ST_LocateAlong wrongly returns multipoint

[schelm903]

I have created a View which shows the derived Point geometries of an event-table with the row "position" (m-values) on a LinestringZM. The geometries are produced with ST_Locate_Along. Whenever an entry on the event table has the exact m-value of a vertex of the linestring and a defined offset, two points are generated.

I am not sure if this is on purpose or a bug as the support of multipoints was added in the past:

Ticket ​https://trac.osgeo.org/postgis/changeset/8758 For our purposes though this behavior is a problem. In my view only one point lying between the two should be generated.

[pramsey]

I am not seeing this.

select ST_AsText(ST_LocateAlong('LINESTRING M (0 0 0, 1 1 1, 2 2 2)', 1.0, 0.5));

                      st_astext                       
------------------------------------------------------
 MULTIPOINT M (0.646446609406726 1.353553390593274 1)

[pramsey]

Feel free to re-open with an example that demonstrates.