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Using the PostGIS shp2pgsql -s 4326 ... I generated the sql file and created my spatially enabled table.

When executing my query: 

select box2d(ST_extent(the_geom)) from feature_data;

I'm returned with:

BOX(490755.1875 5460528,504640.4375 5466997)

My result appears to be in Easting and Northing, but I would like to return the bounding box in latitude / longitude. I have limited experience with GIS. How can I convert this result to the latitude / longitude coordinate system?

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  • It doesn't seem like the shapefile you started off with was using EPSG:4326. Check the projection information using a desktop GIS or reading the information in the .prj file.
    – underdark
    Commented Aug 12, 2011 at 20:40
  • It looks like it's using Transverse_Mercator. The contents of the .proj file: PROJCS["NAD_1983_UTM_Zone_10N",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-123.0],PARAMETER["Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]]
    – Adam Kahtava
    Commented Aug 13, 2011 at 16:15

2 Answers 2

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Looks like your shapefile uses the following projection: http://spatialreference.org/ref/sr-org/6855/

At least this looks like the content of the .prj file you posted: http://spatialreference.org/ref/sr-org/6855/html/

To add this reference system to PostGIS, you can run: http://spatialreference.org/ref/sr-org/6855/postgis/

The correct query then would be:

SELECT box2d(ST_Transform(ST_SetSRID(the_geom,96855),4326)) FROM feature_data;
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use ST_Transform

Returns a new geometry with its coordinates transformed to spatial reference system referenced by the SRID integer parameter. The destination SRID must exist in the SPATIAL_REF_SYS table.

ST_Transform is often confused with ST_SetSRID(). ST_Transform actually changes the coordinates of a geometry from one spatial reference system to another, while ST_SetSRID() simply changes the SRID identifier of the geometry

    SELECT ST_AsText(ST_Transform(ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,
    743265 2967450,743265.625 2967416,743238 2967416))',2249),4326)) As wgs_geom;

 wgs_geom
---------------------------
 POLYGON((-71.1776848522251 42.3902896512902,-71.1776843766326 42.3903829478009,
-71.1775844305465 42.3903826677917,-71.1775825927231 42.3902893647987,-71.177684
8522251 42.3902896512902));
(1 row)

http://www.postgis.org/docs/ST_Transform.html

For you

feature_data(ST_Transform(ST_GeomFromText(ASTEXT(ST_EXTENT(ST_Envelope(wkb_geometry))),YOUR_SRID),4326))

Change 'YOUR_SRID' to your data SRID

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  • 'select ST_Transform(ST_GeomFromText(AsText(ST_Extent(ST_Envelope(the_geom))),4326),4326) from feature_data;' Doesn't return lat / long coordinates, it returns: '0103000020E610000001000000050000005839B4C80CF41D41871659088CD454415839B4C80CF41D415A643B3BDDDA5441BC7493A801CD1E415A643B3BDDDA5441BC7493A801CD1E41871659088CD454415839B4C80CF41D41871659088CD45441' 'select AsText(ST_Extent(ST_Envelope(the_geom))) from feature_data;' returns a polygon in an alternate format also. The result: 'POLYGON((490755.196 5460528.1304375,490755.196 5466996...))' Suggestions?
    – Adam Kahtava
    Commented Aug 15, 2011 at 17:54

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