The rollout of self-driving cars onto metropolitan roadways is proof that lidar systems play a major role as an enabling technology to next-generation solutions. With providers such as Waymo and DeepRoute.ai debuting versions of their self-driving vehicles in North American and Chinese hubs, respectively, lidar technology is more synonymous than ever with autonomous mobility. Courtesy of Leica Geosystems. Advancements to laser sources and optical components are behind the increased durability and high performance of lidar solutions on the market today. These improvements offer users higher stability, increased power efficiency, and better signal clarity. Additionally, systems designers may combine lidar with the capabilities of sensing modalities such as radar and camera imaging, to create increasingly integrated systems that yield data from multiple sensors. A drone carries YellowScan’s bathymetric lidar system. The lidar system uses a green laser at 532 nm for underwater scanning. Courtesy of YellowScan. These benefits extend to off-road applications. Lidar systems are providing engineers and end users with a literal green light to operate in maritime, coastal, and deep-sea environments. The same component- and system-level improvements that are pushing lidar’s sustained adoption for self-driving vehicles are broadening lidar’s utility for underwater industrial applications and subsea research. Quantum lidar Last year, Hoboken, N.J.-based Quantum Computing Inc. (QCI) completed the sale of its quantum lidar prototype to Johns Hopkins University. The prototype system is engineered to float on a raft or mount on the deck of research vessels. The collaborators plan to use it to monitor phytoplankton movement and nutrient distribution, among other studies. Unlike traditional underwater lidar systems, QCI’s prototype detects individual photons rather than relying on the aggregate of many. This single-photon approach has a direct effect on enhanced depth performance. The method enables the quantum lidar mechanism to detect faint signals from only a handful of photons bouncing back from an underwater object, according to QCI CEO William McGann. Further, because quantum lidar solutions such as these precisely record the arrival time of individual photons, the method delivers more accurate distance measurements than alternative techniques. It also enables more effective 3D imaging, and the single-photon mechanics of quantum lidar improve the filtering of background noise. The result is a finer distinguishment between true signal and unwanted interference. “In simpler terms, it’s like listening for a whisper in a noisy room, and our technology is finely tuned to catch that whisper,” McGann said. QCI’s quantum lidar prototype uses a picosecond-pulsed laser with an output power of 3 W at a 1-MHz repetition rate. The system delivers 3-mm resolution and measures depths of ~100 m in clear water, though this range could be extended with a low-repetition-rate laser with sufficient power. To achieve submillimeter resolution, McGann said that the quantum lidar system could be supplemented with quantum parametric mode sorting. The early-stage development of this technology carries a cost and a physical size-of-system that is more applicable to maritime research, but engineering improvements could chart a course for quantum lidar to become more enticing to the underwater surveying, industrial inspection, and environmental monitoring industries, McGann said. Compared to research, subsea industrial applications require different lidar systems with distinct technical and physical parameters. The green light QCI’s quantum lidar system uses a green laser at 532 nm, which is the standard wavelength for lidar for underwater applications. “[Five hundred thirty-two] nm is used because frequency doubling from 1064 nm is a mature path,” said Xiyuan Lu, a postdoctoral researcher in National Institute of Standards and Technology’s Microsystems and Nanotechnology division. “Depending on the ocean water condition, different wavelengths are needed in different cases.” According to Lu, in deep ocean water, for example, blue lasers typically offer better performance than their green wavelength counterparts. In close-to-shore ocean water, or water with more phytoplankton, green lasers provide superior performance. Leica Geosystems’ coastline and river surveying system uses a green laser at 532 nm. According to the company, the solution is 250% faster than previous models for underwater scanning. Courtesy of Leica Geosystems. The use of blue-green light for underwater imaging enables a greater scatter, which, according to McGann, supports greater depth penetration. Water also achieves less absorption of blue-green light than pure green, at 532 nm. And it travels farther, produces better images, enhances contrast, and can even induce fluorescence in certain organisms. Despite these benefits, blue-green light poses challenges for underwater