A standard approach: the state of open standards in GIS

CADalyst, Dec, 2004 by James Sipes

GIS IS EVERYWHERE. VIRTUALLY every city, county, and state has its own GIS data, and the same is true for most major agencies and organizations. Did you know that the Girl Scouts of America have a GIS Day, and that Girl Scouts can earn 10 different mapping and navigation badges? Amazing!

With so many different users, it shouldn't be a surprise that demands on today's GIS programs are staggering. They're run on a wide array of computing environments, including Windows, Macintosh, Linux, and Unix. GIS is used on centralized DBMS (database management systems) that support multiple GIS users, on federated GIS networks based on distributed GIS nodes that share and use each other's geospatial data, on mobile and handheld units that can be taken into the field, and on Web browsers that can reach a broader audience.

Fortunately, GIS programs can meet these demands because in recent years there's been a shift away from proprietary GIS programs and data toward a more open philosophy that encourages interoperability and accessibility. Today, most popular GIS programs use industry-wide specifications and support interoperability. All of this has occurred because the industry adopted a consensus process to advance open standards for geospatial data and technologies.

Benefits of GIS Open Standards

Most computer users understand the need for standards. Where would the Internet be without standard protocols such as TCP/IP and HTTP that allow different computer technologies to be linked together to form a single network? CAD users are familiar with the importance of standards for establishing linetypes, layer names, sheet format, and other information intended to provide a level of consistency among drawings. These standards allow multiple users to work on the same files and make it possible to exchange files with other CAD users and programs.

Sharing and exchanging information is critical to the successful implementation of GIS. If you have to develop all of your own spatial data instead of using data from other sources, it wouldn't be economically viable to develop comprehensive datasets. Twenty years ago, when I first started working with GIS, there was very little geospatial data available, so we had no choice but to digitize our own data. To save time and money, though, we generated only enough digital data to get the job done.

The Web Frontier

Two of the major reasons behind the push toward establishing open GIS standards are the tremendous expansion of the Internet and the emergence of information technology. The Web has become a popular way to access and distribute GIS information, and the development of interoperable interfaces for Internet map servers has been a big part of that trend. The basic idea is to use a standard interface that works with different Web servers and enables interoperability for Web mapping applications. All the end user needs to understand is that accessing maps and other geospatial information is simple and easy.

Most municipalities are putting GIS maps on their own Web sites, and government agencies are getting into the action as well. The EPA (Environmental Protection Agency), for example, provides several online tools for community mapping, including Enviromapper, WME (Window to My Environment), and Maps on Demand. The basic idea is to make geospatial information available to the public. Some of the more complex Web-based GIS mapping programs are interactive, meaning that you can explore alternatives and ask what-if questions in real time as part of a public meeting. Many of the earlier online mapping systems had limited data input and output options and didn't permit new data to be mapped, but that is changing.

Traditionally, Web services have focused on the use of XML (extensible markup language) and the definition of specific XML protocols. Currently, the computing industry has adopted an open ArcXML specification from ESRI to help ensure continuity, and SOAP (simple object access protocol) for XML messaging. SOAP is a protocol that helps facilitate interoperability by defining how XML and HTTP are used to access services, objects, and servers. SOAP is platform-independent, so it can serve as a standard for all systems.

Today the Web offers so many different sources of data that it's difficult to sort through it all. The key now is not to find the data, but to evaluate its quality and figure out what to do with it once you have it. Users no longer have to digitize soil maps or road infrastructure--that information is already available in GIS format. For a given piece of geography, such as a state or a watershed, many organizations and agencies typically collect the same type of data. If users create their own GIS datasets, it's usually because the information isn't readily available. For example, on a recent project we created datasets that focused on viewsheds and the visual quality of landscapes. That information just wasn't available in existing datasets.

Because of established standards, most GIS programs can incorporate information from dozens of different sources. Some of the more robust programs can work with more than a hundred different data formats and can read virtually any GIS format. This means that it's much easier to create data in one program and open it up in another.