"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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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 http://carto.com avec le utilisateur geoinf16.
On utilise la géotable earthquakes (source : http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_month.csv)
SELECT ST_AsText(the_geom), * FROM earthquake
SELECT ST_AsText(ST_Transform(ST_GeometryFromText('POINT(558000 137000)', 21781), 4326)) INSERT INTO earthquakes (place, mag, the_geom) VALUES ('SOMEWHERE, Switzerland', MMM, ST_Transform(ST_GeometryFromText('POINT(XXX YYY)', 21781), 4326));
- Exemple ST_Distance et le type geography : http://postgis.net/docs/manual-2.3/ST_Distance.html
SELECT ST_Distance(
ST_GeomFromText('POINT(-72.1235 42.3521)',4326),
ST_GeomFromText('LINESTRING(-72.1260 42.45, -72.123 42.1546)', 4326)
)
- Exercice ST_Distance (1) : quelle distance sépare chaque séisme de Fukushima (POINT(141.0357 37.4217))
SELECT *,
ST_Distance(
the_geom::geography, ST_GeometryFromText('POINT(141.0357 37.4217)',4326)::geography
) / 1000 as d FROM all_month
- adapter le style
- Exercice ST_Distance (2) : nearest of Fukishima of mag > 6
SELECT *,
ST_Distance(
the_geom::geography, ST_GeometryFromText('POINT(141.0357 37.4217)',4326)::geography
) / 1000 as d FROM all_month WHERE mag > 6 ORDER BY d LIMIT 1