GIS for Tax Purposes
Iowa county integrates GIS with existing automation
By Kevin P. Corbley

Black Hawk County, Iowa, is streamlining its taxation process and improving the accuracy of its assessments by developing a digital basemap and GIS. By the time implementation is completed late this year, the basemap will be integrated with existing tax administration and assessment software, making the county's taxation procedure one of the most fully automated in the nation.
    Similar to other counties, the tax cycle in Black Hawk involves four main offices: recorder, auditor, assessor and treasurer. Automation began in the early 90s when the county developed an in-house software system to manage the tax cycle. This system creates tax bills from assessments, keeps track of revenue collection, and then divides the collected funds among appropriate county agencies.
    While this management system was being developed, the county purchased a Computer Assisted Mass Appraisal (CAMA) package from Vanguard Appraisals Inc. of Cedar Rapids, Iowa. CAMA is a software system and database that takes inputs of key property information and calculates its value based on the fair market values of neighboring parcels.
    In addition, the assessor's office in Waterloo computerized its property record cards, which contain important information about each parcel, including its dimensions and physical description, a detailed report on structures as well as surveys and sketches.
    "All of this existing automation was the motivation for us to build the GIS," said Vicki Atkins, Black Hawk County assessor. "We had a wealth of information on all of the properties in the county and we wanted a way to integrate it so we could perform our jobs more easily and share the information with others."
    A GIS with a digital basemap was the next logical step, she explained, because assessment begins with mapping and always involves complex analysis of geographic, demographic, and statistical data. These tasks can be accomplished quickly in a GIS, dramatically reducing county staff time and saving taxpayers money in the long run.
    "Taxpayers will benefit because our office will become more efficient, and the assessments will be much more accurate," said Atkins. "If an assessment is challenged, we will use the GIS to show graphically how we arrived at a tax calculation."
    Three years ago, the assessor's office began visiting other counties in the Midwest to observe how they had implemented GISs for tax purposes. As a result, Black Hawk decided to purchase MGE software from Intergraph Corp. of Huntsville, Alabama, to develop its GIS. This package was chosen for its complex analysis capabilities and ready compatibility with existing software.
    The assessor's office contracted The Sidwell Co., a West Chicago, Illinois, GIS and mapping services firm, to develop the $1.6 million digital basemap and GIS and then integrate the new system with the CAMA and tax administration packages.

Creating the Basemap
Sidwell has managed the development of numerous GIS projects for cadastral and parcel mapping applications and says creation of an accurate, up-to-date basemap is critical to overall success.
    "Mapping is often the most manual part of the workflow in the assessor's office," said Brent Mainzinger, product development supervisor in Sidwell's information services department. "The basemap is an important element in the GIS because it is a pictorial link between the property and the parcel identification number, which represents its legal description."
    Sidwell's primary objective in Black Hawk has been to use recorded plats and surveys, existing maps and any other source documents available to create a parcel basemap on top of digital orthophotographs. These had been generated about a year earlier by Aerial Services of Cedar Falls, Iowa, which had performed an aerial survey of the entire county at the request of the Black Hawk Engineering Department.
    In the first phase of basemap development, Sidwell technicians went to the appropriate county offices to copy all existing parcel documents on microfilm. These were returned to the company's production floor where they and the digital orthophotos were divided into one-square mile information kits.
    Technicians used heads-up displays and MicroStation GeoGraphics from Bentley Systems Inc. of Exton, Pennsylvania, to draw parcel boundaries within these square-mile areas based on the legal descriptions found on the source documents. The lines were drawn on top of the orthos and saved as MGE files.
    "In some cases, technicians encountered disagreements between property cards and other documents," said Mainzinger. "We then requested the county pull deeds for the property so we could establish the correct parcel ownership and reconstruct its boundaries."
    As parcel maps are completed for each square mile, the technician adds features. Black Hawk has specified inclusion of 80 different map elements, such as government lot lines, water lines, rights of way, parcel numbers, lot numbers, dimensions, and subdivision names.
    A major benefit of using orthophotos as the backdrop for the parcel map is that it avoids the time-consuming process of digitizing planimetric features.
    Houses, sheds, and backyard pools are already visible on the orthophotos and therefore did not have to be added as a GIS vector layer.
    In preparation for the implementation of the basemap and GIS, the service firm also oversaw delivery and installation of new hardware for the system:
- an Intergraph GIS server with a RAID box,
- a Microsoft SQL Server for the tax database,
- three MGE workstations,
- upgrades for 12 other computers.

