Changes between Initial Version and Version 1 of UsersWikiExamplesPolygonOverlaps

Timestamp:

03/10/11 05:39:42 (14 years ago)

Author:

blaggner

Comment:

—

UsersWikiExamplesPolygonOverlaps

@@ +1 @@
+
+== Finding and Editing Polygon Overlaps ==
+
+The function pgoverlap checks a polygon table for overlapping geometries, separating between sliver and non-sliver overlappings. It returns two tables - one table with non-overlapping geometries and adjusted sliver-overlapping polygons and one table with non-sliver overlappings which have to be handled manually afterwards.
+
+Preconditions for successful use of the function:[[BR]]
+- gid column of data type integer or serial, unique, with btree index!! [[BR]]
+- the_geom column of data type geometry and geometry type POLYGON, with gist index!! [[BR]]
+- column of data type integer (name is variable) for subsequent joining of attributes with btree index!! [[BR]]
+- geometries should be valid (otherwise number of exceptions rises)[[BR]]
+
+'''Caution:''' Do not call the functions twice at a time!! - Intermediate tables have fixed names and are locked during function processing (otherwise their content would be overwritten).
+
+'''Example:'''
+
+{{{
+CREATE TABLE pgoverlap_bsp_input (gid serial PRIMARY KEY, a_id integer, the_geom geometry);
+INSERT INTO pgoverlap_bsp_input (a_id, the_geom) VALUES
+(1,ST_GeomFromText('POLYGON((3565961 5361731,3570432 5359825,3574390 5362977,3577469 5360631,3582526 5360192,3591616 5351909,3592715 5343113,3591835 5337395,3586265 5339448,3579008 5336882,3572045 5340254,3567500 5338788,3564421 5342013,3562296 5353301,3566327 5356527,3565961 5361731))',31467)),
+(2,ST_GeomFromText('POLYGON((3587846 5359101,3587353 5362736,3592036 5366371,3598813 5365755,3601708 5361997,3592528 5358855,3587846 5359101))',31467)),
+(3,ST_GeomFromText('POLYGON((3600429 5353669,3606823 5355001,3612240 5361751,3622453 5355801,3637461 5355179,3635951 5340171,3617036 5337240,3605225 5340260,3600429 5353669))',31467)),
+(4,ST_GeomFromText('POLYGON((3580359 5328360,3588529 5330935,3597943 5323120,3606024 5322587,3612951 5315217,3608155 5306691,3603804 5305093,3596166 5306159,3591105 5310244,3584799 5310688,3576540 5317437,3580359 5328360))',31467)),
+(5,ST_GeomFromText('POLYGON((3568123 5343184,3577776 5350721,3586922 5344624,3584890 5336664,3593104 5330312,3586499 5322014,3572187 5325232,3568123 5343184))',31467)),
+(6,ST_GeomFromText('POLYGON((3594628 5349620,3601741 5358935,3617153 5357580,3621387 5348519,3617153 5339712,3610040 5334293,3616137 5322945,3607923 5311598,3600302 5314392,3596068 5319727,3600725 5329974,3596406 5339882,3594628 5349620))',31467)),
+(7,ST_GeomFromText('POLYGON((3622319 5325401,3625029 5327433,3630194 5329466,3635191 5326502,3638747 5317610,3631719 5311598,3622150 5316594,3622319 5325401))',31467));
+
+SELECT _pgoverlap('public','pgoverlap_bsp_input','a_id','pgoverlap_bsp_output','pgoverlap_bsp_todo');
+}}}
+
+'''Function:'''
+
+{{{
+CREATE OR REPLACE FUNCTION _pgoverlap(schema_a varchar, table_a varchar, a_id varchar, table_result1 varchar, table_result2 varchar)
+  RETURNS void AS
+$BODY$
+
+/*
+$Id: pgoverlap_wiki.sql 2011-03-09 15:19Z Birgit Laggner $
+
+pgoverlap - checks table for overlapping geometries seperating between sliver and non-sliver overlappings, returns table with non-overlapping geometries and adjusted sliver-overlapping polygons as well as table with non-sliver overlappings (for later treatment)
+
+schema_a:      database schema where table is located
+table_a:       table name
+a_id:          id column name in table
+table_result1: name of 1st result table (non-overlapping polygons)
+table_result2: name of 2nd result table (overlapping polygons)
+
+Preconditions for successful use of the function:
+- gid column of data type integer or serial, unique, with btree index!!
