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Whether
it's a pad, a pipeline, a telephone pole, a dam, or a mine, laser
surveying systems save end users significant time and money. By Joseph Lynn Tilton |
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When the laser first joined the construction industry as a surveying tool, it was priced somewhere in the stratosphere. Now, thanks to an open market–and continued refinements–users can match their investment, whether $1,000 or $50,000 per implement, to the size and complexity of projects they handle. "The most significant development is the advent of laser diodes," declares Gabriel Tawil, president of Agatec Construction Lasers in Menomonee Falls, WI. "Instead of using tubes as we did in the ‘80s, we’re now using diodes, and those have really brought down the price for a lot of different kinds of lasers. For example, we have a fully automatic horizontal-only laser, the GAT120, that includes a detector and retails for $1,095. "Sure, an optical instrument would cost under $500, but with the introduction of the machine-mounted receiver and the subsequent elimination of the grade checker, you’ve recovered your investment in less than a week." And such a laser can be used for grading and excavating as well as marking elevations. With just a little more of an investment, the contractor merely has to dial in the grade he wants. "And a rotating beam will throw out a beam per the amount of slope he dialed in, and he’s all set to go," adds Tawil. Chuck Kleffner, Agatec distributor and owner of Montana Laser in Bigfork, MT, not only specializes in machine-controlled systems that include laser, sonar, and global positioning systems [GPS], but he has invented a magnetic laser mast for skid-steer and backhoe loader buckets that make for a quick installation on the excavating machine. "Contractors can use their skid-steer bucket to loosen and spread a hard spot, haul gravel for making a pad, or push truck piles to grade in one pass. It’s 50% faster than having someone hold a rod, saving time, labor, and concrete." Cost? Less than $1,500 complete with laser receiver. "When working, contractors will see a recovery rate of $40 to $50 per hour," Kleffner claims. Contractor Gary Linton of GTL Excavating in Missoula, MT, is sold on the device. In fact, he helped in its development. "We do upward of $500,000 a year in building slabs on grade. Our older system was laser, but I had to have a hired hand holding the rod. I’ve known Chuck for the last eight years, so when he told me his idea, I helped him test the first prototype." Linton explains that the device is on a mast that hooks on the back of the skid-steer bucket. "We drilled two holes in the hub of the bucket, then pivoted the mast into those two holes so the magnet could sit on the floor of the bucket. All I have to do is set grade on the laser transmitter, set my receiver on the mast to the grade, turn it on, jump in the machine, and go." He estimates this takes five minutes. "We just finished a 41,000—square foot job for a lumberyard. With a handheld rod/receiver, I was averaging 3,000 to 5,000 square feet of grade work per day, but with the magnetic mast and receiver, I can do 5,000 to 10,000 square feet per day. Plus, I’m saving $100 a day by eliminating one crew member." Linton reports it’s possible to spend the entire day on the machine without getting off to check grade. "I’m doing my work with a 773 Bobcat, and thanks to the magnetic mount, I’ve gone from making $1,000 to $2,000 per slab to a profit of $4,000 to $5,000. Frankly, this is my secret weapon in a tight market." In terms of durability, he points out that his work is chiefly on glacial fill with a lot of pit run material ranging from 1.5- to 6-in. rock with no problems. "Once that magnet locks on, anything that pushes on it locks it harder. I use tracks on my machine when grading, and I can have a bucket boiling over with material and it doesn’t affect the receiver at all."
