Article history: Received 14 November 2009 Received in revised form 29 April 2010 Accepted 6 May 2010

There are many reasons for the popular use of the isotropic or geometrically anisotropic covariance function and variogram in spatial statistics. A less known reason demonstrated in this paper is that an isotropic or geometrically anisotropic model would be the only choice in certain circumstances, for instance, when the underlying random field is smooth enough.

This paper proposes a new covariance matching based technique for blurred image PSF (point spread function) estimation. A patch based image degradation model is proposed for the covariance matching estimation framework. A robust covariance metric which is based on Riemannian manifold is adapted to measure the distance between covariance matrices. The optimal PSF is computed by minimizing the di...

Beamformers are a commonly used method for doing source localization from magnetoencephalography (MEG) data. A key ingredient in a beamformer is the estimation of the data covariance matrix. When the noise levels are high, or when there is only a small amount of data available, the data covariance matrix is estimated poorly and the signal-to-noise ratio (SNR) of the beamformer output degrades. ...

Ensemble–variational data assimilation algorithms that can incorporate the time dimension (fourdimensional or 4D) and combine static and ensemble-derived background error covariances (hybrid) are formulated in general forms based on the extended control variable and the observation-space-perturbation approaches. The properties and relationships of these algorithms and their approximated formula...

Abstract. The success of ensemble data assimilation systems substantially depends on localization, which is required to mitigate sampling errors caused by modeling background error covariances with undersized ensembles. However, finding an optimal localization highly challenging, as covariances, errors, and appropriate depend various factors. Our study investigates vertical based a unique conve...

Nonrigid registration of 3D tomographic images of di erent modalities (e.g., CT and MR images) is a key issue for neurosurgery and radiotherapy planning. Here, we consider image registration based on a set of corresponding anatomical point landmarks and approximating thin-plate splines. With this approach it is possible to take into account landmark localization errors and thus to control the i...

Data assimilation techniques are widely used in hydrology and water resources management to improve model forecast uncertainty by assimilating observations. The big challenge practical applications is how describe uncertainties correctly avoid the occurrence of spurious covariance during data assimilation. In this study, ensemble square root filter (EnSRF) estimate parameters states a groundwat...