Examining covariation among multiple datasets using the Crosscovariance Cloud tool

The Crosscovariance Cloud tool shows the covariance between two datasets. Use the Search Direction tool to examine the cloud. Check if the covariance surface is symmetric and the cross-covariance values are similar in all directions.

If you see that there is a spatial shift in the values of two datasets or unusually high cross-covariance values, you can investigate where these occur. If you note that unusual cross-covariance values occur for isolated locations or within restricted areas of your study site, you may want to take some action, such as investigating those data values, detrending data, or splitting the data into different strata before interpolating it.

Steps:

1. Right-click the point feature layer identifying the first layer in the cross-covariance analysis in the ArcMap table of contents and click Properties.
2. Click the Selection tab.
3. Click the symbol button (located under the with this symbol option).
4. Choose a color and size for the selection.
5. Click OK and then OK again.
6. Repeat steps 1–5 for the second layer to be used in the cross-covariance analysis, but choose different selection sizes and colors.
7. Highlight the layers in the ArcMap table of contents by holding down CTRL while clicking the two layers.
8. Click Geostatistical Analyst > Explore Data > Crosscovariance Cloud.
9. Choose the appropriate attribute for each layer in the Attribute list.
10. Check the Show search direction option.
11. Click the center line of the Search Direction tool and drag it until it points to the angle where you believe there is a shift.
12. Brush some points in the covariance cloud by clicking and dragging over some of the red points. Examine where the pairs of points are on the ArcMap map.