Selection of a subgrid from a spatial monitoring process

We present a different approach that, even without the availability of starting experimental data, selects a sub-grid according to the criterion of spatial optimal coverage of the wafer surface (see also Walvoort, 2010). This approach may also include expert knowledge about those areas where production is less precise because of unavoidable technical reasons and hence may indicate where a higher sampling density must be assured. If sampling measures are available, a validation procedure can be used to select the best sub-map based for instance on the prediction error, by comparing the results obtained using the full and the reduced grid