  In this paper we present an effective coarse space correction addressed to
accelerate the solution of an algebraic linear system. The system arises from
the formulation of the problem of interpolating scattered data by means of
Radial Basis Functions. Radial Basis Functions are commonly used for
interpolating scattered data during the image reconstruction process in graphic
analysis. This requires to solve a linear system of equations for each color
component and this process represents the most time-consuming operation.
Several basis functions like trigonometric, exponential, Gaussian, polynomial
are here investigated to construct a suitable coarse space correction to
speed-up the solution of the linear system. Numerical experiments outline the
superiority of some functions for the fast iterative solution of the image
reconstruction problem.
