The Open GIS Consortium (OGC) is a membership organization dedicated to open system approaches to geoprocessing. Through its consensus building and technology development activities, OGC has had a significant impact on the global geodata and geoprocessing standards community, and continues to promote a vision of OpenGIS technologies that integrate geoprocessing with the distributed architectures of the emerging global information infrastructure. OGC recognizes that the evolution of new technologies and new business models are closely related, so by means of an open and formal consensus process, OGC is creating the OpenGIS Specification, an unprecedented computing framework and software interface specification which is a necessary prerequisite for geoprocessing interoperability.
OGC was founded primarily to address the following needs:
- To integrate geographic information contained in heterogeneous data stores whose incompatible formats and data structures have prevented interoperability. Up to now, this interoperability barrier has seriously limited the ultimate usefulness of GIS technology.
- Improved access to public and private geodata sources.
- The ability for agencies and vendors to develop standardized approaches for specification of geoprocessing requirements for information systems.
- With the GIS industry, to incorporate geodata and geoprocessing resources into national information infrastructure initiatives. These geographic resources must have the ability to be found and used as easily as any other network-resident data and processing resources. To accomplish this level of integration, the industry realizes it needs to synchronize geoprocessing technology with emerging information technology standards based on open systems concepts, distributed processing, and object/component-based software frameworks.
- The need to preserve the value of legacy geoprocessing systems and legacy geodata while incorporating new geopksGET http://siteinfo.a9.com/data/6lSv01dRFLI>
In short, OGC acts as the technical catalyst for merging GIS, GPS, CAD, earth imaging, and spatial databases with virtual reality, multimedia, network computing, and non-spatial desktop applications. It is also forging working relationships for delivering geospatial applications to business, government, education, and entertainment.
Heady Aspirations From Humble Beginnings
OpenGIS is defined as transparent access to heterogeneous geodata and geoprocessing resources in a networked environment. From the beginning, the goal of the OpenGIS Project has been to develop a comprehensive open interface specification that lets developers write software that provides open, interoperable capabilities. The OpenGIS Project began in 1993 with limited support from a few federal agencies and commercial organizations who funded meetings to discuss the feasibility and possible scope of the proposed OpenGIS Specification (OGIS) and specification-writing project. After the original participants determined that a useful specification could be developed, OGC was founded in August 1994 to provide a formal structure and process for developing the specification.
Today, OGC manages the OpenGIS Project as a formal consensus process involving key organizations in the commercial, academic, and government sectors of the geographic information community. All members participate in the OGC Technical Committee and its working groups under the supervision of OGC's Management Committee which develops OGC's business plan and makes all final decisions regarding the scope of the specifications and the project.
The participation of these individuals indicates the degree to which OpenGIS technologies are seen by the organizations they represent to be a necessary next step toward creating a global open system geoprocessing architecture.
OGC Technical Committee
The OGC Technical Committee is the primary operational unit of the OpenGIS Project. It is comprised of the technical representatives of all OGC member organizations and is charged with creating the OpenGIS Specification. The Technical Committee does the bulk of its work through its Working Groups.
The OGC Technical Committee has created an abstract specification, a single detailed guide for writing interoperable geoprocessing software. In order for products to emerge, this needs to be implemented on industry-accepted distributed computing platforms (DCPs), such as OLE/COM, CORBA, and the Internet's http and Java standards. While the Technical Committee continues to develop the remaining parts of the abstract specification, it is also working with vendors and research groups through an RFP (request for proposal) process to develop DCP-specific OpenGIS implementation specifications.
Software products that are compliant with an implementation specification will be interoperable within a DCP. In addition, every effort is made to conform the different implementation specifications and to work with the DCP developers to achieve maximum geoprocessing interoperability between DCPs.
At both Management Committee and Technical Committee levels, OGC maintains an Application Integration structure which focuses on coordinating activities designed to help technology providers address application-specific needs that are common to technology users in industry sectors. The goal of this committee structure is to evaluate, test, implement, and extend the OpenGIS Specification to ensure its practical utility in a wide variety of application areas. By inviting the participation of user communities, OGC can provide community-tailored specifications which enable diverse vendors and integrators to build interoperable products and service environments.
Summary Of OpenGIS Technologies
The OpenGIS Specification is a comprehensive software architecture specification that provides a standard way to represent all kinds of geodata in software and a common set of services to support distributed geoprocessing across heterogeneous hardware platforms. Programming interfaces based on this specification will enable true interoperability between applications on the desktop, and they will enable access to heterogeneous geodata and geoprocessing resources across local and wide area networks.
The OpenGIS Specification releases GIS, remote sensing, and other geoprocessing disciplines from the constraints of proprietary and incompatible data formats and isolated applications, and moves into the world of software components and network-based computing. The OpenGIS Specification is like other distributed object-oriented software systems in its basic approach, but it is the first large-scale application of object technology for managing spatial data in the contexts of global and national information infrastructures.
