Spline

Instructions for use

The spline interpolation method uses the mathematical expression of the minimum surface curvature to simulate the smooth surface passing through a series of sample points.

  • The Source Dataset used for interpolation must have a numeric field as the interpolation field.
  • The spline interpolation method is suitable for the interpolation calculation of a large number of sample points and the requirement of obtaining a smooth surface. The more input points used for interpolation, the smoother the resulting surface. Also, the larger the number of points, the longer it takes to process the output grid.
  • The fixed-length spline method uses values that may lie outside of the sample Layer Bounds to create a smooth surface for the gradient. The variable-length spline method controls the hardness of the surface according to the characteristics of the modeling phenomenon. It uses values that are more tightly constrained by the sample Layer Bounds to create a less smooth surface.

Function Entry

  • Spatial Analysis tab-> Raster Analysis group-> Interpolation Analysis-> Spline.
  • Toolbox, Raster Analysis, Interpolation Analysis, Spline. (iDesktopX)

Parameter Description

  • Set public parameters for Interpolation Analysis, including Source Data, Bounds, Result Data, and Environment Settings. For the settings of public parameters such as source data, Bounds, and Result Data, please refer to Public Parameter Description .
  • Set the sample point search method. Fixed Count, Fixed Radius, and block lookup are supported. For a detailed description of these three lookup methods, see Spline interpolation .

    • Fixed Count: indicates to interpolate by using a fixed number of sample values within the maximum radius.

    • Max Radius: Enter the size of the radius to use for Fixed Count. The default value is 0, which means to use the maximum radius to find.
    • Find Points: Enter the number of points to use for Fixed Count. The default point is 12.

    Fixed Radius: All points within the search radius are involved in the interpolation operation.

    • Search radius: Enter the size of the set search radius. The default lookup radius is 1/5 of the larger value of the length or width of the range of the Dataset participating in the Interpolation Analysis. All the sampling points within the radius range shall participate in the interpolation operation.
    • Minimum number of points: Enter the minimum number of points to be used for Fixed Count. The default is 5 points. When the number of points in the neighborhood is less than specified minimum, the lookup radius increases until it can contain the minimum number of points entered. The maximum value is 12.

    Block Search: The Dataset is divided into blocks according to the set "Maximum number of points in a block", and then the points in the block are used for interpolation.

    • Maximum number of participating interpolation points: Enter the maximum number of participating interpolation points. The default maximum number of participating interpolation points is 200. In order to avoid the occurrence of cracks in the interpolation, the interpolation block used in the actual calculation will expand outward evenly on the basis of each block area, and the "maximum number of interpolation points" determines the size of the block area's outward expansion. Generally, this value should be greater than "maximum number of points in a block" set.
    • Maximum number of points in a block: Enter the maximum number of points in each block. The default maximum number of points within a block is 50. If the number of points in the block is more than this value, the block division is continued; otherwise, the block division is stopped.

      • The setting of the Maximum Number of Participating Interpolation Points and Maximum Number of Points in a Block parameters directly affects the performance of fast lookups. The larger these two values are set, the longer the search will take, so it is recommended that users set more reasonable parameters when setting the parameters for fast search.

  • Tension:: Enter the Tension: value. The default is 40. Tension: It is used to adjust the characteristics of the Raster Data surface of the result. The greater the tension, the smaller the influence of each point on the Calculate Result during interpolation, and vice versa.
  • Smoothness: input the value of Smoothness. The value range is 0-1, and the default value is 0.1. Smoothness refers to the degree of approximation between the interpolation function curve and the point. The greater the value, the greater the deviation between the function curve and the point, and vice versa.
    • Spline interpolation results