Convert from EPSG:4326 to UTM in PostGIS

Question

I would like to convert from EPSG:4326 to UTM (30N/EPSG:32630 or 29N/EPSG:32629) in PostGIS. I do the following query but I get wrong results:

SELECT ST_AsText(ST_Transform(ST_GeomFromText('POINT(36.5277099609375 -5.86424016952515)',4326),32630)) As check;

I get "POINT(5262418.33128724 -839958.963432011)" when it should be something approximate to 243625.00,4046330.00 in UTM 30N. If I do the conversion from 4326 to UTM I get the right result but not from UTM to 4326.

What's wrong with the query?
And are there anyway to get the UTM timezone from the coordinates in EPSG:4326 because I don't know if they belong to 30N or 29N?

Tom-db · Accepted Answer · 2017-04-04T06:31:58.363

1) Your query is correct but you coordinates are inverted. The correct coordinates order in the WKT format is POINT(x y), also POINT(longitude latitude)

This query give you the expected result:

SELECT ST_AsText(ST_Transform(ST_GeomFromText('POINT(-5.86424016952515 36.5277099609375)',4326),32630)) As check;

2) To get the UTM zone from a lat/long geometry you can use this formula:

ST_X(input_geometry)+180)/6)+1

with some adjustments.

For this purpose we use this function:

CREATE OR REPLACE FUNCTION get_utmzone(input_geom geometry)
  RETURNS integer AS
$BODY$
DECLARE
   zone int;
   pref int;
BEGIN
   IF GeometryType(input_geom) != 'POINT' THEN
     RAISE EXCEPTION 'Input geom must be a point. Currently is: %', GeometryType(input_geom);
   END IF;
   IF ST_Y(input_geom) >0 THEN
      pref:=32600;
   ELSE
      pref:=32700;
   END IF;
   zone = floor((ST_X(input_geom)+180)/6)+1;
   RETURN zone+pref;
END;
$BODY$
LANGUAGE plpgsql IMMUTABLE;

Use it with this query:

SELECT get_utmzone(ST_GeomFromText('POINT( -5.86424016952515 36.5277099609375)',4326));

The result should be 32630

There is a little typo above. You must modify: ```SELECT utmzone(ST_GeomFromText('POINT( -5.86424016952515 36.5277099609375)',4326));``` with: ```SELECT get_utmzone(ST_GeomFromText('POINT( -5.86424016952515 36.5277099609375)',4326));``` — aborruso, Apr 03 '17 at 14:54
Source of the function? Perhaps https://lists.osgeo.org/pipermail/postgis-users/2005-December/010253.html — Peter Krauss, Sep 14 '18 at 00:44

score 1 · Answer 2 · answered Sep 28 '15 at 12:42

1

Firs thing is that following documentation of OpenGIS WKT Point(x,y) yours POINT(36.5277099609375 -5.86424016952515) is south of equator so you have to use 29S(EPSG:32729) and 30S(EPSG:32730)

answered Sep 28 '15 at 12:42

Jendrusk

743
3
9

Esteban S · Answer 3 · 2017-05-24T15:04:53.277

0

The reason is because is not POINT(36.5277099609375 -5.86424016952515), but POINT(-5.86424016952515 36.5277099609375)because longitude and latitude depends on the system. Normally X=longitude and Y=latitude, but e.g. in Google Maps X is the lat and Y is the long.

edited May 24 '17 at 15:04

answered Sep 28 '15 at 12:43

Esteban S

1,859
5
22
43

It is not an answer, may be a commet. Is only a reinforce to the 2015 text of Tommaso, *"...your coordinates are inverted"* – Peter Krauss Sep 14 '18 at 00:42

Convert from EPSG:4326 to UTM in PostGIS

3 Answers3