There’s no question 3D laser scanning pays big safety dividends when it comes to keeping surveyors, engineers, operators, and the general public from harm’s way. Laser scanning is fast and operator exposure can be much lower than with traditional methods.
However, laser scanning equipment has its own set of safety issues: equipment has to be operated safely and in compliance with the governing regulations. Failure to pay heed can trigger grievances and stall or even kill projects.
Next month at SPAR 2006, March 27-28 in Houston, we’ll have two industry experts on hand to lead a workshop on the safe use of 3D laser scanning devices in the workplace: OSHA’s Bob Curtis, Director, Program Support Division, Directorate of Science, Technology & Medicine, and Rockwell Laser’s Bill Ertle. Rockwell Laser has agreed to serve as laser safety officer for the conference.
Attendees can join a 90-minute workshop on laser safety.
- Get up to date on what you need to do to keep your worksite safe
- Learn what you need to do to comply with all the regulations
See SPAR 2006 for details.
Eye safety and laser scanning can seem like a hornet’s nest of conflicted vendor claims and government regulations. Manufacturers promote the safety of their devices as a marketing tool; so do the service providers. The debates can be downright confusing, sometimes deliberately confusing. Meanwhile regulations for the safe use of lasers vary throughout the world. In the U.S., manufacturers must comply with regulations for lasers and laser products issued by the Center for Devices and Radiological Health (CDRH) of the Food and Drug Administration (FDA). In Europe and elsewhere, regulations issued by the International Electrotechnical Commission apply. The U.S. Department of Labor, Occupational Safety & Health Administration (OSHA) also weighs in with standards and directives related to exposure to laser hazards. And the American National Standards Institute (ANSI) sets standards that are referenced by the U.S. Department of Labor. Further, some states in the U.S. have adopted their own standards and enforcement plans. Buyers need to consider the potential for workers or the public to be exposed to the laser beam. In particular, will workers on the site be using survey instruments or other optical devices through which the laser beam might accidentally be viewed?
What about the safety dividend part?
Surveying bridges, roads and tunnels can be bad for your health. In New England where I live and elsewhere, traffic density is on the rise, and regrettably we commuters have little patience for lane closures and other disruptions to our daily routine. I’m appalled by the lack of courtesy extended by us drivers as a group to those who wear reflective orange vests to be safe on the job site. We regularly eat in our cars and make telephone calls while negotiating thick traffic, and some of us even put on makeup at 60 miles per hour. Risible perhaps, unsafe certainly – this foolish behavior has proven devilishly difficult to regulate and enforce; occasionally, the results are fatal.
Some survey operations using conventional total station techniques can be particularly hazardous if traffic is not diverted or slowed significantly. Obtaining elevations for a DTM between active traffic lanes on a two-lane, two-way highway exposes the prism holder to hazardous traffic in both directions. Similarly, obtaining elevations from the medians is particularly hazardous to survey crews because it increases double exposure to high-speed traffic. Make this a divided highway with three lanes in each direction, and the party chief is looking at closing the center lane to traffic to obtain elevations on the break lines at the lane lines.
The problem only gets worse when there’s a traffic accident – the timing is unpredictable, of course. The investigating officer faces a tough choice: conclude the capture of critical accident scene geometry and get the traffic moving again or be careful and thorough and gather sufficient evidence required to establish fault and possibly culpability, evidence that is reliable and complete enough in court. Balancing these choices in the face of oncoming traffic can’t be easy. Weighing in on the side of speed is the fact that accidents can beget more accidents, a consequence of rubbernecking inattention and impatience to get moving.
Obviously protecting the safety of survey crews, indeed all construction crews, has to trump inconvenience to the driving public. The statistics support this too. According to the most current information available from the U.S. Department of Labor’s Bureau of Labor Statistics, nine (9) fatalities of architects, surveyors, cartographers, and surveying and mapping technicians were recorded in 2004, an incidence rate of 0.1% of the population.
