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While importing my shapefile data to PostGIS, I did not select the proper Projection.

How do I now change the SRID of the data, without transforming the Coordinates?

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2 Answers 2

With PostGIS 2.x, geometry columns typically use typmods like geometry(Point, 1234). For these you can use ALTER TABLE to directly modify the geometry column type in one step.

For example, to set the SRID of geom in mytable to WGS84, use ST_SetSRID:

ALTER TABLE mytable ALTER COLUMN geom TYPE geometry(Point, 4326) USING ST_SetSRID(geom, 4326);

Note that this will only alter the SRID, but not transform the coordinate data.

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up vote 42 down vote accepted

There is a single line function which does this for you. Just use the following SQL query:

select UpdateGeometrySRID('Schema Name', 'mytable', 'the_geom', newSRID) ;

But, if you are like me, you would be interested in the low level, miniature steps. Logically speaking, the above function is equivalent to the following four step process:

  1. In the geometry_columns table, update the SRID to the required value.

  2. Drop the contraint on the table, by using the following SQL statement

    ALTER TABLE mytable DROP CONSTRAINT enforce_srid_the_geom;

  3. Update the SRID'd of the geometry by using the following SQL statement

    UPDATE mytable SET the_geom = ST_SetSRID(the_geom, newSRID);

  4. Add the contraint back by using the following SQL statement

    ALTER TABLE mytable

    ADD CONSTRAINT enforce_srid_the_geom CHECK (st_srid(the_geom) = (newSRID));

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See postgis.org/docs/ST_SetSRID.html for more info and links –  BradHards Oct 1 '12 at 9:12
@devdatta your 1 line solution worked the best! Didn't have to worry about handling the SRID as a constraint...very simple... –  mapBaker Jun 20 '13 at 22:24
Just a thought: show the single-step solution first. –  Martin F Feb 27 '14 at 17:21
@martinf: I agree it's better with the single step solution at the top. Hence edited. Thanks! –  Devdatta Tengshe Feb 28 '14 at 2:47

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