PostGIS now comes with a set of functions that allow to generate Mapbox Vector Tiles. Among them, the ST_AsMVTGeom allows to transform a geometry into the coordinate space of a tile (typically 4096x4096). Given a geometry containing consecutive points that falls onto the same coordinate after transformation, does the function perform simplication on the fly, or should the ST_Simplify function be called beforehand?

  • Have you experimented to see if there was a difference or reviewed the source?
    – Vince
    Commented Jan 22, 2019 at 0:54

1 Answer 1


Such points get collapsed:

SELECT ST_AsText(ST_AsMVTGeom(ST_GeomFromText('LINESTRING(0 0, 0 0.1, 1 1)'),
                              ST_MakeBox2D(ST_Point(0, 0), ST_Point(4096, 4096))));

 LINESTRING(0 4096,1 4095)

LINESTRING(0 0, 0 0.1) results in NULL, so I don't know why the documentation says that it "might collapse geometry into a lower dimension".

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