"The explosive growth of the GeoWeb and geographic information has made GIS powerful media for the general public to communicate, but perhaps more importantly, GIS have also become media for constructive dialogs and interactions about social issues." - Sui & Goodchild
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Créer une géotable :
CREATE TABLE test (id serial PRIMARY KEY, genre text); SELECT AddGeometryColumn( 'test', 'the_geom', -1, 'GEOMETRY', 2 );
Alimenter la table avec quelques géométries en dur et pas vraiment “spatiales” (SRS = -1 !!):
INSERT INTO test VALUES ( 3, 'batiment1', ST_GeometryFromText( 'POLYGON((10 10,40 20,35 8,12 4,10 10))', -1 ) ); INSERT INTO test VALUES ( 4, 'batiment2', ST_GeometryFromText( 'POLYGON((10 40,20 30,30 40,40 35,50 60,35 80,20 60,10 40))', -1 ) ); INSERT INTO test VALUES ( 5, 'batiment3', ST_GeometryFromText( 'POLYGON((10 95,20 95,20 135,10 135,10 95))', -1 ) ); INSERT INTO test VALUES ( 1, 'pieton1', ST_GeometryFromText( 'POINT(10 70)', -1 ) ); INSERT INTO test VALUES ( 2, 'pieton2', ST_GeometryFromText( 'POINT(30 30)', -1 ) ); INSERT INTO test VALUES ( 6, 'pieton3', ST_GeometryFromText( 'POINT(35 70)', -1 ) ); INSERT INTO test VALUES ( 7, 'pieton4', ST_GeometryFromText( 'POINT(35 60)', -1 ) ); INSERT INTO test VALUES ( 8, 'bordureRoute1', ST_GeometryFromText( 'LINESTRING(1 85,50 85)', -1 ) ); INSERT INTO test VALUES ( 9, 'bordureRoute2', ST_GeometryFromText( 'LINESTRING(1 92,50 92)', -1 ) );
(→ cf. documentation PostGIS Reference)
cf. 2
select genre, ST_Area2d(the_geom) from test where ST_GeometryType(the_geom) = 'ST_Polygon';
select genre, ST_Distance((select the_geom from test where genre = 'pieton2'),the_geom) as dist from test where genre <> 'pieton2' order by dist limit 1;
ou
select genre from test where id <> 2 and ST_Distance( the_geom, (select the_geom from test where id = 2) ) = (select min(ST_Distance( the_geom, (select the_geom from test where id = 2) ) ) from test where id <> 2);
...
(source: Jean David Techer)