Massachusetts Institute of Technology Department of Urban Studies and Planning 11.520: A Workshop on Geographic Information Systems 11.188: Urban Planning and Social Science Laboratory Lecture 10: Introduction to Internet GIS and ArcIMS Nov. 9, 2005, Joseph Ferreira, Jr. Based primarily on lecture notes by Visiting Prof. Zhong-Ren Peng, Fall, 2003 See: Peng and Tsou, Internet GIS, 2003, John Wiley, ISBN: 0-471-35923-8. Main Topic: Introduction to Internet GIS and ArcIMS  Introduction to Internet GIS  State of the Art of Internet GIS  Introduction to ArcIMS The Road Map of GIS Stand-alone GIS Programs  Mainframe-based monolithic GIS programs  Desktop GIS programs  Limited or no communication with other computers (other than transparently via, for example, use of a network file server) Programs need to run on the mainframe or PC where the program resides  Users need access to that machine via a login or dumb terminal session.  Examples: early Arc/Info installed on a stand-alone mainframe or PC. LAN-based GIS Programs  GIS installed on one or more machines on a Local Area Network (LAN)  GIS programs run on local machines but can share data and printing facilities from the data server, or  GIS programs run on a server, user can access it from any machine inside the LAN.  Typical Client/Server architecture.  Examples: Most current GIS programs. Limitations of Stand-Alone and LAN-based GIS Programs  Difficult for user outside the LAN to access.  Difficult to directly access data that are available outside the LAN.  Limited GIS users.  Difficult to mange, update and extend. What is Internet GIS?  Internet GIS is a network-centric GIS tool that uses the Internet as a primary means of providing access to the functionality (e.g., analysis tools, mapping capability) of GIS and to the spatial data and other data needed for various GIS applications. Internet GIS is an integrated client/server, and Web/Server application.  Internet GIS typically uses a Web browser as client.  Internet GIS can be viewed as a distributed, object-oriented system.  Internet GIS is portable and cross-platform. Internet GIS vs Web GIS  What’s the difference between the Internet and the World Wide Web?  Internet refers to the inter-connected computer network, -- infrastructure.  Web is one of many applications that are based on the Internet.  The term Internet GIS focuses the use of a suite of Internet technologies, not only the Web.  Internet GIS thus has more longevity and is a preferred term. Features of Internet GIS  Wide accessibility, users from the world can access GIS data and analysis tools over the Internet.  No GIS software is required to install locally.  Takes advantage of the friendly graphic user interface that is provided by the World Wide Web.  Users can directly manipulate maps and GIS data over the Web.  Internet-aware GIS software can access remote data anywhere on the Internet.  Internet GIS can easily incorporate up-to-date, real-time informationBasic Components of the Internet GIS Internet GIS: State of the Art  Static Map publishing  Static Web Mapping  Interactive Web Mapping  Client-side Plug-ins and Helper Program  GIS ActiveX Controls  Java-based Internet GIS  Distributed Geographic Information Services Server-Side and Client-Side Internet GIS  Server-Side Internet GIS  HTML to GIS server via CGI (Common Gateway Interface) script  Client-Side Internet GIS  Client-side Plug-ins and Helper Program  GIS ActiveX Controls  Java-based Internet GIS  Hybrid of server- and client-side Internet GIS Static Map publishing  Insert Map images in a text file on the Web.  Not a GIS. Static Web Mapping  How does it work?Common Gateway Interface  When information is collected by a browser it is sent to a HyperText Transfer Protocol (HTTP) server specified in the HTML form, and that server starts a program, also specified in the HTML form, that can process the collected information. Such programs are known as "Common Gateway Interface" programs, or CGI scripts (E.O. Johnson).   CGI is a simple interface that links Web browser, server and other external programs.  CGI or Dynamic Link Library (DLL) has three functions:  It receives user inputs and parses them into parameters of variables to be used in GIS programs.  It lets Web servers run other GIS programs.  It interprets output and sends back to browsers. Advantages of Static Web Mapping  A “thin” client (e.g., all data processing is done on the server, while the client is used only for display and user input).  Takes full advantage of all GIS software functionality at the server.  Ubiquitously accessible over the Internet.  Can handle large database to serve spatial queries Drawbacks of Static Web Mapping  Every user request has to go through the Internet to activate a CGI script every time.  Creates heavy traffic over the Internet. Operation is slow, because every command (even very simple ones like zoom and pan) has to be operated on the GIS server.  Maps are static images.  User cannot draw a box or a circle or select polygons on the map images. Examples of Static Web Mapping  VISA International ATM locator (http://www.visa.com/)  ESRI’s MapObjects Internet Map Server (http://metro-trip.ci.waukesha.wi.us/waukesha/)  Map Quest (http://www.mapquest.com/) Interactive Web Mapping (Client-Side Internet GIS)  Interactive Web Mapping programs allow the user to manipulate GIS data and conduct GIS analysis at the client/user side, including:  GIS Plug-Ins and Helper Programs  GIS Java Applets  GIS ActiveX Controls GIS Plug-Ins or Helper Programs  GIS plug-ins are software executables that run on the browser and interpret the GIS data received from the server.  GIS plug-ins are used in extending the browser to process GIS data.  While GIS plug-ins are small applications, GIS helper programs can be large GIS applications or existing GIS software that is located in the user’s local machine.How Do GIS Plug-Ins Work? Partition Points for GIS Plug-In Examples of GIS Plug-ins  Autodesk: MapGuide (http://www.mapguide.com/)  GeoMedia Web Map (for Netscape browser) Advantages of GIS Plug-Ins  GIS plug-ins