basic topology and the Data Model with geo-locations

This is a basic level question about how best to represent
some data.  What is the most effective or the canonical way to
represent this situation in VisAD? This a a thought problem,
not something I am working on.

An aircraft flight makes measurements ("obs") along its path,
a complex 3D curve.
The obs are ordered by an index or by time.  For each obs the
position is also known in latitude, longitude, and elevation.

So we have something like time [or index] -> position(lat,lon,elev) -> obs.

How does CoordinateSystem play a role here?

What kind of a Field would you recommend?

Does it make any difference if the obs at each point are
a single Real, or perhaps a tuple of many measurements, some vectors say?

How is this extended if the "index" becomes 2D or 3D?  You have an
(i,j) or (i,j,k) set which each have a (lat long elevation)?  Here we
are in the case of some meterological grids.

In another matter, is there a VisAD formality or class for 
elevation (height above sea level) and altitude (height above ground)?

Stu

-- 
Stuart Wier                           UCAR Unidata Program Center
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(303) 497-8659                              Boulder, CO 80307
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