U.S.S. Monitor Artifact Scanning and Reverse Engineering
Anchors Aweigh! New High Speed Scanner Captures Nuances of Civil War USS Monitor Artifact
New Leica Scanning Technology Delivers a Bounty of Benefits for Non-Contact Data Acquisition
by Belinda Jones
The treasures that lie beyond the doors of The Mariners Museum in Newport News, Virginia are sure to capture the heart of any history buff. The museum is filled to the crow’s nest with prized artifacts that celebrate the spirit of seafaring adventure. Visitors from around the world experience over 60,000 square feet of gallery space filled Civil War ironclad USS Monitor artifacts and archives, paintings, small craft with rare figureheads, handcrafted ship models and much more. Perched on a 550-acre woodland park, the museum was recently the center of a major data acquisition effort to capture and digitally preserve a key artifact retrieved from the shipwrecked USS Monitor.
On a cold New Year’s Eve in 1862, the USS Monitor met a storm and sank sixteen miles off the coast of Cape Hatteras, North Carolina. In 1973, the wreck of the USS Monitor was discovered and soon many important parts of the ship were recovered from the underwater ruins. By 1975, the wreck of the USS Monitor was designated America’s first National Marine Sanctuary. The site is protected and managed by the National Marine Sanctuary Program of the National Oceanic and Atmospheric Administration.
From 1998 and 2002 NOAA and the US Navy conducted large scale diving operations to reinforce the Monitor’s collapsing hull and recovered hundreds of artifacts, including the anchor, propeller, steam engine, revolving gun turret, and guns. Today, the Mariner's Museum houses more than 1,100 artifacts and the stories of the unique vessels that engaged in the first naval battle between two ironclad warships, the CSS Virginia and the USS Monitor.
Dealing with antiquities that slowly erode over time, The Mariners Museum turned its eye toward high precision scanning technology to digitally capture its artifacts. One artifact on the priority list was the historic anchor, the first major relic recovered from USS Monitor underwater sanctuary. After 140 years underwater, the anchor's surface is very brittle due to its high iron content, and is preserved with a special chemical formula.
"For conservation purposes, our ability to perform current state vs. original state inspection is critical to preserving our high value cultural materials," states Marci Renner, Chief Conservator . "If a crack develops upon the surface of an artifact, we can determine if the situation is worsening. Once the digital data is archived, the integrity of artifacts like the anchor can be inspected on-demand with a very high degree of accuracy."
Data acquisition of historic relics has many challenges for the metrologist. First, the artifact cannot be touched by hand or instrument. Two, the anchor could not be moved or staged. And thirdly, the job would need to be accomplished during the normal museum hours due to very high security at the museum.
Jack Shry and Denny Warren of Leica Geosystems (Lawrenceville, GA) and senior metrologist Steve Hand of MAGLEV Inc. (McKeesport, PA) were not daunted by the two-day endeavor. Due to record-breaking data acquisition capabilities of the new Leica T-Scan, the team could digitally capture the surface very rapidly in a non-contact fashion. Gathering 7000 points per second from the anchor's intricate surface, the hand-held scanner allowed the team to capture the 3D object in a fast, unfettered manner.
The ultra-high speed scanner works in tandem with the Leica Laser Tracker, a portable coordinate measurement system (PCMM) used for industrial measurement and inspection applications. The LTD800 laser tracker yields the fastest measurement cycle in the business for high point density at 3000 points per second. Metrologists can acquire precision data within a measurement volume of up to 30m. The operator can use the handheld scanner to digitize both small and large objects, and gather millions of 3D points in just minutes with an accuracy of better than 100 microns.
Using the scanner, reverse engineering and inspection processes require much less time for set-up and object preparation, often up to a 50% reduction. Leica's unique ability to combine laser tracking functionality with probing and scanning capabilities in the largest measurement volume garners multi-faceted benefits in this type of data gathering environment. This same technology is being used by major manufacturers in aerospace, automotive, and general engineering industries who require portability, the highest precision, and non-contact measurement capability.
"The surface data acquired during this project was very comprehensive…very low in noise, no post processing, and the data was immediately available for view," states Jack Shry, Leica Geosystems East Coast manager. "In fact, at 7000 points per second, the end result looked just like a picture. We required only three setups due to the flexibility of the hand scanner. The scanner's four faces provide multiple angles of access to the object's face. With a laser tracking technology, you can develop a local coordinate system, then tap right into a larger coordinate systems."
The Leica T-Scan worked so intuitively that the Museum workers each had a chance to use the device and take part in the landmark project. The device provides user-friendly pre-alarm - a warning buzzer - to let the user know if they were getting close to breaking a connection with the tracker. Collecting highly accurate data in hard-to-reach areas to achieve total 3D coverage of the anchor was made easy by the tracker's ability to be relocated to various vantage points, and collect multiple data sets in the same coordinate system.
