SPATIAL TECHNOLOGIES: Software Strategy: Online Maps for the Masses31 Jan, 2005 By: James L. Sipes
Programs serve up geospatial data through Web browsers.
The emergence of web GIS has greatly changed the way we access mapping information. The Web is becoming a portal for GIS functionality and data distribution, primarily because it's the most cost-effective way to reach a broad audience and give it access to geospatial data. Broadband Internet connections are fast enough to download even massive amounts of geospatial data.
The biggest benefit of Web GIS applications is that they allow maps to be displayed and queried with any standard Web browser. Applications can access Web services through Web protocols such as HTTP and XML, and users don't need to worry how the application was created. They just know that they can sit down at their computer, fire up their standard Web browser and find the maps they need.
Popularizing GISIt used to be that only technical gurus could use GIS, but that has changed significantly in recent years. Many GIS users today probably don't know the difference between a shape file and a coverage file, and frankly, most probably don't need to. They simply want to access geographic data, assemble it in ways that address specific questions and then see maps that show the results. For example, a couple moving to a new community may want to know where all libraries within a 20-mile radius are located, or a motorist may need to know the quickest way to get from one side of a city to the other.
These types of users typically are not worried about where the data came from, who created it or where it's stored. They just want to be able to log onto the Internet and use their browser to find the answer.
StandardsThe development of standards such as OpenGIS that encourage openness and interoperability has made it possible to build, access and exchange GIS data across different platforms. SOAP (simple object access protocol), Microsoft .NET, J2EE and XML (extensible markup language) are just a few of the common standards that underlie Web-based GIS. Applications based on these standards are platform independent, nonproprietary and scalable without loss of quality across various devices.
Early last year the OGC (Open GIS Consortium) introduced a major new initiative to develop and enhance standards that make it easier to develop and access geographic data via the Internet. The Web-oriented standards that OGC is focusing on include a common architecture, user-defined workflow, information interoperability and location-based services. The OGC is also developing compliance tests for and improving Web-oriented OpenGIS specifications.
Strategies and Tools for Web MappingMany strategies apply to creating a GIS Web mapping application. Some general tips to consider include:
- 1. Build your application on open standards because this will provide the greatest flexibility in the long run.
- 2. Publish data in its native format when possible and avoid using translators or other techniques that require the creation of additional copies of data.
- 3. Increase flexibility by ensuring that the Web mapping solution can link external database tables to spatial layers and objects.
- 4. Provide intelligent data to users and allow them to make their own decisions on how to put it together.
- 5. Allow users to add their own data.
- 6. Ensure that the application is scalable, meaning that applications can work on slow networks as well as faster networks with broader bandwidth.
- 7. Select the right tools for the job.
Not all GIS Web mapping tools are the same, and different developers use them in different ways. They range from those that produce static and dynamic map images to more advanced programs that tap into real-time data. We are seeing more and more integration of spatial databases that can be updated in real time with remote sensing, GIS, GPS, telecommunications and interactive interfaces that allow users to access all this information while sitting in front of their home computer.
In the simplest Web GIS application, a browser is used to request information. That request is forwarded to a Web server that passes it on to a GIS server. The GIS server generates a graphic file, and that graphic file is sent back to the Web server so that the user can see the results. This is an effective way to look at maps, but users typically must select from the options that are provided. They don't have direct access to the GIS data and therefore can't ask their own questions. The United States Census Bureau's Tiger Mapping Service is an example of this type of map generator. It lets users build a custom map for any location in the United States in a matter of minutes.
The two products that are among the most prominent for creating Web mapping sites are Autodesk's MapGuide and ESRI's ArcIMS. MapGuide features a highly scalable server built for network environments and a customizable viewer API (application programming interface).
The City of Vancouver's VanMap Web site uses Autodesk MapGuide to help pull together geographic data from a range of sources and make it available in GIS format to city staff as well as residents. Users can navigate through a variety of maps and access information about the city's infrastructure.
MapGuide comprises three major components: a Server that delivers data to users, an Author that creates maps and embeds them into a Web page, and a Viewer that displays the results to users. All of a map's properties, such as color, line style, layers and viewer functionality, can be defined and created in MapGuide Author or in Autodesk's Envision, a separate companion desktop product for Land Desktop, Map and MapGuide.
With MapGuide, users save applications in a MWF (Map Window File) or MWX (Map Window XML) format, both of which describe how to present the data in the map. These files don't contain the actual spatial data, so a user dynamically requests spatial data when clicking on a MapGuide map and the server then pulls up the requested data.
ArcIMS is a server-based product that provides a scalable framework for distributing GIS services and data over the Web. Its five major components interact with each other to enable users to view and query GIS data with an Internet browser. The Spatial Server processes requests for maps and attribute information, and the Application Server tracks client requests for information. Application Server Connectors link a Web server to an application server. The Manager component combines three separate ArcIMS applications—Author, Designer and Administrator—into one user interface. Finally, the Viewer allows a user to see mapping information.
