GetNodeByPoint
Prev | 10.7. Topology Accessors | Next

## 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.

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

## See Also

AddEdge, GetEdgeByPoint, GetFaceByPoint

Prev | Up | Next
GetFaceContainingPoint | Home | GetTopologyID