The Universal Kriging operation can be directly executed by typing one of the following expressions on the command line of the Main window:
OUTMAP |
= |
MapKrigingUniversal(InputPointMap, Georef, SemiVarModel, LimDist, TrendType, 0, 1) |
OUTMAP |
= |
MapKrigingUniversal(InputPointMap, Georef, SemiVarModel, LimDist, TrendType, 0, 1, 1|0) |
OUTMAP |
= |
MapKrigingUniversal(InputPointMap, Georef, SemiVarModel, LimDist, TrendType, 0, 1, 1|0, min, max) |
OUTMAP |
= |
MapKrigingUniversal(InputPointMap, Georef, SemiVarModel, LimDist, TrendType, 0, 1, 1|0, min, max, No | Average | Firstval) |
OUTMAP |
= |
MapKrigingUniversal(InputPointMap, Georef, SemiVarModel, LimDist, TrendType, 0, 1, 1|0, min, max, Average | Firstval, Tolerance) |
where:
OUTMAP |
is the name of the output raster map. |
MapKrigingUniversal |
is the command to start the Universal Kriging operation. |
InputPointMap |
is the name of the input point map with a value domain. To use a value attribute column from an attribute table which is linked to an ID point map, use InputPointMap.Columnname. |
Georef |
is the name of an existing georeference for the output raster map. |
SemiVarModel |
Model(nugget, sill, range) | Power(nugget, slope, pow) This expression defines the semi-variogram model and its parameters that should be used. |
Model |
Spherical | Exponential | Gaussian | Wave | RatQuad | Circular |
nugget |
value for the nugget, according to your semi-variogram (real value). |
sill |
value for the sill, according to your semi-variogram (real value) |
range |
value for the range, according to your semi-variogram (real value > 0). |
slope |
when using the Power model: value for the 'slope'. When pow is specified as 1 (i.e. thus using a linear model), then slope is the direction coefficient, i.e. Dg/Dh (real value >= 0). |
pow |
when using the Power model: an exponent 0 < real value < 2. When you use value 1, the power model will become linear and the slope will be constant. If the power exponent is 2 the assumed stochastic model (�randomness�) is not always justifiable and the interpolation can become pathological. |
LimDist |
a value for the limiting distance: points that are further away from an output pixel than the limiting distance will not be used in the Kriging equations. Normally, this is a value smaller than the range of the semi-variogram model (0 <= real value < diagonal size of the map). |
TrendType |
0 | 1 | 2 Define the trend surface; either 0 (no trend) , 1 (linear trend) or 2 (quadratic trend). |
0, 1 |
Parameters (angle and ratio) to indicate that there is no anisotropy. If you wish to include anisotropy (not advised), specify the angle and ratio parameters as explained in Anisotropic Kriging : command line. |
1 | 0 |
Specify whether or not an error map has to be created. The error map will contain the square root of the Kriging error variance values, i.e. standard deviations per pixel. When this parameter is not specified, no error map will be created. |
1 |
Create an error map. The error map will obtain the same name as specified for the output Kriging map followed by the additional string _Error. |
0 |
Do not create an error map. |
min, max |
Optional parameters (integer values) to specify the minimum and maximum number of points that should be taken into account per Kriging estimate/prediction, i.e. the number of points within the limiting distance of an output pixel that should be taken into account in the calculation of the output value for that pixel.
|
No | Average | Firstval |
|
|
Choose how to handle possible coinciding points or duplicates. When no method is specified, Average will be used. |
No |
No removal of duplicates. Mind: when there are coinciding points, the Kriging system may become unsolvable and will give undefined values for the pixels for which coinciding points are found. |
Average |
Values of duplicates are replaced by the average (arithmetic mean); the coordinates of the first point are taken as new position. |
Firstval |
Values of duplicates (and their coordinates) are replaced by those of the first point. |
Tolerance |
Optional parameter to specify the distance within which 2 sample points are considered to coincide. When not specified, a tolerance of 0.1 m will be used. |
When the definition symbol = is used, a dependent output map is created; when the assignment symbol := is used, the dependency link is immediately broken after the output map has been calculated.
Example:
The following expression:
OutUniK |
= |
MapKrigingUniversal(MyPoints.MyAttrib, MyGeoref, Spherical(10,70,800), 200, 2, 0, 1, 1, 6, 20, Firstval, 0.2) |
performs Universal Kriging:
The results of the expression are:
Note:
The MapKrigingUniversal(...) expressions can also be used for Anisotropic Kriging. For more information, see Anisotropic Kriging : command line.
See also: