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Hi Alberto,<br>
<br>
<br>
<div class="moz-cite-prefix">On 01/12/2023 13:42, alberto micol
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:BD25F101-9AA0-4E2B-9E17-07E530732F1E@googlemail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
Hi DALers,
<div><br>
</div>
<div>Two strong comments (A and B) and one question (C), regarding
DALI v1.2...</div>
<div><br>
</div>
<div><br>
</div>
<div>A) §3.12 Shape states: "<a id="tth_sEc3.12"
style="color: rgb(0, 0, 0);" moz-do-not-send="true">The
allowed shapes are: <tt>circle</tt>, <tt>range</tt>, <tt>polygon</tt>.”</a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true"><br>
</a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true">ESO
needs to have also: </a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true">-
point</a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true">-
multi-polygon</a></div>
<div>and, because of ALMA, also:</div>
<div>- union of circles and polygons, also with holes, <a
style="color: rgb(0, 0, 0);" moz-do-not-send="true">where
holes are expressed as CW polygons.</a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true"><br>
</a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true">Otherwise
we will not be able to adopt DALI 1.2</a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true"><br>
</a></div>
<div>But it would be best for the standard, if “shape” could be
fully polymorphic, that is, if it could support all the DALI
geometrical types, which are:</div>
<div>- 3.6 Points</div>
<div>- 3.7 Circle</div>
<div>- 3.8 Range</div>
<div>- 3.9 Polygon</div>
<div>- 3.10 MOC</div>
<div>- 3.11 Multi-Polygon <br>
</div>
</blockquote>
<br>
<br>
I agree with you on this point. I also wondered the same thing: why
`shape` is limited to only a small part of all available geometries
being described in DALI?<br>
<br>
<br>
<blockquote type="cite"
cite="mid:BD25F101-9AA0-4E2B-9E17-07E530732F1E@googlemail.com">
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true">B)
§3.9 Polygons states that:</a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true">“In
spherical coordinates […] Vertices must be ordered such that
the polygon winding direction is counter-clockwise (when
viewed from the origin toward the sky) as described in (Rots,
2007). “</a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true"><br>
</a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true">That
is not the correct definition, as it excludes the possibility
to express a hole using a CW polygon.</a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true"><br>
</a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true">As I
expressed at the IVOA in Bologna earlier this year, the only
standard that completely defines spherical polygons is the STC
v1.33, 2007. All other standards (ADQL 2.0, TAP 1.0, DALI
v1.1, etc) do not do the right job. If interested in details,
please see: </a><a style="color: rgb(0, 0, 0);"
moz-do-not-send="true">https://wiki.ivoa.net/internal/IVOA/InterOpMay2023Ops/ESO_VO_Polygon_Tool.pdf </a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true"><br>
</a></div>
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true">My
suggestion is not to define the polygon in DALI, but simply
refer to the definition provided by STC v1.33, 2007, along
with its two very relevant Errata.</a></div>
</blockquote>
<br>
<br>
You're right and I, personally, did not forget your talk in Bologna.
Should we add to the next DAL running meeting a discussion on
polygon in DAL ecosystem? It would be an occasion to start fixing
some of the standards referring or badly defining polygons.<br>
<br>
My guess is that DALI should replace STC in the future....but it is
not yet the case, which leads to an unstable and uncomfortable
situation on some aspects like polygons.<br>
<br>
<br>
<blockquote type="cite"
cite="mid:BD25F101-9AA0-4E2B-9E17-07E530732F1E@googlemail.com">
<div><a style="color: rgb(0, 0, 0);" moz-do-not-send="true"> C)
Does DALI 1.2 allow a user to express spherical coordinates or
geometrical types in non-equatorial frames?</a></div>
</blockquote>
<br>
<br>
As far as I know, no. But I let any DALI author properly answer this
question.<br>
<br>
<br>
Cheers,<br>
Grégory<br>
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