[Techtalk] Data structure for Earth slice data

[Conor Daly]

On Wed, Dec 03, 2008 at 07:06:14PM -0800 or thereabouts, Akkana Peck wrote:
> Kelly Jones writes:
> > What's a good data structure/methodology for representing "slices" of
> > the Earth?
> > 
> > Obviously, the description above is one way to represent the data, but
> > it's not very useful.
> > 
> > I want a representation that will:
> > 
> >  % Tell me if a given latitude/longitude is inside or outside the set.
> > 
> >  % For a given latitude, tell me what longitudes (if any) are inside
> >  the set. Vica versa for a given longitude.
> > 
> >  % Tell me the area of my set.
> > 
> >  % Make it easy to map the boundary of my set
> 
> Then for definitions based on a list of cities and radii from each
> city, like your example, all you need to start out is a list of
> triples to store those data, then write the other functions in
> terms of those.

It strikes me that it would be worth considering doing your primary
representation in terms of the mathematical functions that describe the
earth's surface.  Basically the earth is a squashed sphere (a geoid) which
can be described by a set of equations.  Now, quite how you use these to do
your sets I'm not sure...

Conor
-- 
Conor Daly,                   
Met Eireann, Glasnevin Hill,  
Dublin 9, Ireland             
Ph +3531 8064276 Fax +3531 8064247

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