Here is the map with sampling locations. The locations are scattered yet clustered. The concentration of contaminants have been measured against each locations and the variation in concentration is quiet high. Considering the distribution pattern of sampling wells, would it be wise to pull a spatial distribution map ? Would it be better to use natural neighbor ? Me and my professor had a different opinion. Since the distribution of the points are not uniform, I used Krging to pull a map. But my professor advised me to use NN method since the data points were clustered. I had a difficulty to extrapolate the map beyond the convex hull using NN method. Kriging worked better in terms of both extrapolation and interpolate. Is there any alternative? Please advice. I tried Geostatistical wizard to look at RMS value for different interpolation methods and IDW had the lowest. But the distribution map produced bulls eye effect and my professor asked me to avoid IDW for any geologic map.
Attached is the map.