polygonize - Creating polygons of area surrounded by roads / lines using PostGIS?

I'm currently trying to create polygons that represent the areas surrounded by roads. The roads are stored in PostGIS as points / lines so I have flexibility over what I can do with them.

I'm basically trying to turn the white areas of this example line output into polygons:

Any ideas?

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Here is the PostGIS to achieve this (assuming you have a road table full of lines):

SELECT (ST_Dump(ST_Polygonize(roads.geom))).geom AS the_geom FROM

(SELECT ST_Transform(ST_SetSRID(geom, 27700), 4326) AS geom FROM road_lines) AS roads

Answer

Some hints:

1. You could use the ST_Polygonize processing of PostGIS.


2. You could have a look at this QGIS plugin (I have not tested it myself...)


3. If you speak Java, you could use the polygoniser of JTS.