GIS/CAD Mapping
Mapping the New Millennium
Oakland County, Mich., combines GIS, CAD and mainframe data into a digital base map system.
By Bob Daddow

The Challenge
• Build a highly accurate and seamless database to serve as the primary source of land parcel information for the county tax assessor's office, deeds registry, most county agencies, and many local municipalities;
• Reduce a six-month mapping backlog and reduce the need for remapping in the future;
• Integrate CAD-based and mainframe data into a geographic information system (GIS) format.

The Solution
• Create a next-generation GIS composed of GenaMap GIS and GenaCivil CAD-based civil engineering software from Genasys II Inc., an Oracle relational database and Hewlett Packard (HP) workstations, servers, and terminals.

The Potential Benefits
• Maintain an accurate geodetic control layer based on the State of Michigan Remonumentation Program;
• Create new levels of information sharing and project coordination among government agencies;
• Promote the county maps' adoption by local municipalities.

A County Blossoms in Michigan
Located just northwest of Detroit, Oakland County is Michigan's fastest-growing region. One out of every two new jobs created in the state is located in Oakland County. Nearly $2 billion was spent there on development and new construction in 1994. The county contains 61 municipalities, 1.2 million residents, and more than 427,000 parcels of land, as much as 40 percent of it in areas of forest and farmland targeted for new development.
      Keeping up with such growth has put a terrific strain on the county mapping staff and its traditional paper mapping system. Almost 8,000 changes to the maps have to be made each year, causing a backlog that has stretched to six months.
      A county-wide base mapping project was planned for the complete and accurate representations of the 910-square-mile county's lots, parcels, section corners, rights of way, hydrology, and other attributes. The project would produce output similar to paper Sidwell maps, which have been used since 1971 as the basis for all lot and parcel-related land transactions in the county. The Sidwell system employs a comprehensive and accurate identification system; at the parcel level, it is able to define acreage parcels, subdivision lots, and condominium boundaries.
      In the mid 1990s, the county also needed to comply with the State of Michigan's remonumentation program, calling for an updated GPS survey of all section corners and quarter corners - comprising thousands of coordinates in all.

Planning the GIS
The need for a high degree of accuracy for both the county base map and state survey spurred planners to use coordinate geometry (COGO) as the basis for a next-generation geographic information system (GIS). Digitizing the existing Sidwell maps and rectifying to orthophotography was ruled out in the search for more accurate methodologies.
      The county's Information Technology Department, Register of Deeds, and Equalization Division decided to create a digital base map integrating GIS, CAD and host data. Several key objectives identified were:
• Create a highly accurate geodetic control layer for use with the state's remonumentation program;
• Store and maintain historical lot and parcel records;
• Relate the parcel layers to information contained in mainframe databases in the county;
• Transfer collected information to external agencies that use a GIS.
      The new digital system also had two future-oriented goals: support new digital mapping applications and features (such as utilities, water and sewer maps, and other topological and thematic information); and provide an economical and long-term solution for maintaining the land records of the county.

The Right Team Chemistry
Legacy data and applications from the county, and many of its 61 municipalities, resided solely on mainframes. The county's IT department had begun to right-size applications and move them from the mainframe to a client/server environment as part of a county-wide technology renaissance program. Legal descriptions within the mainframe database are used to build parcel boundaries in the digital base map. The county's first strategic decision was to adopt Oracle as its relational database management system, and to populate the RDBMS with mainframe data.
      The county benchmarked HP, IBM and Sun server platforms for price/performance, Oracle RDBMS support, growth path, operating systems, mainframe coexistence, training and consulting services. County IT personnel selected HP. HP workstations were chosen for their high-performance graphics capabilities, HP X terminals as the clients and HP-UX, HP's UNIX-based operating environment because of its strategic platform for Oracle client/server and GIS applications.
      "We opted for better graphics performance for mapping and other applications," said Dale Kukla, IT GIS program manager of Oakland County. "HP was faster than Sun."
      Following an open procurement and benchmark trial, the county chose GenaCivil, a CAD-based civil engineering and drafting software system with full coordinate geometry functionality. The software was especially suited for building basemap because it was developed by Genasys II Inc., a GIS software company in Fort Collins, Colo., specifically for the integration of surveying and drafting components into the vector GIS environment. Genasys's GenaMap program was also chosen for its full-function GIS that forms topologically structured relationships between common map features and provides a client/server link to the Oracle RDBMS.
      Additionally, Oakland County chose Genasys for its ability to provide professional services to the county, developing a data conversion standard, a full database design, and customized user interfaces for the Equalization Division.

