Scanning the ‘Black Dragon’

USS New Jersey continues to make history with full-scale digital documentation effort.

A 3.854Mb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE

Commissioned in 1939 for naval operations during World War II, only four Iowa-class fast battleships were completed. The first of these, the USS New Jersey–also known as "Big J" or the "Black Dragon"–is the most decorated battleship in naval history, serving in WWII, the Korean War, the Vietnam War (she was the only battleship to provide support in that war), and she even participated in U.S. military operations during the Lebanese Civil War.

New Jersey was decommissioned for the last time in 1991, after a cumulative 21 years of active service, and (like the rest of the Iowa-class battleships) is now operated as a maritime museum in Camden, N.J. The battleship currently receives about 100,000 visitors annually, mostly for "turret tours" that include mock firings of some of New Jersey’s great guns–guns that, in the battleship’s prime, could hit targets up to 23 miles away.

100,000 visitors would be a lot for many attractions, but that’s about half the number of visitors that New Jersey received when she first opened, and battleships are extremely expensive to maintain. So the Battleship New Jersey Museum is always looking for ways to improve access and encourage attendance, while also facilitating ship maintenance and historical preservation.

On Aug. 19, 2014, the museum worked with Leica Geosystems and South Jersey geospatial services firm Haag 3D Solutions, LLC, to embark on a digital documentation process, beginning with a large scan of the New Jersey’s deck, a long internal corridor dubbed "Broadway," the Number 2 Gun Turret, and portions of the exterior hull. It’s believed to be the first large-scale scan of an American battleship–which means that more than 70 years after her 1943 christening, the USS New Jersey is still making history.

A Volunteer Effort
The idea for the project began with Leica Geosystems’ technical sales representative Frank Lenik, PLS, Area 2 director for the National Society of Professional Surveyors and an active participant in the New Jersey Society of Professional Land Surveyors. When Lenik learned that the West Jersey chapter of the society would be celebrating its 150th anniversary in September 2014 aboard the iconic battleship, he saw an opportunity to turn the event into something bigger.

"In reserving the battleship for the anniversary event, we learned that we would have access to the ship for the entire day," he says. "That led to the idea of creating a half-day workshop for surveyors and engineers focused on state-of-the-art 3D data capture and monitoring solutions. Pushing that concept even further, it seemed like a great opportunity to use some of the solutions highlighted in the educational event to digitally document the battleship."

Lenik shared his idea with Rob Ashley, director of field operations for Haag 3D Solutions, and Christopher Zmijewski, the firm’s vice president, who readily enlisted in the project. Haag 3D Solutions has digitally documented a number of historic structures, ranging from locally significant buildings to national monuments, as well as complex industrial facilities, so scanning the battleship was perfectly in line with the company’s capabilities.

An all-volunteer team was quickly assembled between the two organizations, with a survey control crew, two dedicated photographers and three scanning crews assigned to different sections of the Battleship. The team decided to use high-density 3D laser scanning performed with a Leica Geosystems HDS 7000 and two Leica ScanStation P20 scanners, with control surveying and scanning performed by a Leica Nova MS50 MultiStation and high-dynamic range photography gathered by two Canon 18 megapixel DSL cameras. This combination of highly detailed surveying and scanning with high resolution photography would create multiple use scenarios for the museum.

How Do You Scan a Battleship?
Scanning a battleship presents some obvious and not-so-obvious challenges. One challenge is that the ship is constantly moving due to swells and tides. However, Ashley and his team found ways to cope. "When we were actually on the ship, movement wasn’t a big problem–everything was moving together, of course, and so movement didn’t affect our work," Ashley says. "And we found that the scanners’ dual-axis compensators could keep up with the rise and fall due to swells."

But scanning the hull exteriors was another story. The USS New Jersey moves about 6.25 feet up and down in the course of a typical day due to tides, and there is horizontal movement as well, as the battleship moves back and forth on mooring lines. And since hull scanning was done from the adjoining dock, this movement had to be accounted for. "The best we could do was to time the hull scanning for slack tide, when there would be less movement during the hour setups that we needed," Ashley says. "Still, it wasn’t perfect–you can see the effect of movement in the final point cloud. With more effort here, we should be able to improve."

The team only attempted to scan from the dock on the New Jersey side. There was a plausible setup on the Pennsylvania side of the Delaware River, but it was 1,800 feet away; a scan at adequate point spacing would be so slow that movement would be a major factor. If the New Jersey goes to dry dock within a few years, precise hull scans can then be performed and registered with all the work done on the interior and deck.

Another challenge was the battleship’s cramped areas and long, narrow corridors, which are "never fun to survey" according to Ashley. These corridors and small rooms are festooned with hatches, levers, bolt heads, gauges, dials and hundreds of other important details–even projectiles the size of kitchen stools stored in already crowded walkways. The scanning teams had to use 144 scan setups to gather sufficient detail and apply several hundred paper and spherical targets to aid registration. And of course, scrupulous survey practice was required.

There was also the complexity of four scanning teams working simultaneously on separate portions of a long, narrow ship, using three different scanner models. It helped that all the scanners were made by Leica Geosystems. "It got slightly complicated, but there were no problems with registration due to the different scanner models," Ashley says. "We actually registered the work of each scanner separately, and made sure there was sufficient overlap between each team’s work to join up the resulting eight `mini-registrations.’ (Leica’s point cloud processing software) Cyclone has a limit box tool that helped us to check for any `doubling’ of points in overlapping area, which would have indicated registration or control issues."

Less obvious challenges included tourists walking about in the same areas work was being done, along with a Jimmy Buffett concert being held in the stadium adjacent to the ship. Fortunately, the tourists proved to be not too big an obstacle. "We were able to start early and get some complex areas done before visitors arrived," Ashley says. "We did have to do some cleaning later, where people walked through while we were scanning, but Cyclone has a good algorithm for that, and it went quickly."

Easier Access with 3D Visualizations
It was a hard day’s work, followed by the difficult tasks of processing and registering five billion points into a coherent cloud, complete with photorealistic surfaces. But it was a rewarding day too. "The museum operators were very appreciative, and they even let Frank and I fire one of the big guns," says Ashley. "We didn’t get to use an actual projectile, of course, but 30 pounds of powder makes a very satisfying bang!"

There was also the satisfaction of being so tangibly involved with the preservation of a living historical artifact, a machine of war upon which thousands served, and many died–including 790 officers and men in a single storm, the infamous Typhoon Cobra. "Leica Geosystems is so pleased to have been part of this project," says Lenik. "We’ve helped with the scanning of many compelling structures, of course, but something about the USS New Jersey seemed especially important to me–maybe it’s the battles she fought and won, or the fact that she is so obviously a lethal weapon, but just being on her was a thrill, and helping to preserve her is an honor."

The Iowa-class battleship USS New Jersey is decommissioned now, and one hopes that her like is never needed again. But even now she serves, as a reminder of a difficult and dangerous time and as a memorial to those who risked so much in service of our nation’s highest ideals. The volunteers who served on Aug.19, 2014, were also doing their part, by helping to preserve an honorable legacy and making it more accessible to others.

The data is being used immediately for maintenance purposes. "Right away, we were able to give the museum a board layout of the main deck," says Ashley. "The main deck is in disrepair, and restoring it will be a multimillion dollar operation. Our work will help them to do the work in a historically accurate manner, and should also help to trim costs." And also, for the first time, the museum will be able to produce accurate sections and models of the battleship’s scanned portions, aiding all future work in these areas.

Access has always been an issue for museum operators. Many of the New Jersey’s passageways and gun turrets are rather cramped, making handicap access difficult or impossible. "The gun turret we scanned, number two, has only been open for tours for 18 months," Ashley explains. "We scanned all five stories, including the elevator, the projectile storage rooms, the operating room for targeting and firing, and of course the guns themselves. With that work completed, and the high resolution photography, it’s now possible to create a virtual tour of the turret. It’s a ways off, and we’ll be educating the museum on ways to use all the data, but it’s good to know that full accessibility is now a possibility, opening up the battleship to everyone interested, including disabled naval veterans from that era."

And the battleship will also be used for training surveyors. "On the day we did the work, we only got to about 15 percent of the battleship, so we’ll be going back," Ashley says. "The museum will be allowing us to use the ship as a training facility, so the work we do will benefit everybody involved. There are plans to take the ship to dry dock in a couple of years, so that will be a good opportunity to get really accurate external hull scans, which we’ll be able to merge with all the work we’ve done so far."

