Creating maps using diffusion interpolation with barriers

Diffusion interpolation with barriers is an interpolation method that can account for barriers within the study area. It can also use different cost surfaces to modify the interpolation (diffusion) process to more accurately model the phenomenon of interest.

Steps:

1. Click the point layer in the ArcMap table of contents that contains the attributes you are interested in.

   Alternatively, go directly to step 2 and browse to the dataset you are interested in on the first page of Geostatistical Wizard.

2. Start Geostatistical Wizard.
3. Under the Methods section, choose Diffusion Kernel, which is located under Interpolation with barriers.
   Note:

   The lower portion of Geostatistical Wizard shows information about diffusion interpolation with barriers. There is also a link that will take you directly to more detailed information on diffusion interpolation with barriers in the main help system.

4. Under the Input Data section, you should see that Source Dataset has been set to the layer you clicked in the ArcMap table of contents. Under Data Field, choose the attribute that you want to interpolate.

   In addition, you can specify a Weight field. This will weigh the data values and alter the interpolated surface. Including a weight can be a useful option when you want to include a measure of confidence in the data (for example, GPS locations taken inside a forest may be less reliable than those taken in clear areas, so you might choose to assign them less weight in the interpolation).

5. Under the Barrier features section, you can specify a polygon or polyline feature layer that you want to use as a barrier in the interpolation.
6. Under the Barrier raster section, you can specify the Type of cost surface that you want to use to modify the interpolation (diffusion) process. To use a cost surface, you must specify a value for Type and a raster under Source dataset.
7. Click Next.
8. Modify the Bandwidth parameter for the Gaussian kernel.
9. Choose the number of iterations that will be used in solving the equations.

   Step 2 of Geostatistical Wizard is where the parameter values for this method must be defined. You can investigate the effects of changing the values for Bandwidth and Iterations by examining the preview surface on the left-hand side and evaluating the quality of fit of the model on the next page of Geostatistical Wizard.

10. Click Next.
11. Assess the quality of fit of the model using the Predicted and Error graphs, using the Prediction Errors summary information, and by examining particular pairs of measured and predicted values in the table on the left-hand side.

    For more information on how to assess the quality of fit of a model, refer to Performing cross-validation and validation.

12. Once you are satisfied with the model, click Finish.

    A Method Report window appears.

13. Click OK to produce the surface.

    The Method Report window contains a summary showing the dataset, attribute, interpolation method, and parameter values used to create the surface. This information can be retrieved for any geostatistical layer by right-clicking it in the ArcMap table of contents, choosing Properties from the menu, then clicking the Method Summary tab.

The result is a surface generated by interpolating attribute values using diffusion interpolation with barriers. The surface is added directly to the ArcMap table of contents and is displayed using a default color scheme and class breaks, which can be changed by accessing the layer's properties.