GIS and Media fusion
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ogo14:postgisbasics
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ogo14:postgisbasics [2014/05/07 23:33] oertz created |
ogo14:postgisbasics [2018/05/16 10:05] (current) |
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| ====== PostGIS, les bases ====== | ====== PostGIS, les bases ====== | ||
| + | Voyons comment utiliser l'extension PostGIS de Postgresql pour stocker et gérer de l'information géographique dans un SGBD. | ||
| + | |||
| + | Ne pas oublier l'indispensable [[http://postgis.refractions.net/documentation/manual-1.5/|documentation]] avec son chapitre [[http://postgis.refractions.net/documentation/manual-1.5/reference.html|PostGIS Reference]] | ||
| + | |||
| * Créer une //géotable// | * Créer une //géotable// | ||
| <code> | <code> | ||
| Line 5: | Line 9: | ||
| SELECT AddGeometryColumn( 'my4capitals', 'the_geom', 4326, 'POINT', 2 ); | SELECT AddGeometryColumn( 'my4capitals', 'the_geom', 4326, 'POINT', 2 ); | ||
| </code> | </code> | ||
| + | * Alimenter la table | ||
| + | * http://fr.wikipedia.org/wiki/Well-known_text | ||
| + | <code> | ||
| + | INSERT INTO my4capitals VALUES ( nextval('my4capitals_id_seq'), 'Paris', ST_GeometryFromText( 'POINT(2.333 48.867)', 4326)); | ||
| + | INSERT INTO my4capitals VALUES ( nextval('my4capitals_id_seq'), 'Bern', ST_GeometryFromText( 'POINT(7.433 46.95)', 4326)); | ||
| + | INSERT INTO my4capitals VALUES ( nextval('my4capitals_id_seq'), 'Rome', ST_GeometryFromText( 'POINT(12.5 41.883)', 4326)); | ||
| + | INSERT INTO my4capitals VALUES ( nextval('my4capitals_id_seq'), 'Madrid', ST_GeometryFromText( 'POINT(-3.71 40.41)', 4326)); | ||
| + | </code> | ||
| + | * Lire la table et ses données géographiques | ||
| + | <code> | ||
| + | SELECT ST_AsEWKT(the_geom) FROM my4capitals; | ||
| + | SELECT ST_AsGeoJSON(the_geom) FROM my4capitals; | ||
| + | </code> | ||
| + | * Transformer des coordonnées d'une projection à une autre | ||
| + | <code> | ||
| + | SELECT ST_AsEWKT(ST_Transform(the_geom, 21781)) FROM my4capitals; | ||
| + | </code> | ||
| + | |||
| + | ===== Le géoservice Get4Capitals.php ===== | ||
| + | Cet exemple montre comment créer un service sur mesure qui va //publier// l'information géographique de la géotable. Il est notamment faire usage du format GeoJSON pour transmettre ces données au client. OpenLayers saura par exemple l'exploiter facilement. | ||
| + | |||
| + | On a d'abord besoin d'un GeoManager (GeoManager.php) qui sait communiquer avec la geodatabase. | ||
| + | <code> | ||
| + | <?php | ||
| + | class Connection { | ||
| + | |||
| + | private static $CONFIG = "host=172.16.213.132 port=5432 dbname=ogo user=postgres password=postgres"; | ||
| + | private $CONN; | ||
| + | |||
| + | function __construct() { | ||
| + | return $this->CONN = pg_connect(self::$CONFIG) or die('connection failed'); | ||
| + | } | ||
| + | |||
| + | function selectQuery($query) { | ||
| + | $result = pg_query($this->CONN, $query); | ||
| + | if (!$result) throw new ErrorException($query); | ||
| + | return $result; | ||
| + | } | ||
| + | |||
| + | function insertQuery($query) { | ||
| + | pg_query($this->CONN, "BEGIN WORK"); | ||
| + | $result = pg_query($this->CONN, $query); | ||
| + | if (!$result) { | ||
| + | pg_query($this->CONN, "ROLLBACK"); | ||
| + | } else { | ||
| + | pg_query($this->CONN, "COMMIT"); | ||
| + | } | ||
| + | } | ||
| + | } | ||
| + | |||
| + | class Feature | ||
| + | { | ||
| + | var $type; | ||
| + | var $geometry; | ||
| + | var $id; | ||
| + | var $properties; | ||
| + | |||
| + | function Feature($id,$geom,$properties) { | ||
| + | $this->type = "Feature"; | ||
| + | $this->geometry = $geom; | ||
| + | $this->id = $id; | ||
| + | $this->properties = $properties; | ||
| + | } | ||
| + | } | ||
| + | |||
| + | class FeatureCollection | ||
| + | { | ||
| + | var $type; | ||
| + | var $features; | ||
| + | |||
| + | function FeatureCollection() | ||
| + | { | ||
| + | $this->type = "FeatureCollection"; | ||
| + | $this->features = array(); | ||
| + | } | ||
| + | |||
| + | function addFeature($feature) { | ||
| + | array_push($this->features,$feature); | ||
| + | } | ||
| + | } | ||
| + | ?> | ||
| + | </code> | ||
| + | |||
| + | Et voici le service Get4Capitals.php qui pilote le GeoManager selon ses besoins : | ||
| + | <code> | ||
| + | <?php | ||
| + | require_once 'GeoManager.php'; | ||
| + | $conn = new Connection(); | ||
| + | |||
| + | $query = "SELECT name, ST_AsGeoJSON(the_geom) from my4capitals"; | ||
| + | $result = $conn->selectQuery($query); | ||
| + | |||
| + | $i = 0; | ||
| + | $fc = new FeatureCollection(); | ||
| + | while ($row = pg_fetch_row($result)) { | ||
| + | $fc->addFeature(new Feature($i++, (json_decode($row[1])), array("name" => $row[0]))); | ||
| + | } | ||
| + | echo json_encode($fc); | ||
| + | ?> | ||
| + | </code> | ||
| + | |||
| + | __TODO__ | ||
| + | - Tester cet exemple et analyser les différentes étapes du processus | ||
| + | - Terminer l'exemple en exploitant le géoservice dans OpenLayers avec une OpenLayers.Layer.Vector | ||
| + | |||
ogo14/postgisbasics.1399498384.txt.gz · Last modified: 2018/05/16 10:05 (external edit)
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