# GMS:Inverse Distance Weighted

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3D Scatter Point Module

3D Scatter Point
Interpolating with 3D Scatter Points
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3D Scatter Point Display Options
3D Scatter Point Tool Palette
Active/Inactive Points
Inverse Distance Weighted
3D Scatter Point Commands

One of the most commonly used techniques for interpolation of point data is inverse distance weighted (IDW) interpolation. Inverse distance weighted methods are based on the assumption that the interpolating surface should be influenced most by the nearby points and less by the more distant points. The interpolated surface is a weighted average of the point data; the weight assigned to each point diminishes as the distance to the interpolation location increases. Several options are available for inverse distance weighted interpolation. The options are selected using the IDW Interpolation Options dialog. This dialog is accessed through the Options button next to the Inverse distance weighted item in the Interpolation Options dialog.

The options in the dialog are as follows:

• Constant Nodal Functions (Shepard's Method) – The simplest form of inverse distance weighted interpolation. Includes the option to use classic weight function by enter a weighting exponent.
• Gradient Plane Nodal Functions – Variation of Shepard's method with nodal functions or individual functions defined at each point
• Quadratic Nodal Functions – Makes use of quadratic polynomials to constrain nodal functions.
• Subset Definition – Uses a subset of the data points in the computation of the nodal function coefficients and in the computation of the interpolation weights.
An example of the 3D IDW Interpolation Options dialog