Re: basic topology and the Data Model with geo-locations

Hi Doug,

> I'm partial to (time) -> ((lon, lat, alt) -> (obs)). This makes
> resampling by time or space rather convenient. VMET assumes such an
> arrangement.

Well, at any given time, the aircraft is only at one location,
so the domain sampling of ((lat, lon, alt) -> obs) would be
a SingletonSet with manifold dimension = 0.  That is, to
precisely represent the aircraft track.  So you might as
well use (time -> (lat, lon, alt, obs)).  It only takes a
few lines of code to translate between:

  (time -> (lat, lon, alt, obs))


  ((lat, lon, alt) -> (time, obs))

However, if you want to graphically represent the aircraft
track as an animating streamer, then you would produce a
Field with the type you described:

  (time -> ((lon, lat, alt) -> obs))

where the domain Set of each ((lon, lat, alt) -> obs) is
a segment of the aircraft track between the current time
[i.e., domain sample of (time -> ...)] and current time
minus some constant.

> I don't want to start a religious war but I also prefer (lon,lat,alt)
> over (lat,lon,alt) because it relates directly to (x,y,z).

I originally created the system intrinsic RealTupleType
for earth location with the (lon, lat, alt) order, but by
popular demand the system now has intrinsic RealTupleTypes
for both ways.

Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738

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