Composition

The composition type indicates how a sequence of coordinates need to be interpreted.

The GeoDMS supports three composition types:

1. arc: an arc consists of at least a start and end point and 0 or more intermediates per entry.
2. poly or polygon: a polygon consist of at least three points per entry, the last and first point need to be the same to create a closed polygon. The composition type poly is also used to indicate multiple elements in sequence functions.
3. multipoint: a multipoint is an unordered set of points per entry; the coordinates are not connected into a line or ring. It is stored in the same point-sequence storage as arc and polygon.

The composition type is configured for feature attributes of arcs, polygons and multipoints with the keyword arc, polygon or multipoint in the same brackets as the domain unit. A comma separates domain units and the composition type, the order is irrelevant.

Multipoint geometry can be read from vector sources (e.g. ESRI shapefiles or other formats via gdal.vect) and, since GeoDMS 20.2.0, constructed from a point table with points2sequence.

For point feature attributes no composition type has to be configured.