The report treats the problem of determining a global covariance function if the following data are given: the variance of the gravity anomalies, the variance of second-order gradients, the correlation length, and the lower degree variances. The proposed covariance model is a linear combination of the reciprocal distance covariance function and a covariance function of logarithmic type. It is found that the correlation length is already fixed, within rather narrow limits, by the remaining data.