Holes in kriged surface where data points exist??

Discussion created by millar75 on Jun 19, 2011
Latest reply on Jun 20, 2011 by EKrause-esristaff

I am getting an unexpected result when performing universal kriging. There are holes in the kriged surface where data points exist (see attachment). I am having trouble understanding why this is occurring.

I have applied universal kriging to a data set of air pollutant measurements that have a high spatial density (collected via mobile monitoring). I am investigating universal kriging because the data give indication of a global spatial trend that can be explained in terms of pollutant pooling along the valley bottom (log transformation, second order trend removal). I am interested in the very local variation so have chosen a focused search neighbourhood  (max 15, min 1). The output layer has holes where data points actually exist. If I click on the areas where the holes are in the Searching Neighbourhood Window, the neighbours do not seem to be identifiable. The points are black and the Identify panes says Neighbours 0, Prediction <Not Calculated> (see attachment). I have checked the original data to see if there is some sort of anomaly but there doesn't seem to be and all of the data have values >0 so the log transformation shouldn't be the issue.

I am relatively new to spatial interpolation and am wondering if there is something I am missing.

Thanks for the help!