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By Will Smith, marketing manager, Pictometry (www.pictometry.com), Rochester, N.Y., and Phillip Merrill, manager, Digital Imaging, Sanborn (www.sanborn.com), Colorado Springs, Colo.

Technological advancements in aerial imagery continue at an aggressive pace. Such is the case for the use of traditional orthophotos combined with high-resolution digital, oblique imagery.

Merging Technologies
For years, orthophotos have provided precise information needed for geographic information system (GIS), field engineering, asset management, digital terrain model (DTM) data collection and other measurement/surveying applications requiring high accuracy. Besides providing “pretty pictures,” oblique aerial imagery hasn’t been critical in the GIS and mapping world because there was no way to measure it accurately.

In the mid-1990s, this began to change with the availability of digital sensors, direct georegistration and high-speed desktop computing. Taking advantage of these developments, a new approach to oblique digital imagery was developed that integrated geospatial data.

The idea was born at New York’s Rochester Institute of Technology, where Stephen L. Schultz was pursuing his postgraduate studies at the Chester F. Carlson Center for Image Science. He successfully combined high-resolution remote sensing equipment, geopositioning/orientation hardware and specialized computer software to produce

a system that could capture, display and measure oblique digital imagery. By using a patented process, the software was able to extract X and Y coordinates, as well the Z coordinate—a breakthrough in GIS technology.

Richard A. Kaplan, president and CEO of Rochester-based Pictometry International Corp., turned the technology into a product and created a marketing plan for this new form of GIS software and imaging. The emerging product provided a simplified way for measurements such as location, distance, height, elevation, area and other dimensions of buildings, properties and land features to be obtained from the digitally captured oblique imagery. Pictometry’s image-capture process enables every pixel to be mapped to a specific point on Earth. Combined with high-end digital elevation models (DEMs) or Light Detection and Ranging (LiDAR) technology, even more precise location data can be obtained. Pictometry’s software provides a unique approach to the Z coordinate, or height element, allowing users to obtain height and elevation measurements directly on the georeferenced digital, oblique images.

Primary Applications
Today, the growing use of oblique imagery, while uncommon in traditional geospatial applications, is being driven by a new set of users—primarily for public safety, 9-1-1, appraisal and land-use planning applications. These professionals find oblique image content far more intuitive and information rich than what they obtain from traditional orthophotography. Other benefits include the speed at which imagery of a given area (typically a county) can be captured, the ability to integrate the imagery with other third-party systems and the cost savings associated with the imagery’s use.

In the case of public safety applications, metric obliques provide many advantages, including on-the-way tactical planning, identifying the exact location of wireless calls, preplanning homeland security initiatives and rerouting traffic. One of the system’s first on-the-scene uses was by the Arlington Fire Department, which responded to the Pentagon incident on Sept. 11, 2001. Recently, the Sheriff’s Department in Monroe County, N.Y., became the first law enforcement agency in the nation to deploy metric oblique imagery of the county as a standard feature on laptop computers in every squad car.

Milan Svitek, GIS manager for the Los Angeles County Department of Regional Planning, has been combining uses for metric oblique imagery, orthophotos and GIS data.

“We have been able to successfully leverage the feature sets of new technologies, like our oblique data from Pictometry, with our GIS, spatial data, orthophotos and DEMs,” says Svitek. “As a result, we’ve enabled new groups of users for our county ortho and oblique imagery.”

The county will train hundreds of new users, ranging from appraisers to public works and land-use planning professionals, in ways to maximize its geospatial data and oblique imagery.

“Our role as GIS advisors and administrators of geospatial information continues to grow as new agencies participate in the use of our oblique visual database of county images,” explains Nick Franchino, Los Angeles County Department of Regional Planning.

With the integration of third-party GIS data and high-quality DEMs, the accuracy of the metric oblique imagery can be significantly increased.

“Ambiguities that are inherent with orthogonal views are eliminated by using the imagery,” says Richard Kotapish, GIS director for Lake County, Ohio. “Our Planning Commission GIS users have reduced land-use and subdivision field visits by 70 percent compared to those needed with traditional orthophotos.”
Other county departments, such as Property Appraisal and the Storm Water Management Agency, also use metric oblique imagery for their daily operations. In addition, the imagery has allowed the county’s SWAT team and narcotics agencies to optimally place officers during raids, providing details of entries/exits, fencing, windows and flat roofs.

Fusing metric obliques with certified mapping orthophotos enables clients to query mapping and visualization products with a single application. This enhancement will expose a variety of new users to the benefits of remote sensing. Eventually, such visualization solutions will allow the public to use raster content with a simple click of a mouse via the World Wide Web.

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