Point in Coord
Laurent MICHEL
laurent.michel at astro.unistra.fr
Wed Apr 15 18:19:30 CEST 2020
Mark
I see the problem.
This is not an high level demand, but I bet that I'm not the only one
who find it odd that celestial coordinates are not explicitely supported
in STC (MCT in fact).
Anyway, I do not insist, let's move on.
Laurent
Le 15/04/2020 à 16:14, CresitelloDittmar, Mark a écrit :
> Laurent,
>
> To be clear..
> The current arrangement of the objects is:
> current.png
> To add a CelestialPoint would require either:
> + make coords:Point abstract
> + create a coords:GenericPoint + coords:CelestialPoint(lat/lon) +
> coords:CartesianPoint(x,y,z)
> * the specialized Points would need to constrain its
> coordsys.coordSpace to match the type.
> Or
> + add coords:CelestialPoint(lat/lon)
> + add meas:CelestialPosition containing CelestialPoint
>
> The models have been in similar configurations in the past..
> Both add objects, and generate >1 path for representing the same thing,
> (which were negative comments on the earlier versions).
>
> I'm not adverse to the idea, but don't want to go in circles.
> Mark
>
>
> On Wed, Apr 15, 2020 at 3:42 AM Laurent MICHEL
> <laurent.michel at astro.unistra.fr
> <mailto:laurent.michel at astro.unistra.fr>> wrote:
>
> Mark
>
>
> I do not propose to turn back toward Frame-centric coords
> (GalacticPosition...)
> I'm just proposing to add a new class without altering the model
> structure.
> This class would be specific to the celestian sphere (lon/lat) and
> should be attached to a frame (ICRS...) as any other Point.
>
> It would be nice to get feebacks from other people on this.
>
> LM
>
> Le 08/04/2020 à 23:30, CresitelloDittmar, Mark a écrit :
> > Laurent,
> >
> > The hierarchy is: Point references a SpaceSys which contains the
> > SpaceFrame and the CoordSpace (both in composition).
> > Point
> > |-> SpaceSys
> > o-> SpaceFrame
> > o-> PhysicalCoordSpace{Cartesian/SphericalCoordSpace}
> >
> > But that does not negate the question.
> > "However, taking into consideration that spatial coordinates
> is the
> > most used thing in Astronomy, I'm wondering if it wouldn't be
> better to
> > have one specific class for Cartesian points (refering to
> > CartesianCoordSpace) and another for Spherical points (refering to
> > SphericalCoordSpace)."
> >
> > * Earlier drafts of Coords (2018) had Frame-centric coords with
> > standard spaces (CartesianCoord, LongLatCoord)..
> > * Due to feedback on this representation, they migrated in
> 2019 to
> > specialized singular coordinates (X,Y,Z,Long,Lat,R, etc) which
> referred
> > to axes of standard spaces, and were used in frame-centric Measures.
> > Which is what went to the RFC phase.
> > * There, the frame-centric and space-centric Measures were
> generally
> > disliked (GalacticPosition, CartesianPosition)
> > * The RFC actions called for replacing the specialized singular
> > coordinates with a single Point Coordinate, and removing the
> specialized
> > Measures, retaining only the single Position type containing a
> Point.
> > The consequence of users having to interrogate the Position to
> determine
> > the details of frame/space was considered acceptable.
> >
> > Obviously there is a sweet spot there somewhere, but I doubt we can
> > settle into it until we have more implementation experience with it.
> > Adding a CartesianPoint and SphericalPoint which constrains the
> space is
> > a simple update which can be done at any time.
> >
> > Mark
> >
> >
> >
> >
> >
> > On Tue, Apr 7, 2020 at 5:42 AM Laurent MICHEL
> > <laurent.michel at astro.unistra.fr
> <mailto:laurent.michel at astro.unistra.fr>
> > <mailto:laurent.michel at astro.unistra.fr
> <mailto:laurent.michel at astro.unistra.fr>>> wrote:
> >
> > Dear DM
> >
> > I'm exercising with Coords with spatial coordinates.
> >
> > My understanding is as follow:
> > ==============================
> > Spatial coordinates are represented by Point instances that,
> skipping
> > the details, refers to a SpaceSys that refer to a SpaceFrame
> that refer
> > to a PhysicalCoordSpace that is either a SphericalCoordSpace or a
> > CartesianCoordSpace.
> >
> > Point
> > |-> SpaceSys
> > |-> SpaceFrame
> > |->
> PhysicalCoordSpace{Cartesian/SphericalCoordSpace}
> >
> > So a client that gets a Point instance will have to step down
> this
> > cascade and to check the class of the associated
> PhysicalCoordSpace
> > instance before to know whether this point is Cartesian or
> Spherical.
> >
> > Question:
> > ========
> > This is consistent but not very practical. I understand that
> this model
> > provides components for host models that will be designed in
> a way to
> > avoid clients to do such inferences. This could be the case
> with the
> > upgrade of Meas.
> > However, taking into consideration that spatial coordinates
> is the most
> > used thing in Astronomy, I'm wondering if it wouldn't be
> better to have
> > one specific class for Cartesian points (refering to
> > CartesianCoordSpace) and another for Spherical points
> (refering to
> > SphericalCoordSpace).
> >
> > As a side effect this would allow to have one specific spherical
> > CoordSpace for the celestial sphere (lat ,long, R=1).
> >
> > Laurent
> > --
> > ---- 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
> <mailto:laurent.michel at astro.unistra.fr>
> <mailto:laurent.michel at astro.unistra.fr
> <mailto:laurent.michel at astro.unistra.fr>>
> > 67000 Strasbourg (France) Web
> http://astro.u-strasbg.fr/~michel
> > ---
> >
>
> --
> ---- 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 <mailto:laurent.michel at astro.unistra.fr>
> 67000 Strasbourg (France) Web http://astro.u-strasbg.fr/~michel
> ---
>
--
---- 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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