Trend Removal

Use the Trend Removal dialog to remove a trend from your grids.

Trend Removal dialog options

Grid #1 trend	Grid #1 Select a Trend Removal method: "None", "Static", "Slope", 2nd Order Trend and 3rd Order Trend. Script Parameter: GRIDSTCH.TRORDER1 (0: None, 1: Static, 2: Slope, 3: 2nd Order, 4: 3rd order; default: 0)
Grid #2 trend	Grid #2 Select a Trend Removal method: "None", "Static", "Slope", 2nd Order Trend and 3rd Order Trend. Script Parameter: GRIDSTCH.TRORDER2 (0: None, 1: Static, 2: Slope, 3: 2nd Order, 4: 3rd order; default: 1)
Points to use	Select "All Points", "Edge Points", "Overlap Points", or "Overlapping Edge Points" to use for Trend Calculations. Script Parameter: GRIDSTCH.TRCALC (0: All; 1: Edge; 2: Overlap; 3: Overlapping edges; default: 2).

Application Notes

Trend Order

The user may wish to remove a static shift or trend from one or both grids before stitching. The zero-order or static correction removes a single average value from the entire grid. The first-order correction removes a best-fitting plane or slope. Higher orders fit 2nd or 3rd order polynomials in X and Y.

Point Usage

The calculation for the correction may be done in one of four ways; using all the points in the grid, using the edge points, using only the points which overlap with the other grid, or using only the edge points which overlap with the other grid.

Interpolation

Trend calculation and removal are performed subsequent to any interpolation. (Interpolation is optional).

If "edge points" is selected, and there is more than one disjoint section in the grid data, then only the first section that the algorithm encounters is used in the calculation.