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geoinf16:sqlcartodb
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geoinf16:sqlcartodb [2016/11/25 07:43] oertz [SQL Spatial with Carto.com & PostGIS] |
geoinf16:sqlcartodb [2018/05/16 10:05] (current) |
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| ====== SQL Spatial with Carto.com & PostGIS ====== | ====== SQL Spatial with Carto.com & PostGIS ====== | ||
| Carto.com offre un frontale très convivial pour piloter une base de données spatiale utilisant PostGIS (http://postgis.net, https://carto.com/docs/faqs/postgresql-and-postgis). Rapide découverte en deux parties. | Carto.com offre un frontale très convivial pour piloter une base de données spatiale utilisant PostGIS (http://postgis.net, https://carto.com/docs/faqs/postgresql-and-postgis). Rapide découverte en deux parties. | ||
| - | Avant de commencer, il faut se connecter sur carto.com avec le utilisateur //geoinf16//. | + | |
| + | Avant de commencer, il faut se connecter sur http://carto.com avec le utilisateur **geoinf16**. | ||
| ===== Partie 1 ===== | ===== Partie 1 ===== | ||
| + | On utilise la géotable **earthquakes** (source : http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_month.csv) | ||
| + | <code> | ||
| + | SELECT ST_AsText(the_geom), * FROM earthquakes | ||
| + | </code> | ||
| + | |||
| + | * Le frontale offre une preview cartographique et permet de créer une carte sur la base de ce jeu de géodonnées | ||
| + | * Créer votre séisme quelque-part en Suisse (!) | ||
| + | <code> | ||
| + | SELECT ST_AsText(ST_Transform(ST_GeometryFromText('POINT(558000 137000)', 21781), 4326)) | ||
| + | </code> | ||
| + | * A vous de jouer en donnant de bonnes infos | ||
| + | <code> | ||
| + | INSERT INTO earthquakes (place, mag, the_geom) | ||
| + | VALUES ('SOMEWHERE, Switzerland', MMM, ST_Transform(ST_GeometryFromText('POINT(XXX YYY)', 21781), 4326)); | ||
| + | </code> | ||
| + | |||
| + | * Exemple ST_Distance et le type geography : http://postgis.net/docs/manual-2.3/ST_Distance.html | ||
| + | <code> | ||
| + | SELECT ST_Distance( | ||
| + | ST_GeomFromText('POINT(-72.1235 42.3521)',4326), | ||
| + | ST_GeomFromText('LINESTRING(-72.1260 42.45, -72.123 42.1546)', 4326) | ||
| + | ) | ||
| + | </code> | ||
| + | * Exercice ST_Distance (1) : quelle distance sépare chaque séisme de Fukushima - POINT(141.0357 37.4217) ? | ||
| + | <code> | ||
| + | SELECT *, | ||
| + | ST_Distance( | ||
| + | the_geom::geography, | ||
| + | ST_GeometryFromText('POINT(141.0357 37.4217)',4326)::geography | ||
| + | ) / 1000 as d FROM earthquakes | ||
| + | </code> | ||
| + | * Exercice ST_Distance (2) : quel est le séisme de magnitude > 6 le plus proche de Fukushima ? | ||
| + | <code> | ||
| + | SELECT *, | ||
| + | ST_Distance( | ||
| + | the_geom::geography, | ||
| + | ST_GeometryFromText('POINT(141.0357 37.4217)',4326)::geography | ||
| + | ) / 1000 as d FROM earthquakes WHERE mag > 6 ORDER BY d LIMIT 1 | ||
| + | </code> | ||
| + | * Il serait souhaitable d'opter pour une autre approche que ce gourmand ORDER BY. Comment ? | ||
| + | <code> | ||
| + | ... | ||
| + | </code> | ||
| + | |||
| + | ===== Partie 2 ===== | ||
| + | On utilise les deux géotables **highway61** et **musicians** (sources : https://carto.com/academy/d/highway_61.geojson, https://carto.com/academy/d/mississippi_blues_musicians.geojson). | ||
| + | |||
| + | * ST_Buffer et the_geom_webmercator : http://postgis.net/docs/manual-2.3/ST_Buffer.html | ||
| + | <code> | ||
| + | SELECT ST_Buffer(the_geom_webmercator, 50000) as the_geom_webmercator FROM highway61 | ||
| + | </code> | ||
| + | * Exemple ST_Intersects : http://postgis.net/docs/manual-2.3/ST_Intersects.html | ||
| + | <code> | ||
| + | SELECT ST_Intersects( | ||
| + | ST_GeomFromText('LINESTRING(-2 -2, 2 2)', 4326), | ||
| + | ST_GeomFromText('POINT(0 0)', 4326) | ||
| + | ) | ||
| + | </code> | ||
| + | * Exercice ST_intersects : quels sont les musiciens qui sont nés dans cette zone ? | ||
| + | <code> | ||
| + | ... | ||
| + | </code> | ||
| + | * Comme on sait comment cette zone est configurée, on peut aussi utiliser simplement ST_Distance, voire ST_DWithin http://postgis.net/docs/manual-2.3/ST_DWithin.html | ||
| + | <code> | ||
| + | ... | ||
| + | </code> | ||
| + | |||
| + | |||
| + | |||
geoinf16/sqlcartodb.1480056181.txt.gz · Last modified: 2018/05/16 10:05 (external edit)
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