The OpenGIS Specification specifies a well-ordered environment designed to simplify the work of both developers and users. Developers adhering to the specification will create applications able to handle the full range of geodata types and automatically negotiate vast geodata and geoprocessing resources on a network. Users of geodata will be able to share a huge networked data space in which all kinds of spatial data will be usable without difficult and time-consuming batch transfers and conversions, even though the data may have been produced at different times by unrelated groups using different production systems for different purposes.
The OpenGIS Specification architecture provides:
- A single "universal" spatial/temporal data model — the Open Geodata Model (OGM).
- A set of services for manipulating data represented using the OGM — the OGIS Services Architecture.
- A Geographic Information Communities model that addresses the problem of different communities of users using different semantics for the same spatial features. This provides an efficient means for data discovery using catalogs and an efficient means for data integration using semantic translators.
The OGM is the core component of the Specification. It consists of a hierarchical class library of geographic information data types that comprise the shared data environment and unified data programming interface for applications. Every geoprocessing system (GIS, earth imaging, digital cartography, navigation, etc.) has a geodata model where terrestrial objects and events are represented in software. Basically, the OGM provides a means for mapping one geodata model to another.
The OGIS Services Architecture is a consistent open development environment characterized by a reusable object code base and a set of spatial access and spatial processing services. This architecture supports complex query processing and also specifies standard methods for requesting and delivering geospatial transformations and processing tasks. It facilitates transformations between private data and OGM constructs, as well as coordinate conversion and raster/vector conversion. Tools built using these catalog systems will bring to geodata access the same degree of expanded capability that Web browsers and HTML have brought to the much simpler world of text data.
Much of the momentum for the OpenGIS project comes from a need to share geographic information more effectively and to improve the efficiency of communication between individuals and organizations who not only store and manipulate geographic information in different ways on different computer systems, but who think and talk about and visualize geography in very different ways. Undertaking to establish effective data communications within a well defined technical context poses a reasonably limited problem. Undertaking to establish means for sharing information with little or no loss across the technical and human barriers that exist within and among diverse human groups and institutions poses a problem of much greater scope. OGIS must ultimately help solve both the technical and the larger human problem.
The OGC Technical Committee has devised a Geographic Information Communities model to address this problem that provides a framework that uses OpenGIS technologies to dissolve many of the barriers that prevent sharing of digital spatial data and spatial processing services. Some barriers, of course, cannot be overcome by technology. But when semantic translators and other methods become widely used, Geographic Information Communities will be able to see clearly what they might do at the organizational level to overcome such barriers and make their spatial information systems more interoperable with those of other Geographic Information Communities.
Progress Continues Toward Open Geoprocessing
In January, OGC announced that it had received excellent responses to its Requests for Information (RFIs) which are part of the OpenGIS Interoperability Specification effort. The RFIs cover geographic information catalog services and imagery.
Seven organizations submitted information in response to the OpenGIS Catalog Services RFI. These submissions suggest requirements to include in an RFP for standard mechanisms for geographic information in a networked environment of heterogeneous spatial databases. Among the submitters were the ISO (International Standards Organization) Cataloguing Project Team, the US Federal Geographic Data Committee, the US Department of Defense's National Imagery and Mapping Agency, and the Committee on Earth Observation Satellites.
Space Imaging (Thornton, CO), SPOT Image (Reston, VA), TRIFID (St. Louis, MO), and the US DoD National Imagery and Mapping Agency (NIMA) responded to OGC's OpenGIS Imagery RFI to ensure completeness of the imagery parts of an RFP for specifications that will define coverages that include images (such as satellite images) and certain maps (such as digital elevation maps) where each point has a distinct value.
David Schell, president of OGC, said, "Geospatial catalog services will work underneath applications that are as easy to use as a Web browser, and the OpenGIS Project's work with coverages will enable all types of geospatial data to be queried with the same user-friendly tools. Our members are dealing with very sophisticated technologies, but they have their eyes on the non-expert user."
Late in 1996, geographic information system (GIS) vendors cooperated to submit proposed OpenGIS Specifications in response to OGC's first Request for Proposals (RFP) which addresses "simple geometry," (points, lines, and areas) and attributes (such as soil type). Compliant products expected later this year will be able to respond to each others' spatial queries.
Diverse Membership Speeds Accomplishments
The total number of OGC members now exceeds 90 with most of the major design/engineering automation and GIS vendors represented, as well as other organizations from the private and public sectors and academia. Even with such a diverse group of members, cooperation between the members is yielding real progress being made on several fronts.
Software and computer vendors, integrators, data suppliers, telcoms, universities, government agencies, and industry associations join OGC primarily for the following reasons:
- To quickly enact distributed geoprocessing standards, which will not happen without their help.
- As technology users, to shape geoprocessing standards to meet their needs; plan intelligently for technology acquisition and technology-induced organizational change; and evaluate and begin working with technology providers.
- As technology providers, to create sound and timely business and development decisions; ensure that the OpenGIS Specification meets their needs; begin development of OpenGIS-compliant products as soon as possible; form relationships that help their businesses during a risky period of change; and solve shared problems.
