<div dir="ltr">Laurent,<div><br></div><div>To be clear..</div><div>The current arrangement of the objects is:</div><div> </div><div> <img src="cid:ii_k91eaorj0" alt="current.png" style="margin-right: 0px;"><br></div><div>To add a CelestialPoint would require either:</div><div> + make coords:Point abstract</div><div> + create a coords:GenericPoint + coords:CelestialPoint(lat/lon) + coords:CartesianPoint(x,y,z)</div><div> * the specialized Points would need to constrain its coordsys.coordSpace to match the type.</div><div>Or</div><div> + add coords:CelestialPoint(lat/lon)</div><div> + add meas:CelestialPosition containing CelestialPoint</div><div><br></div><div>The models have been in similar configurations in the past..</div><div>Both add objects, and generate >1 path for representing the same thing, (which were negative comments on the earlier versions).</div><div><br></div><div>I'm not adverse to the idea, but don't want to go in circles.</div><div>Mark</div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Apr 15, 2020 at 3:42 AM Laurent MICHEL <<a href="mailto:laurent.michel@astro.unistra.fr">laurent.michel@astro.unistra.fr</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">Mark<br>
<br>
<br>
I do not propose to turn back toward Frame-centric coords <br>
(GalacticPosition...)<br>
I'm just proposing to add a new class without altering the model structure.<br>
This class would be specific to the celestian sphere (lon/lat) and <br>
should be attached to a frame (ICRS...) as any other Point.<br>
<br>
It would be nice to get feebacks from other people on this.<br>
<br>
LM<br>
<br>
Le 08/04/2020 à 23:30, CresitelloDittmar, Mark a écrit :<br>
> Laurent,<br>
> <br>
> The hierarchy is: Point references a SpaceSys which contains the <br>
> SpaceFrame and the CoordSpace (both in composition).<br>
> Point<br>
> |-> SpaceSys<br>
> o-> SpaceFrame<br>
> o-> PhysicalCoordSpace{Cartesian/SphericalCoordSpace}<br>
> <br>
> But that does not negate the question.<br>
> "However, taking into consideration that spatial coordinates is the <br>
> most used thing in Astronomy, I'm wondering if it wouldn't be better to <br>
> have one specific class for Cartesian points (refering to <br>
> CartesianCoordSpace) and another for Spherical points (refering to <br>
> SphericalCoordSpace)."<br>
> <br>
> * Earlier drafts of Coords (2018) had Frame-centric coords with <br>
> standard spaces (CartesianCoord, LongLatCoord)..<br>
> * Due to feedback on this representation, they migrated in 2019 to <br>
> specialized singular coordinates (X,Y,Z,Long,Lat,R, etc) which referred <br>
> to axes of standard spaces, and were used in frame-centric Measures. <br>
> Which is what went to the RFC phase.<br>
> * There, the frame-centric and space-centric Measures were generally <br>
> disliked (GalacticPosition, CartesianPosition)<br>
> * The RFC actions called for replacing the specialized singular <br>
> coordinates with a single Point Coordinate, and removing the specialized <br>
> Measures, retaining only the single Position type containing a Point. <br>
> The consequence of users having to interrogate the Position to determine <br>
> the details of frame/space was considered acceptable.<br>
> <br>
> Obviously there is a sweet spot there somewhere, but I doubt we can <br>
> settle into it until we have more implementation experience with it. <br>
> Adding a CartesianPoint and SphericalPoint which constrains the space is <br>
> a simple update which can be done at any time.<br>
> <br>
> Mark<br>
> <br>
> <br>
> <br>
> <br>
> <br>
> On Tue, Apr 7, 2020 at 5:42 AM Laurent MICHEL <br>
> <<a href="mailto:laurent.michel@astro.unistra.fr" target="_blank">laurent.michel@astro.unistra.fr</a> <br>
> <mailto:<a href="mailto:laurent.michel@astro.unistra.fr" target="_blank">laurent.michel@astro.unistra.fr</a>>> wrote:<br>
> <br>
> Dear DM<br>
> <br>
> I'm exercising with Coords with spatial coordinates.<br>
> <br>
> My understanding is as follow:<br>
> ==============================<br>
> Spatial coordinates are represented by Point instances that, skipping<br>
> the details, refers to a SpaceSys that refer to a SpaceFrame that refer<br>
> to a PhysicalCoordSpace that is either a SphericalCoordSpace or a<br>
> CartesianCoordSpace.<br>
> <br>
> Point<br>
> |-> SpaceSys<br>
> |-> SpaceFrame<br>
> |-> PhysicalCoordSpace{Cartesian/SphericalCoordSpace}<br>
> <br>
> So a client that gets a Point instance will have to step down this<br>
> cascade and to check the class of the associated PhysicalCoordSpace<br>
> instance before to know whether this point is Cartesian or Spherical.<br>
> <br>
> Question:<br>
> ========<br>
> This is consistent but not very practical. I understand that this model<br>
> provides components for host models that will be designed in a way to<br>
> avoid clients to do such inferences. This could be the case with the<br>
> upgrade of Meas.<br>
> However, taking into consideration that spatial coordinates is the most<br>
> used thing in Astronomy, I'm wondering if it wouldn't be better to have<br>
> one specific class for Cartesian points (refering to<br>
> CartesianCoordSpace) and another for Spherical points (refering to<br>
> SphericalCoordSpace).<br>
> <br>
> As a side effect this would allow to have one specific spherical<br>
> CoordSpace for the celestial sphere (lat ,long, R=1).<br>
> <br>
> Laurent<br>
> -- <br>
> ---- Laurent MICHEL Tel (33 0) 3 68 85 24 37<br>
> Observatoire de Strasbourg Fax (33 0) 3 68 85 24 32<br>
> 11 Rue de l'Universite Mail<br>
> <a href="mailto:laurent.michel@astro.unistra.fr" target="_blank">laurent.michel@astro.unistra.fr</a> <mailto:<a href="mailto:laurent.michel@astro.unistra.fr" target="_blank">laurent.michel@astro.unistra.fr</a>><br>
> 67000 Strasbourg (France) Web <a href="http://astro.u-strasbg.fr/~michel" rel="noreferrer" target="_blank">http://astro.u-strasbg.fr/~michel</a><br>
> ---<br>
> <br>
<br>
-- <br>
---- Laurent MICHEL Tel (33 0) 3 68 85 24 37<br>
Observatoire de Strasbourg Fax (33 0) 3 68 85 24 32<br>
11 Rue de l'Universite Mail <a href="mailto:laurent.michel@astro.unistra.fr" target="_blank">laurent.michel@astro.unistra.fr</a><br>
67000 Strasbourg (France) Web <a href="http://astro.u-strasbg.fr/~michel" rel="noreferrer" target="_blank">http://astro.u-strasbg.fr/~michel</a><br>
---<br>
</blockquote></div>