Another low-end receiver helping smaller-size contractors with their surveying needs is the MC-1 from Laser Reference Inc., in Campbell, CA. Sales Manager David Kawano comments, "A laser projects a level beam that rotates like the beam from a lighthouse. This provides the contractor with a level tabletop of light that can be used as a reference for footers, grading, or elevation setting. "Machine-mounted receivers have to be robust to handle vibration and shock, and the display must be visible from a distance of 15 to 20 feet. The MC-1 mounts magnetically to the backhoe stick and allows the operator to take grade readings without leaving the control seat. To take a proper reading, the bucket should be curled in the same position each time a reading is taken, and the stick should be set so that it is plumb." Kawano states that once the device is mounted, anyone who knows how to use a laser will find it easy to operate. "The machine-mounted receiver and magnetic mount sell for $795 and can be paired with a basic rotary laser for a total of around $1,200. A low-cost basic system such as this enables one man to dig septic systems, footers, or trenches without having a grade checker." The device can receive a laser signal in a range of about 120º and features 8 in. of photocell receiving height. It is designed for backhoe or trencher mounting, but it can be adapted to fit a dozer blade on small grading jobs. Mark Spilker, an owner of Upgrade Construction and Drilling Inc. in Danville, CA, reports that the system is utilized in drainage contracts. "Water needs to flow downhill. Sometimes the terrain is so flat that the fall is just a quarter percent or a half percent, yet the last thing we need is a flat pipe." He explains that the self-leveling receiver automatically adjusts itself with 1/100% grade accuracy. "It’s easy to use, and it takes just a couple of hours to get comfortable with. It’s a lot more productive and a lot more efficient than the older model." His partner, Mike Nixon, notes that as temperatures changed, the older laser’s tripod expanded or contracted, throwing the machine out of balance. Today’s equipment readjusts itself. "We don’t have to spend time going back and forth, correcting the tripod." Another laser surveying equipment marketer is Apache Technologies Inc. of Dayton, OH. States Michael Bank, sales and marketing manager, "We supply simple visual indicator systems that sell for $1,300 to $2,500 and are well suited for smaller contractors. "Laser technology’s learning curve is minimal," Bank continues. "The user sets up the visual indicator, then follows the arrow. It’s true that rain can mess up a laser signal, but not many want to dig in a downpour. The technology lets the operator work at any temperature he’s comfortable with. The laser is not the limiting factor for excavation work."
At the other end of today’s surveying technology is GPS, which utilizes satellites to give latitude and longitude, providing most users with centimeter accuracy. Actually, there are more than two dozen satellites circling the earth, handling the signals sent by the surveying equipment, but usually just four are in position at any given time to be used at a specific locale. GPS plays an important role in mapping projects, especially in areas where further development is anticipated. This also is where the cost of surveying equipment grows sharply. "An important factor in surveying, particularly with drain lines, is being able to come back and find the buried pipe five or 10 years later," points out Kevin Shimp, president of Port Industries Inc. in Palmyra, MO. Shimp sells trenching equipment for ag drainage, water lines, fiber optics, and all kinds of utilities. "Another customer base uses pull-behind scrapers, leveling ag land or for site development for golf courses, commercial sites, and homes. Once they have the raw data, there are two distinct software packages to massage that data and get the final design for the kind of work each segment of the industry is trying to do." Shimp points out that whether trenching for ag drainage or land leveling, customers require accuracy rates of 2/100-5/100 in. over the entire job site. "Plus, contractors want to know where that plastic pipe is installed. There is no good way to detect a nonmetallic water-carrying line, so accurate mapping is critical. Years later, the contractor can drive back to the middle of that field and find that drain line to add on to, repair, or change from ag to residential use." Jon Seevers of Seevers Farm Drainage Inc. in Argenta, IL, finds that GPS surveying technology helps keep his annual volume in the $1 million to $1.5 million range each year, with half the work in ag and half in non-ag projects. "The biggest challenge to surveying is the weather. We’ll get a foot of snow, then have blizzardlike conditions for a week. In the early spring we can have rainfall to where the water table is at ground zero. "With our Geostar survey system, though, we can survey more acres in less time, so each window of opportunity is better utilized." He estimates that GPS technology makes his day four to five times more productive. "We used to measure off fields in a grid fashion, using a distance-measuring device. We’d drive through the field, measuring and stopping, taking a shot every 200 feet. With the Geostar we survey on-the-fly on 100-foot intervals, so we create a more accurate topographical map. Where we used to take 200 shots on a 160-acre project, it’s not uncommon now to have 800 to 1,000 elevation shots in a field. "We save a little bit of digging time because we don’t have to take time to verify the survey," continues Seevers. "We know the laydown is true to the survey. The nice thing about GPS is being able to come back later and find those buried lines. Some of our projects are installed in phases over several years, and this technology helps us find where we left off. In the old days, depending on how far from the boundary the line was, it would take more than an hour to find it. Now we can do the same thing in less than 10 minutes." He admits that it takes a few months to become really expert at using this higher technology. "We’ve been doing our design and engineer work for drainage about 10 years, and we are somewhat automated with computers, so the curve to learn this program, which also is computer-based, is not as bad as if we started at ground zero. It’s pretty fail-safe, but you still have to pay attention to what you’re doing." This is flat country, where the average is a foot of fall per 1,000 ft. "You can’t fool water. It’s always going to tell you whether it’s right or wrong," Seevers says. "If the fall isn’t right or the pipe isn’t sized correctly, then you’ll have inadequate drainage and siltation in the pipe. We warranty our workmanship for two years, and generally the pipe manufacturer warranty is for 25 years. Once installed, the drainage pipe is pretty much forever because polyethylene is resistant to any chemicals or corrosives in the soil."
