A technician prepares to scan a portion of the mill building at Kennecott Mines in Alaska. The SX10 captured interior and exterior data at the site.
from setups on the glacial surface. They hope to combine the 3D data and images with historic photos to study the glacier’s shrinkage during recent decades. “In the 1930s you couldn’t see across the valley because the glacier was so tall,” Biddle said. While the SX10 team focused on the mill, Robicheau used the Trimble TX8 scanner to collect high-resolution data on the power plant interior. The interior scans could be tied to control points outside the build- ings, enabling the team to produce on-grid coordinates throughout the structures. The technicians used Trimble Business Center software (TBC) to combine the traverse and GNSS results with scanning data and images from the SX10. They used Trimble RealWorks software to process the TX8 scan data onto the project coordinate system and transferred the finished point clouds to TBC. Because the scans were tightly georeferenced in the field, registration and processing moved rapidly. Multiple scans could be merged and the teams created colorized point clouds for visualization and checking at the end of each workday. High-value visuals Data produced for the project will be used for more than stabilizing and rehabilitating the buildings. For example, for safety reasons the NPS has plans to drop the sagging tram cables to the ground. The imag- ing data allows them to see the conditions directly beneath the cables, which are roughly 30 feet above the surface. Georeferenced imaging will also help site managers assess deteriora- tion of the buildings. By capturing detailed photos at various points in time, it’s possible to produce empirical information on the scope and rate of change to a structure.
Cusick noted that geospatial technology improves the overall quality of the visual data. “It’s not unusual for engineers or archaeologists to capture data using cloth tapes and cellphone cameras,” he said. “The images from the SX10 match the quality of high-resolution, tripod- mounted cameras and exceed the capabilities of most cameras and photographers.” The geospatial approach also solves a nagging issue in managing large quantities of photos. Rather than working with high volumes of files (often indexed with an arcane naming system), photos can be linked to a specific setup or location. A simple click on a map can retrieve the desired images. The survey results can be shared with NPS cultural resources teams to improve visitor access to and understanding of Kennecott’s important sites. Visualization and 3D modeling can be used to increase public awareness and appreciation of historic sites while mitigating challeng- es associated with heavy visitation. To illustrate this, the technicians created a rough, street-level flythrough of the site immediately after the fieldwork. Cusick said the animation illustrates the capability to create a more refined virtual “tour” of the site. “The interpretive staff is very interested in this,” Biddle said. “We can use 3D scanning to provide virtual access and walkthroughs for people with visual or access limitations. Scanning and the associated software is helping NPS preserve our national heritage in both the natural and cultural environments.”
JOHN STENMARK, LS, is a writer and consultant working in the geospatial, AEC, and associated industries. He has more than 25 years of experience in apply- ing advanced technology to surveying and related disciplines.
58
csengineermag.com
july 2018
Made with FlippingBook Annual report