The spatial interpolation method helps to convert point data into a raster surface. This is done by estimating the missing value for the area for which there is no data. So the total number of data points, location, and distribution of data also affect the accuracy of interpolation. In ArcGIS software that I know, there are several ways to do interpolation, namely, inverse distance weighted (IDW), kriging, radial basis, and natural neighbor interpolation, each of which has a different accuracy. Therefore, the interpolation methods should be compared by calculating the root-mean-square error (RMSE) of each interpolation processing. The results prove that the number of control points affects the accuracy of the interpolation.

This interpolation method can also be used to determine the distribution of air temperature, pyroclastic waste, humidity, rainfall, elevation points, and others. All data in the form of points can be interpolated. The accuracy of the interpolation results can be minimized by using more and more quality input data. However, before we can produce the interpolation process, we must have data in the form of points and their coordinates. These coordinates will be useful in creating shapefiles. So that making interpolation can be done easily.

### In the following, I will share how to interpolate the pyroclastic distribution using the IDW method.

- Open the ArcGIS application and make sure you have created a point shapefile that has been included in the results from the field (here I use interpolation boundaries to make it look neat)

- On the ArcToolbox tab select Spatial Analyst Tools > Interpolation > IDW

- Then the IDW window will appear, after that

- Input Point Features: input point shapefile data (.shp)
- Z Values field: input the name of the table in the data point shapefile (.shp):
- Output Raster: click the down arrow and select a folder to save
- Output Cell Size: input the default (can be changed but affects the raster size)
- Power: enter default
- Search Radius: enter default
- Input Barrier Polyline Feature: input the polyline shapefile (.shp) limit data that has been created