Trend Removal

Use the Trend Removal dialog to configure how trends are calculated and removed during grid stitching.

Trend Removal dialog options

Grid #1 trend

Specify the trend removal method for the grid.

  • None (default)– No trend removal

  • Static (zero order) – Removes a constant offset

  • Slope (first order) – Removes a best-fit plane

  • 2nd order trend – Removes curved surfaces using 2nd-order polynomial fits in X and Y

  • 3rd order trend (default) – Removes curved surfaces using 3rd-order polynomial fits in X and Y

Script Parameter: GRIDSTCH.TRORDER1 (0: None, 1: Static, 2: Slope, 3: 2nd Order, 4: 3rd order)

Grid #2 trend

Specify the trend removal method for the grid.

  • None – No trend removal

  • Static (default) – Removes a constant offset

  • Slope – Removes a best-fit plane

  • 2nd order trend – Removes curved surfaces using 2nd-order polynomial fits in X and Y

  • 3rd order trend (default) – Removes curved surfaces using 3rd-order polynomial fits in X and Y

Script Parameter: GRIDSTCH.TRORDER2 (0: None, 1: Static, 2: Slope, 3: 2nd Order, 4: 3rd order)

Points to use

Specify which points are used to calculate the trend:

  • All Points – Uses all data points in the grid

  • Edge Points – Uses only points along the grid edges

  • Overlap Points (default) – Uses only points within overlapping regions

  • Overlapping Edge Points – Uses only edge points within overlapping regions

Script Parameter: GRIDSTCH.TRCALC (0: All; 1: Edge; 2: Overlap; 3: Overlapping edges).

Application Notes

Trend Order

You 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 second- or third-order polynomials in X and Y.

Point Usage

The calculation for the correction may be calculated in one of four ways: using all the points in the grid, using the edge points, using only the points that 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 the grid contains multiple disjoint regions, only the first region encountered by the algorithm is used.

    • See Also: