A Surveying Chronicle
Some surveyors get projects they never dreamed they'd get. For Gremley & Biedermann surveyor Scott Beagles it was 'luck of the draw.' But he'll never forget his survey of the U-505, a German World War II submarine in Chicago.
One of the oldest museums of its kind in the Western Hemisphere, the Museum of Science and Industry in Chicago was faced with a unique challenge: to relocate its popular U-505 submarine to an underground structure currently under construction. Dubbed "The New U-505 Experience," the project is still in progress. To complete the task, the museum turned to Gremley & Biedermann Inc. (G&B, now a division of Professional Land and Construction Surveyors Corp. or PLCS; Chicago).
The museum received the WWII German sub in 1954, 10 years after its capture off the western coast of Africa. Since then, more than 23 million visitors have toured the Unterseeboot, located just outside the museum as a walk-through exhibit. Concern for its aging condition prompted museum officials to design an underground structure based on the sub's measurements. But first the museum had to get the huge sub's (600-750 tons) precise measurements--inside and out.
"It wasn't your basic land survey exercise," says Tom Green, PLS, G&B president. "The crew had to work their way through the inside of the sub, which was small and cramped--not set up for you to measure through. So they came up with some procedures you wouldn't ordinarily use."
On Dec. 17, 2001, G&B surveyors Scott Beagles, PLS, and Mike Dumont showed up at the museum with a Trimble 5600 Total Station with Direct Reflex (DR) technology (Trimble, Sunnyvale, Calif.).
"For a company as old as ours, getting unique and challenging projects isn't surprising," Beagles says, referring to the company's 47-year history. "But I knew surveying a submarine would be one of the most unique projects I've done. And challenging, both in measuring it and in the logistics."
The museum was the first in North America to develop hands-on, interactive exhibits; the sub was no exception. In the past, visitors could walk around the warship outside as well as tour the inner sanctums. A building project in 1985 limited the outside view, but the new location will again allow full exterior tours, giving visitors the opportunity to immerse themselves in lessons of history and technology.
"Only so many people a day can take a tour through the sub," says project manager Richard Klarich, of Jones Lang LaSalle (Chicago), program managers for the U-505 conservation and relocation project. "This [new exhibit] will give visitors the opportunity to have two tour experiences of the historic sub: exterior and interior. It's quite a change."
From Bow to SternG&B's crew set up a local control outside to map the sub's exterior; they then took the control inside the museum, down into the exhibit area and came through pedestrian openings cut in the sub's hull. The crew ran control through the interior, from the fore torpedo room, through the living quarters, to the aft torpedo room--everything from bow to stern.
"Mapping the outside was no problem," Beagles says. "But inside we had to try to achieve an accurate control network through very cramped quarters--with tours going on around us. That was difficult."
The inside control network enabled them to map the original pedestrian openings. When they relocate the sub to the new exhibit area in 2004, these openings will need to line up with an open platform in the new structure, so the measurements were critical.
To ensure he was getting the best vertical results, Beagles took multiple Face 1 and Face 2 measurements of the hull openings with the servo-driven reflectorless total station. Face 1 is the normal mode of using the instrument with the keyboard and face to the operator; Face 2 entails plunging and reversing the telescope, which helps cancel out any measurement errors due to calibration problems.
"I'm actually always amazed with the Trimble 5600 instrument," Beagles says. "When it comes to elevations, the unit excels way beyond any others on the market. People want you to drag out the level and check it conventionally--and they're always amazed at how accurate the 5600 is."
The crew also mapped the sub's top deck, where the machine guns and torpedo tube ports were located, as well as the conning tower and periscopes at 10-ft intervals. The sub had two periscopes: a surface periscope to sight ships to attack with torpedoes, and an aerial periscope to both scan the stars for navigating and search for enemy planes overhead. A highly feared weapon of WWII, submarines were most vulnerable when they surfaced to get air and recharge their electric generators. Planes would often hover overhead, waiting for subs to surface, which they had to do regularly.
Final sub stats: 251.40 ft long x 21 ft wide x ~20 ft high. After completing the survey, the G&B crew thought that was it. But six months later, Beagles was back at the sub, this time with crewmember Matt Schenek.
Survey Times TwoIn May 2002, G&B was asked to measure the elevations of the existing underground parking garage, which they did by running a level circuit down the stairwell. The museum needed the elevations of each level as the sub will be moved to an excavated area adjoining the parking garage; the museum will open the wall between the garage and U-505 for service entrances.
They also had to certify a previous G&B survey, adding all above-ground improvements in the proposed enclosure area. Using the Trimble 5600, the crew performed a topo survey of the museum's north face as well as ground improvements, including flagpoles, sidewalks, underground parking stairwell entrances and utility structures.
The first G&B survey had been done about 10 years earlier using standard technology for the time: no robotics, no DR--or reflectorless--technology. Because the measurements were critical for the relocation, the crew remeasured the most extreme ends of the sub with DR technology, enabling measurements to be made without a prism: they were almost identical. It was a good check--of their work and the technology.
"We were one of the first companies in Chicago to get the Trimble 5600," Beagles says. "The same with DR: I don't know why someone wouldn't get DR, especially for detailed work. It's a wonderful tool for the right applications."
The museum then asked them to use a conventional optical level to verify the hull opening's elevations taken on the first visit: elevations were almost identical to those achieved with the DR total station.
