PostGIS
Description
Returns a set of ordered edges that bound aface. Each output
consists of a sequence and edgeid. Sequence numbers start with value 1.
Enumeration of each ring edges start from the edge with smallest identifier. Order of edges follows a left-hand-rule (bound face is on the left of each directed edge).
Availability: 2.0
This method
implements the SQL/MM specification. SQL-MM 3 Topo-Geo and Topo-Net 3:
Routine Details: X.3.5
Examples
-- Returns the edges bounding face 1
SELECT (topology.ST_GetFaceEdges('tt', 1)).*;
-- result --
sequence | edge
----------+------
1 | -4
2 | 5
3 | 7
4 | -6
5 | 1
6 | 2
7 | 3
(7 rows)-- Returns the sequence, edge id
-- and geometry of the edges that bound face 1
-- If you just need geom and seq, can use ST_GetFaceGeometry
SELECT t.seq, t.edge, geom
FROM topology.ST_GetFaceEdges('tt',1) As t(seq,edge)
INNER JOIN tt.edge AS e ON abs(t.edge) = e.edge_id;