Figure 5.  Performance of IDW (line graphs) at distance exponents of 0.1 to 5.0   for the G₃₀, G₆₁, and G₉₁ data sets and ordinary kriging (bar chart) for the G₃₀ data set. The locations are indicated at the top of the figure and the variables and the units for the rmse values are indicated to the right of the figure.