When running datasets that have duplicate points through a suface interpolator operation (IDW, Spline, Kriging) in Spatial Analyst, the points that are removed are not always the best choices.
When a point coverage contains more than one point with the same XY coordinate, the Spatial Analyst surface interpolators will process them out. The first point encountered at a particular location is retained, and all other subsequent ones are removed from consideration.
This poises a question on the validity of the final result, as the criteria for deciding which value to use for surface interpolation is the order encountered.
Get help from ArcGIS experts
Download the Esri Support App