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I want the Postgres / PostGIS queries to convert the UTM coordinates of the SIRGAS 2000 / UTM zone 20N (EPSG: 31974) projection to the Decimal Degrees projection. Separating longitude and latitude into distinct columns.

  • What did you try to achieve this? – Mazu_R Jul 20 '18 at 14:01
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You can use a combination of ST_Transform to reproject the data, then ST_X and ST_Y to extract the latitude and longitude.

WITH src AS (select st_geomfromtext('POINT(0 5000000)',31974) geom31974)
SELECT 
    ST_transform(geom31974,4326) geom4326,
    ST_asText(ST_transform(geom31974,4326)) txtgeom4326,
    ST_X(ST_transform(geom31974,4326)) longitude,
    ST_Y(ST_transform(geom31974,4326)) latitude
FROM src;
  • I understood, why use reference 4326 and not another? Is this for any input reference? – Adriel Gomes Costa Jul 20 '18 at 18:41
  • Without changing the database, can you retrieve this information (lat lat in decimal degrees) in java? I'm trying but I can not. I am using the JTS from vividsolutions. – Adriel Gomes Costa Jul 20 '18 at 21:37
2

Rather than a conversion of values in your queries, I believe the best solution to be to reproject your data, then to save those geom values as attributes.

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