GetNodeByPoint — Finds the node-id of a node at a point location.
integer GetNodeByPoint(varchar atopology, geometry apoint, float8 tol1
Retrieves the id of a node at a point location.
The function returns an integer (id-node) given a topology, a POINT and a tolerance. If tolerance = 0 means exact intersection, otherwise retrieves the node from an interval.
apoint doesn't intersect a node, returns 0 (zero).
If use tolerance > 0 and there is more than one node near the point then an exception is thrown.
If tolerance = 0, the function uses ST_Intersects otherwise uses ST_DWithin.
Performed by the GEOS module.
These examples use edges we created in AddEdge
SELECT topology.GetNodeByPoint('ma_topo',geom, 1) As nearnode FROM ST_GeomFromEWKT('SRID=26986;POINT(227591.9 893900.4)') As geom; nearnode ---------- 2
SELECT topology.GetNodeByPoint('ma_topo',geom, 1000) As too_much_tolerance FROM ST_GeomFromEWKT('SRID=26986;POINT(227591.9 893900.4)') As geom; ----get error-- ERROR: Two or more nodes found