Combining Local Kriging Variances for Short-Term Mine Planning

Abstract

Estimated grades of different working areas of a mine form the basis of any mine planning. A typical estimation method used in short-term mine planning is simple (linear) kriging. Very often, the mining engineer is not only interested in the individual reliability of the estimates from each working area, but also in the estimation variance of a combination of estimated grades from all working areas. This paper discusses a method for combining local kriging variances to obtain the precision of combined kriging estimator. The method relies on the fact that the local kriging weights and the Lagrange multipliers are linear in support, provided that the same samples are used during the local kriging processes. It is often not practical to use the same samples to krige all the working areas in the mine due to scattered nature of different working areas. Consequently, some adjustment is needed prior to taking advantage of the above property of kriging. This paper stresses the practical aspect of resolving the problem.