"When using the Leica T-Scan, you feel as though you are holding a brush and painting dimensions upon the anchor's surface, said Steve Hand. "The museum's staff could easily participate, and the museum patrons were also very interested in the process. It is a very enlightening visual experience to watch the real-time results on the computer monitor and see the most minute details on the anchor's exterior. The entire project took eight and a half hours of scan time. The accuracy was superlative."
At the end of the project, Hand returned to MAGLEV with anchor data in tow. The surface data accumulated from the scanning session formed the foundation of very detailed 3D computer models created by the MAGLEV team that can be used for measurement, documentation, animation, and archival records. This digital record of the anchor's construction can also be used to monitor the anchor's condition, and to reproduce physical prototypes for merchandising and exhibit purposes.
Hand said, "At MAGLEV, we conducted 0.5 mm processing of the data, and concluded with nearly 6.5 million triangles to represent the high definition surfaces. The data file was nearly 200MB in size.
The initial renderings and animations produced for the Museum were exceptional due to the quality of the scanned data. You could literally see the forging marks on the anchor."
The Mariners’ Museum and NOAA are working toward constructing and opening a new USS Monitor Center in March 2007. A full-scale replica of the Monitor warship will serve as the dynamic focal point of the Center . The Leica data acquisition work, and other scanning projects, will directly contribute to the Museum's ability to create exciting exhibits and rich visualizations of these historic artifacts.
"From a legacy standpoint," concludes Shry, " The Mariners Museum now has an accurate 3D CAD model that will enable them to perform best-fit operations years down the road to determine if the anchor has experienced damage or deterioration. You could process the data down to a 0.1mm level, and the slightest bruise could be detected. "
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Sidebar Information:
The Mariners' Museum
For over seventy years, the history of the ocean and its relationship with humankind has been told and displayed in one of the largest maritime museums in the world.The Mariners’ Museum, an educational, non-profit institution accredited by the American Association of Museums, preserves and interprets maritime history through an international collection of ship models, figureheads, paintings and other maritime artifacts. The Museum is open from 10 a .m. until 5 p.m. daily. Closed Thanksgiving Day and Christmas Day. For information, call (757) 596-2222 or (800) 581-7245, or write to The Mariners’ Museum, 100 Museum Drive, Newport News, VA 23606. The Museum can be reached on the World Wide Web at www.mariner.org.
Leica Geosystems AG
The Metrology Division of Leica Geosystems is a global supplier of comprehensive hardware and software systems to the industrial metrology market. Using state-of-the-art laser technology, Leica’s industrial measurement products make quality control, part mating, assembly and construction of large and small parts easier and more accurate than ever. Leica's Universal CMM combines laser tracking functionality with probing and scanning capabilities in the largest measurement volume. No competitor in the metrology marketplace brings this dimension to the shop floor. Leica’s laser tracker technology is most widely used, with over 1,400 installations worldwide. In addition there are about 1,500 Industrial Theodolite Systems in use which customers confirm the most accurate in their category. More information can be found at www.leica-geosystems.com.
MAGLEV, Inc.
MAGLEV, Inc., a Pennsylvania company, incorporated in 1990, comprised of and supported by numerous private and public entities. Its goal is to support leading technologies in large steel component fabrication and to lead the installation of the first commercial High Speed Maglev in the USA in Pittsburgh, and in subsequent phases to expand across the Region, State, and Country. Currently, MAGLEV, Inc. is performing research under contract to the Office of Naval Research. The Research Facility is located at 1000 Industry Road, McKeesport, Pennsylvania.
Participating Companies in this Case Story
Author: Belinda Jones, HiTech Marketing llc
632 West Pond Meadow Road, Westbrook, CT 06498
(860) 399-1147, belinda.jones@hitechmarketing.com
Contact Information: Leica Geosystems, Inc.
Metrology Division of Leica Geosystems, Inc.
Simona Gambini, Director of Marketing and Communications
Lawrenceville, GA
Tel. 800-367-9453, ext. 1611
Email: simona.gambini@leica-geosystems.com
www.leicageosystems.com/metrology
Contact Information: MAGLEV, Inc.
Steve Hand, Senior Metrologist
shand@maglevinc.com
(412) 948-1905 x6097
http://www.maglevinc.com
Contact Information: The Mariner's Museum
Marcie Renner, Title
100 Museum Drive, Newport News, VA 23606
Phone: (757) 596-2222
Email: mrenner@mariner.org
www.mariner.org
