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

2. 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

3. 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: DistrictFinder/Default.aspx
Can find single addresses
Building an online tool for spatial joins

4. 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

5. 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

6. 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

7. 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

8. 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
Building an online tool for spatial joins

9. 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
Building an online tool for spatial joins

10. 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 ID
address
precinct
223428
16089 Northrup Way
BEL
Building an online tool for spatial joins

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

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

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

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

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

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

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

18. Technical Overview Technical Background
Building an online tool for spatial joins

19. 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( , )),4326)) and intersects (Leg_districts_2001.the_geom,setsrid((MakePoint( , )),4326));
select ndistrict from Leg_districts_2001 where Leg_districts_2001.the_geom && transform(((setsrid((MakePoint( , )),4326))),2285) and intersects (Leg_districts_2001.the_geom,transform(((setsrid((MakePoint( , )),4326))),2285));
Building an online tool for spatial joins

20. Technical Background
Code
Building an online tool for spatial joins

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

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

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

24. 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

25. Open source utilities and websites
Resources
Open source utilities and websites
Geocoder scripts
Census Tiger Line files
PHP
Perl (Active State)
php_perl Extension
PostgreSQL
PostGIS
BerkeleyDB
Building an online tool for spatial joins

26. Articles Build Your Own Geocoding Solution with Geo::Coder::US
Resources
Articles
Build Your Own Geocoding Solution with Geo::Coder::US
By Jason Gilmore
Retrieving Map Location Coordinates
Building an online tool for spatial joins

27. Free and Open Source Software for Geospatial 2007
Resources
Building an online tool for spatial joins

28. New local GIS user group:
Resources
New local GIS user group:
“Cascadia Users of Geospatial Open Source”
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