As we know, Inverse distance weighted (IDW) is an exact interpolation method, which means the interpolated values of the known samples should be the same with its original observed values. But when I used the IDW in Geostatistical analyst (ArcGIS 10) to interpolate, I found that the interpolated minimum value and maximum value are not the same with the observed minimum value and maximum value. Actually I did get a Predication Map using the interpolation method of Geostatistical analyst, its values seemed to be the same with the observed ones, but when I changed it into a raster layer, the values all changed, why? In ArcGIS software, is the IDW interpolation in Geostatistical analyst the same as that in Spatial analyst? Are their equations the same with each other？
Forgive my poor English.