's ok for
>> discovery, but not for a cutout.
>
> Exactly.  Circle is usable for discovery but not very useful to specify
> the ROI for a cutout.  Note that in the discovery use case, there are
> also issues with the size and coverage of the target image - is the
> center of the target image in the specified circular region, or only
> part of the image, is it fully contained, etc. (this was the point of
> the INTERSECT parameter).
>

I don't think I agree.  What's wrong with the following?

Hypothetical use case:  I've got 1000 distant galaxies in the Hubble 
deep field and I want to extract ACS data on each of them.  I'm 
planning on doing some kind of photometry that needs to go out 5" from 
the center.  So I request 1000 cutouts as circles with a radius of 5" 
and the appropriate centers.  I get back 1000 cutouts that are 
presumably rectangles (probably squares but maybe a pixel or two off).

Seems pretty reasonable to me.  It would be much harder if I have to 
first calculate the bounding box in RA/Dec for the circle that I need, 
and it may also be less efficient, since the ACS images may not be 
nicely aligned with the coordinate system in which I specify my box. 
So I'd get back larger boxes than I actually needed -- a factor or two 
more area in the worst case I think.

Recognize that the SIA service is going to have to calculate bounding 
boxes for a misaligned box even if we are going to only allow boxes. 
The circle case will almost always be easier for the SIA service to 
calculate.



	Tom