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How does the Geostatistical Wizard (Kriging) handle coincidental samples?

JohannesKrimm

When using empirical bayesian kriging on data, that has multiple samples present at the same location, the Geostatistical Wizard asks, if I want to use the max / min / mean value or if I want to "include all". Can anyone please elaborate on the difference between "including all" data compared to using, for example, a mean value?

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Accepted answers

Eric6346

If you choose Include All, all of the coincident points will be used to model the semivariogram, and they will each be given their own weights when making predictions. There is also the issue of number of neighbors in the searching neighborhood: Imagine that you have 10 values all sampled at the same location and use Include All, and you set the maximum number of neighbors to 10 in the searching neighborhood. In this case, when making predictions near the coincident points, the coincident points will fill up the entire searching neighborhood, and this could potentially give strange results.

When you choose Mean, the value at the location will be assigned the average of the values of the coincident points. This average will be used to model the semivariogram, and the searching neighborhood will treat it as a single value. The sample size will also be adjusted accordingly.

The logic is analogous for Min and Max coincident point options. The Remove All option will treat coincident points as if the value is Null, and none of the values will be used in the semivariogram modeling or prediction stages of kriging. Again, the sample size will be adjusted accordingly.

From the geoprocessing tools, coincident points are handled with an environmental setting. You can read more about it here: http://desktop.arcgis.com/en/desktop/latest/tools/environments/coincident-points.htm

All comments

JohannesKrimm

Thank you very much for the insight, this helps a lot!

DanPatterson_Retired

Ahhh I never thought it to be buried in Environments...my bad...here is the link for people using 10.2.x for Coincident points in Environments Eric's link will send you to 10.3 help

Eric6346

DanPatterson_Retired

My estimation...unless you can provide a help file link... is that if two observations occur at the same location you are given the option of using each observations value or to take an average of the observations at that location. For example say we have 100 observations spread out over the study area ... also assume that 3 observations are located at position (10,10) each with a different z value... say (10,11,1000). It would be up to you to decide whether to include all observations at that spot ... because they may be valid ... or to take the average as being representative of that location. My only question would be ... do they adjust sample size when they take the average?...in other words...is that location taken as 1 location now (pop. size now 98) if we take the average? or are they treated just as observations which coincidently share X,Y space ... like apartments in an apartment building.

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