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Acquiring Spatial Data from Local Sources May Be More Effective for Regional Work

Lake Michigan Coast of Wisconsin Is Subject of a Two-Year Study

Information managers grappling with issues involving sharing data on a regional scale will be interested in the recently published results of a research project from the University of Wisconsin.

Acquisition and Integration of Digital Parcel Mapping to Support Coastal Management Along the Lake Michigan Coast of Wisconsin is a report that identifies and examines issues associated with acquiring and integrating digital parcel mapping generated at the local level of government. The data will be used to support decision making in coastal resource management along the Lake Michigan coast of Wisconsin. The two-year study was conducted as part of a cooperative agreement between the University of Wisconsin-Madison and the U.S. Army Corps of Engineers, Detroit District.

Above right: An oblique aerial photo of a coastal bluff in northern Sheboygan County (photo credit: Kevin Fermanich).

The author, David A. Hart of the University of Wisconsin Sea Grant Institute and the Land Information and Computer Graphics Facility at the university, says that the adoption and use of GIS at the local level has reached a more mature level. As a result, there is a need to examine the issues associated with building regional-scale GIS applications that implement a "bottom-up" approach to spatial data development.

Going Out of Bounds

Coastal management issues often influence broad geographic areas that supersede political boundaries. Generally, GIS applications for coastal management are built to cover large coastal regions using small-scale, coarse resolution data sets from federal and state government sources, because they are available, affordable, and in a consistent format.

"While it may be easier to integrate small-scale spatial data for regional-scale coastal GIS applications," says Hart, "exclusive reliance on small-scale spatial data limits the effectiveness of coastal management. This is because such systems lack data specific to individual parcels or other land units where many decisions affecting coastal resources are made."

Local governments collect and maintain a variety of land records at a level of detail that is useful for coastal management. They are actively modernizing data associated with parcels, planimetric features, topography, digital orthophotography, land use, zoning, and infrastructure and creating land information systems. In Wisconsin, this modernization is promoted by the Wisconsin Land Information Program, which has generated more than $70 million for local government LIS/GIS implementation since 1991. A survey of 200 city and county governments in the United States published by American Forests in 1998 indicates that 77 percent of the respondents used GIS in 1996, and 87 percent expected to use GIS in 1997.

Acquisition and Integration Issues

The report discusses the status of digital parcel mapping in the Wisconsin counties that border Lake Michigan and presents the findings associated with the acquisition of the digital parcel mapping and the integration of this parcel mapping into a common framework for the entire coast. Esri's ArcView GIS 3.2 was primarily used for this work, along with ArcInfo 7.2 and ArcInfo 8 for the projections.

The study identifies four key issues related to acquiring parcel data from local governments. These include the number of contact points for data requests, the cost of data acquisition, the time required to receive data after the request is made, and the restrictions placed on the use and dissemination of the digital data. While cost and time barriers were significant, restrictions on the subsequent use and distribution of the information by coastal jurisdictions may prove to be the greatest obstacle to the use of regional-scale data integration projects, says Hart.

Left: An ArcView layout of digital parcel mapping for the coast and assessed value for part of Door County.

Nine factors relating to the ability to integrate the data are discussed. Many of them are technical issues. They include (1) the media used for the transfer of files, (2) the size of the files received, (3) the extent to which the parcel data is documented, (4) the software format of the digital files, (5) the number of map tiles comprising digital parcel mapping for the coastal study area, (6) the compilation methods used for digital parcel mapping, (7) the coordinate system and datum, (8) the data structure of the digital parcel mapping, and (9) the status of coding digital parcel mapping with parcel identification numbers along with the ability to create a linkage between digital parcels and tax roll data to support thematic mapping of ownership and assessment information.

Many of these factors added to the time and effort needed to integrate the data, but perhaps the most significant was the lack of adequate documentation of digital parcel mapping by coastal jurisdictions. Lack of documentation added to the amount of time necessary for integration and may affect the ability to assess the suitability of using digital parcel mapping for decision making in a range of coastal management issues.

Making Progress

As of January 2001, digital parcel mapping has been integrated for 506 of 540 miles of shoreline. Tax assessment data, including assessed value, and the mailing address of the property owner, have been linked to digital parcel mapping for 436 of 540 miles of shoreline. A number of important questions can be posed of this data, for example: How many parcels exist along the coast? Who owns these parcels? What is the assessed value of land and improvements of coastal parcels? What type of land uses do tax records show to exist along the coast?

For a copy of the report, contact David Hart (e-mail: dahart@facstaff.wisc.edu, tel.: 608-263-5534).

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