Strassen-und Tiefbau GmbH is advancing drone-assisted road design when building municipal or rural motorways. The construction company from Kirchhundem, now comprised of more than 215 employees, continues to expand its fleet with a wide range of modern surveying applications and new technologies to increase efficiencies and improve workflows. One solution they’ve incorporated is the Microdrones mdMapper1000PPK, a fully integrated UAV system that has increased accuracy and productivity on their construction projects.
High-tech tools can be especially helpful in rural areas such as Kichhundem, a community of about 12,000 residents in the Sauerland region of Germany. For Strassen-und Tiefbau GmbH, incorporating new technology is a priority. The third-generation, family-owned business specializes in earthworks, sewerage and road construction. Managing Director Andreas Behle says that 15 of the company’s 25 excavators are equipped with GPS, along with three bulldozers and a grader. “We want to make sensible use of the opportunities made possible by the digitalization of the construction industry and optimize our processes,” Behle says.
The drive: digitization
With a focus on the future, Strassen-und Tiefbau GmbH leaders continued to invest in modern machinery even through recent boom years in the industry and placed an emphasis on upgrading surveying technology. The company now has 18 GPS rovers, up from two in 2015; and 19 machine control systems after having just one five years ago. “With the machine controls, we can increase the productivity of our fleet and also save material costs in earthmoving and leveling," says Stefan Pieper, a surveyor with Strassen- und Tiefbau GmbH. For example, machine control systems use highly precise positioning data to help operate terrain graders. "This means that almost all accompanying surveying tasks on the construction site are no longer required," Pieper said. "The time-consuming approach to the target dimension is also significantly simplified." For this task, the systems rely on a GNSS receiver to process satellite data, a UTS receiver and an operating unit.
“The wide range of possible uses and the possible production increase immediately convinced us that UAV technology is needed.”Stefan Pieper, a surveyor with Strassen- und Tiefbau GmbH
Drone solution is convincing
Strassen-und Tiefbau GmbH got a look at how drones can help at the annual Construction Live Day of Sitech Deutschland GmbH, a German Trimble distributor, in Hamm in February 2018. Pieper demonstrated a test flight with a quadcopter, recording inventory data over about 12 acres in just a half-hour. “The wide range of possible uses and the possible production increase immediately convinced us that UAV technology is needed, despite the high investment costs,” he says.
So, they bought a quadcopter two months later and used it for numerous flights through September. They were satisfied initially with the results, though Pieper says that battery performance deteriorated after a few months. Costs tied to replacing the battery were in the “four-digit range.” A battery failure switched the drone into an emergency mode in flight that caused the machine to land, regardless of the surroundings. This means that it could damage buildings or even bystanders on the ground since it could no longer be manually controlled. “This is intolerable for our company, especially since our excellent reputation in our region is at stake," Behle says. At the same time, the company determined that a drone was still indispensable for the business.
High quality requirements
Looking for alternatives, Behle, Pieper and colleagues came across a tried-and-tested solution from Microdrones, the Siegen-based company located just about 18 miles from Kirchhundem. Microdrones had a reputation for safety, reliability and the best flight characteristics, which fit with Strassen-und Tiefbau GmbH’s requirements. Company officials viewed a Microdrones test flight in Siegen. They then visited the Intergeo 2018 conference in Frankfurt before deciding to place an order for the Microdrones mdMapper1000PPK.
Pieper says Strassen-und Tiefbau GmbH was even more impressed after evaluating the quality of data following a test flight. For example, the image on the mdMapper1000PPK taken with the integrated Sony RX1R II camera was more detailed and accurate than what the company had been used to in spite of flying at a higher altitude. “What used to be possible at a flight altitude of (nearly 100 feet) is now possible at almost 200 feet," Pieper says. Every paving stone was visible. Not only was quality better, but productivity increased because a higher altitude allows for more ground to be covered from the air. This gave added value to Strassen-und Tiefbau GmbH’s investment. "In addition to the high-image resolution and quality that the Microdrones mdMapper1000PPK brings with it, the solution also won us over with its high airspeed and low wind sensitivity," Behle says.
Another special feature of the Microdrones mdMapper1000PPK is the so-called Post Processing Kinematic (PPK) process to determine accuracy, which uses algorithms after the aerial survey to determine exact positioning instead of measuring in real time. Both the ground unit and the rover - which is usually mounted on the drone during measurement - record raw GNSS data which is processed after the aerial survey. Compared to the real-time method, the PPK method allows the drone to be used without being connected to the mobile radio network, meaning that it can also be used in the most remote areas of Sauerland.
Document Earth movement
How exactly does Strassen-und Tiefbau GmbH use the drone? “Although most customers do not yet require the use of a drone, the system makes our work a lot easier,” Pieper says. “For example, we can document how much earth we had to move and derive our bills for the client. We also have proof for the client of the work we have done. "
Using the mdMapper1000PPK is now standard to document inventory and construction progress, with Strassen-und Tiefbau GmbH conducting 40 aerial surveys last year. "Thanks to the simplified workflow and the improved processes … the solution pays for itself," Behle says. The time saved allows employees to focus on other important tasks. Pieper says that site managers are requesting to use the drone more after growing more familiar with how and when to use the machine.
Derive and evaluate point cloud
Strassen-und Tiefbau GmbH employs three pilots to operate the drone. They took a course at the Microdrones office in Siegen and acquired their license in Hanover. "The courses were very positive," Pieper says. "Our pilots can work even more precisely and efficiently."
Besides documenting construction progress, the company uses the mdMapper1000PPK for surveying tasks. Strassen-und Tiefbau GmbH can also use photogrammetry software (Pix4D) to derive a point cloud from recordings. Point clouds can be used to create a digital ground model (DGM) of landforms and show items like planned roads, Pieper says.
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