Building an online tool for spatial joins using open source software Karsten Vennemann Seattle

Talk Overview Who, Why and What Tool Workflow - - - - Why this tool ? Definitions and Examples Technical Background Resources - - - - Why this tool ? What does it do ? - - - - Steps to retrieve results - - - - Tool live demo - - - - How does it work ? - - - - How can you build your own ? Building an online tool for spatial joins

Why this online tool ? Why open source software ? Who, Why and What Why this online tool ? Why open source software ? Finding the Legal District in which a member of an organization lives is important information for many environmental voter advocacy groups. While this easily can be accomplished using commercial GIS tools, most of those Non-Profit organizations lack the resources and/or technical staff to support the use of such software. Adding Legislative District information is usually done manually. In Washington State there is the online district finder tool available: http://apps.leg.wa.gov/ DistrictFinder/Default.aspx Can find single addresses Building an online tool for spatial joins

About this tool Windows and Linux server platforms Who, Why and What About this tool Windows and Linux server platforms based on open source software any type of spatial join based on street address in WA state (US) and a polygon layer For simplicity we will focus on a technical overview on how a web based tool can allow users with little or no GIS knowledge to attach legislative district information for Washington State to their membership lists. Building an online tool for spatial joins

Workflow for the tool can be broken up into four main parts Tool Workflow Workflow for the tool can be broken up into four main parts File upload to the server (text or Excel file containing address list via web interface ) Geocoding - Retrieval of coordinates (latitude/longitude) for the address (geocoded using 2006 Tiger line data, PHP and Perl) Spatial Join - Matching the Legislative District information (Query onto a PostGIS Database) 4) Transfer result information (streaming the results to the client computer text or MS Excel file) Building an online tool for spatial joins

Workflow for the tool can be broken up into four main parts Tool Workflow Workflow for the tool can be broken up into four main parts File upload to the server (text or Excel file via web interface ) Geocoding - Retrieval of coordinates (latitude/longitude) for the address (geocoded using 2006 Tiger line data, PHP and Perl) Spatial Join - Matching the Legislative District information (Query onto a PostGIS Database) 4) Transfer result information (streaming the results to the client computer text or MS Excel file) Building an online tool for spatial joins

Definitions and Examples What is Geocoding ? Interpolation of real world coordinates for a given location Most geocoders use address information to interpolate (estimate) the real world position along streets using blocks and intersections as landmarks Variety of free tools available - most popular: Google and Yahoo maps API, geocoder.us Also Tiger line geocoder for Post GIS => Geocoder::US a Perl module Open source can download source code and install on your own server uses Berkeley DB format to store Tiger data - high compression fro data - whole US Street data 750 MB (24 GB of uncompressed Tiger data) Building an online tool for spatial joins

Definitions and Examples What is a Spatial Join ? A spatial join operation adds information based on the geographical location of one feature to another ID precinct 352 BEL 48-2776 Building an online tool for spatial joins

Definitions and Examples Spatial Join A spatial join operation adds information based on the geographical location of one feature to another ID address 223428 16089 Northrup Way ID precinct 352 BEL 48-2776 Building an online tool for spatial joins

Definitions and Examples Spatial Join A spatial join operation adds information based on the geographical location of one feature to another ID address 223428 16089 Northrup Way ID precinct 352 BEL 48-2776 ID address precinct 223428 16089 Northrup Way BEL 48-2776 Building an online tool for spatial joins

Spatial Join Definitions and Examples Building an online tool for spatial joins

Spatial Join Definitions and Examples Building an online tool for spatial joins

Live Tool Demo Definitions and Examples Building an online tool for spatial joins

Live Tool Demo Definitions and Examples Building an online tool for spatial joins

Live Tool Demo Definitions and Examples Building an online tool for spatial joins

Live Tool Demo Definitions and Examples Building an online tool for spatial joins

Live Tool Demo Definitions and Examples Building an online tool for spatial joins

Technical Overview Technical Background Building an online tool for spatial joins

Technical Overview Text or Excel file is read with php Technical Background Technical Overview Text or Excel file is read with php Get user input to select address fields Address is concatenated and feed into the geocoder::US Perl module from within php lat/long returned Spatial query using lat/long results from geocoding => in Post GIS one simple SQL query is called to retrieve the LD number Output of results Sample sql queries select ndistrict from Leg_districts_2001 where Leg_districts_2001.the_geom && (setsrid((MakePoint(-122.206834, 47.611421)),4326)) and intersects (Leg_districts_2001.the_geom,setsrid((MakePoint(-122.206834, 47.611421)),4326)); select ndistrict from Leg_districts_2001 where Leg_districts_2001.the_geom && transform(((setsrid((MakePoint(-122.206834, 47.611421)),4326))),2285) and intersects (Leg_districts_2001.the_geom,transform(((setsrid((MakePoint(-122.206834, 47.611421)),4326))),2285)); Building an online tool for spatial joins

Technical Background Code Building an online tool for spatial joins

Perl integration for Geo::Coder::US Technical Background Perl integration for Geo::Coder::US Building an online tool for spatial joins

Query in PostGIS Technical Background Building an online tool for spatial joins

Spatial Indexes Source: “Introduction to PostGIS”, Paul Ramsey, Refractions Research Building an online tool for spatial joins

How can you build your own tool ? Technical Background How can you build your own tool ? Install • Apache I or II Webserver (or IIS) PHP (php_Perl.dll, php_pgsql.dll etc.) Perl (5.8 or higher, geocoder::US module and several others from CPAN) PostgreSQL PostGIS, load polygon data Obtain US Census Tiger Line data for states in question Load Tiger data into BerkeleyDB (utility comes with Geo::Coder::US) author some PHP/Perl scripts Building an online tool for spatial joins

Open source utilities and websites Resources Open source utilities and websites Geocoder scripts http://geocoder.us Census Tiger Line files http://www.census.gov/geo/www/tiger/ PHP http://www.php.net/downloads.php Perl (Active State) http://www.activestate.com/Products/ActivePerl php_perl Extension http://devzone.zend.com/node/view/id/1712 PostgreSQL http://www.postgresql.org PostGIS http://postgis.refractions.net BerkeleyDB http://www.oracle.com/database/berkeley-db/index.html Building an online tool for spatial joins

Articles Build Your Own Geocoding Solution with Geo::Coder::US Resources Articles Build Your Own Geocoding Solution with Geo::Coder::US By Jason Gilmore http://www.developer.com/tech/article.php/3557171 Retrieving Map Location Coordinates http://www.developer.com/tech/article.php/3548171 Building an online tool for spatial joins

Free and Open Source Software for Geospatial 2007 http://www.foss4g2007.org/ Resources Building an online tool for spatial joins

New local GIS user group: Resources New local GIS user group: “Cascadia Users of Geospatial Open Source” http://groups.google.com/group/cugos Next meeting today April 25th, 5:30 pm In the LizardTech offices, located near Pioneer Square: The National Building Suite 200 1008 Western Avenue Seattle, WA 98104 Building an online tool for spatial joins