SAGA-GIS Tool Library Documentation (v7.2.0)

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.

Description: See J. Haber, F. Zeilfelder, O.Davydov and H.-P. Seidel, Smooth approximation and rendering of large scattered data sets, in 'Proceedings of IEEE Visualization 2001' (Th.Ertl, K.Joy and A.Varshney, Eds.), pp.341-347, 571, IEEE Computer Society, 2001.
www.uni-giessen.de/www-Numerische-Mathematik/davydov/VIS2001.ps.gz
www.math.uni-mannheim.de/~lsmath4/paper/VIS2001.pdf.gz

Parameters

 NameTypeIdentifierDescriptionConstraints
InputPointsShapes (input)SHAPES--
Target System (*)Grid (optional input)TARGET_TEMPLATEuse this grid's system for output grids-
OutputTarget GridGrid (output)TARGET_OUT_GRID--
OptionsAttributeTable fieldFIELD--
Target Grid SystemChoiceTARGET_DEFINITION-Available Choices:
[0] user defined
[1] grid or grid system
Default: 0
CellsizeFloating pointTARGET_USER_SIZE-Minimum: 0.000000
Default: 1.000000
LeftFloating pointTARGET_USER_XMIN-Default: 0.000000
RightFloating pointTARGET_USER_XMAX-Default: 100.000000
BottomFloating pointTARGET_USER_YMIN-Default: 0.000000
TopFloating pointTARGET_USER_YMAX-Default: 100.000000
FitChoiceTARGET_USER_FITS-Available Choices:
[0] nodes
[1] cells
Default: 0
Grid SystemGrid systemTARGET_SYSTEM--
Minimal Number of PointsIntegerNPMIN-Minimum: 0
Default: 3
Maximal Number of PointsIntegerNPMAX-Minimum: 11
Maximum: 59
Default: 20
Points per SquareFloating pointNPPC-Minimum: 1.000000
Default: 5.000000
ToleranceIntegerKSpline sensitivity, reduce to get smoother results, recommended: 80 < Tolerance < 200Minimum: 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_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>	Left
	Floating point
	Default: 0.000000
  -TARGET_USER_XMAX:<double>	Right
	Floating point
	Default: 100.000000
  -TARGET_USER_YMIN:<double>	Bottom
	Floating point
	Default: 0.000000
  -TARGET_USER_YMAX:<double>	Top
	Floating point
	Default: 100.000000
  -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