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geoinf15:postgis0
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geoinf15:postgis0 [2017/11/15 23:16] oertz |
geoinf15:postgis0 [2018/05/16 10:05] |
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| - | ====== Spatial database :: PostGIS ====== | ||
| - | Voyons comment utiliser l'extension PostGIS de PostgreSQL pour stocker et gérer de l'information géographique dans un SGBD. | ||
| - | |||
| - | ===== Une première "geotable" ===== | ||
| - | * Créer une //géotable// | ||
| - | <code> | ||
| - | CREATE TABLE my4capitals (id serial PRIMARY KEY, name text); | ||
| - | SELECT AddGeometryColumn( 'my4capitals', 'the_geom', 4326, 'POINT', 2 ); | ||
| - | </code> | ||
| - | * Alimenter la table (cf. 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_AsText(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)), ST_AsEWKT(the_geom) FROM my4capitals; | ||
| - | </code> | ||
| - | |||
| - | ===== Géoservice Get4Capitals.php ===== | ||
| - | Cet exemple montre comment créer un service sur mesure qui va //publier// l'information géographique de la géotable. Il est notamment fait usage du format GeoJSON pour transmettre ces données au client. OpenLayers saura par exemple l'exploiter facilement au travers d'une couche ol.Vector et le format ol.format.GeoJSON. | ||
| - | |||
| - | <code> | ||
| - | <?php | ||
| - | require_once 'GeoManager.php'; | ||
| - | $conn = new Connection("host=127.0.0.1 port=5432 dbname=php user=admintoto password=blablatutu"); | ||
| - | |||
| - | $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> | ||
| - | |||
| - | On a besoin d'un GeoManager (GeoManager.php) qui sait gérer les requêtes avec la geodatabase et encoder les résultats par un flux GeoJSON. | ||
| - | <code> | ||
| - | <?php | ||
| - | class Connection { | ||
| - | |||
| - | private $CONFIG; | ||
| - | private $CONN; | ||
| - | |||
| - | function __construct($cfg) { | ||
| - | $this->CONFIG = $cfg; | ||
| - | return $this->CONN = pg_connect($this->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> | ||
| - | |||
| - | __TODO__ | ||
| - | - Tester ce géoservice et analyser les différentes étapes du processus (veiller à reconfigurer les paramètres de connexion) - évt utiliser l'astuce de Daniel http://mediamaps.ch/wiki/doku.php?id=geoinf14:postgis0 | ||
| - | - Terminer l'exemple en exploitant le géoservice dans OpenLayers avec une ol.layer.Vector comme vu dans [[geoinf15:ol3tuto#ex5asource_de_donnees_openlayersformat|Ex5A]]. | ||
geoinf15/postgis0.txt · Last modified: 2018/05/16 10:05 (external edit)
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