While drainage lines mapping and installation can prove challenging, perhaps an even larger challenge is utility mapping, such as that undertaken by Middle Tennessee Electric Membership Corporation in Murfreesboro, TN. The co-op has 139,000 members and supplies power to a 30-mi. radius. Middle Tennessee Electric needs to know the location of every power pole in four counties, as well as all installed or planned underground lines. Supplying the equipment is Laser Technology Inc. of Englewood, CO. "It’s one of the large-scale mapping projects than can utilize a geographic information system [GIS]," reports Steve Colburn, director of customer service. "Middle Tennessee has our Impulse 200 laser, which has distance-measuring capability as far as 2,000 feet per reading. It also has a vertical angle sensor so it can measure changes in elevations. The third part of the equation for locating an object is the horizontal angle, so they have our Mapstar Electronic Compass Module and a GPS." As with other laser-based systems, this makes it possible for one person to do the mapping. "Another big advantage is there’s no need to climb a fence or cross private property because the position can be obtained from 2,000 feet away." Colburn figures this cuts down access time enough that it can double or triple field productivity. "While it’s true the cost for this equipment is several thousand instead of several hundred dollars for a compass, a chain, and a clinometer, with the increase in productivity and decrease in personnel, just one project can recover the cost of the investment." Regarding the learning curve, Colburn states, "Because we are fitting instruments into the hands of nonsurveyors, we’ve intentionally programmed them to be very easy to learn. A typical system requires just a half day of training [for the operator] to be proficient at it." Jeff Brockette, field engineering inspector for Middle Tennessee, explains, "We use our equipment, which includes GPS backpacks and units, to get pole locations, underground transformer locations, switching locations, and subdivision lot lines and in some cases even to map large buildings. The biggest reason for going from paper to GIS mapping with GPS surveying tools is for more accurate data on our maps. Our crews rely on those maps for emergency repairs or installations while contractors rely on the maps to avoid digging into existing utilities." Brockette, who has been with Middle Tennessee for a dozen years, adds, "One of the big advantages in going to this system is that we can update our maps almost instantly. We used to rely on jobs going to the control center for hand-posting and not get updated for two to three months." He points out that with the impulse laser, they can place an antenna atop the vehicle, drive down the road, and shoot the laser to existing poles. "And we can enter the offset, so we’re mapping the road and poles at the same time. We can do a 30-pole subdivision in an hour’s time. Before, mapping 30 poles would have taken a least a half day." Brockette reports that, for their applications, it takes about a week of field experience to become expert at using it. "Once a technician learns how to use the technology, it’s pretty easy. In our case, the need is for submeter accuracy. With the older system there was a lot more human error involved." He frankly notes that the climbing error rate came because of the increased pressure to get more done without adding to the crew. As development pressures increased, so did the error rate. "We’ve been using this system for eight months, and we feel like we’re doing a more accurate job. A lot of times we can use it from inside the vehicle, even when it’s raining slightly. You can’t shoot a laser through glass, so the window has to be down." In terms of distances, he says, "We generally feel comfortable with 600 to 800 feet. I’ve been out and shot 1,500 and 1,700, but it’s hard to know whether we’re hitting on the pole accurately, so we tend to limit our shots to 800 feet." He observes that using the impulse laser in conjunction with the Mapstar Compass Module, as well as with GPS, makes it possible to stand in one location and shoot at different poles. "We use the compass and laser in conjunction with one another and shoot angles and distances. This allows us to work around tall buildings and speeds up city mapping quite a bit." Fighting Vibrations Beneath the Streets of Berlin In the heart of Berlin, Germany, subsurface specialists and divers have