Multiple Feature Tagging and QC
Like a lot of governmental organizations developing GISs, Black Hawk expects to make its system accessible to other agencies and the general public via the Internet. In developing the basemap, Sidwell was able to take advantage of a new MGE feature called Multiple Feature Tagging that should make publishing GIS data on the Web much easier.
    Multiple Feature Tagging allows a single line on the basemap to carry pointers to several features of the GIS. For example, lines representing boundaries for lots, parcels, and subdivision boundaries may all coincide on the map. Instead of drawing overlapping lines, the technician simply assigns the same line different feature names which reside in the GIS database.
    "We used this extensively for the first time in the Black Hawk project. It really keeps the files sizes of the maps down and makes maintenance and display much more efficient," said Mainzinger. "This will make the maps much easier to access and display on the Internet."
    Sidwell also uses the MGE GIS software to perform quality control on the completed basemap files before they are shipped to Iowa. The software enables the technicians to write rules that govern the compilation and operation of the GIS basemap, for instance, specifying that all parcels must be closed and have an attached identification number in the database.
    "The software checks the basemap parcel by parcel looking for inconsistencies and making sure all features and lines conform to the mapping standards established for the project," said Mainzinger.
    In addition, a Sidwell senior mapper examines each feature visually and confirms that it agrees with the source material.

Integration with Legacy Systems
Sidwell has been delivering the completed basemap parcels piecemeal to the county and adding them to the GIS, which is already operational. Company technicians on-site have integrated MGE with the county's tax administration software by writing an interface program in Microsoft Access.
    The in-house package is programmed to identify changes to parcel records on a daily basis. For instance, information related to new property owners or divided lots will be flagged when they enter the system. The interface program searches the administration software every night and downloads all of these changes as ASCII files. These are loaded into the GIS, updating relevant tables. These two systems track a total of 500 columns of information.
    Sidwell delayed linking the GIS with CAMA until recently when the software developer released the assessment package as a Windows application, which made it much easier to integrate. The GIS will read assessment information directly from the CAMA package because the latest release of MGE software supports both RIS and ODBC database access.

Analyzing Tax Data
The assessor's office expects to use the GIS extensively for the property analysis work routinely performed as part of its tax assessment duties. Black Hawk is tracking values within neighborhoods by grouping similar properties.
    The GIS is being used to display these groups so that when an assessment official goes on site for a review, information on all of the similar lots in the neighborhood can be printed on one sheet for quick reference.
    "We will be doing analysis for many of our own projects," said Atkins, "but we also field a lot of requests from other county offices for demographic information, and this will assist in fulfilling them."
    One project conducted last year by a local university would have been ideal for the GIS had it been on line, Atkins said. The university was attempting to gather information on the locations, ages and conditions of all single family dwellings in Waterloo for a federal funding proposal. Without the GIS, the assessor's office had to print out thousands of paper sheets with descriptions of individual properties for the students to sort through manually.
    "We could have just given them a single map generated by the GIS," said Atkins. "It would have saved us and the students countless hours of work."
    County administrators agree the new GIS is too valuable a resource to keep to themselves. They plan to publish some information on CDs and eventually make it available over the Internet.
    In the near-term, however, once the GIS is fully operational, the assessor's office intends to link with the imaging system in the recorder's office. When a new deed is filed, it will be scanned so the property information is automatically entered into the GIS without manual inputs.
    "That will really close the loop," said Atkins. "Our entire tax cycle will be automated then."

About the Author:
Kevin Corbley is a consultant and freelance writer specializing in GIS, remote sensing and GPS. He is located in Denver and may be reached at 303-722-0312 or by e-mail at [email protected].

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