How coincident data is handled in the Geostatistical Analyst extension
Some input datasets may have several points with the same x,y coordinates. If the values of the points at the common location are the same, they are considered duplicates and have no effect on the output. If the values are different, they are considered coincident points. Deterministic interpolation methods require a single value at each location.
Kriging, however, can accommodate coincident points in the form of the measurement error term when describing the nugget.
The Geostatistical Wizard prompts you for a response when coincident points are encountered. However, the tools in the Geostatistical Analyst toolbox require you to set the Coincident points environment variable. If this environment variable is not set, the default setting of averaging the values at the same locations will apply to all Geostatistical Analyst geoprocessing tools.
The Coincident points environment variable is not honored by the Geostatistical Wizard since this setting applies only to the geoprocessing environment and the geoprocessing tools.