WD-DALI-1.1 polygon winding direction

[Patrick Dowler]

So just to be clear and minimalistic, I think the only correction to
the text in rev 3530 is that the view if from outside looking toward
the origin. Is that correct? I will also add a reference to STC but I
think this change would make the DALI text minimal and consistent.

Pat

On 9 September 2016 at 01:02, Marco Molinaro <molinaro at oats.inaf.it> wrote:
> Hi Pat, Arnold, all,
>
> 2016-09-08 18:56 GMT+02:00 Patrick Dowler <pdowler.cadc at gmail.com>:
>> So, should I change the wording to say "when viewed from outside the
>> unit sphere" and add STC reference? I want to say the minimum and
>> leave the definitive specification in the hands of STC, but if we make
>> readers go look it up in STC they will be annoyed.
>
> I agree on referencing STC (even if it's not trivial because it would be nice
> to have a pointer to 2.0 or general STC), but summarizing it in DALI.
> I'm ok with the wording, is the group agrees (warning: if no one protest
> means agreement).
>
> Maybe, Arnold, can you suggest something
> short and clear to put in DALI?
> The reference text you replied is probably bullet-proof but too long for
> the DALI spec (at least that's my opinion).
>
> Cheers,
>      Marco
>
>>
>> Pat
>>
>> On 8 September 2016 at 01:00, Felix Stoehr <fstoehr at eso.org> wrote:
>>> Dear all,
>>>
>>> after some side-discussions with Marc I believe the following is true:
>>>
>>> - STC-S declares clockwise and counterclockwise with respect to the
>>> celestial coordinate frame (north up, east to the left as seen from earth)
>>>
>>> - this is consistent with the footprintfineder.py output and thus all
>>> the MAST/ALMA/ESA spectra
>>>
>>> - area calculations will be correct in this definition and coordinate frame
>>>
>>> - it is a bit counter-intuitive, because it means that anticklockwise
>>> polygons in that definition are clockwise if you look up on the sky from
>>> earth.
>>>
>>> It might be worthwile to declare in WD-DALI-1.1 the coordinate system in
>>> which the clockwise/anticlockwise are defined, i.e. in which system to
>>> "hold the clock".
>>>
>>> Best regards,
>>>
>>> Felix
>>>
>>
>>
>>
>> --
>> Patrick Dowler
>> Canadian Astronomy Data Centre
>> Victoria, BC, Canada



-- 
Patrick Dowler
Canadian Astronomy Data Centre
Victoria, BC, Canada