Capability extension for describing whole sky maps

[Arnold Rots]

Isn't this all really a matter of projections?
And isn't that described pretty completely in FITS WCS paper 2?

  - Arnold

On Thu, May 20, 2010 at 5:10 PM, Tom McGlynn <Thomas.A.McGlynn at nasa.gov>wrote:

> It seems to me that there are three things being combined here:
>
>   All-sky data
>   Hierarchical imaging
>   HEALPix projection
>
> The first and last don't seem particularly special to me: many surveys have
> had all-sky coverage for a long time.  Nor does HEALPix seem particularly
> different.
> It's just another projection, albeit one that a lot of software does not
> yet
> support.  What strikes me as distinctive for the new Aladin service is the
> hierarchical imaging, which I don't think is well described in our current
> framework.
>
> So I think that's the element I'd emphasize rather than HEALPix which I see
> as a detail
> in a particular implementation.  E.g., WWT proides a similar service using
> the TOAST
> projection and I believe GoogleSky does the same using a Cartesian
> projection (or maybe
> even Mercator).
>
>        Regards,
>        Tom
>
>
> Pierre Fernique wrote:
>
>>
>> Dear registry members,
>>
>> As I presented Tuesday 18 May during the App session at Victoria
>> interop, I was suggesting an extension of the "capability" section for
>> describing whole sky maps/surveys (for those who do not follow this
>> talk, here the pdf -
>>
>> http://www.ivoa.net/internal/IVOA/InterOpMay2010Applications/AladindemonstrationInteropVictoria2010.pdf
>> ).
>> Do you think that it is a good idea. And if yes, may you help me for
>> describing it properly in the schema of the registry.
>>
>> Here is my draft :
>>
>> <capability xsi:type= "SimpleAllSkyAccess">
>> <interface type="HEALPIXmap">
>> <accessURL use="base">http://..</accessURL>
>> <HEALPix>
>> <frame>Gal</frame>
>> <tileFormat>FITS</tileFormat>
>> <treeDepth>12</treeDepth>
>> </HEALPix>
>> </interface>
>> …
>> </capability>
>>
>> type : HEALPIXmap, HTMmap,... = sky tessellation method
>> frame : GAL, ECL, EQU = tessellation reference frame
>> titleFormat : FITS, PNG, JPG .... = image format for individual tile
>> treeDepth: number = hierarchical depth (in Healpix = Norder, or
>> log2(NSIDE))
>>
>> This kind of "SimpleAllSkyAccess" resource may be queried just by tile
>> ID as parameter. For Healpix it is a couple : Norder/npixNumber. For HTM
>> it will be the triangle ID...
>>
>> http://base.adresse..cgi?tile=ID
>>
>> With this very simple interface, any body should be able to build a
>> client for displaying this kind of resources.
>>
>> Thanks
>> Pierre Fernique
>>
>>
>
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