Angus W. Stocking, P.S. is a licensed land surveyor who has been writing about infrastructure since 2002.

A Solid Workflow for Big Laser Scanning Projects

At Haag 3D Solutions, big scanning projects have become routine and scanning crews are often on the road for days at a time working on complex interiors, such as factories and plants, or large scale topographic projects. The firm has developed a sturdy data workflow to ensure quality and to keep their suite of scanners–and staff–working continually, with little down time. Director of Field Operations Rob Ashley shares a few tips:
Scanning stations are always preplanned with plenty of overlap to ensure good registration. "On big projects especially, where we might have two or more scanners working at once, we not only plan overlaps within the stations of the individual scanners, we also plan big overlaps between the various scanners being used," says Ashley. "That way, after we assemble the multiple point clouds from each scanner into `mini-registrations’, we’re able to assemble those mini-registrations into one big cloud with plenty of ways to check registration quality."
Organizing millions of points is always a chore, especially when multiple scanners are used on a project, and Haag has developed a couple of methods that work. "The easiest way to identify which points are from which scanner is to use prefixes in the file name," Ashley explains. "In our older scanners, like the Leica HDS 7000, you can set a prefix in the field. For newer scanners like the Leica ScanStation P20, we find that we have to do some renaming in (Leica) Cyclone Navigator–that can be a little tedious, but it’s worth it." Another convention developed at Haag is to use dates as prefixes; this is especially handy on multi-day projects. And on interior scans of multi-floor buildings, floor numbers are often used as prefixes.
Field processing of scanner data is minimal; there is more emphasis on downloading the data at the end of each day, backing up data on portable hard drives and importing into Cyclone. "That way, I can check for errors first thing in the morning," Ashley says. `Errors’ in this context are points that fail to download due to, for example, a scanner going out of level tolerance during a scan. "If we did a hundred stations in a day, I want to see a hundred downloads," Ashley explains. In some cases, on very long projects or during extended travel swings, hard drives will be shipped back to the office from the field.
Daily downloads, screened for errors, allow Ashley to wipe the internal hard drives of scanners before each day’s work. "We’ve learned over time that if we want to keep our scanners working continuously, the instrument has to work flawlessly," Ashley explains. "Keeping the internal hard drives clean is an important part of this; otherwise, the scanner’s maintenance routines are triggered more often, and they take longer to complete."
Tracking targets is as important as tracking points. One innovative tip Ashley passes on is to sequentially number black and white paper targets. "We have a Word template that we use to print out numbered targets with incrementally increasing numbers," he explains. "Since we can see those numbers in the raw point clouds, it makes it very easy to know which targets we’re working with."
Paper notes remain an important part of the scanning workflow. For one thing, they are a good way to track unnumbered targets. "In some situations, like a multi-floor scan, we’re using swivel or sphere targets over and over, in similar locations from floor to floor. Good sketches, with a target numbering scheme, are very important for our office guys," Ashley says. Paper notes are also a good reference for control networks; control points and scan stations are included in sketches, along with targets. "As we run control traverses through buildings, we make a point of picking up any targets we see. This gives us an independent check on registration and georeferencing accuracy, and is useful for contractors doing layout and dimension checking."
In the office, Leica Geosystems’ point cloud processing software Cyclone is "… basically the only thing we use," according to Ashley. Early processing steps completed with Cyclone include registration, quality checks, and georeferencing. Many of these steps have been vastly optimized with some of the tools in the newly released version 9.0.
Cyclone’s section tools are a key routine used for quality assurance. "This is something I tend to go over early with new hires," says Ashley. "It doesn’t seem to be common at some firms, but we think it’s essential." Basically, Cyclone is used to look at multiple horizontal and vertical planes in big jobs, concentrating on the overlap areas used for registration. "Doubled lines and other anomalies tell us something isn’t right."
After that, processing depends on the deliverable requested by the client. Common requests are Revit 3D models and topographic surveys completed in Civil 3D. And sometimes clients are looking for just a point cloud. "We try to be flexible," Ashley says. "Our basic workflow creates a clean, accurate point cloud that is suitable for just about any work the client is doing."

A 3.854Mb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE