The document provides an introduction to using PostGIS to add spatial capabilities to PostgreSQL applications. It discusses installing PostGIS, importing spatial data, performing spatial queries and functions, and using the results in applications. Examples demonstrate basic PostGIS concepts like spatial queries, functions for area, distance and geometry operations.

1. Using PostGIS to add some spatial flavor to your applications Steven Citron-Pousty Applied Technology Leader ICF/Jones & Stokes

9. Two more things you need to understand Almost there – I promise

11. Shapefiles when is a file not a file

12. Projections and Datums

23. <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>

25. Select using the geometry

30. 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);

31. Do something with the geometry after selection

33. Calculating Area SELECT sum(ST_Area(z.the_geom)) FROM zoning AS z WHERE z.comb_zn LIKE 'NR%'; sum -------------------- 0.0131834159551545

34. 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)‏

35. 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

36. Buffering

37. 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

39. Spatial Operators

40. 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)))');

42. Select ST_NPoints(the_geom) FROM watercourses WHERE gid IN (12, 14, 17); st_npoints ------------ 265 68 48

43. SELECT ST_NPoints(ST_Simplify(the_geom, 0.00001)) FROM watercourses WHERE gid IN (12, 14, 17); st_npoints ------------ 65 19 18

44. SELECT ST_NPoints(ST_Simplify(the_geom, 0.0001)) FROM watercourses WHERE gid IN (12, 14, 17); st_npoints ------------ 18 6 7