Also, because of the historical nature of the building, trying to build (or hang) exterior scaffolding was seen as extremely risky, to both human life and building. Thus, this unique type of surveying was deemed necessary.
So, what does rope-access surveying entail?
Learning the Ropes
Rather like getting a pilot's license, being certified to do rope access by the Society of Professional Rope Access Technicians (SPRAT) requires both formal training and actual "flying" time on the rope. You can be certified at various graduated levels.
A SPRAT Level I Worker needs to complete a four-day rope-access training course, pass a Level I written exam, and pass a field evaluation by a certified SPRAT evaluator. To go on to a Level II certification as a Lead Technician requires six months on the job and 500 logged rope hours, and passing a Level II test and field evaluation. A Level III Supervisor has to complete an additional 500 hours at Level II, then pass a written Level III test and additional field evaluation.
Obviously, it's no light commitment and requires some 40 hours of training just to get your foot in the door — or, rather, your boots out on the roof.
Just because someone is SPRAT-certified, however, doesn't mean that person is qualified to do building field surveying. The whole point of getting rope-access skills is to get a trained set of eyeballs up close and personal with a particular field condition. Only someone with the proper construction experience in the field can properly evaluate whether a piece of terra cotta has light surface cracking that is repairable or more serious damage that requires full replacement. Photography and even video are no match for a trained set of eyes on the spot.
Immediate CAD Documentation on Tablet PCs
Now, add into the above requirements the ability to do CAD documentation on the spot.
How many of you have gone out in the field with a clipboard making handwritten notations all over the place on a preliminary set of plans, only to go back in the office and find that you either can't read what you wrote or forgot to check a certain condition or take a certain dimension. Obviously, if you can readily do it in the field in the CAD file itself, you are way ahead of the game — especially if, in this case, missing a detail would mean going back out on the rope!
Tablet PCs make the documentation work a little easier in this case. The system used by Vertical Access is called TPAS (Tablet PC Annotation System) and is a customized add-on utility that allows input of both graphical and numerical data directly into the CAD file.
In addition, libraries of notes on existing conditions, material descriptions, and likely field notations are developed ahead of time, so that they can be "dragged and dropped" to a particular input point. Polylines are used to delineate crack location, path, and length, so that all the dimensional data can be determined later.
For rope-access surveyors, the tablet PC is hung from a rope. "Everything is hung from a rope," says Lisa Howe, but "it's actually easier than it sounds."
Also hung from the rope or the belt is a rugged digital camera that maintains a wireless link with the tablet PC. When a picture is taken, the surveyor taps in an insertion point in the CAD file at the proper location, which then creates a hyperlink between the CAD file and the stored photo itself.
How many times have you gone through your folder of field shots, only to forget exactly where a particular shot was taken? This system makes sure that error doesn't happen and aids in the evaluation, design, and bidding process, allowing any user to tap on the CAD file hyperlink and immediately get a digital photo of the field condition.
Another tool used by rope-access surveyors is videoconferencing. In the case of our intrepid architects on the face of the U.S. Post Office building in Brooklyn, the team didn't just rely on the surveyors out on the wall.
When faced with certain tricky conditions, the surveyors could turn on the camera and begin a videoconference with a team of consultants who were safe, warm, and dry inside the field office. The consultants could confer in real time over the way to handle a particular condition and ask for additional angles or shots before making their evaluation. This is a good way to get a dozen trained eyes on a problem rather than just two.
When envisioning the need for rope surveying, one immediately pictures difficult exterior architectural conditions that make scaffold and crane access difficult. Such surveying is also done inside buildings, however, as recently demonstrated at the Old South Church in Boston, where work on an underground subway station renovation had caused a major crack in the main east wall of this historic landmark.
Scaffolding in front of the stained-glass rose windows would not only have been unsightly, but also extremely difficult over the existing organ pipes and chamber compartments. So, in came rope-access surveyors, swooping in like Spiderman (or Spiderwoman in this case) to get a close inspection of the cracked plaster and wall.
Lessons for Us All
While most field condition surveying is not as dramatic as rope-access surveying, this all-inclusive method of direct, in-the-field CAD-notation surveying can provide lessons to all of us on how to do our jobs better even in more mundane situations. CAD in the field can serve to eliminate a host of common translation and transition errors that we all make in the typical field-clipboard-brought-back-to-the-office approach.
A standard template library of field notes can further ease the process. Perhaps a tablet PC with touchscreen input is worth the added cost. Furthermore, tying field photographs to CAD files with hyperlinking can be extremely useful at all phases of the job.
While few of us need to buy jumpsuits and belt harnesses, it might not be a bad idea to create some type of vest to which all your needed tools — digital camera, video camera, tablet PC, laser rangefinder, digital voice recorder, cell phone, water bottle, etc. — can be easily stored or accessed.
Only a very few of us would be qualified to answer the classified ad that began this article. But while rope-accessing surveyors remain rare, some key components of their work could be applied more broadly to improve the field survey documentation work that the rest of us do from the ground.
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Evan H. Shu, FAIA is an architect with Shu Associates Inc. in Melrose, Massachusetts. He is a contributor to The Architect's Handbook of Professional Practice and is publisher and editor of Cheap Tricks, a monthly newsletter for DataCAD users and computer-using architects. More by Evan H. Shu
This article was reprinted from the March 2009 issue of Cheap Tricks © Shu Associates Inc. with permission of the publisher.