I have two Postgres tables with different SRIDs: 4326 and 900913. I want to convert the latter to 4326. I first changed the SRID using:
Select UpdateGeometrySRID('table', 'geomcolumn', 4326).
I then transformed the reference data using:
update table set geomcolumn = ST_Transform (geomcolumn, 4326).
This seemed to work. But when I changed the SRS setting of the relevant layer in TileMill to WGS84, I get this error:
Detected out of bounds geographic extent.
Presumably the transformation didn't work but it's not clear why.