"Running a control inside was a very difficult process, so it made sense that if you ran a level you would come up with discrepancies," Beagles says. "But there were hardly any differences: kudos to the 5600's ability to carry out very accurate vertical information.
"I think for what was needed, the inside mapping and the details, the Trimble 5600 probably was the best choice of an instrument to complete the work."
Lessons in the DetailsEarly this year, the museum requested more detailed measurements: propeller heights, support brackets, diveplanes, etc.
"We needed to start understanding submarine terminology to know what they meant when they asked for certain pieces and parts on the sub," Beagles says. "It's one thing to point to a picture, but if we needed to define the limits of the bow planes, which helped the boat submerge, we needed to know more clearly what those were. "
Or stern planes, which enable the sub to surface. Or the conning tower. Or which periscope was which. So began the crew's history lesson.
On the U-505Built in 1940, the WWII Type IX-c U-505 Unterseeboot was commissioned for action in Hamburg, Germany, in 1941 and helped sink eight allied ships (three American, two British, one Norwegian, one Dutch and one Columbian) for a total tonnage of 44,962 tons.
On June 4, 1944, the U-505 was attacked by the USS Guadalcanal Task Group 22.3, an American hunter-killer group of six ships under the command of Captain Daniel V. Gallery that were on patrol and targeting enemy subs off the coast of West Africa. Forced to the surface by depth charges, the U-505 was captured and a volunteer boarding party of nine sailors from the destroyer escort USS Pillsbury took control. As the Americans were boarding the sub, the Germans were abandoning and trying to sink the U-boat; Navy sailors quickly found and closed an open valve in the control room where water was pouring in.
It was the first time an enemy warship was captured on the high seas by U.S. Navy sailors since the 19th century, when the USS Peacock seized HMS Nautilus in 1819 as part of the War of 1812.
The U-505's capture was significant in other ways: on board was the German's secret coding device, called an enigma, as well as 900 lbs of technical and secret publications, and two acoustic torpedoes. The Allies had already broken the enigma codes but this was a long and difficult process to accomplish each day. The capture of the U-505 codebooks and machines enabled the Allies to continue breaking the daily coded messages during the critical months of the invasion of Normandy. The acoustic torpedoes were also important captures. Allies were able to reverse engineer the torpedo and to build more efficient counter measures. So it could potentially be said that the capture of the U-505 submarine perhaps ultimately helped shorten the war.
The sub was taken to the states and later slated for scuttling (sinking) as target practice. But Admiral Gallery wanted it saved as a memorial, and with Father John Gallery, a Chicago priest, called on the Museum of Science and Industry in Chicago. So it was that the sub found its new home as a permanent exhibit and memorial to more than 55,000 American sailors and merchant mariners who lost their lives at sea in the two world wars. In 1989, the U-505, the only Type IX-c boat still in existence, was designated a National Historic Landmark. And the rest is history...
The Submarine's SubpartsMany of the measurements the museum now requested were of projections below the sub's deck that might affect moving and mounting the warship on its new support stands. So Beagles and crewmember Adam Metz mapped the size and length of the rudders, bowplanes, sternplanes, propellers and other projections.
"They were very concerned about mapping everything that stuck out of the sub: the length, height, width and where it was on the sub related to our control network," Beagles says.
Because the new location would allow visitors to walk around the sub's exteriors, these measurements were also critical for safety reasons: with them, architects could accurately position the railings keeping visitors away from any dangerous protrusions.
The museum also asked for the sub's drip line, that is, if water dripped from the sub's top, where would the widest part be? The U-boat's hull is curved, but you can't visually determine the widest part, nor could the crew use normal methods to measure it. They decided to use an inverted prism pole plumbed by a separate rod bubble using negative target heights for points above their reach. They aligned the rod every 10 ft along the hull, and measured the incremental changes around the sub.
"Most people take positive rod shots, where the rod sticks up from the ground target," Beagles says. "We had the opposite: we had things up in the air, but couldn't get to them on top--so we'd stick the prism pole upside down. We did a lot of inverted rod shots."
The sub's widest point was, as it would seem, midway between the deck and keel. However, the sub's coloring--part black, part gray--added to the difficulty in visually determining that point: 2 to 3 ft below the separation of the colors.
"We wouldn't have been able to do it any other way," Beagles says.
They also measured the support structure. The sub was set on four concrete stands. When originally set in place, permanent plates had been welded onto the sub's sides; these had been used to lift the sub into the air with a crane, pour the concrete supports and set it down on the stands. The museum needed the precise location, height, width and angle of the plates so that the new stands would fit the existing plates.
"The support bracket measurements were very important," Klarich says. "In locating the openings in the sub in relation to the rest of the submarine, it was critical for our architect to be able to plan how this was all going to fit inside the new enclosure. We wanted the platform to be right at the floor level of the submarine."
Then there was the relocation route.
The Final RegisterConcerned about needing to remove anything that would obstruct the submarine during relocation, the museum requested that G&B re-certify their initial above-ground survey. They wanted to show all utility improvements made on the site since the last survey, as well as improvements made for the widening of Lake Shore Drive, the adjoining road that runs along Lake Michigan. Beagles' crew completed a topo survey, showing all lightposts and trees, including size, and aerial improvements such as electric and telephone wires.
"We surveyed anything in the path of relocation--nothing unusual," Beagles says. "The unusual part was that it was for relocating a WWII submarine. I've toured the sub by myself and with my son. But I never considered anyone would want to map it. It shows you just never can tell."