213 representing one rock class, labeled Rock_1 to Rock_5. Each indicator takes value 1 when the original Rock variable matches the corresponding class, and 0 otherwise (Table 1). Figure 1a shows a point map of the sample locations colored by their Rock values. As observed, the sampling exhibits an incipient spatial pattern, but with some areas more densely sampled than others. Such clustering may lead to biased estimates of global proportions if sample proportions are used directly. To obtain more representative global proportions, a nearest-neighbor interpolation is applied to mitigate the effects of sample clustering. Figure 1b presents the nearest neighbor interpolation map obtained using a search radius of 500 m. Figure 2 compares the original global proportions derived directly from the sample data (a) with those obtained via nearest-neighbor interpolation (b). Table 1 – First and last records from the dataset used in this study. Sample number X (m) Y (m) Rock Rock_1 Rock_2 Rock_3 Rock_4 Rock_5 1 2386 3077 3 0 0 1 0 0 2 2544 1972 2 0 1 0 0 0 … … … … … … … … … 258 3859 4022 3 0 0 1 0 0 259 2593 3312 3 0 0 1 0 0 Figure 1: (a) Sample locations colored according to rock categories. (b) Nearest neighbor estimation map of rock categories with sample locations overlaid.
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