How to Convert UTM Coordinates to Lat/Long Values

To convert UTM X/Y values into latitude/longitude coordinates, you need to know the SRID (Spatial Reference System Identifier) of your dataset. This identifier is essential for properly transforming your geographic data.

Solution

Use a combination of PostGIS functions to perform the conversion. The approach leverages three key functions: ST_Transform, ST_SetSRID, and ST_MakePoint.

Here’s the query structure (using SRID 25831 as an example):

UPDATE table_name
   SET the_geom =
            ST_Transform(
                ST_SetSRID(
                    ST_MakePoint(x, y),
                    25831
                ),
                4326
            )

How it works:

• ST_MakePoint(x, y) creates a point geometry from your UTM coordinates
• ST_SetSRID(..., 25831) assigns your dataset’s SRID to the point
• ST_Transform(..., 4326) converts the point to standard latitude/longitude (SRID 4326)

The key is identifying your dataset’s correct SRID before executing the transformation query.