Tool Cubic Spline Approximation

This tool approximates irregular scalar 2D data in specified points using C1-continuous bivariate cubic spline.
Minimal Number of Points: minimal number of points locally involved in spline calculation (normally = 3)

Maximal Number of Points:npmax: maximal number of points locally involved in spline calculation (required > 10, recommended 20 < npmax < 60)
Tolerance: relative tolerance multiple in fitting spline coefficients: the higher this value, the higher degree of the locally fitted spline (recommended 80 < k < 200)

Points per square: average number of points per square (increase if the point distribution is strongly non-uniform to get larger cells)

Author: Pavel Sakov, CSIRO Marine Research

Purpose: 2D data approximation with bivariate C1 cubic spline. A set of library functions + standalone utility.

References

Haber, J., Zeilfelder, F., Davydov, O., Seidel, H.-P. (2001): Smooth approximation and rendering of large scattered data sets. In Ertl, T., Joy, K., Varshney, A. [Eds.]: Proceedings of IEEE Visualization. pp.341-347, 571, IEEE Computer Society.

Author: O. Conrad (c) 2008
Menu: Grid|Gridding|Spline Interpolation

Parameters

	Name	Type	Identifier	Description	Constraints
Input	Points	Shapes (input)	`SHAPES`	-	-
Input	Target System (*)	Grid (optional input)	`TARGET_TEMPLATE`	use this grid's system for output grids	-
Output	Target Grid	Grid (output)	`TARGET_OUT_GRID`	-	-
Options	Attribute	Table field	`FIELD`	-	-
	Target Grid System	Choice	`TARGET_DEFINITION`	-	Available Choices: [0] user defined [1] grid or grid system Default: 0
	Cellsize	Floating point	`TARGET_USER_SIZE`	-	Minimum: 0.000000 Default: 1.000000
	West	Floating point	`TARGET_USER_XMIN`	-	Default: 0.000000
	East	Floating point	`TARGET_USER_XMAX`	-	Default: 100.000000
	South	Floating point	`TARGET_USER_YMIN`	-	Default: 0.000000
	North	Floating point	`TARGET_USER_YMAX`	-	Default: 100.000000
	Columns	Integer	`TARGET_USER_COLS`	Number of cells in East-West direction.	Minimum: 1 Default: 100
	Rows	Integer	`TARGET_USER_ROWS`	Number of cells in North-South direction.	Minimum: 1 Default: 100
	Fit	Choice	`TARGET_USER_FITS`	-	Available Choices: [0] nodes [1] cells Default: 0
	Grid System	Grid system	`TARGET_SYSTEM`	-	-
	Minimal Number of Points	Integer	`NPMIN`	-	Minimum: 0 Default: 3
	Maximal Number of Points	Integer	`NPMAX`	-	Minimum: 11 Maximum: 59 Default: 20
	Points per Square	Floating point	`NPPC`	-	Minimum: 1.000000 Default: 5.000000
	Tolerance	Integer	`K`	Spline sensitivity, reduce to get smoother results, recommended: 80 < Tolerance < 200	Minimum: 0 Default: 140
(*) optional

Command-line

Usage: saga_cmd grid_spline 6 [-SHAPES <str>] [-FIELD <str>] [-TARGET_DEFINITION <str>] [-TARGET_USER_SIZE <double>] [-TARGET_USER_XMIN <double>] [-TARGET_USER_XMAX <double>] [-TARGET_USER_YMIN <double>] [-TARGET_USER_YMAX <double>] [-TARGET_USER_COLS <num>] [-TARGET_USER_ROWS <num>] [-TARGET_USER_FITS <str>] [-TARGET_TEMPLATE <str>] [-TARGET_OUT_GRID <str>] [-NPMIN <num>] [-NPMAX <num>] [-NPPC <double>] [-K <num>]
  -SHAPES:<str>             	Points
	Shapes (input)
  -FIELD:<str>              	Attribute
	Table field
  -TARGET_DEFINITION:<str>  	Target Grid System
	Choice
	Available Choices:
	[0] user defined
	[1] grid or grid system
	Default: 0
  -TARGET_USER_SIZE:<double>	Cellsize
	Floating point
	Minimum: 0.000000
	Default: 1.000000
  -TARGET_USER_XMIN:<double>	West
	Floating point
	Default: 0.000000
  -TARGET_USER_XMAX:<double>	East
	Floating point
	Default: 100.000000
  -TARGET_USER_YMIN:<double>	South
	Floating point
	Default: 0.000000
  -TARGET_USER_YMAX:<double>	North
	Floating point
	Default: 100.000000
  -TARGET_USER_COLS:<num>   	Columns
	Integer
	Minimum: 1
	Default: 100
  -TARGET_USER_ROWS:<num>   	Rows
	Integer
	Minimum: 1
	Default: 100
  -TARGET_USER_FITS:<str>   	Fit
	Choice
	Available Choices:
	[0] nodes
	[1] cells
	Default: 0
  -TARGET_TEMPLATE:<str>    	Target System
	Grid (optional input)
  -TARGET_OUT_GRID:<str>    	Target Grid
	Grid (output)
  -NPMIN:<num>              	Minimal Number of Points
	Integer
	Minimum: 0
	Default: 3
  -NPMAX:<num>              	Maximal Number of Points
	Integer
	Minimum: 11
	Maximum: 59
	Default: 20
  -NPPC:<double>            	Points per Square
	Floating point
	Minimum: 1.000000
	Default: 5.000000
  -K:<num>                  	Tolerance
	Integer
	Minimum: 0
	Default: 140