Spatial Technologies: A Standard Approach15 Dec, 2004 By: James L. Sipes
The state of open standards in GIS
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.
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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 StandardsMost 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 FrontierTwo 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.
GIS, by its very nature, requires a broad-based approach. One of the best ways to expand GIS capabilities is to integrate data by combining different spatial databases. A geodatabase provides a common framework for different types of data and controls how users can access, modify, store, and process this data. Many national governments throughout the world are involved in developing spatial data infrastructures that will help make geospatial data more readily available for all users, including governmental agencies, academia, and the private sector. These NSDIs (National Spatial Data Infrastructures) focus on the development of standards, the sharing of data via a National Geospatial Data Clearinghouse, and the development of the National Digital Geospatial Data Framework. There's also a growing need to address economic, social, and environmental issues that aren't limited by political boundaries. The GSDI (Global Spatial Data Infrastructure) is intended to support global access to geospatial information.
Standards OrganizationsThrough the years, many attempts at establishing GIS standards have failed because they weren't well engineered. The successes we've seen recently with GIS standards are due in large part to the many organizations directly involved in creating, reviewing, and publishing these standards. There are literally dozens of organizations, and all have the same basic goal—to make GIS more accessible and easier to use.
To name a few:
- 1. ISO (International Organization for Standardization)
- 2. ANSI (American National Standards Institute)
- 3. ODC (Open Data Consortium)
- 4. American Society of Photogrammetry and Remote Sensing
- 5. Digital Geographic Information Working Group
- 6. Federal Geographic Data Committee
- 7. Global Spatial Data Infrastructure
- 8. International Hydrographic Organization
- 9. Spatial Technologies Industry Association
- 10. W3C (World Wide Web Consortium)
The ISO is one of the major standards organizations. ISO TC 211, the ISO Technical Committee on Geographic Information and Geomatics, is working on establishing a structured set of standards for geographic information. The committee has developed dozens of work items that range from standards to reports, reference models, guides, and guidelines for other work items. These standards address the acquisition, processing, analysis, assessment, presentation, and transfer of digital data between different users, systems, and locations. They also include methods, tools, and services for data management.
The object of the ISO/TC is to link its work to appropriate standards for information technology and data, where possible, and to provide a framework for the development of sector-specific applications using geographic data. To obtain a copy of fact sheets of the various ISO Standards, go to its Web site (www.isotc211.org).
This September, the Open GIS Consortium changed its name to the Open Geospatial Consortium, or OGC, to better reflect its interest in the broader geospatial marketplace that goes beyond GIS. OGC is one of the leading standards organizations addressing interoperability for geospatial technologies. More than 250 international companies, government agencies, and universities participate in a consensus process to develop standards for things such as the geospatial information available on the Web, wireless and location-based services, and mainstream information technology.
The OGC has focused on the development of a series of interoperability specifications for GIS on the Web, and these are its most widely adopted standards. Two other OGC standards being embraced by GIS developers are GML (Geography Markup Language), which describes how geographic information is to be transported and stored, and OpenGIS Location Services, for route determination.
Implementing StandardsDozens, if not hundreds, of projects are underway that involve open standards. ESRI, Autodesk, MapInfo, Oracle, and other companies are working with the OGC to develop the OpenLS specification. OpenLS is designed to support interoperable solutions that link location and other geospatial data with wireless technology.
Location-based services are important because cell phone companies are trying to meet the requirements of Enhanced 911, the E911 service that will allow emergency service personnel answering a 911 cell phone call to locate the caller within 50'. ESRI and Autodesk are also working with ISO on standards for navigation that are expected to be merged with OpenLS.
ESRI's ArcGIS Data Interoperability Toolkit, an extension to ArcGIS 9, is a set of OGC-compatible interface connectors that can be used with ESRI Web-enabled software. The toolkit allows ArcGIS users to exchange geospatial information with every other connected ArcGIS user and with users of any other OGC-compatible programs or applications.
GRASS (Geographic Resources Analysis Support System) is an open-source GIS that has been around for years and is popular with universities and federal agencies. Community Map Builder provides an open-source framework that allows communities to jointly build geographic databases and share them over the Web. GeoTools Corp.'s Geotools 2 is an open-source, Java-based GIS toolkit that simplifies the process of developing OpenGIS-compliant applications. It's not an application per se, but is intended for those who want to build applications or add spatial support to existing programs.
ESRI's Geodatabase XML is an open interchange format that will allow the exchange of information between geodatabases and other external systems. XML is a simple, very flexible text format designed specifically for large-scale electronic publishing. XML is also playing an increasingly important role in the exchange of data on the Internet.
Partnerships between standards organizations and GIS developers are critical in the process of developing standards. Developers of the most popular GIS programs are actively involved in helping define, test, and implement standards.
Interoperability to ContinueMost GIS developers have adopted broader standards that focus on information technology and Web interactivity, and most industry experts predict that this move toward interoperability will continue.
For software developers, this means that it will be easier to write programs that use geospatial data. For users, open GIS standards mean that they won't be locked into a proprietary system, but instead can choose the GIS tools that best fit their needs. They also can access and use the vast amount of geospatial data that already exists in cyberspace.
James L. Siptes is the founding principal of Sand County Studios in Seattle, Washington.
About the Author: James L. Sipes
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