Name
GetNodeByPoint — Finds the node-id of a node at a point location.
Synopsis
integer GetNodeByPoint(varchar atopology, geometry apoint, float8 tol1);
Description
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.
If 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.
![[Note]](../images/note.png)
|
|
|
If tolerance = 0, the function uses ST_Intersects otherwise uses ST_DWithin. |
Performed by the GEOS module.
Availability: 2.0.0
Examples
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