ArcNews Online

Spring 2002
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County of Los Angeles' Assessor's Office

Web-Based Property Assessment System Implemented with GIS

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Results of a search on a selected parcel.

For forward-thinking government entities like the County of Los Angeles' Assessor's Office, a revolution is taking place. Agencies are leveraging the Internet to serve constituents with valuable information about their communities and at the same time saving money, time, and resources. It's simply government operating at maximum efficiency. A key part of this revolution involves Internet GIS.

The Los Angeles County Assessor's Office is one branch of the County's Property Taxation System. Other branches include the Offices of the Registrar-Recorder, Auditor-Controller, and Treasurer-Tax Collector. The Assessor's responsibilities include serving the public, locating and identifying ownership, establishing values, completing an assessment roll, and applying all legal exemptions. Under the County Assessor's Office is the Assessor's Mapping Services Section.

For decades, the ownership and property tax data sets were recorded on thousands of paper maps. These maps span Los Angeles County, which is the most populous county in the nation and is larger in population than 42 states in the United States. Los Angeles County's approximately 9.9 million residents live within its 4,083 square miles, making it one of the largest counties in terms of area as well. In the past, property and tax maps were only available to citizens who visited the Assessor's offices and made requests for hard-copy information.

The Assessor's Mapping Services Section began automating its map-making and editing efforts with GIS in the late 1980s. Through the years, the organization grew and matured as a GIS site, and in 1997, Mapping Services acquired ArcIMS with the goal of providing data more easily to the public via the Internet.

"We wanted to provide a service to constituents that made parcel and property value information available so that they, in turn, could make informed decisions," says Richard N. Quacquarini, chief cadastral engineer, Office of Los Angeles County Assessor's Mapping Services Section. "We wanted something that was intuitive and very user friendly and provided the targeted functionality whether a user has a slower dial-up connection or a faster broadband connection."

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Image of the Assessor's map showing a selected parcel.

Also integral to their two system configurations are ArcGIS, ArcSDE, and ArcView 3.2; one system is on-site providing production needs, and the other is off-site providing Web applications.

The Assessor's system is called the Property Assessment Information System (PAIS). Users access PAIS through a standard Web browser to research assessment information for individual parcels, print Assessor's maps, and search for sales within the past two years. Users can pan and zoom and view indexed parcel information including property values, parcel numbers, sales data, and more.

Whether running a query based on a parcel number, address, or street intersection or merely panning and zooming around a map, users can quickly access linked Assessor's information via digital maps on the Web. The Assessor contracted Esri to help in the development of PAIS, which includes data from Rand McNally's Thomas Bros. Maps and the County Department of Public Works and a link to the Treasurer-Tax Collector's Web page.

"The Web site lets a real estate agent select a subject property and then buffer out 500 and 1,000 feet or one-fourth, one-half, and one mile to identify all properties that have sold in the past two years," says Steve Trammell, Esri cadastral solutions manager. "Real estate professionals account for a significant amount of the public service counter traffic because they are looking to establish acceptable buying and selling prices on a property."

According to Trammell, a real estate agent can identify comparable properties (with similar square footage, bedrooms, and baths) to determine a baseline selling price. These professionals would normally have to telephone the Assessor's Office or visit the Registrar-Recorder's Office to get this kind of information.

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Selecting radius buffer (500 foot to 1 mile) to limit search for sales.

PAIS features a seamless GIS parcel map base with links to scanned versions of the actual hard-copy assessment maps. The response time on the 2.3 million parcel GIS database is very quick, and users can quickly link to a scanned map for legal description information and lot dimensions.

"It's an example of true public access with ArcIMS providing the technology architecture for access to very detailed map data," adds Trammell. "This is a very successful site and represents a huge savings in public counter labor costs."

In October 2001, there were four million page views with 1.4 million map requests. This represented 80,000 actual visits to the site by 20,000 unique visitors.

For more information, contact Richard Quacquarini, chief cadastral engineer, Office of Los Angeles County Assessor (tel.: 213-974-7351, e-mail:

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