OpenSource GIS 2004 Ottawa, Canada Introduction to PostGIS PostGIS Basics for the New User Paul Ramsey & Chris Hodgson Refractions

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OpenSource GIS 2004

Ottawa, Canadawww.refractions.net

Introduction to PostGIS

PostGIS Basics for the New User

Paul Ramsey & Chris HodgsonRefractions Research

OpenSource GIS 2004


PostgreSQL

• 1986 : Postgres project at Berkley– Successor to Ingres– Relational Model– Complex Objects– Extensibility

• 1995 : Postgres95 adds SQL Support

• 1996 : Open Source Community

OpenSource GIS 2004


PostGIS

• PostgreSQL 7.1 (Tuple Toaster)• Real GIS Support• First Release in 2001• OpenGIS “Simple Features for

SQL”• Current Release 0.8.2

OpenSource GIS 2004


Why PostGIS?

• Because Databases are Better than Files!

• Unified Storage, Management, Access– SQL Everywhere

• Transactional Integrity– Multiple Users, Multiple Edits

OpenSource GIS 2004


PostGIS Users

• Data Handlers• Unified Access Language (SQL)• Unified Metadata Location

– GlobeXplorer– i-cubed– Refractions

OpenSource GIS 2004


PostGIS Users

• Real Time Systems Developers• Unified Access Language (SQL)• Standard Access Protocols

– JDBC– ODBC

OpenSource GIS 2004


Team CIMAR : DARPA Grand Challenge

OpenSource GIS 2004


PostGIS Users

• Spatial Infrastructures

LANW

MS

/ WFS

PostGIS

Internet

JUMP

QGISWFS

Client

WMSClient

OpenSource GIS 2004


PostgreSQL

• Version 7.5 Native Windows Support

OpenSource GIS 2004


Windows PostgreSQL

\bin Executables \include Include files for compilation\lib DLL shared library files\share Extensionsenv.bat Command promptinitdb.bat Initialize \data areapgstart.bat Start the database server

OpenSource GIS 2004


Create a Database

• createdb postgis– Make the database

• psql postgis– Connect to the database

• create, insert, select– Try the database

OpenSource GIS 2004


Load PostGIS

• PostgreSQL Extension– libpostgis.so– postgis.sql

• Requires PL/PgSQL• createlang plpgsql postgis• psql -f postgis.sql postgis• psql -f spatial_ref_sys.sql postgis

OpenSource GIS 2004


Simple Spatial SQL

POINT(5 5)

POINT(5 0)

POINT(0 5)

POINT(0 0)

OpenSource GIS 2004


Load Shape Files

• select count(*) from bc_roads• select count(*) from

bc_voting_areas

OpenSource GIS 2004


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bc_pubs

OpenSource GIS 2004


bc_roads

OpenSource GIS 2004


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bc_hospitals

OpenSource GIS 2004


bc_municipality

OpenSource GIS 2004


bc_voting_areas

OpenSource GIS 2004


bc_voting_areas

OpenSource GIS 2004


Creating Spatial Indexes

OpenSource GIS 2004


Using Spatial Indexes

select gid, name from bc_roads where crosses( the_geom, GeomFromText(‘LINESTRING(…)’,42102) )

select gid, name from bc_roads where crosses( the_geom, GeomFromText(‘LINESTRING(…)’,42102) )and the_geom && GeomFromText(‘LINESTRING(…)’,42102)

OpenSource GIS 2004


Query Plans

OpenSource GIS 2004


#---------------------------------------------------------------------------# CONNECTIONS AND AUTHENTICATION#---------------------------------------------------------------------------

# - Connection Settings -

#listen_addresses = 'localhost' # what IP interface(s) to listen on; # defaults to localhost, '*' = any

#port = 5432max_connections = 100#superuser_reserved_connections = 2#rendezvous_name = '' # defaults to the computer name

# - Security & Authentication -

#authentication_timeout = 60 # 1-600, in seconds#ssl = false#password_encryption = true#db_user_namespace = false

#---------------------------------------------------------------------------# RESOURCE USAGE (except WAL)#---------------------------------------------------------------------------

# - Memory -

shared_buffers = 1000 # min 16, at least max_connections*2, 8KB each#work_mem = 1024 # min 64, size in KB#maintenance_work_mem = 16384 # min 1024, size in KB#max_stack_depth = 2048 # min 100, size in KB

#vacuum_cost_page_hit = 1 # 0-10000 credits#vacuum_cost_page_miss = 10 # 0-10000 credits

Postg

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ptim

izatio

n

OpenSource GIS 2004


Data Integrity

Valid Invalid

OpenSource GIS 2004


Distance Queries

select sum(upbc) as unity_voters from bc_voting_areas where the_geom && setsrid( expand(‘POINT(…)’::geometry,2000) 42102 ) and distance( the_geom, geomfromtext(‘POINT(…)’, 42102) ) < 2000;

OpenSource GIS 2004


Spatial Joins

• Associate two tables based on a spatial relationship, rather than an attribute relationship.

OpenSource GIS 2004


select m.name, sum(v.ndp) as ndp, sum(v.lib) as liberal, sum(v.gp) as green, sum(v.upbc) as unity, sum(v.vtotal) as total from bc_voting_areas v, bc_municipality m, where v.the_geom && m.the_geom and intersects(v.the_geom, m.the_geom) group by m.name order by m.name;

OpenSource GIS 2004


Overlays

• Table on table overlays are possible with the Intersection() function.

• Our example will only overlay one polygon with another table.

OpenSource GIS 2004


create table pg_voting_areas as select intersection(v.the_geom, m.the_geom) as intersection_geom, area(v.the_geom) as va_area, v.*, m.name from bc_voting_areas v, bc_municipality m where v.the_geom && m.the_geom and intersects(v.the_geom, m.the_geom) and m.name = ‘PRINCE GEORGE’;

OpenSource GIS 2004


Coordinate Projection

SRID=42102;MULTILINESTRING((1004687.04355194 594291.053764096,1004729.74799931 594258.821943696))

SRID=4326;MULTILINESTRING((-125.9341 50.3640700000001,-125.9335 50.36378))

OpenSource GIS 2004


Exercises &Questions

Documents

OpenSource GIS 2004 Ottawa, Canada Introduction to PostGIS PostGIS Basics for the New User Paul Ramsey & Chris Hodgson Refractions