Using PostGIS To Add Some Spatial Flavor To Your Application
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Using PostGIS To Add Some Spatial Flavor To Your Application
- 1. Using PostGIS to add some spatial flavor to your applications Steven Citron-Pousty Developer Evangelist deCarta
- 9. Two more things you need to understand Almost there – I promise
- 11. Shapefiles when is a file not a file
- 22. <MultiGeometry> <Polygon> <outerBoundaryIs> <LinearRing> <coordinates>-118.90476592 907,35.4477387779291 -118.904082378315,35.4465853812531 -118.904745088997,35.447 2133838697 -118.90476592907,35.4477387779291</coordinates> </LinearRing> </outerBoundaryIs> </Polygon> </MultiGeometry>
- 24. Select using the geometry
- 27. Let’s find all the parcels in Agricultural Zones SELECT p.gid FROM parcels AS p, zoning AS z WHERE z.comb_zn LIKE 'A%' AND ST_Within(p.the_geom, z.the_geom);
- 28. Do something with the geometry after selection
- 30. Calculating Area SELECT sum(ST_Area(z.the_geom)) FROM zoning AS z WHERE z.comb_zn LIKE 'NR%'; sum -------------------- 0.0131834159551545
- 31. Turn polygons into points SELECT gid, asText(ST_Centroid(the_geom)) FROM waterbodies WHERE gid = 124; gid | geometry -----+------------------------------------------- 124 | POINT(-118.427120958287 35.6702299014044) SELECT gid, asText(ST_PointOnSurface(the_geom)) FROM waterbodies WHERE gid = 124; gid | geometry -----+------------------------------------------- 124 | POINT(-118.449967685908 35.6911672413056)
- 32. Create new tables using a select CREATE TABLE biglake WITH OIDS AS SELECT gid, the_geom FROM waterbodies WHERE gid = 124; SELECT ST_AREA(the_geom) FROM biglake; st_area --------------------- 0.00313986591299908
- 33. Buffering
- 34. Some SQL to buffer SELECT ST_Area(ST_Buffer(the_geom, 0.1)) FROM biglake; st_area -------------------- 0.0718529848413709 Remember that is used to be 0.003
- 37. Clip to the bounding box SELECT gid, ST_Intersection(the_geom, 'SRID=4326;MULTIPOLYGON((( -119.5 35.0, -119.0 35.0, -119.0 35.5, -119.5 35.5, -119.5 35.0)))') FROM watercourses WHERE ST_Intersects(the_geom, 'SRID=4326;MULTIPOLYGON((( -119.5 35.0, -119.0 35.0, -119.0 35.5, -119.5 35.5, -119.5 35.0)))');
- 39. Select ST_NPoints(the_geom) FROM watercourses WHERE gid IN (12, 14, 17); st_npoints ------------ 265 68 48
- 40. SELECT ST_NPoints(ST_Simplify(the_geom, 0.00001)) FROM watercourses WHERE gid IN (12, 14, 17); st_npoints ------------ 65 19 18
- 41. SELECT ST_NPoints(ST_Simplify(the_geom, 0.0001)) FROM watercourses WHERE gid IN (12, 14, 17); st_npoints ------------ 18 6 7