[Obscore1.1] WD comments

[Arnold Rots]

Along a new thread, the _dim items had escaped my notice.
As discussed, the word "dimension" is confusing in this context
and people started wondering about units.
It is defined in the text as "number of samples".
It seems to me that better choices for "dim" would be:
len[gth], nsamp, num, nbr, or even npix (most samples will be pixels).

I also noticed that the time scale is completely missing from the
time axis. Anyone interested in accurate timing might want to know
what timescale the resource is using - TT, TDB, TAI, UTC, GPS, ...

Cheers,

  - Arnold

-------------------------------------------------------------------------------------------------------------
Arnold H. Rots                                          Chandra X-ray
Science Center
Smithsonian Astrophysical Observatory                   tel:  +1 617 496
7701
60 Garden Street, MS 67                                      fax:  +1 617
495 7356
Cambridge, MA 02138
arots at cfa.harvard.edu
USA
http://hea-www.harvard.edu/~arots/
--------------------------------------------------------------------------------------------------------------


On Wed, Jul 15, 2015 at 9:43 AM, Arnold Rots <arots at cfa.harvard.edu> wrote:

> This may get complicated.
> In principle, I agree, but some axes may actually be binned, such as chip
> coordinates and pulse height...
>
>   - Arnold
>
>
> -------------------------------------------------------------------------------------------------------------
> Arnold H. Rots                                          Chandra X-ray
> Science Center
> Smithsonian Astrophysical Observatory                   tel:  +1 617 496
> 7701
> 60 Garden Street, MS 67                                      fax:  +1 617
> 495 7356
> Cambridge, MA 02138
> arots at cfa.harvard.edu
> USA
> http://hea-www.harvard.edu/~arots/
>
> --------------------------------------------------------------------------------------------------------------
>
>
> On Mon, Jul 13, 2015 at 8:45 AM, Laurent MICHEL <
> laurent.michel at astro.unistra.fr> wrote:
>
>> Hello,
>>
>> I do not think that t_dim is better suited than e_dim or s_dim to specify
>> the number of events. Finally, an event is just a point within a 4dims
>> space (S1/S2/E/T) and none of these axes has a special role.
>> Considering that, I think the number of events should be reported in all
>> *_dim columns. The ambiguity about binned axes or not is removed by the
>> appropriate "dataproduct_type" value.
>>
>> Laurent
>>
>>
>> Le 25/06/2015 03:06, Douglas Tody a écrit :
>>
>>> On Wed, 24 Jun 2015, CresitelloDittmar, Mark wrote:
>>>
>>>> pg 25: Axes dimensions
>>>>  Outside of the pixelated image context, what values do these hold?
>>>>  For example, the sparse cube (ie: event list).  do each of these hold
>>>>  the #events? or are s_dim1,s_dim2 ==  the span along that axis? and
>>>>  if so, in what frame?
>>>>  It seems that #events is closest to the description as the number of
>>>> samples.
>>>>
>>>
>>> For event data which is not imaged, such as an event list, probably the
>>> best one can do is have t_dim specify the number of events.  The spatial
>>> coverage would be specified with s_fov and the spectral coverage with
>>> em_min/max.  The binning on the spatial and spectral axes is meaningless
>>> and should be zero.  If a precomputed image for the observation is also
>>> provided, that would have all the dim values and would share the same
>>> obs_id.
>>>
>>>      - Doug
>>>
>>
>> --
>> ---- Laurent MICHEL              Tel  (33 0) 3 68 85 24 37
>>      Observatoire de Strasbourg  Fax  (33 0) 3 68 85 24 32
>>      11 Rue de l'Universite      Mail laurent.michel at astro.unistra.fr
>>      67000 Strasbourg (France)   Web  http://astro.u-strasbg.fr/~michel
>> ---
>>
>
>
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