Internet-enabled GIS Using Free and Open Source Tools


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Presented at the MAC URISA spring meeting on May 12th.

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  • So, what exactly is open source? If you're not familiar with the term, it is almost as simple as it sounds. \"Open Source\" is software where the source code has been made freely available for viewing, adapting and redistributing. But it's more than just software, it's community-driven software. Programmers dedicate time and energy to develop these software tools to fill a gap in the current software market or improve on what is currently being offered. Open Source software is a precursor to the Open Content movement that has been generating buzz in the media as music and video are being resampled and redistributed. Open Source is really about this culture of collaboration. Some observations about open source development were first covered by Eric Raymond in his 1997 essay \"The Cathedral and the Bazaar\"
  • Well, ESRI is our Cathedral. They have developed the software that has created de facto standards for GIS analysis and storage. The wizards and monks producing ArcGIS 9.4 are hard at work and occasionally they entice us with a glimpse of the new software, but we're not actually going to get our hands on it until they bless the latest version with a release. Being the Cathedral, they offer everything under one roof, which is plus considering you can get all you need from them.
  • On the other hand, the Bazaar of open source GIS is comprised of individuals and a few small firms dedicated to creating and updating GIS software that fills a certain niche. The vendors in the Bazaar give you free access to the latest versions of their software. They'll give you access to nightly builds, so you can use (and bug test) the functionality introduced that day. There isn't a complete open source GIS package yet that can do everything from desktop to server to mobile. However, due to the fact that all of these open source programs in the Bazaar speak the same languages, you can mix and match your server-side GIS implementation. So you decide which program is right for your application.
  • Open Source can be accessible. - Simply making data \"accessible\" via FTP and ZIP files is no longer enough. The public needs access to digital cartography. Digital cartography differs from a PDF of a map in that it is interactive, intuitive and engaging.
  • Open Source can be dependable. - The NYCityMap is what most people would classify as an \"enterprise\" level application. It handles a massive amount of GIS data and must be able to serve hundreds of concurrent users.
  • Open Source can be easy. – The White House added this map of those responding to the President's call for change. Each one of those points is a story submitted to the White House. The only way to effectively show the distribution of those responding to the call is with a map. This map, using OpenLayers, is easy to add to the page and cost the government zero in licensing.
  • Internet-enabled GIS Using Free and Open Source Tools

    1. 1. Internet-enabled GIS Using Free and Open Source Tools John Reiser
    2. 2. 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 quot;The Cathedral and the Bazaarquot;
    3. 3. The Cathedral and the Bazaar quot;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.quot; quot;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.quot;
    4. 4. 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?
    5. 5. The Cathedral
    6. 6. The Bazaar
    7. 7. 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
    8. 8. 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 • quot;Open Source doesn't come with supportquot; is no longer a valid excuse • Several companies now provide support to OS GIS packages
    9. 9. 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
    10. 10. Making GIS Accessible
    11. 11. NYCityMap
    12. 12. Delivering On Change
    13. 13. 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)
    14. 14. Configuration of a Web Map MapServer Server Client GIS Data GeoServer TileCache OpenLayers Map Other WMS Cache
    15. 15. 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
    16. 16. 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
    17. 17. KML • Once a quot;closedquot; 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
    18. 18. 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
    19. 19. MapServer –
    20. 20. 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
    21. 21. GeoServer –
    22. 22. 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
    23. 23. 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
    24. 24. 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
    25. 25. TileCache –
    26. 26. 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
    27. 27. 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
    28. 28. OpenLayers –
    29. 29. OpenLayers • JavaScript library for implementing a quot;Google Mapsquot; 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
    30. 30. Information Warehouse
    31. 31. NuMapsDemographicDrapes
    32. 32. Freedom to Mix and Match • You could develop your interactive map using entirely open source software – quot;OpenGeo Architecturequot; • You can mix and match parts as necessary – ArcGIS &OpenLayers – MapServer& Google Maps/Google Earth • Open standards give you the freedom of choice
    33. 33. Open Source Community • The strength of OS software comes from the community • quot;Given enough eyeballs, all bugs are shallow.quot; • Propose or contribute new functionality • Community is not limited to software
    34. 34. 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
    35. 35. OpenStreetMap –
    36. 36. GeoNames –
    37. 37. GeoCommons –
    38. 38. GeoCommons Finder!
    39. 39. GeoCommons Maker!
    40. 40. 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
    41. 41. Resources • Open Source Initiative – • Open Source Geospatial Foundation (OSGeo) – • Source images for quot;Cathedralquot; & quot;Bazaarquot; are GNU licensed images from Wikimedia Commons – – • Full text of quot;The Cathedral and the Bazaarquot; is available online: – • Web Mapping Illustrated is a great resource for developing your own web maps – • Whitepaper on quot;OpenGeoquot; Architecture from GeoServer – (published April 2009)