Re: visaddigest V1 #4

Hi Ian,

> The easiest way to provide for this type of thing, would be to have a
> simple interpreter that
> mapped grid coordinates to world coordinates. Then you could say things like:
>      select grdextract( grid, spec,
> "X=f(x,y,z,t),Y=g(x,y,z,t),Z=h(x,y,z,t),T=k(x,y,z,t)")
>      from table;
> where f,g,h, and k are arbitrary expressions, probably involving lookup
> tables, trig and log terms, etc.

Such mappings between coordinate systems are handled in VisAD
by the visad.CoordinateSystem class. Extensions of this class
define the mathematical specifics of coordinate transforms in
their implementations of the toReference() and fromReference()