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Home arrow News arrow American Surveyor Lidar Content arrow Digitizing the Legacy - Scanning Mt. Rushmore   LiDAR News     

Digitizing the Legacy - Scanning Mt. Rushmore Print E-mail
Written by Elizabeth Lee   
Saturday, 25 September 2010

A 2.137Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

"We are missing data on Washington's brow and cravat."

"Even with the data from the scans on the talus slope?"

"The angle is just too steep. We have to use the rig."

"What about the scans from Lincoln, or the chins?"
Two clicks brought up a different modelspace.

"No,the angle was too oblique to catch the front of Washington."

"We designed the rig to be ambidextrous for a reason."

This was the exchange that ultimately led to the Leica 6100 being suspended upside down from a specialized rig developed to position the scanner against the presidential faces of Mt. Rushmore...

The problem: we didn't have enough data on Washington. We needed a revolutionary idea to complete the scan of the hero of the American Revolution. It was Day 13 of the first comprehensive laser scan of America's most recognizable faces. Gathered in the data command center were Douglas Pritchard of the Glasgow School of Art and the Centre for Digital Documentation and Visualisation (CDDV), Justin Barton and yours truly, both from CyArk, the non-profit working to digitally preserve the worlds most important cultural heritage sites.

Doug's scanning expertise goes far beyond the work at Mt. Rushmore to other great projects like Rosslyn Chapel in Scotland and the Schoenbrunn Palace in Vienna. Leading the Scottish CDDV team, Doug had planned and executed all scans of the mountain. While Doug coordinated the scanning teams and locations on the mountain, Justin had been registering and reviewing data. Now, with the project almost complete, the two were working together to identify where these last critical scans needed to take place. After much discussion, the group decided to "pull a 180" and position the laser scanner upside down to complete our scan of President Washington.

Thirteen days earlier the Scottish CDDV and Californian CyArk teams had arrived in Rapid City, South Dakota to kick off the first international project of the Scottish 10 as part of the CyArk 500 (see note at end). The project brought together a diverse team of surveyors, architects, archaeologists, Harley-riders, ex-military personnel, interpretive rangers, historians, film makers, Americans, Canadians and Scotsmen. It was put in motion in October of 2008, when NPS Mt. Rushmore staff approached CyArk about a solution for digitally mapping the monument for preservation as well as educational and interpretive reasons. Discussions between the park and CyArk continued in the development of a plan, when in April 2009 the Scottish government made the commitment to help CyArk and the National Park Service. This commitment came after CyArk founder Ben Kacyra met with then Scottish Minister of Culture, Michael Russell.

Upon learning of the CyArk 500 Challenge, Russell was inspired to help the cause through the creation of the Scottish 10 within the CyArk 500. Through the Scottish 10, Historic Scotland and the Glasgow School of Art would combine expertise to form the CDDV. The CDDV is responsible for the delivery of the Scottish 10, the digital preservation the five UNESCO world heritage sites in Scotland, and five international sites. Mt. Rushmore was selected to be the first international site. Following a formal announcement of the project at a July 4th celebration at Mt. Rushmore, the teams got to work in planning the monumental undertaking.

The first step in the project was to establish a site wide control network. The network was developed and executed locally. The Rapid City branch of RESPEC Engineering installed and located the control network on the mountain. Wyss Associates, Inc. Installed and located the control network throughout the park grounds. RESPEC Engineering was also responsible for the integration of the two control networks through five common points throughout the park. The placements of points on the mountain were particularly challenging, with some of the points only being accessible through the help of the NPS Rope Access team and the use of secure lines and harnesses.

The majority of the control network was completed in April 2010. Additionally, temporary control was established during the terrestrial scanning portion of the project. The temporary control in combination with the network was used to locate scanning targets and geo-reference the laser scan data sets to assure optimal accuracy.

When the teams from CyArk and the Scottish CDDV arrived in May, they brought an array of scanning technology to provide both engineering-grade data for tasks such as rock-block monitoring, analysis, and site resource management, as well as a base data set to create virtual tourism and educational materials for public outreach and data dissemination. Complete coverage of the sculpture was a necessity for the engineering and interpretive needs of the park, therefore, it was critical that all surfaces be scanned at a high level of accuracy and resolution.

A special tripod rig was designed by CyArk, engineered by Hermanson Egge Engineering, and manufactured by All Metal Manufacturing locally in Rapid City. The rig was used to capture views of the sculpture that could not otherwise have been obtained. The biggest design challenge was to minimize the vibration and deflection characteristics of the tripod rig. Hermanson Egge Engineering was able to meet the stringent deflection and vibration characteristics using lateral bracings. The weight of the rig was also critical in the design, as it had to be as light as possible for easy maneuverability by the NPS Rope Access team. The rig was ultimately made from aluminum tubes instead of heavier carbon steel. What arrived at the site was a piece of engineering artwork, complete with a beautiful bright yellow powder coating.

