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Cadastral GIS of Real Value

Cadastral GIS applications, while not as glamorous as GIS applications for emergency response or law enforcement, enhance the performance of the assessor's office and often provide the foundation for the development of GIS throughout a local government.


Tax maps maintained as part of a GIS are more easily updated,

Cadastral data defines the geographic extent of the past, current, and future rights and interests in real property and the spatial information needed to describe that geographic extent. These rights and interests are contained in land record documents.

The cadastral data for a county, known as the tax assessment role, is maintained by the county assessor's office. Assessors do not determine tax rates, nor do they collect or figure taxes-they value real property for taxation purposes. This ensures the equitable distribution of a community's tax burden.

Property taxes are the major source of revenue that allows local governments to provide community services such as fire and police protection. The quality of the work performed by this office directly impacts the financial security of a community.

Tax maps were originally drawn by hand on Mylar or linen. These maps were difficult to keep up-to-date and cumbersome to store and retrieve. Multiple copies of maps sometimes contained different or conflicting information. Tax maps maintained as part of a GIS are more easily updated, organized, and shared across departments in a local government. Parcels can be linked to data stored in a Computer Assisted Mass Appraisal (CAMA) system, a widely used system for storing tabular information on real property.

Working Better and Smarter

GIS also benefits assessors by improving the quality of valuations. More factors relating to each property can be considered when determining value. Instead of hunting through paper maps or searching CAD documents, an assessor can query and not only find the parcel immediately but also access related information that previously was kept in separate tabular databases or in filing cabinets. Square footage and acreage calculations can be performed on the fly.

"Location, location, location," the mantra of real estate agents, holds true for assessors as well. Knowing the location of the subject property in relation to factors such as flood zones or water frontage improves valuation. By querying the GIS, assessors can identify all properties with similar use codes, sizes, locations, or other features that affect value in a specified area.

GIS is also a tool for working smarter. Thematic mapping makes it easy to spot such things as disparities between selling prices and assessed values or missed assessments. Land and building values can also be analyzed by neighborhood to help identify areas of concern. Homogeneous areas can be identified so that mass appraisal techniques can be used to streamline work.

Working smarter extends to the management aspects of running an assessor's office. GIS can help manage personnel and chart work flow. By using ArcView Network Analyst with ArcView GIS or the network module of ArcInfo, assessors can be routed to inspections in the most efficient manner.

GIS also improves assessor response to tax relief requests. Many county governments have developed public access applications that allow property owners disputing tax valuations to find out the values of other similar houses in their area. The Bexar Appraisal District in Texas created the Customer Query System, a countertop application that saves time for both staff and property owners by letting owners quickly search for comparable sales. For many, valuation concerns end with this information. In cases when valuations are contested, GIS provides valuable tools for assessors defending valuations.

Serving Property Data

cost surfaces

Thematic mapping makes it easy to spot such things as disparities between selling prices and assessed values or missed assessments.

Internet Map Server technology is a very cost-effective method for getting up-to-date property information to both the public and other municipal agencies, departments, and groups. The North Metro I35W Corridor Coalition, a group of seven Minnesota counties, has worked with Esri business partner PlanSight LLC in developing a 55,000-parcel database and online data warehouse, atlas, and custom desktop mapping applications that share parcel information.

In addition to the very crucial role of the assessor's office in revenue generation for local government, assessor data is often the basis of many enterprise GIS implementations. Parcel information supplies the location information, which can be combined with databases in the planning, building, and revenue departments of a city.

The Newest Reason to Use GIS: ArcGIS

ArcInfo 8 has given assessors even more reasons to use GIS. The latest release of ArcInfo improves data management with seamless ArcSDE layers and ease of use through ArcMap and ArcCatalog. The desktop environment, with a familiar Windows GUI, can be easily learned by former CAD users or persons new to GIS. Users can be highly productive by taking advantage of tools such as Parcel Editor. Using ArcMap templates greatly automates the creation of assessor map pages.

The release of ArcInfo 8 and the ArcGIS geodatabase object-modeling environment has allowed the creation of data model templates tailored for specific industries. Data models are being developed for hydrology/water resources, roads/transportation, energy networks, biodiversity/conservation, environmental facilities, forestry, and land parcels. The data model is part of a parcel solution, ArcGIS Parcel, engineered by Esri and its business partners.

Developing ArcParcel

A consortium of companies and users in this industry is helping to develop a model that really works and will extend the core platform of ArcGIS. The data model will help users manage land parcels. SDS and NovaLIS, Esri business partners and members of the Parcel team, are defining the core parcel editing requirements for ArcInfo. These companies have formed a strategic partnership and will develop land records management tools that will be included in SDS and NovaLIS solutions. The parcel data model is open and will be shared through a geodatabase template and publicized in an Esri book, sample database, and UML diagrams.

The ArcSurvey Extension

Cadastral GIS will also be supported by the development of ArcSurvey. This extension to ArcInfo on the desktop introduces a measurement data format and will provide a unified system for working with measurements and features at the same time in the same environment. Cartographic elements and survey objects can be viewed at the same time. ArcSurvey will support multiple coordinates for the same point-one set of current coordinates and many historical coordinates.

new course

Students enrolled in GIS Applications for Tax Assessors will learn to apply common GIS technical skills to solve real tax assessment problems.

Support for cadastral GIS includes a new course offered by the Esri Virtual Campus. Students enrolled in GIS Applications for Tax Assessors will learn to apply common GIS technical skills to solve real tax assessment problems. "Introduction to Tax Assessment," a learning module in this course, may be taken at no charge.

More than ever before, GIS is the best choice for creating and maintaining cadastral information. In the ArcGIS environment users have a robust data model, superior query and mapping functionality, productivity tools, and the ability to share data over the Internet or organizational Intranets.


For more information on Cadastral GIS, contact
Steve Trammell
Esri Cadastral and Land Record Solutions Manager
Tel: 909-793-2853, ext. 1-2366

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