teamed up with civil engineers to fight water and creeping sand with concrete, steel, and brains. The south-to-north axis between the Potsdamer Platz, the Brandenburg Gate, the Reichstag, and the site of the future main rail station is one enormous construction site. A major challenge to engineers is groundwater that saturates Berlin’s sandy subsurface at a level of about 10 ft. Accordingly, tunnel foundations have been designed with concrete tanks to resist lift. The Berlin Senate Administration and the German Railways assigned Messmer’s Berlin survey office the responsibility for establishing triangulation points over a 2- x 8-km area, a task accomplished with Leica Instruments’ TC2002 total stations, NA3003 digital levels, and GPS systems. Now the location of every point within the grid is known with an accuracy of 3.3 mm. Despite the proven accuracy of the equipment, this has not been a simple undertaking.
GPS surveying and mapping played a major role in helping to double the water storage capacity for the Los Angeles, CA, area via the East Side Reservoir Project, located 85 mi. east of Los Angeles near Hemet. That $1.2 billion project took 10 years of planning and involved moving more than 100 million yd.3 of material. In this case, the GPS technology was enhanced via RTK, or real-time kinematics. "RTK is the most accurate form of GPS equipment," explains Ron Iyemura, sales manager for Pacific Crest Corporation of Santa Clara, CA. "These high-end RTK systems have multiple channel receivers, which help provide greater accuracy. These products are capable of getting positions with subcentimeter accuracy." They’re also fast. "Once the user establishes good connections with the satellites, he is able to go from one spot to another, saving information to put into the computer. Once the base is set up, users can go as far as 10 kilometers away and continue to survey, although they are well out of the line of sight for the base GPS receiver." Pacific Crest provided the radio-link kits designed specifically for the RTK survey and mapping systems. "We supply radio links for all of the major GPS/RTK systems out there. The Survey Grade systems–those with the subcentimeter accuracy–will run between $40,000 and $50,000 for one base and one rover. You can use one base and many rovers, as they did in the Hemet project." Dave De Groot, senior project manager for the survey contractor Psomas, headquartered in Costa Mesa, CA, points out that the new reservoir gives Metropolitan Water District (MWD) a six-month supply of water. "The survey aspect of the project ran about $10 million. But it could have been double that had we not had GPS and the survey methods that we used." De Groot says Psomas had six survey crews, with MWD supplying two more full-time crews and one office surveyor onboard at all times. "Our main job was to determine how much material had been excavated from the dam footings and how much of each type of material was put back into the dam." The project lies in a valley with no natural water source. It included building a pumphouse with 12 pumps, each capable of pumping 1,320 gal. of water per second to get water up to the inlet/outlet structure and then into the reservoir. Also, the site called for three dams altogether. The west dam has a maximum thickness of 1,800 ft. at the footing and is about 8,500 ft. long. The east dam is 1,200 ft. wide at its maximum but is 12,500 ft. long, with the saddle dam 400 ft. thick and 2,600 ft. long. "The west dam was excavated 45 to 50 feet below grade, while the east dam went down nearly 100 feet in some areas. The embankments amounted to 133 million yards and included 12 different kinds of material, all obtained from the site. That material included everything from zone seven, which is like sand-trap sand, to 36-inch boulders." He notes that Psomas kept two continuous operating base stations so they could go out at any time, turn on their GPS rover units, and get signals from the operating base. Another challenge was surveying for nearly a mile of tunnels, measuring 16 ft.2 The tunnels are for access to the footings and reinforcement areas in the dams. De Groot reports the project was finished in December 1999 and will take at least four years to fill to its capacity of 848,000 ac.