+- the_geom column of data type geometry and geometry type POLYGON, with gist index!!
+- column of data type integer (name is variable) for subsequent joining of attributes, with btree index!!
+- geometries should be valid (otherwise number of exceptions rises)
+
+Caution: Do not call the function twice at a time!! - Intermediate tables have fixed names and are locked during function processing (otherwise their content would be overwritten).
+
+Copyright (C) 2011 Johann Heinrich von Thünen-Institute (vTI) - Federal Research Institute for Rural Areas, Forestry and Fisheries, Institute of Rural Studies, Braunschweig, Germany (http://www.vti.bund.de)
+Version 0.1
+contact: birgit dot laggner at vti dot bund dot de
+
+This is free software; you can redistribute and/or modify it under
+the terms of the GNU General Public Licence. This software is without any warrenty and you use it at your own risk.
+*/
+
+DECLARE
+
+i integer;
+sql_1 text;
+
+
+BEGIN
+
+--find all overlappings with geometrytype Polygon:
+
+EXECUTE
+'DROP TABLE IF EXISTS '||schema_a||'.pgoverlap_tmp1;';
+
+EXECUTE
+'CREATE TABLE '||schema_a||'.pgoverlap_tmp1 (
+gid serial,
+a_'||a_id||' integer,
+b_'||a_id||' integer,
+a_geom geometry,
+b_geom geometry,
+i_geom geometry,
+area numeric,
+perimeter2 numeric,
+perimeter2_uc numeric,
+cmp numeric,
+sliver character varying(1)
+ );';
+
+RAISE NOTICE 'Find all overlappings with geometrytype Polygon. ';
+
+EXECUTE
+'INSERT INTO '||schema_a||'.pgoverlap_tmp1 (
+a_'||a_id||', b_'||a_id||', a_geom, b_geom, i_geom)
+SELECT DISTINCT
+sel.a_'||a_id||',
+sel.b_'||a_id||',
+sel.a_geom,
+sel.b_geom,
+sel.i_geom
+FROM (
+SELECT
+a.'||a_id||' AS a_'||a_id||',
+b.'||a_id||' AS b_'||a_id||',
+a.the_geom AS a_geom,
+b.the_geom AS b_geom,
+(ST_Dump(ST_Intersection(a.the_geom,b.the_geom))).geom AS i_geom
+FROM
+'||schema_a||'.'||table_a||' a
+LEFT JOIN
+'||schema_a||'.'||table_a||' b
+ON a.the_geom && b.the_geom
+WHERE
+a.gid < b.gid AND
+ST_Intersects(a.the_geom, b.the_geom)) AS sel
+WHERE
+ST_GeometryType(sel.i_geom) NOT IN (
+''ST_Point'',
+''ST_LineString'',
+''ST_MultiPoint'',
+''ST_MultiLineString'',
+''ST_Line'');';
+
+EXECUTE
+'CREATE INDEX pgoverlap_tmp1_gid_btree
+ON '||schema_a||'.pgoverlap_tmp1
+USING btree(gid);';
+
+EXECUTE
+'CREATE INDEX pgoverlap_tmp1_a_'||a_id||'_btree
+ON '||schema_a||'.pgoverlap_tmp1
+USING btree(a_'||a_id||');';
+
+EXECUTE
+'CREATE INDEX pgoverlap_tmp1_b_'||a_id||'_btree
+ON '||schema_a||'.pgoverlap_tmp1
+USING btree(b_'||a_id||');';
+
+
+--Check for sliver polygons
+
+RAISE NOTICE 'Check for sliver polygons. ';
+
+--1. Calculation of area and perimeter:
+
+EXECUTE
