Interpolation of Rainfall: Inverse Distance Weighted (IDW) Method
In order to estimate rainfall in any given point by using different rainfall measuring stations (rain gauges), you need an interpolation function that estimates the rainfall at any point in the given area (watershed).
The inverse-distance method or inverse-distance weighting (IDW) method is one of the classic methods for estimating rainfall. The weight assigned to each measurement station is inversely proportional to the distance from the estimation point.