-ft., or about 262 billion gal. of water. A longer-term project has been the Phelps Dodge Sierrita mine near Sahuarita, a dozen miles south of Tucson, AZ. The copper and molybdenum open-pit mine started operating in 1957 and is 2 mi. across from east to west and 1.5 mi. across from north to south. It’s 1,700 ft. deep at the moment and has perhaps 20 years of productive life remaining. Kevin Tush, commercial manager in mining and earthmoving technology for Caterpillar in Peoria, IL, explains that they are in alliance with Trimble Navigation for equipping their massive earthmoving machines with GPS technology. "These machines are doing a lot of road building and earth shaping utilizing GPS technology instead of staking the ground. The driver of the vehicle has a computer screen in front of him, keeping him in position and on the correct grade." Tush points out that this technology actually uses four technologies: global positioning, wireless communications via an onsite dedicated radio network between office and machine, an onboard computer, and an office computer. "All people involved in management of the site can interact with the machines in the field. This sure beats frantic runs with a pickup truck in case of a mistake." He says the Caterpillar operator utilizes the onboard display to tell what needs to be cut or filled to achieve final grade. "It decreases the error rate significantly. Machines in the field in essence become full-time survey tools, with an on-the-go accuracy of 2 to 4 centimeters in the horizontal and 3 to 6 centimeters in the vertical. This technology helps the operator improve production by 19% to 45% over traditional operating methods. "The other thing we find with the Caterpillar onboard systems is that the operator gets real feedback on his productivity. Human nature kind of takes over, and the operators keep trying to improve their output. They use the technology to determine what methods are more efficient. It makes an average operator a good operator and makes a good operator a great one." Regarding how long it takes for the average excavator to get accustomed to the technology, Tush notes that a typical installation takes about a week to set up, including training office staff and machine operators in their portions of the technology. "We find when there’s a mixed fleet, operators want to go with the machines equipped with this technology." He says Orange County, CA, utilizes GPS technology on its landfill operation and is able to provide a consistent 7-9 in. of cover versus 3-18 in. in the old days. "It’s saving them huge dollars in both dirt and covering expenses. It also allows the operator to measure the rebound of the garbage so he knows when it’s not going to compact anymore." Russell Hewlett, senior mine engineer for the Phelps Dodge Sierrita mine, notes that GPS surveying helps lengthen the life of the mine and makes 24-hour-a-day mining practical–both of which are essential to this mine. "This is the lowest-grade copper mine in the world," he candidly comments. "We’ve gone from the old days of transit and chain to using GPS on the machines, including our loading fleet of four electric shovels: two PNH 4100s with 56-yard dippers and two PNH2300s with 28-yard dippers. The material is transported out of the pit in our fleet of 22 240-ton Caterpillar trucks, with ore material going to one destination, the overburden going to the overburden stockpile, and the leach material going to the leach stockpiles." Hewlett explains that utilizing GPS on the excavation equipment allows the mine to do a superior job of getting the right material in the right place. "Misdirected loads still happen, but the incidence has changed from 7% to 3%. Other mines boast when their 20% in misdirected loads is down to 15%, but our ore grade is so low, if we weren’t down to 3%, we’d be gone." Also reduced is total roadwork. "GPS surveying technology allows us to reduce the amount of roadwork by 25% to 30% because we can use the information to create 3D models, and the equipment builds that 3D model. Operators have the display right on the screen for cuts and fills and what the alignments are. So in the middle of the night, when stakes would have been wiped out, those machines still have control." Hewlett says the mine first went to GPS some five years ago, adding the onboard portion a couple years ago. "We took on laser technology in the very late ‘70s and early ‘80s, but the final tweaking with GPS has had a dramatic effect, so we’ll keep digging." And so will all other end users of today’s laser survey technology. Author Joseph Lynn Tilton is a frequent contributor to Grading & Excavation Contractor.
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