Broadband Internet connections are fast enough to download even massive amounts of geospatial data. The Geography Network, which was created with ArcIMS, is intended to be an Internet-based forum for viewing and accessing spatial data from both commercial and public-domain sources.
ESRI offers two other products of note. ArcWeb Services is a subscription-based service that provides features for users interested in Web mapping. ArcWeb Services eliminates the overhead cost for a company because ESRI handles data storage, maintenance and updates. National Geographic's MapMachine (figure 1), which uses ArcWeb Services, is accessed more than a million times a week by visitors who browse through the hundreds of maps available at the site.
Figure 1. National Geographics MapMachine uses ESRIs ArcWeb Services. More than a million viewers a week browse through the hundreds of maps on the site.
ESRI's Business Analyst Web Services combines GIS Web services, GIS technology and data to integrate business reports and maps into Web applications.
Milton, Ontario, Canada, uses Orion Technology's OnPoint for its Web-based GIS service. Orion's OnPoint is a Web GIS application that uses ESRI's ArcIMS to let users publish geographic data on the Web. Authorized users can edit spatial data, and multiple users can edit the same dataset at the same time. Milton's site is intended for both internal use by staff as well as external use by residents who want to know more about their community.
The city plans to expand existing services by including Orion's OnSite application. OnSite focuses on economic development by allowing prospective businesses to search through available properties, review demographic data and business trends, analyze potential competition associated with a particular property and study zoning and other factors that may influence business decisions.
Dbx Geomatics's SVGMapMaker uses the SVG (scalable vector graphics) standard to create Web-ready map content directly from MapInfo Professional. The W3C (World Wide Web Consortium) developed SVG to display 2D vector graphics on the Web. XML controls the display of text, raster images and vector shapes such as lines, arcs and polygons. One reason I like SVGMapMaker is that it can be used to import and export MapInfo maps into Adobe Illustrator, an application I use a lot.
In this article
Intergraph's GeoMedia Web Map is Windows-based software that lets users combine and distribute GIS and other data over the Internet. GeoMedia Web Map uses GIS data in native formats from many different software systems.
MapQuest Site Advantage is a Web service designed to allow businesses to incorporate interactive maps, door-to-door driving directions and location-search features into their Web sites.
WebView is an extension for ArcView GIS and ArcGIS. A wizard leads users through the steps required to upload images on a Web site and add GIS functionality such as zooms, pans and hot links.
MapServer is an open-source development environment for building spatially enabled Internet applications. MapServer runs on most commercial platforms, including Linux, Apache and Macintosh. MapServer is not a full featured GIS system—it simply provides the core functionality to support the development of Web applications. MapInfo's MapXtreme is built on Microsoft Visual Studio's .NET, which lets developers create mapping applications for both the Web and the desktop using the same infrastructure.
FlashOne of the simplest ways to make maps available on the Web is to use Flash players that can read GIS files. Professional Web developers already make extensive use of Flash in some of the most graphic and interactive sites on the Internet, and the components needed for Flash applications are widely used and freely available. No special plug-in is required for Flash, and maps are typically displayed in Flash vector format, which means they display quickly because of their small size.
One example of a Flash site is the United States Fish and Wildlife Service's educational portal, called Changes: The Lower Columbia River Then and Now. The site looks at the seven Fish and Wildlife refuges in the Lower Columbia River ecosystem. It starts with an overview of the landscape at the time of Lewis and Clark's Corps of Discovery (1805-1806) and then hands control to the user to study the changes that have occurred since then. Changes is a multimedia experience that offers more than just access to georeferenced maps. The site is built around a custom Flash application that connects with ArcIMS and ArcSDE to provide the mapping content and controls for the site.
Other Flash-based applications include Loris Vector Map Engine, Demis Web Map Server and GeoFlash Explorer. Map Bureau's pointMapper is a scriptable mapping component for Web pages that uses Flash to provide an alternative to more complex GIS solutions.
Data AccuracyMany experts predict that Web will soon become the interface of choice for most people looking for geospatial information. With so many users accessing such a vast array of digital data, one question that needs to be addressed is, "How accurate is this geospatial information?" Most users don't know what data they are accessing, how old it is or where it came from, so they have no way of knowing if the information is any good. Have you ever stopped to ask someone for directions, only to be sent the wrong way? If users access an online route mapping program and it delivers incorrect directions, they will be just as lost.
Organizations that choose to make geospatial data available online should make every effort to keep it accurate and current. Users should visit Web sites of agencies and organizations that they are familiar with to help ensure the validity of the information they work with.
James L. Sipes is the founding principal of Sand County Studios in Seattle, Washington.