lidar; silicon detectors are less efficient in this range. Photomultiplier tubes and/or superconducting nanowire single-photon detectors (SNSPDs) offer alternatives, but each comes with its own drawbacks. Photomultiplier tubes are bulky and sensitive to magnetic fields. SNSPDs, meanwhile, require cryogenic cooling and are costly. Manned aerial lidar Earlier this year, Leica Geosystems, a Hexagon subsidiary, introduced a coastline and river surveying system that uses a green laser at 532 nm. For underwater scanning, according to the company, the solution is 250% faster than previous models. A visible green laser at 532 nm is typically used for underwater lidar applications. Green lasers are optimal for use in close-to-shore ocean water. Courtesy of 3D at Depth. From 2012 until the rollout of the solution earlier this year, Leica used 515-nm sources for its bathymetric lidar systems. According to Anders Ekelund, vice president of airborne bathymetric lidar at Hexagon, the physical difference between 515 and 532 nm is minimal. Leica has favored a 515-nm solution due to an increase in efficiency in internal system components. Leica’s newly introduced system is designed for manned aircraft. It integrates bathymetric lidar, topographic lidar, and high-resolution imaging into a single system. The solution synchronizes and co-aligns the 1030-nm pulses, used for water surface measurements, with the 515-nm laser pulses. The “topo-bathy” system can cover 360 sq km/h. According to Ekelund, the increased scanning speed lowers users’ flight costs and increases revenue potential. Its depth penetration ranges from ~40 m in clear waters to 20 m in moderately clear waters to 10 m in turbid waters. The system can capture 1 million bathymetric and 2 million topographic data points/s, with high-resolution imagery at a 5-cm ground sampling distance. Its capture rates were up to 1000 kHz for bathymetric data and 2 MHz for topographic data, and its scan speeds were up to 84 Hz, or 168 scans/s. This increased performance enables geospatial data to be scrutinized via AI-driven analysis, which is critical for alerting government agencies to shoreline retreats, shifting riverbeds, and underwater infrastructure vulnerabilities, according to Ekelund. Leica’s solution is not the only one of its kind on the market. Last year, Teledyne Optech introduced a system that combines bathymetric and topographical lidar sensors and a multispectral camera. With a coverage rate of 50 sq km/h for coastal areas, the manned aircraft system offers real-time processing that allows data to be mined as it is collected. “Data is being collected to be actioned, whether it is an industrial application like monitoring disturbances around a pipeline, or disturbances in a port, or an offshore infrastructure. Real-time processing enables a faster response to data, which in turn will deliver a faster resolution,” said Malek Singer, a senior product manager for Teledyne Optech. The bathymetric element of the Teledyne Optech system features a high-power laser that uses both a 1064-nm IR wavelength for mapping the water surface, and a 532-nm green wavelength for mapping submerged terrain. This combination of IR and visible green wavelengths contributes to higher georeferencing accuracy, because their returns are coaxial and there is more precision in the refraction correction between the surface of the water and the bathymetric system, according to Singer. It uses four shallow channels, each pulsing at up to 60,000 shots/s. The topographic subsystem pulses up to 2 million points/s. It can collect data independently at up to 1200 m of altitude. However, the 50 sq km/h coverage rate for coastal areas is contingent on maintaining an altitude of 475 m. The coverage rate could be accelerated at higher altitudes, but this would decrease the system’s depth potential, which ranges from 45 m in clear waters to 25 m in more typical water conditions to 5 m in dark waters with organic bottoms. “Systems have historically benefited from bigger lasers — higher-power lasers with more sensitive optics,” Singer said. “That trajectory has been successful, and we expect it to continue to improve in developing lasers with shorter pulse widths, higher pulse repetition frequencies, and [in] digitizing hardware with higher sample rates.” Unmanned aerial lidar Bathymetric lidar systems for manned aircraft are designed for large-scale projects exceeding 100 sq km per day. For smaller-scale projects, unmanned aerial vehicles (UAVs) are a better option. Drones equipped with bathymetric lidars can fly at low altitudes, which supports greater depth penetration even though it is limiting to the potential area that the system can cover. The coverage area of UAVs is further constrained by slow collection speeds and flight times that last ~30 min before the battery needs to be exchanged, according to Ekelund. Nevertheless, the trade-off between a smaller coverage area and a deeper penetration may