How Inverse Distance Weighted (IDW) Works In ArcMap

Inverse distance weighted (IDW) interpolation explicitly makes the assumption that things closer to one another are more alike than those that are farther apart.

To predict a value at unknown location, IDW is best tool.

Image by Mojca JJ from Pixabay

IDW assumes that each measured point has a local influence that diminishes with distance. It gives greater weights to points closest to the prediction location, and the weights diminish as a function of distance, hence the name inverse distance weighted.

Performing IDW

Go to IDW as shown in screen below Geostatistical Analyst -> IDW

IDW Tool in ArcMap

Creating a IDW Map

Load the layer for which you have to predict data at unknown points, e.g. my data layer is reyprecip

1. Click on the point layer on which to perform IDW in the ArcMap table of contents.

2. Start the Geo statistical Analyst. OR

3. Go to search type IDW select IDW Geostatistical Analysis

4. Specify the desired parameters in the IDW Set Parameters dialog box

Choose for Z value = Tm, OR data column which you want to predict.

5. Click Ok

IDW Tool Interface

8. Examine the results, points shown below are known raster is predicted value.

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