Class: QgsDerivativeFilter

Adds the ability to calculate derivatives in x- and y-directions.

Needs to be subclassed (e.g. for slope and aspect).

Class Hierarchy

Base classes

QgsNineCellFilter

Base class for raster analysis methods that work with a 3x3 cell filter and calculate the value of each cell based on the cell value and the eight neighbour cells.

Subclasses

QgsAspectFilter	Calculates aspect values in a window of 3x3 cells based on first order derivatives in x- and y- directions.
QgsHillshadeFilter	A hillshade filter.
QgsSlopeFilter	Calculates slope values in a window of 3x3 cells based on first order derivatives in x- and y- directions.

Methods

calcFirstDerX	Calculates the first order derivative in x-direction according to Horn (1981)
calcFirstDerY	Calculates the first order derivative in y-direction according to Horn (1981)

class qgis.analysis.QgsDerivativeFilter

Bases: QgsNineCellFilter

calcFirstDerX(self, x11: float, x21: float, x31: float, x12: float, x22: float, x32: float, x13: float, x23: float, x33: float) → float

Calculates the first order derivative in x-direction according to Horn (1981)

Parameters:

• x11 (float)

• x21 (float)

• x31 (float)

• x12 (float)

• x22 (float)

• x32 (float)

• x13 (float)

• x23 (float)

• x33 (float)

Return type:

float

calcFirstDerY(self, x11: float, x21: float, x31: float, x12: float, x22: float, x32: float, x13: float, x23: float, x33: float) → float

Calculates the first order derivative in y-direction according to Horn (1981)

Parameters:

• x11 (float)

• x21 (float)

• x31 (float)

• x12 (float)

• x22 (float)

• x32 (float)

• x13 (float)

• x23 (float)

• x33 (float)

Return type:

float