+'UPDATE '||schema_a||'.pgoverlap_tmp1 
+SET area=ST_Area(i_geom),
+    perimeter2=ST_Perimeter(i_geom)^2;';
+
+--2. Calculation of circle perimeter with area equal to area of the polygon:
+EXECUTE
+'UPDATE '||schema_a||'.pgoverlap_tmp1 
+SET perimeter2_uc=4*pi()*area;';
+
+
+--3. Calculation of Compactness Index (cmp):
+
+EXECUTE
+'UPDATE '||schema_a||'.pgoverlap_tmp1 
+SET cmp=perimeter2_uc/perimeter2;';
+
+--4. Decision: sliver polygon, true or false?:
+
+EXECUTE
+'UPDATE '||schema_a||'.pgoverlap_tmp1 SET sliver=''t'' WHERE area < 10;';
+
+EXECUTE
+'UPDATE '||schema_a||'.pgoverlap_tmp1 SET sliver=''t'' WHERE cmp < 0.13;';
+
+EXECUTE
+'UPDATE '||schema_a||'.pgoverlap_tmp1 SET sliver=''f'' WHERE sliver IS NULL;';
+/*
+EXECUTE
+'UPDATE '||schema_a||'.pgoverlap_tmp1 SET sliver=''f'' WHERE area > 150;';
+*/
+
+--Create table for sliver polygons:
+
+EXECUTE
+'DROP TABLE IF EXISTS '||schema_a||'.pgoverlap_tmp2;';
+
+EXECUTE
+'CREATE TABLE '||schema_a||'.pgoverlap_tmp2 (
+gid serial,
+a_'||a_id||' integer,
+a_geom geometry,
+i_geom_union geometry,
+the_geom geometry
+);';
+
+RAISE NOTICE 'Processing sliver polygons. ';
+
+EXECUTE
+'INSERT INTO '||schema_a||'.pgoverlap_tmp2
+(a_'||a_id||', a_geom, i_geom_union)
+SELECT a_'||a_id||', a_geom, CASE WHEN ST_Union(i_geom) IS NULL THEN ST_Collect(i_geom) ELSE ST_Union(i_geom) END
+FROM '||schema_a||'.pgoverlap_tmp1
+WHERE sliver=''t''
+GROUP BY a_'||a_id||', a_geom;';
+
+i:=0;
+
+sql_1:='SELECT gid FROM '||schema_a||'.pgoverlap_tmp2 ORDER BY gid;';
+
+FOR i IN EXECUTE sql_1 LOOP
+BEGIN
+
+EXECUTE
+'UPDATE '||schema_a||'.pgoverlap_tmp2 SET the_geom=ST_Difference(a_geom, i_geom_union) WHERE gid='||i||';';
+
+EXCEPTION WHEN internal_error THEN
+
+EXECUTE
+'UPDATE '||schema_a||'.pgoverlap_tmp2 SET the_geom=ST_Difference(ST_Buffer(a_geom,0.0), ST_Buffer(i_geom_union,0.0)) WHERE gid='||i||';';
+
+END;
+END LOOP;
+
+EXECUTE
+'CREATE INDEX pgoverlap_tmp2_a_'||a_id||'_btree
+ON '||schema_a||'.pgoverlap_tmp2
+USING btree(a_'||a_id||');';
+
+
+--Create table with IDs of sliver polygons:
+
+RAISE NOTICE 'Creating table with IDs of sliver polygons. ';
+
+EXECUTE
+'DROP TABLE IF EXISTS '||schema_a||'.pgoverlap_tmp3;';
+
+EXECUTE
+'CREATE TABLE '||schema_a||'.pgoverlap_tmp3 (
+'||a_id||' integer);';
+
+EXECUTE
+'INSERT INTO '||schema_a||'.pgoverlap_tmp3 ('||a_id||')
+SELECT DISTINCT a_'||a_id||'
+FROM '||schema_a||'.pgoverlap_tmp2;';
+
+EXECUTE
+'INSERT INTO '||schema_a||'.pgoverlap_tmp3 ('||a_id||')
+SELECT DISTINCT a.b_'||a_id||'
+FROM
+'||schema_a||'.pgoverlap_tmp1 a
+LEFT JOIN
+'||schema_a||'.pgoverlap_tmp2 b
+ON a.b_'||a_id||'=b.a_'||a_id||'
