Re: 200046: basic topology and the Data Model with geo-locations

  • To: Don Murray <dmurray@xxxxxxxxxxxxxxxx>
  • Subject: Re: 200046: basic topology and the Data Model with geo-locations
  • From: Doug Lindholm <lind@xxxxxxxx>
  • Date: Thu, 06 Apr 2000 16:53:40 -0600
Don Murray wrote:
> 
> >From: "From: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>" <billh@xxxxxxxxxxxxx>
> >Organization: .
> >Keywords: 200004062200.QAA23842
> 
> Hi Bill-
> 
> >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.
> 
> Actually, there isn't an intrinsic for LatLonAlt (but it
> would be nice).  The SpatialEarth*DTuple intrinsics are
> (lon, lat) and (lon, lat, alt), but the coordinate systems

Sorry, those are my fault. ;-) But I use them every day.

> in VisAD (visad.data.mcidas.AREACoordinateSystem,
> visad.bom.Radar*DCoordinateSystem and visad.jmet.GRIBCoordinateSystem)
> that use lat/lon have references of order (lat, lon), so
> RealTupleType.LatitudeLongtitudeTuple was added.  Most of
> the time that I've seen earth coordinates documented, it has
> been (lat,lon) (ex: 40N 105W) rather than (lon,lat).  So,
> for me adding alt would give (lat, lon, alt).  Since
> Radar3DCoordinateSystem uses the order (lat,lon,alt) perhaps
> having this intrinsic would be good also.  That way people
> could choose either way.
> 

I agree.

OK, I am quite ignorant on the CoordinateSystem class. As I understand
it, I can have one field with domain (lon, lat, alt) and another with
(x,y,z) and they would work together if (x,y,z) were created with the
appropriate CoordinateSystem mapping (x,y,z) to (lon, lat, alt). Am I
close? Does that mean I could resample the first field with a set of the
type (x,y,z)? What about a CoordinateSystem that would allow co-mingling
of (lon, lat, alt) and (lat, lon, alt)? Am I missing the boat here? I'd
sure like to be able to resample with different yet topologically
consistent sets. And I'd like to be able to add my (x,y,z) field to my
display with (Longitude -> XAxis)... maps without having to add (x ->
XAxis)... maps.

Doug

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