As an example of progress, earlier this year a group of GIS technology providers including Bentley Systems, demonstrated a CORBA/Java-based method for interoperability of GIS data and systems based on object-oriented technology. The software architecture, was presented to the entire OGC technical membership community in response to their formal request for a CORBA compliant implementation. Bentley’s submission was developed in cooperation with Genasys, Lockheed Martin, Mitre Corp., Oracle, Sedona Graphics, and Sun Microsystems.
David Schell, president of OGC said, "We are pleased that Bentley has been such an active and contributing participant in our specification activity. It was gratifying to see the working prototype of the CORBA-based interface put forward by Bentley."
This implementation is significant because CORBA could well become the preferred communication vehicle for sharing GIS information between systems. Its architecture of multiple platform support is compatible with existing GIS systems and the trend toward data-servers and Internet clients. If accepted by OGC, the implementation will become the industry’s CORBA-based interoperability benchmark to be used between member GIS systems.
The CORBA implementation was based on Bentley’s ProActiveM technology and an objective version of MicroStation GeoGraphics that offers comprehensive interoperability of GIS data and systems.
OGC is creating the Open Geodata Interoperability Specification (OGIS), a set of software specifications for sharing geographic information across tools and organizations. Last summer, OGC issued a request for proposal (RFP) for interface standards in the areas of CORBA, OLE, ODBC, and the Internet. Final decisions on these standards are planned for later in 1997.
In January, Microsoft Corp. (Redmond, WA) became a Principal Member of the Consortium. As a Principal Member, Microsoft has a seat on OGC's Management Committee, which oversees the OGC Technical Committee that plans cooperative industry development programs.
Carl Stephen Smyth, Lead Geographer in Microsoft's Geography Product Unit, said, "We were happy to join the OGC industry effort. The goal of interoperable geo-information is very important to us and we look forward to helping ensure its early commercial success."
Consortium members recently showed cooperation in responding to OGC's first RFP for simple geographic features by creating a draft engineering specification for standard interfaces that will enable diverse OLE/COM-based software systems to access each other's geographic data. Competing GIS vendors Intergraph (Huntsville, AL), Autometric (Alexandria,VA), ESRI (Redlands, CA), Laser-Scan (Cambridge, UK), MapInfo (Troy, NY), Smallworld (Englewood, CO), and integrator Camber Corp. (Huntsville, AL) met several times to merge their proposed specifications into a single submission for Microsoft's OLE/COM platform.
Intergraph led the team that responded to the RFP for OLE/COM. Preetha Pulusani of the Infrastructure Product Center, Intergraph Software Solutions, explained, "Intergraph has been closely associated with and witness to the tremendous growth of 32-bit Windows in our market segments, ever since our early adoption of Windows NT. The significant investment we made on this platform beginning in 1992 has yielded extremely positive returns and user acceptance. Software based on Windows NT is now the fastest growing segment of the GIS market."
"We are excited to have Microsoft in the Consortium. Like all OGC members, Microsoft has a strong interest in network-based computing that involves geographic information," said OGC’s David Schell.
Another prominent GIS/CAD provider, Autodesk, was an early OGC supporter and member that has for some time led an effort to open standards with its own DXF data file transfer format. It has also instituted into its products the Industry Foundation Classes (IFC) and Guidelines, which were created in conjunction with the Industry Alliance for Interoperability (IAI) within the AEC industry. Autodesk is compelled to support the OGC standards throughout its entire mapping and GIS product family. Because more maps reside in Autodesk’s DWG format than any other, the company’s reason for involvement in OGC goes without saying. "Industry growth has been hampered by competing proprietary technologies, and we are committed to creating an environment where GIS information can be freely shared, regardless of platform," said Joe Astroth, vice president of Autodesk’s GIS Market Group.
This statement is especially noteworthy because until now, proprietary, complex, and incompatible data formats and non-interoperable geographic processing systems severely limited the use of digital geographic information and the growth of the GIS market. OGC is working to ensure that geographic information of all kinds will be able to fulfill its potential role in emerging national and global information infrastructures.
The Importance Of OGC
The continuing work of OGC is extremely important, especially in light of the fact that new GIS products and users are proliferating. It is, therefore, essential that standards be established for data that is interoperable and useful between different users, products, and platforms. The GIS industry itself realizes the importance of the outcome of the OGC and its members are exhibiting unusual behavior toward that end — they are cooperating to meet the needs of users in the currently mixed up world of too-often proprietary GIS data.
Since we feel that the work of the OGC and its implications are of vital importance to many of our readers, we will devote considerable space to this endeavor as the standards for geodata and geoprocessing evolve over the next several months.
In our next installment, we will cover how the Federal Geographic Data Committee (FGDC) is developing the National Spatial Data Infrastructure (NSDI) as a standard for ensuring consistency in digital geospatial data.n
Contact: OpenGIS Consortium http://www.opengis.org