With five scanners, 11 DSLR cameras, a huge supply of targets and tripods, and the newly constructed tripod rig, the team was ready for anything when they arrived on site in May. Unfortunately, the team's arrival at Mt. Rushmore coincided with several inches of snow. In addition to the snow, while on site the team experienced everything from rain, to snow, to heavy fog, to brilliant sunshine, to tornado warning winds, to hail the size of golf balls, to perfectly calm days. It certainly kept things interesting. Thankfully the team was flexible on their work hours, even starting as early as 5:00 a.m. to make the most of the good days.

Given the snow and rain the first week of the project, the only thing to scan was the interior of sculptor Gutzon Borglum's studio. This data will be used to create a tour of the studio and Borglum's scale models used to design the sculpture. Borglum designed on the scale model in his studio and carried out his vision on the mountain. Although Borglum's model of the sculpture shows the presidents sculpted complete to their waists, that amount of detail on the actual sculpture was never completed. The scans and video fly-throughs created from the data will be particularly useful to the park for interpretation during the winter months when the studio is closed to the public.

Through the rest of the two weeks on site, the team captured 224 scans, over a hundred of those on the mountain. The project deployed up to three capture teams operating five scanners at once, in various locations throughout the park and on the mountain. Four Leica manufacture scanner models were used: the ScanStation 2, the HDS6000, the HDS6100, and the new ScanStation C10. Each scanner model was strategically placed within the site to utilize its unique strengths; for example the ScanStation 2 with its long-range capabilities was used along the base of the mountain. The speed and dense data capture abilities of the 6000 and 6100 were used to capture all of the details in the canyon behind the sculpture and throughout the park grounds. Because of its blend of range and speed, the C10 was used as the workhorse atop the mountain for wide-view scans of the sculpture.

The onboard controls on the C10 and 6100 were essential to using the scanner in precarious positions on the mountain. In one setup location, the NPS ropes team and Douglas Pritchard of CDDV repelled with the scanner from atop the monument down to the top of Washington's shoulder. With the scanner secured on the shoulder and the scan settings selected, Pritchard and the ropes team then repelled off the side of the shoulder to avoid obstructing the scan.

To ensure accuracy and complete coverage of the mountain, a data command center was set up on site, and all team members were equipped with two-way radio systems. CyArk's Justin Barton used Leica's Cyclone software to do daily registrations of the data. This allowed the scan-team members on the mountain or on the visitor's trail to radio the command center for up-to-date information on the scans and instant feedback on proposed scanner setup locations.

At the end of the two-week period, the team had achieved incredible results. Not only had the team captured the mountain, but the majority of the park had also been mapped in 3D. The initial registrations were looking really good, with just a few areas missing. Committed to see the project successfully completed, several team members extended their stays in Rapid City to execute the final scans. It was ultimately decided that the final necessary scans would be done with the tripod rig. The team had already executed several scans with the rig and achieved good results, so final scans were not considered to be a problem. There was one catch. The scanner would be inverted on the rig, hanging the machine upside down from Washington's brow, several hundred feet above the ground.

The team pulled it off without a hitch. Arriving at the park at 5 a.m. that morning, the team ascended the mountain as the sun was coming up. After rotating the plate that held the scanner 180 degrees, the scanner was placed into a special locking tribrach and positioned on the rig just behind Washington's head. Then the ropes team went to work. Exchanging technical commands, the team lowered the rig into position on Washington's brow. Once in place and secure, the command was given and Doug Pritchard controlled the scanner from a laptop within WiFi range. The results were incredible. With final scans complete, the ropes team utilized the park high-line system to safely transport all equipment off the mountain.

When combined with the other scans of the project, these final scans resulted in the first comprehensive documentation of Mt. Rushmore. With the capture of this American icon complete, CyArk and Scottish teams are now at work creating the engineering and educational deliverables to supplement the laser scan data in the CyArk archive. There Mt. Rushmore will sit alongside world treasures from around the globe as the team takes on the remaining sites in the Scottish 10 and works toward the completion of the CyArk 500.

The Scottish 10 is a collaborative project between Historic Scotland, the Glasgow School of Art Digital Design Studio, and CyArk to digitally preserve 10 significant heritage sites.

The CyArk 500 is a global effort to digitally preserve 500 of the world's most important heritage sites.

The Mt. Rushmore Digital Preservation Project is a five-year partnership between the United States National Park Service and the Kacyra Family Foundation/ CyArk. The laser scanning portion of the project was made possible through the generous contribution of the Scottish Ministers as the first international project in the Scottish 10.

Originally trained as an archaeologist, Elizabeth Lee has conducted fieldwork for CyArk all over the world. Prior to joining CyArk, she founded the UC Berkeley/CyArk Visualization Lab and served as instructor for the UC Berkeley/CyArk Internship Program. Ms. Lee currently directs all aspects of CyArk's digital preservation project work and development, as well as professional development, training and university outreach.

A 2.137Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

 
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