Interpolation/Extrapolation (Velocity Picking)
There are two types of interpolation that can be done from the Interpolation tab in the Velocity Picking window.
Interpolating the volume from the picks
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As you pick, Insight will interpolate the picks to create a complete velocity model.
- Select the Extrapolate check box to create a velocity model that is complete within the entire area of the input gathers (for a 3D volume, a rectangle surrounding the gathers). Leave the box unchecked if you wish to only interpolate areas between picks.
- If you do not Extrapolate, define the Search distance (m) in which data must be found to interpolate the volume. A point that is beyond this distance from its nearest neighbour will not be interpolated.
- At Spreading power, type the value for the Voronoi area weight used in the operation (see Horizon Interpolate/Extrapolate).
- Type the Smoothing power used in the operation. This defines the inverse distance power (see Horizon Interpolate/Extrapolate).
The example below illustrates the difference between an interpolated and extrapolated velocity model.
Interpolate vs extrapolate

Interpolating picks at a new location
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When you pick at a new location, if the interpolated velocity model covers that location, additional picks are automatically made to match the interpolated velocity. These two parameters control this interpolation of new picks.
- Maximum Picks — Select the maximum number of picks Insight can automatically add. To disable any automatic picks, type 0.
- Minimum Spacing (ms) — Select how far apart each automatically-added pick should be from one another.