polygon operators - ObjectVision/GeoDMS GitHub Wiki
Back to Geometric functions
- area - calculates the surface area of each polygon
- centroid - center of mass of each polygon
- mid - a point in the polygon, cheaper than centroid
- outer_single_polygon - outer ring of a single polygon (drops holes)
- outer_multi_polygon - outer ring(s) of each multi_polygon (drops the holes)
- geos_buffer - buffer of a (multi)polygon, geos implementation
- canyon - street-canyon heights for road points from surrounding heights
- 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)
Ring order (winding) operators:
- reverse_polygon - reverse the winding order of every ring, without changing the sequence layout
- fix_winding_order - give every ring the clockwise-outer / counter-clockwise-hole order, deriving the ring roles from their nesting; repairs half-flipped multi-polygons that a reversal cannot
- has_correct_winding - True for each element whose ring order is certifiably correct; the replacement for the
area(g) < 0test, which misses a half-flipped feature - [fix_polygon]] - [[fix_winding_order]] plus repair of self-intersections and other invalidity ([GEOS MakeValid)
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_minkowski_sum - grow each geometry by a kernel: the kernel as a polygon argument, or one of six named shapes at a given size
- geos_minkowski_difference - shrink each geometry by a kernel; the eroding counterpart
- 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 potentially developed operators:
- geos_simplify_single_polygon - simplify the geometry of a single polygon; see geos_simplify_multi_polygon
- geos_buffer_single_polygon - creates a buffer polygon for each single polygon; see geos_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- removed in 20.13.0: never implemented; use bg_buffer_multi_polygon or geos_buffer_multi_polygon- 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_polygon_filtered, bp_union_polygon_filtered, bp_split_polygon_filtered, bp_split_union_polygon_filtered - bp-set operations that drop rings smaller than the given area
- bp_polygon_inflated, bp_union_polygon_inflated, bp_split_polygon_inflated, bp_split_union_polygon_inflated - bp-set operations after growing the polygons with the given distance
- bp_polygon_deflated, bp_union_polygon_deflated, bp_split_polygon_deflated, bp_split_union_polygon_deflated - bp-set operations after shrinking the polygons with the given distance
- bp_minkowski_sum - grow each geometry by a kernel: the kernel as a polygon argument, or one of six named shapes at a given size
- bp_minkowski_difference - shrink each geometry by a kernel; the eroding counterpart
bp kernel-suffix variants- DEPRECATED since 20.18.0: the 48 namesbp_polygon_i4HV…bp_split_union_polygon_dXD(12 kernels x {plain, union, split, split_union}) that carried the kernel shape in the operator name. They still work but warn, naming the replacement. The kernel is an argument now: use bp_minkowski_sum / bp_minkowski_difference on the result of the same operator without the suffix. See the migration table on Boost polygon functions.- 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 their geos equivalents):
- 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_minkowski_sum - grow each geometry by a kernel: the kernel as a polygon argument, or one of six named shapes at a given size
- bg_minkowski_difference - shrink each geometry by a kernel; the eroding counterpart
- 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_minkowski_sum - grow each geometry by a kernel, through
CGAL::minkowski_sum_2: the exact one of the four backends - cgal_minkowski_difference - shrink each geometry by a kernel; the eroding counterpart
- 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)