Interpolation Options

Use the Interpolation Options dialog to improve the suture path selection in grids with many holes. It is not recommended for general interpolation of grids.

Interpolation Options dialog options

Interpolation method

Select the interpolation method to use, "Linear", "Cubic" or "Akima".

Script Parameter: GRIDSTCH.SPLINE

Maximum interpolated gap

The maximum gap to interpolate across. By default, this is blank, and no interpolation is performed.

Script Parameter: GRIDSTCH.GAP

Application Notes

Interpolation

Grids may have gaps or holes inside the overlap region. The presence of gaps will affect the behaviour of the stitching methods. In the blending method, the gaps will be interpreted as grid edges, so that the contribution of the grid with the gap in it will be reduced to 0 at the gap edges. In the suture method the automatic suture path will tend to avoid the gaps, because it chooses the path midway between the edges of the two grids. These effects may be reduced or eliminated by choosing to interpolate the gaps prior to the stitching process. By default, the interpolation value is left blank, and no interpolation is performed.

Gap Size

The Gap Size is in "Cell" units. If the gap size is set to a value "X", then all gaps in the data smaller than size "X" will be interpolated prior to stitching. If the gap size is set to 0.0, all gaps will be interpolated. If the gap size is not specified, no interpolation is performed prior to stitching. Using a gap of 0.0 can produce undesirable effects if large "bays" appear in the data, including streaking in the output grid in filled-in areas. Interpolation is done across rows, and then across columns.

Spline Method

The spline method determines how values are predicted in areas without data. Three methods are available, Linear, Cubic, and Akima. The linear spline assumes a simple linear variation between the values bounding the gap. The cubic spline is a minimum-curvature method. In cases where the data contains rapid changes in gradient, the minimum curvature (cubic) spline may produce undesirable highs or lows in the final grid. This most commonly occurs across lines with poor line-to-line correlation of the data. The Akima spline method does not suffer as much from this problem, although it does tend to produce sharper corners around actual data points and the resulting grid tends to be less smooth.