Suture Options

Use the Suture Options dialog to configure how two grids are stitched into a single grid.

Suture Options dialog options

Suture path

Select the suture path:

  • Automatic (default)

  • Interactive

  • Grid 1 Edges

  • Grid 2 Edges

The Interactive option cannot be used for multiple grid stitching.

See the Application Notes below for more details.

Script Parameter: GRIDSTCH.PATH

Correction weighting

Specify how corrections are distributed between grids.

Default: 0.5

Script Parameter: GRIDSTCH.WEIGHTING

Correction width (cells)

Specify the width of the correction zone, in cells, on either side of the suture path.

Allow at least eight cells to ensure a smooth suture.

Default: 32

Script Parameter: GRIDSTCH.WIDTH

Application Notes

The Suture Method

The suture method defines a line along which the two grids are joined. This line lies entirely within the overlapping region of the two grids. Portions of the grids outside the selected regions (the “cut-off” areas) do not contribute to the final stitched grid.

Along the suture path, differences between the grid values are corrected by adjusting values on either side of the path. For example, if the value in grid #1 is 1.0 larger than the value in grid #2, at a point along the suture path, the discrepancy may be reduced by averaging the two values.

Adjacent points may then be adjusted to ensure a smooth transition between the grids. This routine uses a multi-frequency approach, in which corrections are distributed across the grids in proportion to the wavelength of the mismatch along the suture path. This ensures that the transition remains smooth, regardless of the amplitude or wavelength of the features intersected by the suture path.

Suture Path

The available options are:

  • Automatic: The suture path is generated to run approximately through the middle of the overlapping region, maintaining a roughly equal distance from the overlap boundaries.

  • Interactive: The suture path is defined manually using the current map. If no map is active, one will be requested.

  • Grid 1 Edges and Grid 2 Edges: The path follows the boundary of the selected grid.

Interactive Suture Path

When the Interactive option is selected, the path must be defined within the overlapping region.

  • The start and end points within the overlap are fixed by the geometry of the overlapping area and cannot be modified.

  • Any portions of the user-defined path outside the overlapping region are ignored.

  • If the defined path does not include valid start or end points, the user-defined path is altered to use them by joining the first and last points of the user-defined path within the overlap to the fixed start and end points.

The resulting path must not cross invalid (dummy) cells or non-overlapping regions, otherwise an error will occur.

A single user-defined path can be used to traverse two or more separate overlap sections by inserting at least one “outside” point as a separator between each overlap segment. (All “outside” points are ignored when calculating the suture path from a user-defined path.)

"Postage Stamp Stitching"

"Postage stamp" stitching may be accomplished using the Grid 1 Edges / Grid 2 Edges path selections. This method is useful when inserting a smaller grid entirely within a larger grid.

The contents of the entire smaller grid may be preserved by selecting the Grid 1 Edges / Grid 2 Edges path corresponding to that grid – the suture path will entirely enclose the smaller grid.

The path creation algorithm may run into difficulty when the Grid 1 Edges / Grid 2 Edges path is selected if the boundaries of the grid are not sufficiently smooth. It may be necessary to smooth jagged edges, remove "peninsulas" or fill in "bays" using interpolation (see below) in order for the path to be determined unambiguously.

Automatic Suture Path

The Automatic option generally produces smoother paths because of the averaging effects of using edges from both grids simultaneously and finding the midpoints between them.

Correction Weighting

A value in the range 0 to 1 controls how corrections are distributed between the two grids.

  • A value of 0 applies all corrections to grid #1

  • A value of 1 applies all corrections to grid #2

  • A value of 0.5 distributes corrections evenly between both grids (default)

By directing all corrections toward one grid or the other, one grid can remain unaltered up to the suture path.

Correction Width

Corrections are applied on either side of the suture path, up to the specified correction width.

The total width of the correction zone is twice the correction width. Larger values result in smoother transitions but increase processing time, as a larger portion of the grid is affected.

See Also: