Using PostGIS To Add Some Spatial Flavor To Your Application

Using PostGIS to add some spatial flavor to your applications Steven Citron-Pousty Developer Evangelist deCarta

Agenda ,[object Object],[object Object],[object Object],[object Object],[object Object]

Assumptions about you ,[object Object],[object Object],[object Object],[object Object],[object Object]

What is PostGIS ,[object Object],[object Object],[object Object]

Competitive Offerings ,[object Object],[object Object],[object Object],[object Object],[object Object]

Installing ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Other Steps ,[object Object],[object Object],[object Object]

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

Shapefiles when is a file not a file

More Projection Goodness ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Projecting using ogr2ogr ,[object Object],[object Object],[object Object]

Now let’s make some SQL ,[object Object],[object Object],[object Object]

Y’all know what to do with SQL ,[object Object],[object Object]

Let’s get this party started ,[object Object],[object Object],[object Object],WTF!

Well Known Text (WKT) ,[object Object],[object Object],[object Object],[object Object]

Lesson Learned ,[object Object],[object Object],[object Object],SELECT asKML(the_geom) FROM watercourses WHERE gid = 17;

Inserting a new record ,[object Object],INSERT INTO firestations(station_na, the_geom) VALUES('Best LittleFire House in CA', ST_SetSRID(ST_MakePoint(-119.5, 34.5), 4326) );

Distance ,[object Object],SELECT gid FROM waterbodies WHERE ST_DWithin('SRID=4326;POINT (-119.103762382096 35.4122898449297)', the_geom, 0.005); gid ----- 4 5 6 7 8

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);

Do something with the geometry after selection

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

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)

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

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

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)))');

Simplifying geometries ,[object Object],[object Object],[object Object]

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

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

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

So how do you bring this together in an app ,[object Object],[object Object],[object Object]

Where do you go now - PostGIS ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Where to get Data ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Map API to use ,[object Object],[object Object],[object Object],[object Object]

Using PostGIS To Add Some Spatial Flavor To Your Application

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Using PostGIS To Add Some Spatial Flavor To Your Application