calculates Cartesian (x,y,z), projected from the centre of the sphere
to the earth surface, returns cartesian (x,y,z)
used to calculate "true" centre of set of lat longs
Usage
pro2sph(x, y, z)
Arguments
x
East to West coordinate in metres
y
South to North coordinate in metres
z
height coordinate in metres
Value
x,y,z
References
Descartes, R., 1637. Discours de la methode. A Leyde, De l<U+2019>imprimerie de I. Maire, Paris.