+WHERE b.a_'||a_id||' IS NULL;';
+
+
+--Insert non-sliver polygons into seperate table:
+
+BEGIN
+EXECUTE
+'SELECT DropGeometryTable('''||schema_a||''','''||table_result2||''');';
+EXCEPTION WHEN undefined_table THEN 
+END;
+
+EXECUTE
+'CREATE TABLE '||schema_a||'.'||table_result2||' (
+ gid serial PRIMARY KEY, 
+ a_'||a_id||' integer,
+ b_'||a_id||' integer
+ );';
+
+EXECUTE
+'SELECT AddGeometryColumn('''||schema_a||''', '''||table_result2||''',''a_geom'',(SELECT DISTINCT ST_SRID(the_geom) FROM '||schema_a||'.'||table_a||'),''POLYGON'',2);';
+
+EXECUTE
+'SELECT AddGeometryColumn('''||schema_a||''', '''||table_result2||''',''b_geom'',(SELECT DISTINCT ST_SRID(the_geom) FROM '||schema_a||'.'||table_a||'),''POLYGON'',2);';
+
+EXECUTE
+'SELECT AddGeometryColumn('''||schema_a||''', '''||table_result2||''',''i_geom'',(SELECT DISTINCT ST_SRID(the_geom) FROM '||schema_a||'.'||table_a||'),''POLYGON'',2);';
+
+RAISE NOTICE 'Inserting non-sliver polygons into seperate table. ';
+
+EXECUTE
+'INSERT INTO '||schema_a||'.'||table_result2||' (
+ a_'||a_id||',
+ b_'||a_id||',
+ a_geom,
+ b_geom,
+ i_geom)
+SELECT 
+ a_'||a_id||',
+ b_'||a_id||',
+ a_geom,
+ b_geom,
+ i_geom
+FROM '||schema_a||'.pgoverlap_tmp1
+WHERE sliver=''f'';';
+
+
+--create table with IDs of non-sliver polygons:
+
+RAISE NOTICE 'creating table with IDs of non-sliver polygons. ';
+
+EXECUTE
+'DROP TABLE IF EXISTS '||schema_a||'.pgoverlap_tmp4;';
+
+EXECUTE
+'CREATE TABLE '||schema_a||'.pgoverlap_tmp4 (
+'||a_id||' integer);';
+
+EXECUTE
+'INSERT INTO '||schema_a||'.pgoverlap_tmp4 ('||a_id||')
+SELECT DISTINCT a_'||a_id||'
+FROM '||schema_a||'.'||table_result2||';';
+
+EXECUTE
+'INSERT INTO '||schema_a||'.pgoverlap_tmp4 ('||a_id||')
+SELECT DISTINCT a.b_'||a_id||'
+FROM
+'||schema_a||'.'||table_result2||' a
+LEFT JOIN
+'||schema_a||'.'||table_result2||' b
+ON a.b_'||a_id||'=b.a_'||a_id||'
+WHERE b.a_'||a_id||' IS NULL;';
+
+
+--Insert geometries without overlappings into new table:
+
+EXECUTE
+'DROP TABLE IF EXISTS '||schema_a||'.pgoverlap_tmp5;';
+
+EXECUTE
+'CREATE TABLE '||schema_a||'.pgoverlap_tmp5 (
+ gid serial PRIMARY KEY, 
+ '||a_id||' integer,
+ the_geom geometry
+ );';
+
+EXECUTE
+'INSERT INTO '||schema_a||'.pgoverlap_tmp5
+ ('||a_id||', the_geom)
+SELECT 
+ a.'||a_id||',
+ a.the_geom
+FROM
+'||schema_a||'.'||table_a||' a
+LEFT JOIN
+'||schema_a||'.pgoverlap_tmp3 b
+ON a.'||a_id||'=b.'||a_id||'
+LEFT JOIN
+'||schema_a||'.pgoverlap_tmp4 c
+ON a.'||a_id||'=c.'||a_id||'
+WHERE
+b.'||a_id||' IS NULL AND
+c.'||a_id||' IS NULL;';
+
+
+--Create and merge result table:
+
+BEGIN
+EXECUTE
+'SELECT DropGeometryTable('''||schema_a||''','''||table_result1||''');';
