In the estimation of reserves the known values of the variables of interest from surrounding drill holes are used to compute or estimate the unknown value of the orebody over a given region or at a given point of interest. The classical means of doing this are: 1. The Polygonal Method - where the region is divided into polygons centred on bore holes, each variable is then assumed to have constant value over each polygon._x000D_
2. Inverse distance methods, where the variable is assumed to vary linearly with the distance between the known values of the drill holes._x000D_
3. Inverse distance squared method - a quadratic variation is assumed for the variables between the bore holes.