GEOSPATIAL INTEROPERABILITY: FROM SENSORS TO DECISION SUPPORT

Geospatial interoperability standards are increasing the discovery, access and use of sensed data in research and applications. It is critically important for informed decisions that the vast data and processing resources of the geosciences community become available as part of the Web.

The Open Geospatial Consortium (OGC) has developed web-based interoperability extending from sensors to decision support services. OGC interoperability for sensors builds on the OpenGIS® Web Map Service (WMS), Web Feature Service (WFS) and Web Coverage Service (WCS). It is now practical to fit sensors of virtually any type or connection to the Web. They can be controlled through open interfaces, and their data can be output for an array of uses.

This paper reviews previously developed OGC Web Services to set the stage for description of OGC's current development. Three OGC developments are reviewed: Sensor Web Enablement (SWE), Geo-Processing Workflow, and Geo-Decision Support Services (GeoDSS). These three developments provide the specifications necessary for the acquisition, processing and tailoring of sensor data using web services.

The OGC is an international voluntary consensus standards organization of more than 300 companies, government agencies and universities. OGC members participate in a consensus process to develop publicly available geoprocessing interface and encoding standards that enable integration of geospatial content and services into enterprise systems and that "geo-enable" the Web, wireless and location-based services, and mainstream information technology.

The OGC documents described in this article are available at http://www.opengeospatial.org/specs/

- OGC Web Services

OGC Web Services (OWS) are open standards for geospatial interoperability on the Internet. The OWS specifications and architecture have been developed by the members of the OGC in an interoperability test and development program and adopted in a consensus specification program. Below we list some of the adopted OpenGIS Implementation Specifications that are most relevant to web-based interoperability extending from sensors to decision support services. • Web Map Service (WMS) • Web Feature Service (WFS) • Web Coverage Service (WCS) • Web Map Context (WMC) • Catalog Service (CAT) • Geography Markup Language (GML)

Previously developed OGC Web Services such as WMS, WCS, and WFS are now in the marketplace. Hundreds of thousands of map layers are available from WMS's around the world. Just as the World Wide Web opened up a whole new information space, OGC web services opens up a vastly expanded geospatial web.

- Sensor Web Enablement

Members of the OGC are building a unique and revolutionary open platform for exploiting Web-connected sensors. Such sensors and devices include, for example: flood gauges, air pollution monitors, stress gauges on bridges, mobile heart monitors, Webcams, and satellite-borne earth imaging devices. In much the same way that HTML and HTTP standards enabled the exchange of any type of information on the Web, the OGC Sensor Web Enablement (SWE) initiative is focused on developing standards to enable the discovery and exchange of sensor observations, as well as the tasking of sensor systems.

SWE standards that have been built and prototyped by members of the OGC include the following pending OpenGIS Specifications: • Observations & Measurements (O&M) • Sensor Model Language (SensorML) • Transducer Model Language (TML) • Sensor Observation Service (SOS) • Sensor Planning Service (SPS) • Sensor Alert Service (SAS) • Web Notification Service (WNS)

The sensor web standards infrastructure defined by these specifications constitutes a revolution in the discovery, assessment and control of live data sources and archived sensor data. The goal is to make all types of Web-resident sensors discoverable, accessible and, where applicable, controllable via the World Wide Web.

- GeoProcessing Workflow

Making sensor data widely available through the WWW will allow better-informed decision-making. In many cases the sensor data must be processed to create the information specifically relevant to a decision. OGC has defined and initially developed a set of geo-processing services that extract context-specific information from sensor data. Typically several geo-processing services must be applied to sensor data. Such chains of services define workflows that can be automated for reuse in a variety of communities. OGC has applied workflow technologies to the automation of geo-processing service chains to support decisions based on sensor data.

Recent OGC Interoperability Program Initiatives have developed workflow for decision support. The Web Processing Service (WPS) is a generic interface for multiple types of geo-processing. Several types of WPS's were used to process data from WFS and WCS access services. This service chain was automated using the Business Process Execution Language (BPEL)

OGC continues to develop geo-processing services and to refine the practice of chaining the services using BPEL. The chaining of geo-processing services is one method to create geospatial information to better inform critical decision-making. The ultimate challenge is to enable the geographic imagery collected from different sources to become an integrated digital representation of the Earth widely accessible for humanities critical decisions.

- Geospatial-Decision Support Services (GeoDSS)

Traditionally, decision support systems have been monolithic applications that run on workstation class computers. Decision Support Services (DSS) extends this previous body of work into the distributed services environment. In the Geospatial Decision Support Services (GeoDSS) initiative, open specifications are being developed that enable decision makers to integrate geospatial data and services from a variety of sources into the operating environment that best supports optimal decision making. Elements of GeoDSS include the following:

• Schema Tailoring and Maintenance • GeoSemantic Web • Symbology Management • GeoDSS Integrated Client

The key concept of GeoDSS is that a decision maker is able to sit down at a single workstation, identify any resource any where, access that resource, bring it into their operational context, and integrate it with other resources to support the decision process. All of this takes place in a global enterprise made up of many different organizations and many different information communities.

It is critically important for informed decisions that the vast data and processing resources of the geosciences and remote sensing community become available as part of the Web. Application communities need Internet-enabled interactive and interoperable access to data from observations and models for decision support systems Bringing data archives and active remote sensors on-line supports the flow of geospatial information supporting policy makers, operational managers, (including governments at all levels), and the citizens of the our world