Radial basis function approximation of noisy scattered data on the sphere

In this paper we consider the approximation of noisy scattered data on the sphere by radial basis functions generated by a strictly positive definite kernel. The approximation is the minimizer in the native space for that kernel of a quadratic functional in which the smoothing term is a multiple of the square of the native space norm. The balance between data fitting and smoothness is controlled by a smoothing parameter, the choice of which should depend on the nature and magnitude of the noise. The main results concern the choice of that smoothing parameter, under the assumption that the noise is deterministic rather than random. Four strategies for choosing the smoothing parameter are considered: Morozov’s discrepancy principle, and three a priori strategies. For each of these strategies we derive an L 2 error bound. The error bounds are similar, with the discrepancy principle giving marginally the best bound. A numerical example supports the theoretical results.