+EXCEPTION WHEN undefined_table THEN 
+END;
+
+EXECUTE
+'CREATE TABLE '||schema_a||'.'||table_result1||' (
+gid serial PRIMARY KEY,
+'||a_id||' integer
+);';
+EXECUTE
+'SELECT AddGeometryColumn('''||schema_a||''','''||table_result1||''',''the_geom'',(SELECT DISTINCT ST_SRID(the_geom) FROM '||schema_a||'.'||table_a||'),''POLYGON'',2);';
+EXECUTE
+'ALTER TABLE '||schema_a||'.'||table_result1||' DROP CONSTRAINT enforce_geotype_the_geom;';
+
+
+--Insert Difference (sliver overlappings) into result table:
+
+EXECUTE
+'INSERT INTO '||schema_a||'.'||table_result1||' (
+'||a_id||',
+the_geom
+)
+SELECT
+a_'||a_id||',
+(ST_Dump(the_geom)).geom
+FROM
+'||schema_a||'.pgoverlap_tmp2
+WHERE ST_IsEmpty(the_geom)=''f'';';
+
+
+--Insert unchanged polygons (sliver overlappings) into result table:
+
+EXECUTE
+'INSERT INTO '||schema_a||'.'||table_result1||' (
+'||a_id||',
+the_geom
+)
+SELECT DISTINCT
+a.b_'||a_id||',
+a.b_geom
+FROM
+'||schema_a||'.pgoverlap_tmp1 a
+LEFT JOIN
+'||schema_a||'.pgoverlap_tmp2 b
+ON a.b_'||a_id||'=b.a_'||a_id||'
+WHERE 
+a.sliver=''t'' AND
+b.a_'||a_id||' IS NULL;';
+
+
+--Insert non-overlapping polygons into result table:
+
+EXECUTE
+'INSERT INTO '||schema_a||'.'||table_result1||' (
+'||a_id||',
+the_geom
+)
+SELECT
+'||a_id||',
+the_geom
+FROM '||schema_a||'.pgoverlap_tmp5;';
+
+
+--Update geometries already processed as sliver overlappings which also have non-sliver overlappings:
+
+EXECUTE
+'UPDATE '||schema_a||'.'||table_result2||' t SET a_geom=a.geom FROM (SELECT '||a_id||', CASE WHEN ST_Union(the_geom) IS NULL THEN ST_Collect(the_geom) ELSE ST_Union(the_geom) END AS geom FROM '||schema_a||'.'||table_result1||' GROUP BY '||a_id||') a WHERE t.a_'||a_id||'=a.'||a_id||';';
+
+EXECUTE
+'UPDATE '||schema_a||'.'||table_result2||' t SET b_geom=a.geom FROM (SELECT '||a_id||', CASE WHEN ST_Union(the_geom) IS NULL THEN ST_Collect(the_geom) ELSE ST_Union(the_geom) END AS geom FROM '||schema_a||'.'||table_result1||' GROUP BY '||a_id||') a WHERE t.b_'||a_id||'=a.'||a_id||';';
+
+EXECUTE
+'DELETE FROM '||schema_a||'.'||table_result1||' WHERE '||a_id||' IN (SELECT '||a_id||' FROM '||schema_a||'.pgoverlap_tmp4);';
+
+--Remove tmp tables:
+
+EXECUTE
+'DROP TABLE '||schema_a||'.pgoverlap_tmp1;';
+EXECUTE
+'DROP TABLE '||schema_a||'.pgoverlap_tmp2;';
+EXECUTE
+'DROP TABLE '||schema_a||'.pgoverlap_tmp3;';
+EXECUTE
+'DROP TABLE '||schema_a||'.pgoverlap_tmp4;';
+EXECUTE
+'DROP TABLE '||schema_a||'.pgoverlap_tmp5;';
+
+
+END;
+$BODY$
+  LANGUAGE 'plpgsql' VOLATILE
+  COST 100;
+ALTER FUNCTION public._pgoverlap(varchar, varchar, varchar, varchar, varchar) OWNER TO postgres;
+}}}