ST_SetPoint

What is ST_SetPoint?

ST_SetPoint replaces the vertex at a given zero-based index of a LineString with a supplied point. The total vertex count does not change.

ST_SetPoint(geometry linestring, integer zerobased_index, geometry point) → geometry

The input must be a LineString and the index must be in range.

When would you use ST_SetPoint?

Use ST_SetPoint to correct an individual bad coordinate — fixing a misplaced endpoint of a street centreline, moving a pipeline control vertex to match as-built data, or nudging a GPS track fix to the nearest road. It is the targeted complement to bulk operations like ST_Translate or ST_Affine.

In data-quality pipelines, ST_SetPoint is often driven from a reference table of known corrections that specify feature id, vertex index, and desired coordinate.

FAQs

Does ST_SetPoint add or remove vertices?

No. Only the existing vertex at the given index is replaced. Use ST_AddPoint to insert or ST_RemovePoint to delete.

What if the index is out of range?

PostGIS raises an "Invalid offset" error. Always check ST_NPoints(geom) before calling.

Does ST_SetPoint work on Polygons?

No. Only LineStrings. For polygon rings, extract the ring, set the point, and rebuild with ST_MakePolygon.

Does it preserve Z and M?

The replacement point's Z and M ordinates are copied onto the LineString's vertex. Make sure the point matches the line's dimensionality or Z/M may be lost.