Table of Contents
ITGIS_InterpolationSplines interface
DK11 for ActiveX | TatukGIS_XDK11.ITGIS_InterpolationSplines | Interfaces | Methods | Properties
Implementation of the Completely Regularized Splines (CRS) interpolation method.
Syntax
// C# public interface ITGIS_InterpolationSplines: ITGIS_VectorToGridAbstract { }
' VisualBasic Public Interface ITGIS_InterpolationSplines Implements ITGIS_VectorToGridAbstract End Class
// Oxygene type ITGIS_InterpolationSplines = public interface( ITGIS_VectorToGridAbstract ) end;
Implements
Methods
| Name | Visibility | Description | |
|---|---|---|---|
| AttachDelphiObj | public | Only for internal use of TatukGIS. (Inherited from ITBaseObject) |
|
| DelphiObj | public | Only for internal use of TatukGIS. (Inherited from ITBaseObject) |
|
| Generate | public | Populates a pixel (grid) layer with values resulting from computations based on the set of sample points from the vector layer. (Inherited from ITGIS_VectorToGridAbstract) |
|
Properties
| Name | Visibility | Description | |
|---|---|---|---|
| Coordinate | public | Defines which coordinate is taken as interpolation value if the interpolation is not based on an attribute field; default is Z. (Inherited from ITGIS_VectorToGridAbstract) |
|
| DefaultValue | public | If UseDefaultValue is true, then this value will be set for each grid cell for which the interpolated value cannot be computed. (Inherited from ITGIS_VectorToGridAbstract) |
|
| MaxPoints | public | The maximum number of input data points used to interpolate at each grid cell; default is 4. | |
| MinPoints | public | The minimum number of input data points used to interpolate at each grid cell; default is 4. | |
| Radius | public | Applies only to the windowed method (Windowed = True). | |
| Tension | public | The tension (smoothing) factor. | |
| UseDefaultValue | public | If true, then each grid cell for which the interpolated value cannot be computed will be set to DefaultValue. (Inherited from ITGIS_VectorToGridAbstract) |
|
| Windowed | public | If True then the windowed version of the algorithm is used; true by default. | |
Remarks
Method
The principal of the Completely Regularized Splines interpolation method is to minimize the overall surface curvature. It produces the smoothest results among the vector-to-grid interpolation techniques.
Usage
There are two different scenarios for generating a splines interpolated grid:
- based on a Z, M, or Z+M coordinate value:
- set the
Coordinateproperty to the desired option - pass an empty string as the field name to the
Generatemethod
- based on an attribute field value:
- pass the field name to the
Generatemethod - with the above, the
Coordinateproperty is neglected
The Tension parameter is a smoothening factor - the smaller the tension the less rapid changes in the interpolated values. For best results it must be experimentally adjusted for each input dataset. The most common values of Tension (that are good to start with) are in the range of 0,00001 to 0,1.
Use a windowed version of the algorithm (Windowed=True) for large datasets (thousands of points and more). For up to a few hundred points, the non-windowed (full sample) algorithm is efficient enough and gives best possible results. The Radius property is the size of the window in map units. The MinPoints/MaxPoints properties define the minimum/maximum number of sample points necessary/taken to interpolate a grid value.
Pros
- smoothest results of all the interpolation methods (if this is the goal)
- interpolated values exceed the range of minimum to maximum values of the input data
Cons
- for many applications (like terrain models), the results are too smooth and seem unnatural
- works badly on input data with extreme value changes at short distances (because it amplifies the differences)