Inverse Distance Weighting

The inverse distance weighting gridding method is a weighted average interpolator that can be exact or smoothing. Data points are weighted through the use of a weighting power that determines how weighting factors decrease as the distance from a grid node increases.

The larger the weighting power, the less effect data points far from a grid node have during interpolation. As the weighting power approaches 5, the grid node values approach the value of the nearest data point. Thus, large weighting powers result in grids that closely honor your input data.

As a result, they can also produce isolated closures with concentric contours (bull’s eyes). A smoothing factor can be added to lessen this effect but data will not be as closely honored.

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