Wisconsin Geospatial News

WLIA Task Force Tackles Coordinate Systems

The Wisconsin Land Information Association (WLIA) Wisconsin Coordinate Systems Task Force has developed a proposal to resolve ease of use issues with respect to the definition and application of the Wisconsin County Coordinate System within commercial software. This is music to the ears of many who have struggled with local data integration and coordinate transformation problems.

The task force last met November 23, 2004 in the most recent of a series of nearly monthly meetings since April. In that time, significant progress has been made in documenting the evolution and current status of commonly used coordinate systems in Wisconsin. In addition to the current proposal, the task force has also chosen to address other issues. As this work progresses, the State Cartographer’s Office will actively post information to our website, as well as provide reports in a variety of forums to keep you informed of the latest developments.

The task force, formed by State Cartographer Ted Koch, was brought together initially to address technical support issues faced by its members. In particular, many GIS, surveying, and engineering professionals have struggled with data conversion to and from a Wisconsin County Coordinate System (WCCS) within commercial GIS, CAD, or GPS software. As stated in the proposal, though mathematically sound, the County Coordinate Systems are based on a non-standard design. As a result, technology vendors have inconsistently interpreted requirements for converting coordinates to or from WCCS. This has led to much confusion among users of these vendors’ technologies.

Task force goals include: a proposal to standardize the definitions of the Wisconsin County Coordinate System, registration of all coordinate systems specific to Wisconsin with a recognized standards body, and development of educational and “best practices” materials.

Task at Hand – A Proposal
After about six months of unearthing references and original documentation on how and why we use the coordinate reference systems the way we do today, the task force developed proposed solutions to the apparent incompatibilities within commercial software. The proposal includes an initial cost estimate to redesign the existing system, and suggests possible funding sources. At the October meeting, the task force passed motions to approve the proposed recommendations, and to proceed with presenting the proposal to leadership of various stakeholder groups including WLIA, the Land Information Officers’ Network (LION), the Wisconsin Society of Land Surveyors (WSLS), and the Wisconsin County Surveyor’s Association. Some of these organizations have already expressed their support.

The Nuts-n-Bolts
So what’s in the proposal? Under the expert leadership of surveying professor Jerry Mahun (Madison Area Technical College) and engineering professor Al Vonderohe (UW-Madison), the task force suggests a redesign of the mathematical foundation for the Wisconsin County Coordinate System. The redesign will not significantly change the ouput projected surfaces. In a nutshell, this means that existing mapped data already in a county coordinate system can be redefined under these new parameters without doing any data conversion. Initial tests have shown that discrepancies across a given county for moving from the old system to the new system would not exceed 5 millimeters (approximately ¼ inch.)

The largest benefit of this new approach, if implemented, is consistent definition and transformation of data in county coordinate systems using generally applied methodologies by technology vendors. The “new” parameters would also be registered with the European Petroleum Survey Group (EPSG), the current de facto maintenance organization for a worldwide database of coordinate reference systems. Finally, a collection of test data and best practices will be assembled and distributed to assist users.

Stay tuned
The task force presented some initial information earlier this fall at the ESRI Wisconsin Users Group meeting. Watch for additional appearances at the annual meeting of the Wisconsin Society of Land Surveyors and Wisconsin Land Information Association.