Internet-enabled GIS Using Free and Open Source Tools John Reiser [email protected].

Internet-enabled GIS Using Free and Open Source Tools

John [email protected]

What exactly is Open Source?

• Freedom to allow others to adapt and reuse while retaining some rights over code

• Community-driven software• Precursor to the Open Content movement• Eric Raymond's "The Cathedral and the Bazaar"

The Cathedral and the Bazaar

"I believed that the most important software needed to be built like cathedrals, carefully crafted by individual wizards or small bands of mages working in splendid isolation, with no beta to be released before its time."

"The Linux community seemed to resemble a great babbling bazaar of differing agendas and approaches out of which a coherent and stable system could seemingly emerge only by a succession of miracles."

No Miracles Necessary

• Open source does work• Thousands of software packages are available

under open source licenses– Operating systems, development tools, web

browsers, web and file servers, communications tools, graphic design applications, etc…

• All with no upfront monetary cost• How does GIS fit in?

The Cathedral

The Bazaar

Open Source GIS

• Software that allows us to share our data with everyone using open standards

• Software that we can modify and improve• GIS data released under an open license• GIS data updated and enriched by community

input and participation

Open Source GIS

• Developing an open source GIS has many benefits– Low-cost of entry– Adaptable and extendable– Entry into the greater open source community

• "Open Source doesn't come with support" is no longer a valid excuse

• Several companies now provide support to OS GIS packages

Sharing Data: Accessibility

• We can easily share data now– FTP– ZIP files posted to the web

• Helps GIS users, but outsiders are left in the dark• Inviting, easy to use map interfaces are the new

way to share

Making GIS Accessible

NYCityMap gis.nyc.gov/doitt/nycitymap/

Delivering On Changewhitehouse.gov/change/

Getting the parts together

• Protocols– Web Map Service– Web Feature Service– Keyhole Markup Language

• Server side tech– MapServer and/or GeoServer– Tilecache

• Client side– OpenLayers– Google Maps and Virtual Earth (free but not OS)

Configuration of a Web Map

MapServer

GeoServer

GIS Data

Other WMS

TileCache

Map Cache

OpenLayers

Server Client

Web Map Service

• WMS is a protocol for requesting rendered map tiles from a GIS server

• Allows access to the attribute information via XML

• REST-ful protocol – necessary info within the URL

Web Feature Service

• WFS allows for retrieval of GIS features and properties from a remote server

• WFS also allows updating GIS data on a remote server

• Returns XML data

KML

• Once a "closed" language, Google pushed for its adoption as an open standard

• KML is a subset of XML and related to GML• KML stores vector data along with symbology • KML can act as a wrapper for WMS services

Choosing a Server

• MapServer and GeoServer fill similar roles, but there are some things to consider in choosing:– Hosting environment– Focus on rendering data or manipulating data– Familiarity with command-line interface– Patience

MapServer – mapserver.org

MapServer

• MapServer is robust software– launched mid-1990s, currently version 5.4.0

• MapServer is lightweight• Runs in either Apache httpd or IIS• MapServer supports many file formats• Easy to install • More difficult to configure

GeoServer – geoserver.org

GeoServer

• GeoServer is also robust software– launched 2001, currently version 1.7.4

• Written in Java, runs in Apache Tomcat• Complicated to install in shared hosting

environment• Easy to configure

Tile-based Mapping

• Common complaint of ArcIMS is that the service is painfully slow

• The map extent is rendered from GIS data for every request

• Caching pre-rendered maps allows the server to send a static file without GIS processing

Tile-based Mapping

• Enforce a set of scales at which the map is rendered

• Break each map scale into a grid of rendered map tiles

• Map tiles can be stored on disk after rendering• Removes the need to render from data for each

map request• TileCache can manage the rendered tile cache

TileCache – tilecache.org

TileCache

• TileCache sits between the client and server• Client requests map tiles (using WMS)• TileCache checks the stored tiles• If it exists, it returns the rendered tile to client• If tile is missing, it passes the request to a GIS

server• Once it receives the rendered tile, TileCache

stores the tile and sends it to the client

TileCache

• Written in Python, with extensions for server environment

• Can cache tiles directly from MapServer or any WMS-capable GIS server

• Can reduce the strain on infrastructure and lower costs

OpenLayers – openlayers.org

OpenLayers

• JavaScript library for implementing a "Google Maps" style interface

• Allows interactive mapping within most modern web browsers

• Originally from the same company as TileCache, now a project of OSGeo

• Supports both WMS and WFS• Supports tiles from Google Maps, Virtual Earth• Highly customizable

Information Warehousenjgin.state.nj.us

NuMaps DemographicDrapesdemos.numaps.com.au

Freedom to Mix and Match

• You could develop your interactive map using entirely open source software– "OpenGeo Architecture"

• You can mix and match parts as necessary– ArcGIS & OpenLayers– MapServer & Google Maps/Google Earth

• Open standards give you the freedom of choice

Open Source Community

• The strength of OS software comes from the community

• "Given enough eyeballs, all bugs are shallow."• Propose or contribute new functionality• Community is not limited to software

Collaboration

• Data can benefit from collaboration• Parcels from a surveyor and tax assessor• Free alternatives to high-cost data– OpenStreetMap

• POI databases become truly valuable once released to the crowd to update

• Just beginning to explore the value in Volunteered Geographic Information

OpenStreetMap – openstreetmap.org

GeoNames – geonames.org

GeoCommons – geocommons.com

GeoCommons Finder!

GeoCommons Maker!

Open Source Community

• Equality, transparency and collaboration• A community of passionate individuals• Use the software and become part of something

greater• Consider sharing your data with the community

Resources• Open Source Initiative

– http://www.opensource.org/

• Open Source Geospatial Foundation (OSGeo)– http://www.osgeo.org/

• Source images for "Cathedral" & "Bazaar" are GNU licensed images from Wikimedia Commons– http://commons.wikimedia.org/wiki/File:Catedral_Metropolitana_de_Sao_Paulo_1_Brasil.jpg– http://commons.wikimedia.org/wiki/File:Bd_bazaar.jpg

• Full text of "The Cathedral and the Bazaar" is available online:– http://www.catb.org/~esr/writings/cathedral-bazaar/

• Web Mapping Illustrated is a great resource for developing your own web maps– http://oreilly.com/catalog/9780596008659/

• Whitepaper on "OpenGeo" Architecture from GeoServer– http://opengeo.org/publications/opengeo-architecture/ (published April 2009)