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How do I know if a point (or a coordinate lon-lat) is inside of a MULTIPOLYGON using PostGIS?

I tried with ST_Contains(), but being a MULTIPOLYGON always return False.

Also I tried with ST_Dump() for transform to a simple POLYGON but I didn't get that to work.

I used:

SELECT ST_GeomFromText(the_geom,900913)

and then:

SELECT ST_Contains("previous select result", ST_GeomFromText('POINT(lon lat)',4326))
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  • Did you actually create a new table with single part polygons using ST_Dump?
    – Micha
    Commented Aug 31, 2016 at 10:37
  • Make sure your geometries are valid Commented Aug 31, 2016 at 10:42
  • I use: SELECT ST_GeomFromText(the_geom,900913), and next: SELECT ST_Contains("previous select result", ST_GeomFromText(\'POINT(lon lat)\',4326))
    – josemi
    Commented Aug 31, 2016 at 10:49
  • Please edit the question to include clarifications. It's not fair to those who would answer to need to mine the comments for critical information.
    – Vince
    Commented Aug 31, 2016 at 11:07
  • 2
    ST_Contains will always return false when the point and polygon do not share a coordinate system. You need to project (ST_Transform) one or the other (or both, thought that seems wasteful).
    – Vince
    Commented Aug 31, 2016 at 11:43

1 Answer 1

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The problem is that the point and the shape are not projected to the same coordinate system; one or the other needs to be converted, using ST_Transform() like this:

SELECT ST_Contains('the_geom',ST_Transform(ST_GeomFromText('POINT(lon lat)',4326),900913))

Thanks to Vince for the hint.

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