English surveying firm Benchmark Surveys experienced a substantial productivity boost from the very first project for their new GNSS system--and on many jobs since. A difficult topographic survey for the widening of a narrow airport bypass road presented challenges for both traditional total station surveys and GNSS. High hedges and dense vegetation would have been a costly and time-consuming proposition were it not for the combination of the enhanced GNSS capabilities and no-calibration tilt compensation of their Trimble R12i GNSS System. Not only was the survey completed in a fraction of the originally estimated time, but it was completed entirely with the new system.
A Knack for New Tech
Based in Southwest England, Benchmark Surveys has grown a broad portfolio of services by keeping on the leading edge of technologies and continually innovating.
“There are only seven of us, but we cover quite a lot with that seven,” says Benchmark’s James Richards, Land, Utility, and Measured Building Surveyor. “I cover land, utilities, GPR and measured building surveys. We have a drone team of two, and a utilities specialist, but we change roles quite a bit to help each other out and learn new skills—it keeps it interesting for everyone.”
The small firm has always been a bit of a pioneer. Richard’s mother, who broke role barriers as a quarry surveyor, founded the company in the 1990’s. (See sidebar: “Helen’s Journey.”) Known for its knack with new tech, UK Trimble distributor KOREC felt Benchmark would be a good candidate for the Trimble R12i GNSS System. And they were.
The very first survey Benchmark deployed the R12i on would have been a challenge for any combination of surveying equipment. “There is a narrow road—barely wide enough to be called a lane—between an industrial park and Exeter Airport,” says Richards. “For a widening project, the engineers needed a topographic survey a full 10 meters either side of the road.”
The route is edged by high hedges and is lined with thick, tangled foliage and large trees. It would not be possible to simply set up a total station and shoot the entire 20-meter swath. And older GNSS systems would not be able to locate key features under such thick foliage.
“The R12i was able to fix and get points in places we could have never acquired with any other GNSS kit we’ve used,” says Richards. “With the tilt compensation, we could reach under the edge of hedges, shrubs, up against buildings and walls, and safely reach out into the lane.”
The R12i brings a double tech boost. One is in the advanced GNSS processing of Trimble ProPoint GNSS Technology, which can process multiple constellations and multiple signals from each in a deft mix-and-match that Trimble says can bring an estimated 30 percent gain over previous models in difficult sky-view environments. ProPoint is powered by large processors included in the R10-2, R12, and R12i models. The second new feature is no-calibration tilt compensation. The R12i uses a combination of inertial sensors and the GNSS-derived trajectory of the antenna to provide the orientation of the pole while MEMS tilt sensors compute the tilt. Prior to the advent of tilt compensation, GNSS surveying required plumbing of the rod for every observation. Some earlier models used magnetic orientation, but that was subject to magnetic disturbances and required frequent, time-consuming calibration. No more; the R12i is ready to go immediately and stays calibrated by normal movement of the pole during the course of the survey.
“The R12i enabled me to go behind the hedge rows of the road, measuring all the edges of the buildings, and get levels on all the concrete foundations,” says Richards. One spot was tough, he said, with a tree overhanging a drainage ditch in thick foliage with five pipes coming across the ditch. “With a total station I would have needed to take the active control rod and try to stick it in and get it level, but with the R12i tilt we were able to put the end of the rod on the pipes and got them all that way. I managed to get more points than I would have ever measured traditionally—a lot more points. It was brilliant!”
Richards had estimated seven days for the survey but completed it in two—all with the R12i.
Confidence and Adaptation
Proving the performance of their new system was important for Benchmark. “We’d surveyed a landfill site years ago with total stations. We had a lot of points such as manholes with which we could check the R12i,” says Richards. “Surprisingly, the new points matched previous positions within more than acceptable tolerances.” They were surprised the GNSS positions matched so well with the conventional points as many of those were completely covered by dense foliage and trees. Benchmark did additional tests as this was their first experience with the tilt compensation features as well. “It took a bit of getting used to,” says Richards. “The tilt changes the way we work, but once we got confidence in it, we’ve been able to use it on most jobs.”
Benchmark has recently used the R12i on a survey for a planned solar farm. It encompassed some rural fields with hedges and trees along the boundary and drainage features. They surveyed these with ease with the R12i and did not have to use their total station.
For large topographic surveys, Benchmarks sometimes uses drones. But for one recent project in a drone-restricted area, Richards mounted the R12i on a quad (ATV). “It was a 300-acre site, a farm that will be developed for housing. The tilt improves what we can do with the ATV, and we did checks to be sure. We set it up in Trimble Access to take continuous points every 8 meters. I completed it in four days on the ATV with over 25,000 points. We also had to map the farm structures and trees; we did that all with the R12i as well.” Richards notes that this may become their primary method for large topographic surveys, as there are other advantages over a drone, like no need to set aerial ground control points, no post-processing and better precision for each point.
Benchmark uses their new R12i with corrections from the UK Trimble VRS Now positioning services network, as well as in base-rover mode, using their R10 as the base receiver. Within the first six months of owning an R12i, Benchmark has been able to revise workflows, instruments used, project cost estimating, and business practices. They are continually finding new uses for this new system that works in places they would have never tried with older GNSS gear.
Gavin Schrock, PLS is a licensed land surveyor, technology writer, and editor of a geomatics publication, based in the Pacific Northwest.