Earth Imaging Journal: Remote Sensing, Satellite Images, Satellite Imagery
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By Mladen Stojic, president, Hexagon Geospatial (www.hexagongeospatial.com), Norcross, Ga.

 

Potential Cover

The property appraisal process can present a host of business and technical challenges that can be supported by geospatial solutions. For example, by automatically comparing old and new image data, geospatial technology can detect new buildings, connected additions, swimming pools, parking lots, out buildings and more.

Technological advances notwithstanding, property appraisals are about people. Property owners want more frequent and accurate valuations to take advantage of rising real estate markets or, as the market falls, for possible tax savings. Appraisers get caught between property owners’ demands, an expanding urban society in which even those living in totally built-out locales are constantly remodeling or even demolishing structures to replace them with more up-to-date and valuable construction, and the demands of the revenue-challenged governments that employ the appraisers.

All too often, it’s the property appraisers vs. the changing world. Appraisers are tasked with the staggering job of keeping up with changes to every property. For example, Harris County, Texas, which includes the city of Houston, has about 1 million properties, and approximately 20 percent of them have to be assessed each year.

Geospatial Assistance

Homeowners are enthralled at seeing satellite imagery of their property via Google Earth. Now technology companies have been challenged to come up with different ways to marry aerial and satellite imagery, computers on the ground, and hand-drawn paper sketches and maps to offer solutions that aid the appraisal process, improve property record keeping and retrieval, and help derive valuation forecasts for budget building.

Aerial and satellite sensor capabilities developed during wars in Afghanistan and Iraq have been adapted for civilian needs, including those of property appraisers who seek geospatial help.

Computer-aided mass appraisal (CAMA) systems, which use algorithms to match inputs of property descriptions and comparable values with often-volatile market trends, have grown in capability. Such growth has fostered a demand for more ways to drive the process and direct the people who manage it.

Aerial and satellite sensor capabilities developed during wars in Afghanistan and Iraq, as well as the collaboration tools used to fuse them—often in 3D—to produce a timely intelligence product, have been adapted for civilian needs, including those of property appraisers who seek geospatial help to meet the following challenges:

  • Reduce field-appraisal trips and improve results of the on-site visits appraisers make.
  • Eliminate duplicate data entry between field appraisal data collection and input into CAMA systems.
  • Improve property valuation through accurate, up-to-date CAMA sketches in a geographic information system (GIS) for comparable analytics as well as property orientation and viewsheds available from a GIS.
  • Decrease citizen challenges, phone calls and appeals.
  • Manage large volumes of image data to support appraisal workflows

A Collaborative Approach

Change Detection (1)

Geospatial Appraisal provides appraisers with a tool they can use in the field or office to update property attributes and create accurate sketches in a geospatial environment.

Hexagon Geospatial recently partnered with Apex Software to help meet such demands. Besides saving customers money, the Hexagon-Apex partnership “can increase the valuation potential by having accurate and current georeferenced and oriented CAMA sketches in a GIS available for comparable analytics,” said David Holmes, a business development manager for Hexagon Geospatial.

To do so, the two companies created Geospatial Appraisal, which integrates Hexagon’s GeoMedia Smart Client tools with Apex Sketch version 6, a new Apex GIS utility, and optionally the Leica DISTO laser measuring tool, providing appraisers with a tool they can use in the field or office to update property attributes and CAMA sketches in a geospatial environment. This allows appraisers to avoid manually or digitally drawn “redlines” that identify changes.

Property Appraisal

Parcel Change Detection uses ERDAS IMAGINE to compare old and new image data to detect property changes.

With Geospatial Appraisal, CAMA sketches can be layered with satellite imagery and/or roof outlines, property record cards and even pictures of a building to ferret out discrepancies among the elements—all on a computer screen within a geospatial context. Property edits are captured and uploaded directly to a CAMA system, eliminating duplication and many of the errors typically associated with the manual process currently used in most localities. Such a solution can also cut administrative costs.

Hexagon Geospatial also offers a semi-automated Parcel Change Detection workflow using ERDAS IMAGINE, which compares old and new image data to calculate the probability of changes based on spectral values. Parcel Change Detection can pick up changes representing property additions, swimming pools, parking lots or even roof changes. By generating a priority list of properties that may have changed, appraisers can visit those first to better use their time and resources. Changed properties requiring new appraisals sometimes can be found with input from construction or remodel permits, but often improvements are made without a permit. Automated change detection helps appraisers catch them.

As population and property development grow, so do the records they generate, requiring users to spend many hours processing, retrieving and researching property records. To streamline such efforts, Hexagon Geospatial created an imagery data management and distribution system that uses ERDAS APOLLO, a comprehensive data management, analysis and delivery tool that allows an organization to catalog, search, discover, process and securely disseminate volumes of file-based and Web-enabled data. Streamlined data access speeds up appraisals as well as customer service processes by employing and managing geospatial workflows. Such technology allows users to streamline property appraisals and focus on what matters most. After all, the process is about people.

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