cartagen.square_polygon_orthogonal

square_polygon_orthogonal(polygon, orientation='mbtr', force_all=True, angle_tolerance=8.0, correct_tolerance=0.6, remove_flat=True)

Squares a building by forcing it into an orthogonal coordinate system.

This algorithm described by Hakim and Tsai [1] is a heuristic approach that leverages the Manhattan World assumption. It identifies the orientation of the building and performs a global rotation to align the footprint with the X/Y grid. Facades are then classified and merged into strictly horizontal or vertical lines. Perfect 90-degree corners are reconstructed via direct line intersections before an inverse rotation is applied to restore the building to its original geospatial location.

Parameters:

• polygon (Polygon) – The polygon to square.

• orientation (str, optional) –

  The method to calculate the orientation of the polygon. This defines the dominant axis used for the global rotation.

  • ’primary’ calculates the orientation of the longest side of the provided polygon.

  • ’mbr’ calculates the orientation of the long side of the minimum rotated bounding rectangle.

  • ’mbtr’ calculates the orientation of the long side of the minimum rotated bounding touching rectangle.

  • ’swo’ or statistical weighted orientation calculates the orientation using the statistical weighted orientation method.

• force_all (bool, optional) – If set to True (default), every segment is snapped to whichever cardinal direction (H or V) it is closest to, regardless of the deviation. The angle_tolerance and correct_tolerance parameters are ignored in this mode. Set to False to apply tolerance-based squaring: only segments within angle_tolerance of a cardinal direction are snapped, and vertices already within correct_tolerance of right or flat are left alone.

• angle_tolerance (float, optional) – Only used when force_all is False. Tolerance in degrees within which a segment is snapped to the nearest cardinal direction. Segments whose deviation exceeds this value are left unchanged (‘U’).

• correct_tolerance (float, optional) – Only used when force_all is False. Tolerance in degrees below which a vertex is considered already correct and skipped.

• remove_flat (bool, optional) – If set to True, vertices whose interior angle is flat (close to 180°) after squaring are removed from the result.

Returns:

Polygon

See also

square_polygon_naive

Squares a polygon according to its orientation, vertex by vertex.

square_polygon_ls

Squares a polygon using the method of least squares.

polygon_orientation

Calculate the orientation of a polygon.

References

[1]

Yofri Furqani Hakim and Fuan Tsai. Building footprint extraction for large-scale basemaps using very-high-resolution satellite imagery. Buildings, 2026. URL: https://www.mdpi.com/2075-5309/16/3/675, doi:10.3390/buildings16030675.

Examples

>>> polygon = Polygon([(0, 0), (0, 1), (1.1, 1), (1, 0)])
>>> square_polygon_orthogonal(polygon)
<POLYGON ((0 1, 1.05 1, 1.05 0, 0 0, 0 1))>

(Source code)