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Is there an easy way to retrieve the line segment of a point on a linestring using PostGIS?

To map a point onto a linestring, I use ST_(3D)ClosestPoint. Now I would like to find the index of the line segment on that linestring, the closestpoint is on.

Turf.js is returning that inline with its nearestpointonline function. That returns the line segment index, the distance between point and line, the distance along the linestring together with the closest point on the linestring in one call.

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This probably has to be done by iterating over the line segments and finding the index of the one with minimum distance to the point.

This would be a nice addition to the ST_(3D)ClosestPoint functions.

| improve this answer | |
  • Yes, that is what I feared. In the end, PG is doing the exact same thing already in the background (but most likely much more efficient ;-) +1 on the addition. Even though, I don't know, how to return objects/several values in SQL statements... – ASI Jul 28 at 7:54

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