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IDW (SA) erroneous output when imposing barrier

Question asked by keithnabbott on May 3, 2018
Latest reply on May 10, 2018 by keithnabbott

ArcGIS v.10.3.1 for Desktop.

I'm using the  IDW (Spatial Analyst) tool to interpolate water quality data for the Island of Newfoundland. I wanted to impose a barrier to separate data collected on one side of a ocean bay from influencing results on the opposite side of the bay. The IDW tool output is wrong when imposing a barrier. For instance, the data range is incorrect (should be 0-63, not 0-13), and the input data does not correspond with the IDW output data classes. I've attached a PDF that shows the two IDW outputs: (1) no barrier imposed, and (2) barrier imposed. 

Any idea what is happening when the barrier is imposed?