Point of Beginning

Reflectorless Revolution

March 1, 2004
A South Florida firm thanks technological advancements for more opportunities and safer conditions.

There may be times in surveyors' careers when clients require specific information that cannot be gathered due to cost or safety considerations, or that is simply beyond the surveyors' current ability to collect. Thankfully, as new technologies and innovations infiltrate the surveying profession, these instances become fewer. For many surveyors, the electronic distance measurement (EDM) device helped to revolutionize field production. The greatest limitation on this device was the use of a prism necessary to reflect the light wave back to the EDM. In recent years, however, a generation of new distance measuring devices has reduced or removed this limitation: reflectorless technology. This innovation-the reflectorless total station-has been considered a boon to many surveyors, including several users at Craven Thompson and Associates (CTA) a Fort Lauderdale-based consulting firm providing civil engineering, land surveying, land planning and landscape architecture services throughout South Florida. CTA crew members have been able to gather field data much more efficiently with their reflectorless total stations-some data they say that was virtually unattainable before.

The reflectorless total station has been considered a boon to many surveyors, including several users at Craven Thompson and Associates.

Working on the Railroad

One of CTA's greatest clients for years has been the South Florida Regional Transportation Authority, operator of South Florida's 72-mile South Florida Rail Corridor, a commuter railroad that stretches across Miami-Dade, Palm Beach and Broward Counties. CTA performed work on the rail corridor beginning in 2000, later becoming part of the project management committee headed by DMJM+Harris, a transportation and infrastructure consulting firm. Through this association, CTA acquired work to determine the heights and clearances of the highway overpass near the railroad corridor for the transportation agency. The commuter/commercial rail line crosses a well-trafficked tidal river, the New River, in Broward County, Fla., and parallels Interstate 95, the over-populated expressway that led to its expansion. As part of the scope of this survey, CTA was requested to locate pilings, establish elevations at the bottom of the overhead spans and position the bridge overhang of a portion of I-95. Aside from the roadway being quite busy and extremely dangerous, it also spans 60 ft above the water with multiple structures for directional lanes and off-ramps.

"Sometimes we had to measure up to a girder that was 75 ft high," says Joey Litchfield, a CTA crew chief and surveyor for almost 24 years.

Scott Reid, PSM, one of CTA's survey project managers, decided that the most feasible way to locate these structures would be to use a reflectorless total station. "Without the reflectorless these measurements would either have to be abandoned or be very difficult," Reid says. "Taking a horizontal and vertical location of the bottom of a busy urban overpass 60 ft in the air is almost impossible without the reflectorless total station."

So a reflectorless total station is what they got. Doug Davie, PSM, CTA's vice president/director of survey, decided on the Leica Geosystems (Norcross, Ga.) TCR 703.

"We wanted to increase our field crew abilities and provide a good quality product for our clients," Davie says. "It's part of our strategy to constantly expand our inventory with the latest technologies."

It was this strategy that allowed CTA to fulfill the transportation authority's needs and keep its long-time client.

The reflectorless abilities of the total station on this portion of the rail line project showed benefits quickly for CTA's surveyors. Since many areas of the project area were dark, the instrument's laser helped out greatly. "The laser really helped us to see the edges of girders to get height differences," Litchfield says. "From it, we got perfect coordination."

Using other methods to perform the bridge work would have been practically illogical. CTA crews could have used triangulation; however, the redundancy of measurements that would have had to be taken, the poor geometry afforded by the site due to its linear nature, and lower accuracy for certification deemed this older method impractical. Technology, after all, advances the techniques of the practitioner; it's the mere definition of progression. Another alternative would have involved extensive safety precautions including the closing of a portion of the highway and some type of vehicle like a boom truck to lower field personnel to the area where measurements were needed.

For Litchfield and his crew, the work on the bridge with their reflectorless total station proved to be a rousing success in terms of time and mission accomplishment. "One of the best things I've seen [with the total station] is that we paid for it in one project," Litchfield says.

Signs of the Times

Almost two years after the completion of the bridge project, CTA crews were again given the opportunity to use their handy total station. DMJM+Harris called on CTA to locate billboard signs above the ground and above the track around the railroad corridor.

"The only real way to get these heights was with a reflectorless total station," Reid says.

Otherwise, he says, they would have had to get somebody to climb up those billboards with a prism. With the total station's shooting range of more than 240 ft and its two-second feedback time with the reflectorless feature, CTA was able to complete the measurements of the billboard heights quickly and accurately.

"It [the total station] comes in handy in so many different ways. You just gotta be creative with it," Litchfield says.

CTA's reflectorless technology aided in the data collection on a busy urban overpass 60 ft in the air.

Reflective Advances

Upon success of the railroad corridor survey and the nearby bridge, CTA surveyors have applied their reflectorless technology on various other projects. When asked to determine the height of a bascule bridge near the rail line in both the open and closed positions to determine the heights at both points, CTA again turned to reflectorless technology.

"The bascule bridge was difficult," Reid says. "Trilateration is ineffective without sound geometric placement of your control, which wasn't possible in this instance, and to actually send someone with a prism presented a logistical and safety factor that could not have been resolved."

