Guofeng Cao CyberInfrastructure and Geospatial Information Laboratory Department of Geography National Center for Supercomputing Applications (NCSA) University of Illinois at Urbana-Champaign Geog 480: Principles of GIS

Spaital Database (PostGIS) Handson

PostGIS PostGIS “spatially enables” the PostgreSQL open source relational database. The database can then be used to store and query spatial data (points, lines and polygons). PostGIS o High performance, robust spatial database built on PostgreSQLPostgreSQL o Provides spatial representations of geometry types (points, lines, polygons)geometry types o Support for common and advanced spatial operations such as geometry creation and conversion, reprojection, buffer, convex hull, generalization, union, and morecommon and advanced spatial operations o Geodetic support for measurements across the globe/dateline Geodetic support o Widely supported as a spatial database back-end to client and server software

Several Pre-installed Tables

Connecting to Geog480 server

Connecting to Database psql -U username -d database_name o username = geog480 o database_name = tutorial o Enter passwd when prompted (same as username) Postgres Commands o \l List all accessible databases o \dt List all the tables in current DB o \? Help o \q Quite

Create a sample spatial table CREATE TABLE geometries_your_netid (name varchar, geom geometry); Insert a point: INSERT INTO geometries_your_netid VALUES ('Point', 'POINT(0 0)'); Insert a line: INSERT INTO geometries_your_netid VALUES (‘LineString', 'LINESTRING(0 0, 1 1, 2 1, 2 2)'); Insert a polygon: INSERT INTO geometries_your_netid VALUES ('Polygon', 'POLYGON((0 0, 1 0, 1 1, 0 1, 0 0))'); Populate geometry_columns table: Select Populate_Geometry_Columns();

Other geometry types you could try Insert a polygon with hole: INSERT INTO geometries_your_netid VALUES('PolygonWithHole', 'POLYGON((0 0, 10 0, 10 10, 0 10, 0 0),(1 1, 1 2, 2 2, 2 1, 1 1))'); Insert a geometry collection: : INSERT INTO geometries_your_netid VALUES('Collection', 'GEOMETRYCOLLECTION(POINT(2 0),POLYGON((0 0, 1 0, 1 1, 0 1, 0 0)))');

Query the spatial data table SELECT name, ST_AsText(geom) FROM geometries_your_netid; Query length of linestring: SELECT ST_Length(geom) FROM geometries WHERE name = 'Linestring'; Query area of polygons: SELECT name, ST_Area(geom) FROM geometries WHERE name LIKE 'Polygon%';

Import Shape Files into Databases Step 1: shp2pgsql -c -i -s 4326 /srv/cigi/example/states/states.shp public.postgis_states_your_netid > $HOME/states.sql Step 2: psql -U geog480 -d tutorial -f $HOME/states.sql Query: select state_name, state_fips, ST_AsText(the_geom) from postgis_states_your_netid where state_name ilike 'illinois';

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