GRAVITY EMPIRICAL COVARIANCE VALUES FOR THE CONTINENTAL UNITED-STATES

Variances and correlation distances for 3637 30 multiplied by 30 arc min areas using over 544,000 terrain-corrected Bouguer anomalies have been determined for the continental United States. Short correlation distances are associated with the midcontinental gravity high and areas near the Pacific Coast. The parameters are quite similar in some areas but vary greatly in other areas. In general, the covariance functions must be considered nonstationary. However, the values can be used to properly compute uncertainties in predicted gravity when using the systematic surfaces and interpolation coefficients from which the statistical information was obtained. Also areas requiring additional observations in order to obtain better surface fits can be easily identified.