Point in Coord

[Laurent MICHEL]

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
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