cartagen.smooth_wma

smooth_wma(geometry, iterations=1, weights=[1.0, 2.0, 1.0])

Smooth a line or polygon using a low-pass filter.

This algorithm described in McMaster [1] for a generalization purpose applies a weighted moving average (WMA) window over the vertices. The default weights [1, 2, 1] heavily weight the central point to suppress unwanted short-wavelength noise while minimizing overall geometric shrinkage.

Accept Multi geometries. If a polygon is provided, it also applies the smoothing to its holes using the same parameters.

Parameters:

• geometry (LineString, MultiLineString, Polygon, MultiPolygon, LinearRing) – The geometry to smooth. If an open line is provided, the endpoints are preserved. If a closed ring or polygon is provided, the smoothing wraps around.

• iterations (int, optional) – Number of iterations to apply the filter. Default is 1.

• weights (sequence of odd length, optional) – Weights for the moving average window. Default is [1, 2, 1].

Returns:

LineString, Polygon, MultiLineString, MultiPolygon, LinearRing – Smoothed geometry of the same type as input.

Notes

This algorithm can also become a simple moving average smoothing algorithm if you set the weights to [1, 1, 1].

See also

smooth_gaussian

Smooth a line or a polygon and attenuate its inflexion points.

smooth_platre

Smooth a line and preserve the integrity of sharp turns.

smooth_snake

Smooth a line or polygon using the snake method.

smooth_taubin

Smooth a line or polygon and prevent shrinkage.

smooth_topographic

Smooth a line or polygon and mimic hand-made cartographic generalization.

Examples

>>> line = LineString([(0, 0), (1, 1), (2, 0), (3, 1), (4, 0)])
>>> smooth_wma(line, 1)
<LINESTRING (0 0, 1 0.5, 2 0.5, 3 0.5, 4 0)>

(Source code)