SSAP and images

[Doug Tody]

Hi Guy -

I see what you are getting now, thanks.  The SSAP specification itself
does not currently specify the datatype of Coverage.Location.Value (it
is hard to get this level of detail in the printed document). If you
want this level of detail it is much better to look at the data model
spreadsheet (at https://webtest.aoc.nrao.edu/ivoa-dal/ssap-keywords.xls
for the moment). This spells out every last detail for every SSAP
or Spectrum data model element.  You can also look at the reference
implementation and see what it returns for a query.

Coverage.Location.value is specified as being of type double,
arraysize=2.  In the SIA spec, POS_EQ_RA_MAIN and POS_EQ_DEC are
explicitly of type double.

I agree that we should clarify this in the SSAP specification itself.

 	- Doug


On Wed, 2 May 2007, Guy Rixon wrote:
>> 
>>> Anita,
>>> 
>>> by my reading of the SSAP spec, the position encoding is part of the 
>>> Spectrum data model:
>>> 
>>> Coverage.Location.Sky.Value pos.eq RA and Dec deg, R
>>> (or sexagesimal string)
>>> 
>>> If I understand this correctly, each column of the VOtable returned by SSA 
>>> is a node in the Spectrum data model, with an associated Utype. This 
>>> position node is defined as a coordinate pair, so the column isn't a 
>>> scalar, numeric type. It would have to be either a string or an array of 
>>> float or double. Would the array form work for you? I guess the string 
>>> form covers the case where the coordinates are sexagesimal.