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geos_buffer_multi_point

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MaartenHilferink edited this page Jun 14, 2026 · 4 revisions

Geometric functions > geos_buffer_multi_point

syntax

  • geos_buffer_multi_point(multipoint_data_item, buffer_distance, nrPointsInCircle)

description

geos_buffer_multi_point(multipoint_data_item, buffer_distance, nrPointsInCircle) creates a buffer polygon around each coordinate of the multipoint_data_item. The result is a polygon data item with the same domain as the multipoint_data_item.

The buffer_distance is a Float64 value that specifies the radius of the buffer in the units of the coordinate system of the multipoint_data_item.

The nrPointsInCircle is a UInt8 value that specifies the number of points used to approximate the circle per source point. A higher value results in a smoother buffer but increases computation time. The minimum value is 3.

The geos_ prefix of the function name indicates that the implementation of the operator uses geos.

applies to

changed restriction

Since version 20.2.0 the first argument is expected to have multipoint composition. Passing an arc or polygon attribute is deprecated: it still works but produces a deprecation warning, and is slated to become an error in a future major version. Construct genuine multipoint geometry with points2multi_point. Before 20.2.0 this operator accepted arc or polygon geometry (their coordinates were treated as a set of points).

buffering the vertices of arc or polygon geometry

If you want to buffer the vertices of an existing arc or polygon attribute as a set of points, first convert that geometry to multipoint composition. Decompose it into its vertices with sequence2points and rebuild a multipoint with points2multi_point, grouping by the relation back to the original geometry:

// geom is an (arc) or (polygon) attribute on domain district
unit<uint32> vertices := sequence2points(district/geom);   // point, sequence_rel (-> district), ordinal
attribute<fpoint> mpoints (district, multipoint) := points2multi_point(vertices/point, vertices/sequence_rel, vertices/ordinal);
attribute<fpoint> buffer_geometry (district)     := geos_buffer_multi_point(mpoints, 50.0, 8b);

The buffered result is the same as it was when arc or polygon geometry was passed directly before 20.2.0; the conversion only makes the multipoint composition explicit, so no deprecation warning is issued.

conditions

  1. buffer_distance must be a positive value.
  2. nrPointsInCircle must be at least 3.

since version

7.202

example

attribute<fpoint> points          (road, multipoint) := points2multi_point(point, Sequence_rel, ordinal);
attribute<fpoint> buffer_geometry (road)             := geos_buffer_multi_point(points, 50.0, 8b);

see also

GeoDMS ©Object Vision BV. Source code distributed under GNU GPL-3. Documentation distributed under CC BY-SA 4.0.

GeoDMS ©Object Vision BV. Source code distributed under GNU GPL-3. Documentation distributed under CC BY-SA 4.0.

GeoDMS

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