Litchfield says the reflectorless total station was also quite practical in its as-built application of a condominium complex that was built halfway before construction seized almost 18 years ago. CTA crews were asked to go back to the site to locate columns and walls so the structural engineers could perform design-fit-build plans according to today's specifications. "To shoot with prisms, we'd miss a quarter of an inch because of offsets, etc.," Litchfield says. And the laser again lended aid, Litchfield notes, since they had to work inside the building about two floors below light.

A Class Act

When the call came in to CTA a couple of years ago for work on the new state-of-the-art Performing Arts Center of Greater Miami, an analysis of CTA's inventory was done to be sure they could perform the work. That work consisted of a lot of layout, all of the control layout, doing the as-builts and checking the plumbness of walls.

The inventory Reid supplied showed the reflectorless total station, but he knew that Litchfield's crew used it on other projects. It was evident that another unit was needed. So, supervisors bought another of the same to supplement CTA's inventory.

The reflectorless capability of the total station was a blessing and a necessity for John Venezia, field crew party chief for the Performing Arts Center project, and his two-man crew. "They [the Center's engineers] required some as-builts on the face of the wall as well as the exterior face of the elevators. You're talking about going up four stories and doing an as-built every four to five stories," Venezia says. The as-builts along the face of the wall were taken in a 4' to 5' square grid for a planar view. Some of the walls are not 90 degree angles. The engineers needed to ensure that the finished construction met the parameters set for a decorative face to be applied later in the project.

That was in the beginning. Now Venezia and his crew are onsite at the Arts Center "about a couple of days a week. There was a time [at the start] where I was down there every day of the week. Initially we were doing a lot more work, we were doing the pilings and the as-builts on the pilings. Once that was done, the layout people could do the majority of the work. Now [for us] it's more detailed things."

That detailed work includes providing the control on the project and laying out the grid lines according to the design plans. And if the old saying that "it's all in the details" is true, at least in CTA's case, it can perhaps be attributed to their tools. It is the little things that may now be forgotten that deem the total station a benefit.

"Before we got the reflectorless, we were swung around in a "┬śman basket' with suspended panel wire. There's a lot of stuff that people aren't aware of," Venezia says.

The total station's laser has been another token of wealth for CTA crews on the Performing Arts Center project. When much of the work involves being in thick darkness, a laser indicator can make all the difference in the world.

"We're laying out walls for one of the masons and we're using the laser because it's so dark in spots," Venezia says. "My instrument man, he can't see me through the scope, but I can see him." He continues, "You trust the information your instrument is giving to you. It enables me to go beyond what I can reach. A lot of times it adjusts to acquire where we want to be, my instrument man will sight it and I'll know where I need to be. The greatest advantage [of the reflectorless total station] is that it doesn't limit me in what I can reach. If I can't physically get to a corner of a building, I can still get that corner of the building [with the total station]. It expands what you're able to do-in construction and in places where your tolerances are very minute."

And when it comes to accuracy both Litchfield and Venezia say the reflectorless units have produced very satisfying results.

"I've done comparisons," Venezia says. "On this job, they've given us such strict tolerances-to the thousandth, an eighth of an inch, and we've been checking and re-checking what we've been doing. I've found very minute descrepancies in the distances but it's probably how I'm holding the instrument or the peanut on the ground."

Rather than getting permission to climb up this billboard using a prism, CTA surveyors used a reflectorless total station to collect measurements quickly, accurately and safely.

A Hardware and Software Marriage

Although advanced hardware features can benefit surveyors greatly in their work, it is the marriage of hardware and software that breeds complete success. And since CTA's hardware and software work together nearly seamlessly, productivity has increased for its crews.

The Leica TCR703 that Litchfield and his crew use is mated to a TDS (Tripod Data Systems, Corvallis, Ore.) Recon running TDS Survey Pro software, which replaced a Hewlett-Packard iPAQ 3765 Pocket PC and an HP48GX prior to that.

With the successful transition from CTA's HPGX and HP iPAQ units to the TDS Recon unit, CTA sees more TDS Recons in their future. The main reason is software issues, according to Reid. "The Recon has recently gone to the Windows Mobile 2003 software, which has advantages over the older Windows CE OS," Reid says. "So far the Recon has proved to work fine in field conditions."

Venezia says his instrument man finds the TDS software quite advantageous, especially in regard to time savings.

"The software is set up quite well," Venezia says. "It saves us a lot of field time doing calculations. When we have large jobs that require a lot of data points and coordinate values we can download right from the handheld into the computer. And when you're able to directly download it from the computer, you're taking out that one step, saving a lot of time."

This is a characteristic much appreciated by Venezia and his instrument men, especially on the Performing Arts Center project where they located more than 2,000 points for pilings.

A Reflection of Progression

From chains to EDMs to reflectorless technology, the surveying profession has seen some great changes in the tools offered them. Realizing the benefits of progression and improvements in the equipment and software provided for surveyors today can present more opportunities, easier data collection and great time savings. Certain projects can be completed with less safety precautions and more accuracy.

"I suspect that as our current inventory of instruments is replaced that more of the reflectorless instruments will be purchased as they allow more flexibility in the field for overcoming obstacles," Reid says.

With this mindset, CTA is sure to benefit from advanced technology and not have to turn away any clients.