COGO
COGO involves calculating the location and position of parcel boundaries based on their legal range and bearing measurements from established section corners or from surveyed traverses measured relative to section corners. These boundaries must then be rotated to fit the preferred coordinate system. Obtaining the legal parcel measurements requires extensive data retrieval from recorded plats and condominiums, official deeds, and tax records.
      Under a professional services contract in the first phase of the project, Genasys worked with the county mapping staff to develop a point-and-click display using the graphical user interface program built into GenaCivil. The interface automated much of the time-consuming data extraction and mathematical computation procedures. It also automatically assigned and symbolized map features to the appropriate CAD layers without direction from the county map staff.
      Automation of the basemap development with GenaCad, a module of GenaCivil, reduced staff hours on the project by 40 percent.
      GenaCivil allowed Oakland County to conduct COGO data entry for subdivision plats, acreage parcels, and condominium plats. It also allowed importation of legal descriptions from the mainframe database and automatic generation of property boundary geometry.

Converting CAD to GIS
CAD databases are not designed for calculation and manipulation of aerial features, which was a major drawback for a GIS like the one planned by Oakland County. Also, a primary function of the system was the Equalization Division's computation of tax assessments based on land area.
      Genasys has written an automated script to translate the CAD basemap into the GenaMap GIS format. The translator will remove the double lines that CAD software places between features and will redistribute features from the 42 CAD layers into 11 GIS index maps.
      The GIS layers are arranged thematically for ease of use by each major county department. As part of the county's plan to create a client/server environment for the GIS, offices can share information from locations across the county. Genasys also created automated scripts to extract records from three county mainframe databases and input them into the single Oracle database.
      This database will be queried by GIS users to provide county-wide access to data previously available only to some departments and often duplicated by separate county offices.
      Oakland County and Genasys are conducting user group meetings with representatives from all 61 communities in the county. The groups are offering their suggestions on how certain elements of the basemap, and later the GIS, may be modified during development to meet specific user needs.

The Final Result
The system was implemented on a network linking its three sponsoring agencies, the IT department, Equalization Division and Register of Deeds, each with HP workstations running in a full-function user environment for GenaCivil and GenaMap. The system is connected to the Advanced County of Oakland Regional Network (ACORN), a high-speed fiber-optic network connecting 14 campus buildings to the central IT center in Pontiac, Mich. The center is a repository for legacy and client/server data and provides connectivity to more than 100 remote sites and 5,000 networked devices.
      In light of Oakland County's rapid growth, the Equalization Division views the GIS as a necessity for tax assessment and many other county functions. The GIS will directly convert geographic information to appraisal information and allow the Equalization Division's staff to visualize land value patterns in properties and neighborhood markets.
      Convenience for the staff and better service to citizens are two important factors driving the GIS development, but legal issues were also of prime importance in the county's decision to use COGO. Correctly drawn parcel descriptions tied to section corners are the only legal basis for tax assessments. If the county used another procedure to build the basemap, a taxpayer could challenge the legality of the assessments and demand a new property survey, and the county would have to comply.
      When county administrators tell their peers in their counties that Oakland County is using COGO to build the GIS basemap, they usually say, "That's the way we wanted to do it but we were afraid it would take too long." Oakland County's response to this statement, is that COGO may take longer than digitizing existing maps or flying aerial surveys, but it will pay off in the future because the county will never have to replace its basemap with a more accurate one.

About the Author:
Bob Daddow serves as project manager for Oakland County, Mich. He may be reached at 810-858-0490 (phone) or 810-452-9172 (fax).

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