Geostatistical Modelling

Extension and Estimation Variance

By definition the extension variance is the variance of the error made in assuming that the assay of a sample taken in a panel extends over the whole of the panel. The sample can be located anywhere inside or outside the panel, and depending on the relative location of the sample to the panel the extension variance could alter accordingly. For instance, a sample taken at a corner of a panel would receive a much higher extension variance than one from the centre of the panel.

Consider the situation where we want to estimate the value of a block of ore from the values of n samples nearby, whether inside or outside the block. The variance of the error made in estimating such a block is then defined as "estimation variance". There is no difference between the extension and estimation variance, except one assumes the extent of a single sample to a block where as the other one is the estimation of a block by using more than one sample in the neighbourhood.