[Argentina] Consulta base de datos espacial en Postgis

[Dannenberg Guillermo Adrián]

Buenas tarde, quizas alguien me pueda dar una mano, ya que arranque hace 
poco en el tema.

En una base de datos espacial en Postgis, tengo dos tablas:
Una tabla llamada forestal_ln la cual contiene LINESTRING.
Una tabla llamada forestal que cuenta con algunos campos y dos campos 
geométricos: 'centroide' que contiene geometría de tipo POINT y 
'geometria' que contiene geométrica de tipo MULTIPOLYGON.
En donde cada centroide de la tabla forestal se encuentra encerrado por 
varias líneas de la tabla forestal_ln.
Les agradecería mucho si pudieran orientarme en:
1) ¿qué procesos podría correr para asegurarme de que esas lineas 
verdaderamente encierran un solo centroide? Verificar la topologia.
2) (más importante) ¿cómo puedo crear los polígonos a partir de esas 
lineas y actualizar con esos polígonos creados el campo geometria de la 
tabla forestal?

Los datos con los cuales estoy trabajando:

CREATE TABLE forestal(
id serial NOT NULL,
tipo varchar(6),
densidad real,
CONSTRAINT forestal_pkey PRIMARY KEY(id)
);
SELECT AddGeometryColumn ( 'forestal', 'centroide', 22185, 'POINT', 2);
SELECT AddGeometryColumn ( 'forestal', 'geometria', 22185, 
'MULTIPOLYGON', 2);

INSERT INTO forestal (tipo,densidad,centroide) 
VALUES('PMT',85.2,ST_GeomFromText('POINT(5500060 6500180)',22185));
INSERT INTO forestal (tipo,densidad,centroide) 
VALUES('PCRTA',52.42,ST_GeomFromText('POINT(5500080 6500270)',22185));
INSERT INTO forestal (tipo,densidad,centroide) 
VALUES('CA',42.26,ST_GeomFromText('POINT(5500120 6500100)',22185));
INSERT INTO forestal (tipo,densidad,centroide) 
VALUES('AMJ',86.6,ST_GeomFromText('POINT(5500210 6500190)',22185));
INSERT INTO forestal (tipo,densidad,centroide) 
VALUES('ODM',8.6,ST_GeomFromText('POINT(5500220 6500070)',22185));
INSERT INTO forestal (tipo,densidad,centroide) 
VALUES('EMDF',27.8,ST_GeomFromText('POINT(5500220 6500110)',22185));
INSERT INTO forestal (tipo,densidad,centroide) 
VALUES('DHRT',36.27,ST_GeomFromText('POINT(5500220 6500280)',22185));
INSERT INTO forestal (tipo,densidad,centroide) 
VALUES('FM',73.24,ST_GeomFromText('POINT(5500230 6500260)',22185));

CREATE TABLE forestal_ln(
id serial NOT NULL,
CONSTRAINT forestal_ln_pkey PRIMARY KEY(id)
);
SELECT AddGeometryColumn ( 'forestal_ln', 'geometria', 22185, 
'LINESTRING', 2);

INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500030 6500230,5500030 
6500050)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500030 6500290,5500030 
6500250)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500030 6500050,5500160 
6500050)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500160 6500050,5500280 
6500050)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500280 6500090,5500280 
6500050)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500280 6500090,5500280 
6500140)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500280 6500150,5500280 
6500140)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500280 6500150,5500280 
6500220)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500190 6500220,5500280 
6500220)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500190 6500230,5500100 
6500230)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500190 6500220,5500190 
6500230)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500100 6500230,5500030 
6500230)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500030 6500250,5500120 
6500250)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500180 6500250,5500120 
6500250)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500180 6500250,5500280 
6500250)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500280 6500250,5500280 
6500270)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500280 6500290,5500280 
6500270)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500280 6500290,5500090 
6500290)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500030 6500290,5500090 
6500290)',22185));

INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500090 6500290,5500180 
6500270)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500180 6500270,5500220 
6500270)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500220 6500270,5500120 
6500250)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500220 6500270,5500280 
6500270)',22185));

INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500100 6500230,5500100 
6500170)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500100 6500170,5500030 
6500050)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500100 6500170,5500160 
6500170)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500160 6500170,5500160 
6500150)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500160 6500150,5500160 
6500140)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500160 6500140,5500280 
6500140)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500160 6500140,5500160 
6500090)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500160 6500090,5500280 
6500090)',22185));
INSERT INTO forestal_ln (geometria) 
VALUES(ST_GeomFromText('LINESTRING(5500160 6500090,5500160 
6500050)',22185));

Gracias y saludos..

Guillermo A. Dannenberg