Drill hole spacing should be optimized at all stages of a mining project on the basis of detailed cost/benefit analyses.

Geostatistics provides the most robust and objective framework to carry out such drill hole spacing analyses. Geostatistics allows you to quantify the value of acquiring more information in terms of uncertainty reduction. The cost of acquiring information can then be benchmarked against the gains in precision it provides.

The value of information can be assessed and optimised on both global and local scales:

Globally, global estimation techniques are used to carry out DHSA studies for coal, iron ore, bauxite and a wide variety of bulk commodities. DHSA enables you to attach a level of precision to the estimation of global quantities (e.g. average value over a 5 yr period) and provide relevant inputs to:

• Derive robust resource classification schemes (link with Res Class.);
• Optimize drilling budgets; and
• Maximise the ground covered for fixed drilling costs.

Locally, conditional simulation can be used to assess:

• The local impact of acquiring additional information (offering the ability to optimise pre-exploitation or grade control drilling grids); and
• The response of the mine plan to resource uncertainty and thus optimize the density and location of new information to minimize identified risks.