5

ST_Shift_Longitude(geom) (renamed to ST_Shift_Longitude in PostGIS 2.2) adds 360 to longitudes below 0, thereby (for lon-lat coordinates like WGS84) moving the part of the world "left" (west) of the 0-meridian to the "right" (east) of the "right" (eastern) antimeridian. So this turns a flat -180°…+180° map "split" around the international date line into a flat 0°…+360° map "split" at Greenwich.

Is there any function that does the reverse (i.e. subtracting 360 from longitudes above 180) to get back from a flat 0°…+360° map "split" at Greenwich to a flat -180°…+180° map "split" at the antimeridian?

In PostGIS ≥ 2.3 I could use ST_WrapX(shifted_geom, 180, -360), I guess, but in PostGIS 2.1 and 2.2 ST_WrapX isn't available, yet.

I tried ST_MakeValid(shifted_geom) and ST_Transform(shifted_geom, 4326), but both return the shifted_geom unchanged.

3

Use shifted_geom::geography to cast the shifted_geometry to a geography:

SELECT ST_AsText(
    'POLYGON(
        (
            176.792 -12.2085,
            182.1313 -12.2085,
            182.1313 -20.8999,
            176.792 -20.8999,
            176.792 -12.2085
        )
    )'::geometry
);
--                                              st_astext                                             
-- ---------------------------------------------------------------------------------------------------
--  POLYGON((176.792 -12.2085,182.1313 -12.2085,182.1313 -20.8999,176.792 -20.8999,176.792 -12.2085))
-- (1 row)

(Mike T's answer to Best-practices for databases and APIs with geographic data spanning the antimeridian made me aware that

[c]asting a EPSG:4326 geometry to a geography type also normalizes the coordinates

which solves this nicely.)

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