kNN with distance weighting may be problematic for interpolation

[jmp75]

Consider an area such as around Canberra; east there are numerous bores with 'Shale' lithology. At interpolation this seems to dominate including far away from it where there should be other lithologies. A high density of uniform classification near one geolocation may have undue influence far away from it. Proximity should have more weight in this circumstance.