polygon operators - ObjectVision/GeoDMS GitHub Wiki

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• area - calculates the surface area of each polygon
• centroid - center of mass of each polygon
• centroid_or_mid - the centroid if located within the polygon, otherwise a mid-point
• poly2grid - a grid representation of polygons
• poly2grid_untiled - a grid representation of polygons (untiled variant)
• poly2allgrids - a cross-table representation of polygons and raster cells
• poly2allgrids_uint64 - a uint64 cross-table representation of polygons and raster cells
• lower_bound - the lowest X and Y values of the points in each polygon
• upper_bound - the highest X and Y values of the points in each polygon
• center_bound - the center X and Y values of the points in each polygon
• points2polygon - create polygons from sequences of points
• sub (difference) - element-wise cutout of one polygon from another, where both domains match or one is void
• mul (polygon intersection) - element-wise overlap of two polygon arrays, where both domains match or one is void
• add (union) - element-wise union of two polygon arrays, where both domains match or one is void
• box_connectivity - find connected polygons based on bounding box overlap (faster, but less precise than polygon_connectivity)

Operators based on the geos library (recommended: faster, reliable, supports float64/dpoint coordinates):

• geos_buffer_multi_polygon - creates a buffer polygon for each multi polygon
• geos_difference - element-wise difference of two polygon arrays (A minus B); also invoked by the - operator for fpoint/dpoint coordinates
• geos_intersect - element-wise intersection of two polygon arrays; also invoked by the * and & operators for fpoint/dpoint coordinates
• geos_overlay_polygon - spatial overlay between two polygon datasets, producing all intersecting pairs with their intersection geometry
• geos_polygon - clean and validate polygon geometry using GEOS
• geos_polygon_connectivity - find all pairs of adjacent or overlapping polygons
• geos_simplify_multi_polygon - simplify the geometry of a multi polygon
• geos_split_polygon - split multi-polygons into individual single-polygon parts, each as a separate domain entry
• geos_split_union_polygon - dissolve polygons (optionally grouped by attribute), then split into individual parts
• geos_union - element-wise union of two polygon arrays; also invoked by the + and | operators for fpoint/dpoint coordinates
• geos_union_polygon - dissolve all polygons into one, optionally grouped by a partition attribute
• geos_xor - element-wise symmetric difference of two polygon arrays; also invoked by the ^ operator for fpoint/dpoint coordinates

To be developed operators:

• geos_simplify_single_polygon - simplify the geometry of a single polygon; see bg_simplify_multi_polygon
• geos_buffer_single_polygon - creates a buffer polygon for each single polygon; see bg_buffer_multi_polygon
• geos_outer_single_polygon - selects only the outer ring of a single polygon; see bg_outer_multi_polygon
• geos_outer_multi_polygon - selects only the outer ring of a multi polygon; see bg_outer_multi_polygon

Operators based on the boost polygon library (usually slower than the bg_-variants, and can only process integer coordinates):

• bp_buffer_multi_polygon - creates a buffer polygon around each multi polygon (integer coordinates)
• bp_difference - element-wise difference of two polygon arrays (integer coordinates)
• bp_intersect - element-wise intersection of two polygon arrays (integer coordinates)
• bp_overlay_polygon (or old syntax overlay_polygon - spatial overlay between two polygon datasets, producing all intersecting pairs (integer coordinates)
• bp_polygon - clean and validate polygon geometry using Boost Polygon (integer coordinates)
• bp_polygon_connectivity (or old syntax polygon_connectivity) - find all pairs of adjacent or overlapping polygons (integer coordinates)
• bp_split_polygon (or old syntax split_polygon) - split multi-polygons into individual single-polygon parts (integer coordinates)
• [bp_split_union_polygon]] (or old syntax [[split_partitioned_union_polygon]]) - dissolve polygons (optionally grouped by attribute), then split into individual parts (integer coordinates). Combination of [[split_polygon]] and [partitioned_union_polygon
• bp_union - element-wise union of two polygon arrays (integer coordinates)
• bp_union_polygon (or old syntax union_polygon (dissolve) or partitioned_union_polygon (dissolve by attribute)) - dissolve all polygons into one, optionally grouped by a partition attribute (integer coordinates)
• bp_xor - element-wise symmetric difference of two polygon arrays (integer coordinates)
• polygon inflated - increases each polygon by expanding its boundary outward
• polygon deflated - decreases each polygon by contracting its boundary inward

*Several boost polygon functions can be combined in a single operator; for the full list of those combinations, see here_

Operators based on the boost geometry library (float64/dpoint coordinates; largely superseded by geos_ variants):

• bg_buffer_multi_polygon - creates a buffer polygon for each multi polygon
• bg_buffer_single_polygon - creates a buffer polygon for each single polygon; see bg_buffer_multi_polygon
• bg_difference - - element-wise difference of two polygon arrays
• bg_intersect - element-wise intersection of two polygon arrays
• bg_outer_multi_polygon - selects only the outer ring of each multi polygon (removes holes)
• bg_outer_single_polygon - selects only the outer ring of each single polygon; see for documentation: bg_outer_multi_polygon
• bg_overlay_polygon - spatial overlay between two polygon datasets, producing all intersecting pairs
• bg_polygon - clean and validate polygon geometry using Boost Geometry
• bg_polygon_connectivity - find all pairs of adjacent or overlapping polygons
• bg_simplify_multi_polygon - simplify the geometry of a multi polygon
• bg_simplify_polygon - DEPRECATED: simplify the geometry of a single polygon; see for documentation: bg_simplify_multi_polygon
• bg_split_polygon - split multi-polygons into individual single-polygon parts
• bg_split_union_polygon - dissolve polygons (optionally grouped by attribute), then split into individual parts
• bg_union - element-wise union of two polygon arrays
• bg_union_polygon - DO NOT USE: current implementation does not produce reliable results
• bg_xor - element-wise symmetric difference of two polygon arrays

For examples, see here.

Operators based on the cgal library:

• cgal_difference - element-wise difference of two polygon arrays (CGAL)
• cgal_intersect - element-wise intersection of two polygon arrays (CGAL)
• cgal_overlay_polygon - spatial overlay between two polygon datasets, producing all intersecting pairs (CGAL)
• cgal_polygon - clean and validate polygon geometry using CGAL
• cgal_polygon_connectivity - find all pairs of adjacent or overlapping polygons (CGAL)
• cgal_split_polygon - split multi-polygons into individual single-polygon parts (CGAL)
• cgal_split_union_polygon - dissolve polygons (optionally grouped by attribute), then split into individual parts (CGAL)
• cgal_union - element-wise union of two polygon arrays (CGAL)
• cgal_union_polygon - dissolve all polygons into one, optionally grouped by a partition attribute (CGAL)
• cgal_xor - element-wise symmetric difference of two polygon arrays (CGAL)