be appealing for several industrial applications, such as pipeline and subsea cable inspections, oil and gas, offshore wind farm development, and port and harbor maintenance. Last year, aerial solutions firm Volatus Aerospace entered into a partnership with Dragonfly, a drone developer. The collaborators are combining Volatus’ bathymetric lidar systems with Dragonfly’s heavy-lift drones to provide precise underwater mapping and improved efficiency in oil and gas exploration. “The size and weight reduction of bathymetric lidar systems over the last few years has opened new possibilities for deployment on drones, giving them more access for surveying hard-to-reach areas, expanding the range of applications,” said Lee Dodson, strategic projects leader for Volatus Aerospace. For underwater surveys, Volatus uses a bathymetric lidar system developed by YellowScan, a company whose system uses the 532-nm wavelength with 3-cm precision and a laser range of up to 120 m. A stingray data scan, captured via subsea lidar. Courtesy of 3D at Depth. Obtaining accurate results in hard-to-reach areas feeds into considerations of water quality and other environmental factors. “Depth penetration is highly dependent on water clarity, with turbid or murky waters significantly reducing accuracy and range,” Dodson said. “Additionally, reflections from surface waves, bubbles, and submerged vegetation will introduce noise and reduce data quality. “Complex bottom topography and high reflectance variability also affect results: Lidar technology cannot overcome these physical limitations. Only integration with other types of sensors can overcome these challenges. More advancements in laser power in smaller systems and improved AI and algorithms may overcome some limitations, but there is not much else that can be done with this technology due to its dependence on light penetration.” Subsea lidar Due to water clarity limitations, bathymetric lidar, which is typically airborne, becomes ineffective beyond depths of 50 to 75 m. Beyond these depths, subsea lidar — deployed via remotely operated vehicles (ROVs) and/or autonomous underwater vehicles (AUVs) — operates more effectively in complete darkness and high-pressure environments, according to Brook Rodger, director of business development for 3D at Depth. In 2017, the Longmont, Colo.-based company introduced a subsea lidar system that can be operated at depths of up to 4000 m. This year, it plans to debut a model with a depth rating of 6000 m. Though 3D at Depth’s subsea lidar systems are typically used for oil and gas and nuclear facility inspections, last year, a deployment of its 4000-m technology used the solution to scan the Titanic. The company’s subsea lidar systems use Nd:YAG lasers that operate at 532 nm and achieve submillimeter measurement precision. Demand for higher-resolution measurements with 0.001-in. accuracy or better is especially high in the nuclear industry. The laser and optics in 3D at Depth’s most recent model, with a 6000-m depth rating, provide a wider field of view, smaller package volume, and improved signal clarity for deepwater environments and high-speed scanning, according to Rodger. In addition to these improvements, the 2025 system offers data collection capabilities that are 10× faster than previous models, enhanced by real-time processing optimizations and AI-driven enhancements. The system also has a smaller footprint, making it easier to integrate with a wider range of vehicles, from ROVs to torpedo-style AUVs. Its 360° scanning capabilities make it ideal for pipeline inspections, both internal and external. The system has a pulsed time-of-flight measurement method with a pulse rate between 200 and 300 kHz and a range of up to 45 m. “A few years ago, real-time lidar scanning from an AUV was considered impractical due to power and data limitations. Today, our lidar systems can autonomously collect and process high-resolution 3D data while operating untethered, revolutionizing offshore inspections, decommissioning, and marine research,” Rodger said. MBARI, the Monterey Bay Aquarium Research Institute in Moss Landing, Calif., is among the early adopters of 3D at Depth’s subsea lidar system. Since 2013, it has used iterations of 3D at Depth’s subsea system attached to ROVs to scan the ocean floor and study deep-sea creatures. Now, the use of the company’s latest subsea lidar system in an AUV is especially appealing to the nonprofit oceanographic research center. ROVs tethered to vessels only enable researchers to scan a 100- × 100-m patch of ocean floor in one day. Using the subsea system with an AUV would enable personnel to scan vastly larger swaths. “It is going to be faster, it is going to produce more data, it is going to be a wider swath, and it is going to be a simpler, smaller low-power system,” said David Caress, MBARI’s principal engineer of seafloor mapping. “And the reason that is so important is because we want to put this on an AUV.”