[R-sig-Geo] spatial modelling projection question

[Edzer Pebesma]

On 05/13/2014 08:19 PM, Dominik Schneider wrote:
> so my question is: Wouldn't it make more sense to do spatial modeling with
> a true distance projection, i.e. longlat, than an equal area projection for
> which distances are skewed? What makes the variogram model potentially

I would say yes, but haven't given it much thought.

> inappropriate on a sphere (overlooking the fact that the earth isn't really
> a sphere)?

Some variogram models are not positive definite (or semi-negative
definite) in some spaces; linear-with-sill is only valid in 1 D,
circular only in 2D, spherical only in 3D. Spheres, or ellipsoides, are
another thing when measuring surface lines.

See also http://dx.doi.org/10.1007/s11004-011-9344-7
-- 
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster
Heisenbergstraße 2, 48149 Münster, Germany. Phone: +49 251
83 33081 http://ifgi.uni-muenster.de GPG key ID 0xAC227795

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