# Weighted Averaging

The gridding methods in Surfer use weighted average interpolation algorithms. This means that, with all other factors being equal, the closer a point is to a grid node, the more weight it carries in determining the Z value at that grid node. The difference between gridding methods is how the weighting factors are computed and applied to data points during grid node interpolation.

To understand how weighted averages are applied, consider the equation shown here.

Given N data values:

the interpolated value at any grid node (for example,) can be computed as the weighted average of the data values:

where

 Gj = interpolated grid node value at node j; N = number of points used to interpolate at each node; Zi Z value at the ith point wij weight associated with the ith data value when computing Gj

Grid Data

Gridding Methods

Choosing Methods Based on the Number of XYZ Data Points

Exact and Smoothing Interpolators

General Gridding Recommendation

Grid Function

Producing a Grid File from a Regular Array of Z Values

Anisotropy