New South Wales OpenGIS(R) Web Feature Service Specification to Share Natural Resources Information

by Maurits van der Vlugt And Jonathan Doig

A Data Sharing Challenge

"There is so much data out there, why can't we just use it?" If you work in geospatial technology, there's no doubt you've heard this sentiment. The question is even more important if these anecdotal numbers are anywhere near true: More than 80 per cent of all data has a spatial component, and more than 80 per cent of the time spent on spatial information projects is wasted on non-productive activities such as data acquisition, negotiation, loading and transformation.

In the state of New South Wales (NSW), Australia the Community Access to Natural Resources Information (CANRI) program has addressed this issue with significant success. CANRI has implemented a framework for online data sharing between NSW government agencies and community organizations using OpenGIS specifications The CANRI portal serves as the NSW focal point for all natural resource-related applications, atlases and metadata.

In September 2002, the Open GIS Consortium (OGC) released a specification for interoperable access to vector databases: the OpenGIS Web Feature Service Implementation Specification (WFS). CANRI, which co-sponsored the development of the specification, has since developed a pilot project outside the OGC-controlled laboratory environment.

History

In 2000, 16 state agencies formed the CANRI program. CANRI aims to break down the technological and institutional barriers of data and information sharing between agencies in the natural resources sector, leading to more effective decision making and improved information for the community.

CANRI's technological challenge involves spatial data interoperability. How could the group enable direct, online access to a range of spatial databases residing on different hardware and software systems in different agencies, in different geographies, to make them accessible to all who need them? The solution relies on an open standards-based framework that doesn't depend on a single vendor. The OGC provides such a framework with its OpenGIS Specifications, a group of open interfaces supported by major GIS and technology vendors and service providers. OGC specifications allow, for instance, an Intergraph Web viewer to directly query spatial data from an ESRI (ArcIMS), MapInfo (MapXtreme) or Oracle database.

Most everyone reading this article has taken interoperability for granted in selecting and setting up stereo equipment. We happily plug together CD players, amplifiers and loudspeakers from different vendors, fully expecting them to work as one, which they nearly always do. OGC specifications provide a similar type of "plug and play" connectivity for GIS data and processes, on the Web and other networks.

In 2001 CANRI sponsored the OGC's Open Web Services Testbed, where specifications such as WFS were further enhanced from their first iterations. OGC specifications currently form the backbone of the CANRI framework. This makes it possible for all CANRI agencies to use each other's spatial data, as well as data from Commonwealth agencies including the Bureau of Rural Science and from overseas data sources such as U.S.-based NASA. CANRI, like these agencies, also makes its data accessible to outside users and applications.

Web Map Service Answers Many Questions

Web Map Service (WMS) was the first OpenGIS specification for the Web, released three years ago. It defines a set of queries against spatial databases, returning a map image (in JPG, GIF or PNG format) to the requesting client. The emergence of WMS was a breakthrough for interoperable Web mapping. Many vendors now include WMS capabilities in their products, so a client can issue a WMS map request across the Internet to a Web map service without having to know the underlying GIS format, or even what type of software is in use. CANRI participants use WMS interfaces extensively.

WMS works well for the 90 per cent of users who need map viewing and very basic query functionality ("what's this that I'm clicking on?"). Its simplicity is its strength, and because it needs only very thin clients, it can even be deployed quickly and easily.

Beyond Web Map Service: Testing Web Feature Service

Users or applications that want more flexibility and functionality run into the limitations of WMS. These typically more advanced users need to access raw data (points, lines, polygons) to query, filter, edit or download the spatial objects and their attributes. The OpenGIS Web Feature Service Interoperability Specification (WFS), released in September 2002, provides tools for that level of interoperability.

CANRI's WFS pilot tested the new specification, as implemented by different vendors, in the context of the CANRI framework. The CANRI team wanted to see whether or not the new technology would integrate with the CANRI front-end to create meaningful, user-friendly applications.

CANRI also wanted to demonstrate the feasibility of using the WFS specification to access water quality monitoring data from different agencies. The pilot focused on integration and presentation of water quality data from the NSW Key Sites Water Quality Monitoring Program, which samples phosphorus, electrical conductivity and turbidity on a monthly basis to illustrate trends for NSW rivers.

The pilot also took data from the Integrated Data Management System (IDMS) for the Hawkesbury-Nepean Catchment Water Data project. This project's goal was to develop a common infrastructure for data accessing for the regional water-monitoring community, and to foster greater integration of water monitoring and information sharing between state and local government stakeholders.

The data resided in two separate databases: the Key Sites data was stored in Oracle Spatial while the IDMS data resided in a PostGres SQL database. Sydney-based GIS contractor Navigate hosted the WFS hosting the Key Sites data using the ESRI ArcIMS WFS connector running against ArcSDE on Oracle. Social Change Online used its own WFS Point & Find product to make the IDMS data available.

Social Change Online's WebMap Composer served as the online viewing application (the "client"). End users can access maps of water quality monitoring sites plotted on top of background maps served by WMS services from other agencies. They can also generate summary statistics over groups of sites (for example, those within a catchment) and download attribute data for desktop processing.

The project achieved its main objectives and successfully demonstrated the feasibility of a user-friendly implementation of the specification in the CANRI framework. Because some of the software was pre-release, not all functionality was available. Those issues have been resolved in the mean time.

The project developed a common data model (an XML schema) for water quality measurements and observations. Both WFS servers map their internal data structure to this model, which enables interoperable data query and retrieval. The pilot data model will serve as a starting point for the development of a NSW government-wide water quality data model.

The WFS pilot application is available online. It presents the locations of sample points, overlaid onto selected background maps from services available via the CANRI catalogue, so that users can query multiple heterogeneous water quality data sources, applying one or more of the following criteria: custodian, area of interest or time period. A user can query an individual observation location and report the associated discrete sample data in table form.

Next Steps

The next steps on the CANRI agenda are to implement commercially released OGC-compliant software components and to further develop shared data models. This will help CANRI to further share and utilize Australian spatial data resources as more and more of these become available.

CANRI's commitment to OpenGIS specifications is shared by ANZLIC's ASDI Standing Committee and a growing and active Australian OGC membership base, which plans to establish an OGC regional affiliate office in Australia by mid 2003.

The WFS pilot project has moved NSW natural resource management agencies another step towards improved information sharing and delivering better and more cost-effective services to the wider community.

A version of this article appeared in the April/May 2003 issue of Position Magazine.

About the Authors Maurits van der Vlugt is a senior GIS consultant with Sinclair Knight Merz Pty Ltd in Sydney. Jonathan Doig is the CANRI program director at the NSW Department of Land and Water Conservation. The following organisations contributed actively to the success of the WFS Pilot Project: NSW Department of Land and Water Conservation (DLWC); NSW Environmental Protection Authority; Sinclair Knight Merz; Social Change Online; Navigate; ESRI Australia.