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Home arrow News arrow American Surveyor Lidar Content arrow Scanning Deadwood   LiDARmag     

Scanning Deadwood Print E-mail
Written by Cyn René Whitfield   
Saturday, 27 October 2007

A 2.026Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

Not documenting an historic area like Deadwood, South Dakota in Lawrence County was a gamble. The city was named for the dead trees that were found in the narrow canyon (Deadwood Gulch) where the historic Main and Sherman streets were originally laid out. Cradled in a narrow gulch of pine-covered bluffs amongst the Black Hills, an entire city on the National Historic Register was sitting ripe for devastation by fire. The National Trust for Historic Preservation has placed the entire historic district on its list of the 11 most endangered sites.

Lessons learned of past historic main streets throughout the United States being lost forever was the driving factor of the City of Deadwood's decision to "preserve" its historic community through documentation. It was a lesson learned hard in 1878 when the city again rose from the ashes as miners, merchants, bankers, and saloon keepers began to rebuild. The city had even felt the effects of an earthquake in 1966.

In the spring of 2003, TSP Architects of from Rapid City, South Dakota and other support teams positioned themselves with Cyrax 2500 3D laser scanners to document 5,992 linear feet of building facades along downtown main street, approximately one-half mile on each side.

In the quarter century after the great fire, Deadwood had experienced an extraordinary building boom, and the gold-rich town created a sparkling gallimaufry of late nineteenth- and early twentieth-century styles. Eye-catching versions of the Italianate, Richardsonian Romanesque, Second Empire, Queen Anne, and classical revival are now part of historic downtown Deadwood. Many of the saloons, gaming houses and hotels on Main Street have Italianate features, and some of the facades suggest the false fronts that decorated the earlier, less substantial structures.

"No traditional method of documentation would give the detail of structures like these with elements of rough-faced stone and ornamental iron balcony," said Mitch Schefcik, one of the original team members that is now Optira, Inc. "We needed an authentic and exact documentation for the possible recreation of turn-of-the-century carefully restored architecture. John Wayne, Pearl Buck, Babe Ruth, President Theodore Roosevelt and others have left their marks here in this historic one-of-a-kind Wild West town. 3D laser scanning was the only clear option," said Optira, Inc., President/CEO Schefcik.

In 2003, the technology was fairly new. Cyra, maker of the Cyrax 2500, would advertise "You simply orient the scanner toward the scene, select the desired measurement area and measurement resolution, and then auto-scan. Complete surface geometry of exposed surfaces is remotely captured in minutes in the form of dense, accurate `3D point clouds', ready for immediate use."

"What is often overlooked is the importance of survey control when documenting using 3D laser scanners," said Michael Frecks, Vice President of Optira, Inc and a land surveyor for 29 years. "We felt it was important to involve a survey company that was local to the area for not only both familiarity but for commerce."

Deadwood's unique coordinate system was another reason to have local involvement. Black Hills Surveying, Inc. of Spearfish, South Dakota was selected for the job. The history of the area is one of a mining community whose land information from the late 1800s was built on a coordinate system based on the center of Homesteak Mining Company's Open Pit Mine and land management office in the late 1800's through the 1980's. In the early 1990s the City of Deadwood passed an ordinance that established this system as the official coordinate system.

Black Hills Surveying President Randy Deibert was instrumental in the establishing the more than 20 of the original monuments of the area, as well as creating a comprehensive topographical map of Deadwood Main Street for the historic reconstruction scheduled for the early 1990s.

"The Deadwood Coordinate System is an extension of the Homesteak Coordinate System which includes Mining District Monuments and a long history of coordinates for hundreds of existing parcels of land," said Deibert. "The horizontal values utilized this existing system which created an immediate GIS reference for the parcels. The vertical component was a result of the current FEMA bench marks used for flood plain management in the area."

Control was placed along the main street, as well as an additional control set inside the historic United Methodist Church. The building was marked for demolition. Its relationship to the district and recordation of its condition was the impetus for documentation of the entire main street. This demolition would prove to be a "test" scenario of the purpose of pre-documentation. The church was modeled in a 3D environment and virtually placed into the recorded scene through the use of laser scanners and survey control.

"The error in the control traverse is directly related to absolute positioning of the scans. But the scans have a relative accuracy of one-half inch to themselves, so control is very important, especially because there were 376 scan control points," said Frecks. Each of Deadwood's highly detailed 244 scans took approximately 15 minutes, requiring about 30 minutes for each of the 100 scan locations. To speed up the process, the team set up using two scanners facing opposite locations (northeast and southwest) simultaneously to capture the 77 building facades with control.

Black Hills Survey crews were one day behind the scanning teams providing control. A traverse of approximately 10 primary turns was used on the main street to provide control from the existing monuments of the local system. Additional side shots to all of the scanning reference points located on and inside the buildings were also collected. In total, the survey side of the project took eight field days, including a day and a half delay due to rain.

Four targets were placed at each scan scene to tie the scan data to the survey control. Each target was shot twice and the average value was assigned to the target. Upon completion the survey data was applied creating a database in real local coordinates.

The algorithm automatically computes pair-wise registrations between individual scans, builds a topological graph, and places the scans in the same frame of reference. The methods can be extended to automate the texture mapping process as well, to create both geometric and photometric realistic models.

Since the documenting of Deadwood, Optira, Inc has been at the forefront of historic documentation by keeping up with the evolution of 3D laser scanning technology through its newest adaptation of 4D embedded metadata. These Building Information Modeling (BIM) processes are to acquire building spatial data in three dimensions with high fidelity and low processing time and place the data into a "living environment". "The scans needed to be at a density to support maximum data mapping without running the cost too high," said Frecks.

The Deadwood Documentation Project was partially funded by the CyArc Foundation, located in the San Francisco Bay Area, as a premier pilot program. Since the documentation of Deadwood, CyArc has evolved as an archive and associated web portal that allows data to be accessed by site managers, researchers, students, and the general public.

"Preserving cultural heritage sites is an important challenge. These sites are subject to much abuse, from erosion to vandalism, and as long-lived artifacts, they have gone through many phases of construction, damage, and repair. Keeping accurate record of these sites using 3D high definition documentation and modeling technologies lets site managers and preservation professionals do a better job of cultural resource management. As visualization technologies, they provide tools for education allowing a wider audience to virtually see, learn, and tour these sites," said Ben Kacyra, founder of CyArk High Definition Network and the father of 3D laser scanning.

Cyn René Whitfield has been involved with marketing for land surveying and 3D/4D laser documentation for a combined 24 years. She is the Marketing Coordinator for Optira Group in Omaha, Nebraska and a serves on the Board of Directors for Landmarks, Inc.

A 2.026Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

 
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