Are there any new remedies? Can safety be enhanced at the same time as minimizing the economic burden and aggravation of lane closures?
There are obviously no easy answers. However, for some operations, 3D laser scanning offers significant safety benefits over conventional total station- and prism reflector-based data collection. Why? Mainly because elevation data can often be captured from the roadside, a safe distance from approaching traffic. Locating the scanner on both sides of an overpass can mean no lane closures. Signal noise from passing vehicles and the like can be removed in back office post-processing of the data provided several scans from the same location. Marty Dunn, vice president, METCO Services, Inc., Warren, MI, recently finished scanning the intersection of I-96 and I-75 located in Royal Oak, Madison Heights and Hazel Park, MI, the busiest in southeast Michigan with an average traffic flow of 360,000 vehicles per day. Dunn reports his crew was able to survey the intersection without touching a paved surface, a feat he says would be “nearly impossible and certainly impractical to achieve with conventional total station technology.”
Despite the advantages of 3D scanning, there are some challenges to using these instruments for road work. Scanners give best results when the beam is normal to the measured surface. When scanning road surfaces, this means getting the scanner high up to reduce the oblique angle shots. Some innovative service providers have fabricated boom mounts for their scanners to address this issue. The need for accurate control also remains no matter what capture technique is used.
Some manufacturers are beginning to develop dynamic survey capabilities to allow capture from a moving, ground-based vehicle. Applying scanner-mounting technology and methods learned from airborne scanning from both fixed- and rotary-wing aircraft seems to be the way to remove humans from harm’s way in dense, high-speed traffic situations. Prototype systems have been developed that integrate an IMU (inertial measurement unit) together with GPS to provide real-time information about not only scanner position but bearing and heading. The technical challenges of making systems robust enough for everyday work are not easy; signal post-processing burdens are substantially increased over conventional techniques also. Not too surprisingly, the added incentive of avoiding hostile gunfire or other confrontation has motivated development in this arena. Terrapoint Systems, Ottawa, Canada, trialed a system in the fall of 2003 in Afghanistan, for example. Expect to see more development of this kind.
The safety advantages of 3D laser scanning compared with conventional total station work or tape, level and plumb bob methods is by no means limited to bridge, road and tunnel work. Surveying bulk-material piles with total stations can be risky work if it entails walking over a shifting pile with a rod-mounted prism; long-range time-of-flight scanners have proven themselves effective performers for these applications. In nuclear power plant modifications, as-built geometry extracted from scan data is used to simulate and sequence operations in high-dose environments, reducing total exposure.
For industrial plant work, the judicious use of 3D scanning can reduce or eliminate the need for scaffolding and its attendant risks. In many instances the result is superior too because the surfaces to be measured are not blocked by scaffolding. Some of the motivations for developing advanced dimensional control techniques for construction and revamp of offshore oil and gas production facilities can be traced to the explosion of the Piper Alpha production platform on July 6, 1988 in the North Sea, in which 167 workers perished. Following this horrific incident, the oil and gas industry looked for new ways to reduce the requirement for field work under hot conditions. Dimensional control was seen as a way to reduce the requirements for hazardous field operations such as cutting and welding of pipe spools. While much dimensional control work is executed using total station-based measurement, increasingly laser scanning is used to survey offshore platforms for revamp purposes. In cases where platforms are damaged by extreme weather conditions, Hurricanes Ivan and Katrina in the Gulf of Mexico for example, laser scanning has been used effectively for damage assessment. Laser scanning offers high value for assessing damaged areas that are potentially hazardous because of stored mechanical energy. Using laser scanning, these areas can be assessed without direct physical access.
The lesson for all these industries? When a new technology comes along that bests current safety practice, it merits a close look. No organization has unlimited budgets for new technology, even when it delivers a safety benefit. However, when new technology offers improved economics as well, it ought to be a no-brainer. 3D laser scanning has proven itself not just as safe as current methods but actually safer in many cases, and it delivers real economic benefit in the bargain – what are we waiting for?