By Joseph Bartorelli, president and chief operating officer, Vertical Mapping Resources Inc. (www.verticalmapping.com), Scottsdale, Ariz.
 

In business for just three years, Vertical Mapping Resources Inc. (VMR) has built a reputation as a photogrammetric engineering and land information company that completes highly accurate aerial mapping projects ahead of schedule. Two large projects recently wrapped up in New Mexico and Arizona typify the business strategy that has created early success for the firm.
 

“We decided from the start to use all-digital processing and to choose one vendor as supplier of all components in the processing line,” says Vertical Mapping CEO Kurt Okraski. “This ensures that every software module is compatible and every system works together. This has been extremely valuable to us.”
 

In assembling its processing line, the firm selected Z/I Imaging hardware and software solutions from Intergraph Mapping and Geospatial Solutions, Huntsville, Ala. VMR’s commitment to state-of-the-art digital processing technology, especially auto-correlation of elevation models, has been a major factor in enabling it to complete projects quickly.
 

“Auto-correlation alone has cut our processing time from about four hours to just 30 minutes to produce the grid points in one elevation model,” claims Okraski. “That adds up to saving weeks’ worth of work in a large project.”

Satisfying Mapping Clients
A big time savings is exactly what Souder, Miller and Associates (SMA) wanted when it contracted VMR to map an 85-square-mile area around the village of Doña Ana, N.M. The Santa Fe, N.M.-based civil and environmental engineering firm had been hired by the Doña Ana Mutual Domestic Water Consumers’ Association to perform a preliminary design of a regional sewer and water treatment system.
 

The design had to be completed fast because partial funding for the $37 million project was available on a use-it-or-lose-it basis. SMA needed at least six months to generate the initial design for 120 miles of sewer line. In spring 2003, SMA asked VMR to provide black-and-white orthophotography, two-foot contours and digital terrain models (DTMs). The project required a spatial resolution of six inches and a map scale of 1:1,200 for the orthophotography.
 

“Orthophoto resolution and contour accuracy are critical in a sewer design, especially in a valley like Doña Ana that has a lot of construction obstacles,” explains Karen Perez, senior engineer at SMA.
 

According to Perez, agricultural areas such as Doña Ana often contain deep irrigation ditches that must be factored into sewer pipe design. The lines and pipes must be designed to run beneath the ditches, canals and other depressions. If the contours are inaccurate, the design may cause excavation work to penetrate an irrigation structure or come to the surface at the wrong spot.
 

VMR arranged for a subcontractor to fly the area with a Z/I Imaging RMK TOP 15 aerial camera in April 2003. Processing began as soon as the film reached the VMR laboratory. The final products were delivered to the environmental engineering firm by late August 2003.

“The accuracy of the contours and surface models is amazing,” relates Perez. “We have gone into the field and taken profiles of the irrigation ditches, and they match the contours. Between this accuracy and the resolution, which allowed us to find even the smallest ditches in the orthos, we were able to finish the preliminary design with far less field work than is usually required.”
 

A dramatic decrease in the need for quality control is what impressed Prescott, Ariz., city employees about the VMR products they received in the spring of 2004. The photogrammetric firm flew the town in November 2003 with black-and-white and color film, and finished delivering end products in June 2004—three months ahead of schedule.
 

“The deliverables are great because we don’t spend much time performing quality control,” says Jason Brown, GIS specialist in Prescott Valley’s Public Works Department.
 

Public Works is responsible for maintaining the town’s 23-seat GIS for use in multiple applications by several departments. Prescott Valley typically updates the GIS every three or four years with new planimetrics and topographic mapping and digital orthophotography.
 

In 2003, the department asked VMR to update the town’s data sets by providing new orthophotography, DTMs and one-foot contours. Another requirement was to update the town’s planimetrics features, such as buildings and roads with new housing subdivisions, and smaller objects, including utility infrastructure. The new maps were prepared at a scale of 1:480 and covered the 175-square-mile project area.

VMR began delivering the color orthos and contours in early spring 2004. While reviewing the new data, Public Works officials realized how outdated the older orthos were and how inaccurate some of the mapping had been.
 

“The high level of accuracy that we are finding in these new data sets really gives our people a lot more faith in the GIS products,” explains Brown. “When city engineers lay out street locations in a new subdivision, they need to know the source data is accurate, and we are really pleased by what has been delivered.”

Benefiting from Automation
Mapping customers are becoming increasingly aware of the many benefits offered by all-digital and automated photogrammetric processing. VMR confirmed that many people inquire into the firm’s use of advanced techniques before awarding a contract. What they find at VMR is a processing line built around the Z/I Imaging ImageStation SSK Professional system, which includes a package of applications for photogrammetric file management, stereo image display, feature collection, model setup and orientation, and DTM collection.
 

“Z/I Imaging has automated the parts of the process that don’t need operator brain power, so we can focus our time and expertise on those parts that do,” says Okraski.
 

Automation begins in the aircraft where the firm uses POS Z/I, an inertial position and orientation system that directly georeferences aerial images. The system integrates Global Positioning System (GPS) and inertial measurement with post-processing software to generate accurate position and orientation angles for the center of each image at exposure.
 

“It basically does the exterior orientations for the project so the entire AT block is set up and we can immediately import control points and start taking photo measurements,” explains Okraski.
 

Once the film is scanned, the data go into ImageStation Automatic Triangulation where image-point extraction and aerial triangulation are completed semi-automatically. For relatively large-area projects like Doña Ana and Prescott, VMR relies on the ImageStation Automatic Elevations module to generate elevation models through auto-correlation.

“Auto-correlation has really arrived as a practical technology,” says Okraski. “It just blankets the imagery with points, similar to [light detection and ranging technology]. But unlike LiDAR, you don’t have huge file sizes to deal with. … And if you collect break lines first, ImageStation Automatic Elevations won’t put points on them, which means there is less to clean up during editing.”
 

This is the step with which VMR significantly reduces overall project time. For example, the Prescott Valley project included 700 exposures and about 400 terrain models that had to be collected. At the requested grid spacing of 30 feet, each model contained 2,500-2,800 points. With manual collection, processing would have required about four hours per model, but ImageStation Automatic Elevations did each in 30 minutes, cutting 1,400 hours from the overall production schedule.
 

“You really see accuracy improvement [vs. manual collection] in imagery that is washed out, has sun glare or film-processing damage,” explains Okraski. “A human operator sees distortions on screen, but the computer sees the numbers in the histogram.  It compares tonal qualities of the histograms over three images at a time, and it just nails the elevation values.”
 

For smaller projects and complicated urban terrain, VMR sticks to manual collection of DTMs, elevation points and break lines using a module included in ImageStation. After processing has been completed, the data sets are fed seamlessly into ImageStation OrthoPro to generate ortho images in a single workflow environment.
 

Concludes Okraski, “There is no need for data conversion and no problem with incompatibility. … Everything fits together. When we started the business, we could have purchased less expensive processing components from a variety of suppliers, but we stuck to our concept of buying the whole line from Intergraph, and now we do amazing things with it.”        

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