We often hear the anecdote about an early lidar scanner that could take a shot every few seconds, yet it held a value proposition for certain applications. As the capabilities of successive mapping and surveying systems change rapidly, so does the conventional wisdom about which are best for various applications. Transportation corridor mapping — be it for improvements design, as-built surveys, asset management or digital twinning — has always been a balancing act between precision and efficient large-scale data capture.
“I remember 15 years ago, during my university time, the scanner was the size of a dining table,” said Andrei Gorb, segment manager for mobile mapping and unmanned aerial vehicle (UAV) systems, CHCNAV. At the top end of the mapping food chain were terrestrial scanners, targets, bore sighting, and registering point clouds mostly manually. As cumbersome and time-consuming as the legacy tools and methods were, these options still offered efficiency gains compared to conventional surveying with total stations. Then a decade ago, mobile-mapping systems began to change that paradigm. Departments of transportation found that mobile-mapping systems could meet their requirements for many design projects, and certainly for asset inventory and management. Unmanned aircraft systems (UAS) were not quite there yet.
The tech used depended on the application. “First, there was road maintenance, to understand the road condition,” Gorb said. “Previously, UAS did not meet the high requirements: centimeter in absolute and millimeter in relative. We now have mobile-mapping solutions, from us and other suppliers, that can be in the 8-9 mm absolute accuracy range on short road surfaces.” Yet for many transportation applications, the absolute accuracy may not be as important as the relative precision. This is where years of development in UAS has made the difference.
CHCNAV was not alone in recognizing that the gap was closing, and the company planned ahead. “Previously, UAS would fly for under an hour, and were mostly carrying cameras or early lidar, which was not suitable for highways,” Gorb said. “A few years of development, and we see it is practical to meet requirements with UAS flying between 50 and 100 meters — in Europe, many local regulations forbid flying above 120 meters anyhow.” Gorb attributes the advances to lidar sensors that UAS can carry. These sensors have become much better and less expensive. Plus, platforms like vertical-take-off-and-landing (VTOL) systems can stay in the air much longer.
The UAS boom of the past 10 years saw the dominance of consumer-prosumer market UAV platforms becoming quite commoditized, with certain vendors gaining majority market share. CHCNAV, instead, sought to develop enterprise solutions, for both mobile and UAS systems — large-platform rotor, fixed-wing and VTOL platforms. The company offers an amalgam of hardware and software, from Riegl scanner heads on some of their mobile-mapping systems to Honeywell inertial navigation systems (INS) for some of their UAS solutions.
Gorb echoes what we hear from many mapping practitioners, saying ground-control points are not as necessary in the densities required for legacy mobile and UAS mapping. He explained that everything from strip adjustments to processing of GNNS/IMU data has tightened both precision and accuracy. “We have a tactical-grade IMU in both our mobile mapping and UAS solutions, for a high-end trajectory,” Gorb said. “So, it means that we can get the same high-accuracy point cloud for highways from the ground and the air perspectives.”
