1550‑nm LiDAR for Aerial/UAV Mapping and the ROCK Ultra System: A White Paper

Introduction

Light detection and ranging (LiDAR) is a remote‑sensing technique that measures the time it takes for laser pulses to travel to objects and return. By combining time‑of‑flight measurements with precise attitude data from global navigation satellite systems (GNSS) and inertial measurement units (IMUs), LiDAR generates highly accurate three‑dimensional point clouds. Aerial LiDAR penetrates vegetation and produces multiple returns, enabling “bare‑earth” models even under dense forest canopies. Modern airborne systems operate at various wavelengths: green 532 nm lasers are used for bathymetric surveys while near‑infrared wavelengths (905 nm, 1064 nm and 1550 nm) are preferred for topographic mapping. This paper explains why 1550 nm lasers are gaining prominence in aerial/UAV LiDAR systems and outlines how ROCK Robotic’s ROCK Ultra leverages these advantages to deliver a step‑change in efficiency and data quality.

Why 1550 nm Lasers?

Eye‑safety and regulatory freedom

• Safer for human eyes. The cornea, lens and vitreous humor absorb wavelengths longer than 1.4 µm so strongly that very little 1550 nm light reaches the retina. A 1550 nm lidar can therefore emit much higher optical power without risking retinal damage. At the same output power a 1550 nm laser is 40 times safer than a 905 nm laser, and Leishen Intelligent confirms this advantage. This eye‑safety allows the transmitter to emit more photons per pulse, leading directly to longer range, higher resolution and improved resistance to ambient light.
• High photon budget. Luminar’s design lab notes that 1550 nm systems can send 17 times more photons than 9xx‑nm systems; the extra photons can be traded for 4× the detection range or 17× the resolution.
• Manned‑aircraft compatibility. Because little 1550 nm light reaches the retina, these lasers are invisible to pilots and night‑vision goggles, mitigating the risk of distracting manned aircraft. The U.S. Federal Aviation Administration classifies 1550 nm lasers as Class 1 eye‑safe when properly engineered, enabling high‑power transmissions without requiring special coordination.

Range and measurement precision

• Extended detection distance. 1550 nm lasers can operate at much higher peak powers. MDPI’s LiDAR hardware review notes that 1550 nm sensors have a more relaxed power limit than 905 nm ones, which allows longer detection distances and greater anti‑interference capabilitiesmdpi.com. Typical 905 nm lidar achieves ~200 m range at 10 % reflectivity; 1550 nm units routinely exceed 500 m at low reflectivity and over 1000 m for bright targets.
• Smaller spot and better collimation. 1550 nm beams are better collimated and have a spot size four times smaller than 905 nm at 100 m. Leishen notes that the spot diameter of a 1550 nm laser at 100 m is ¼ that of a 905 nm laser. Smaller footprints improve ground resolution and reduce mixed‑pixel errors.
• Enhanced penetration of haze and dust. The MDPI review explains that laser penetration through suspended particles improves as wavelength increases; haze particles (~1000 – 2000 nm) scatter 905 nm light strongly but allow better propagation of 1550 nm beams. Consequently, 1550 nm lidars provide longer range and higher SNR in hazy or dusty air.

Multiple returns and canopy penetration

• High‑power pulses yield multiple echoes. Newer airborne LiDARs operate at pulse repetition rates ≥1 MHz and can record multiple returns from a single pulse. Newport/MKS states that multi‑return systems increase point density and improve mapping of forest canopies and tree crowns. 1550 nm systems are typically single‑laser scanners with high peak power, enabling deep penetration and multiple echoes without saturating detectors.
• Bare‑earth recovery. Multi‑return 1550 nm lidars can reliably differentiate canopy layers and ground surfaces even in dense forests.

Reduced solar and ambient interference

• Lower solar irradiance. Luminar highlights that far less sunlight reaches the earth at 1550 nm than at 905 nm; therefore the “floor” for detection noise is lower. 1550 nm sensors enjoy a higher signal‑to‑noise ratio in bright sunlight, which is critical for daytime UAV operations.
• Better atmospheric transmission. Newport notes that atmospheric transmission at 1550 nm is “quite good”. Combined with higher allowable power, this gives 1550 nm systems very long slant ranges and enables UAVs to fly at higher altitudes while maintaining ground‑point density.

Challenges and trade‑offs

While 1550 nm systems have clear advantages, several disadvantages must be considered:

• Cost and detector availability. 1550 nm detection requires indium‑gallium‑arsenide (InGaAs) or germanium photodetectors. These sensors are more expensive and have lower detectivity than silicon detectors, though the price gap is narrowing. The higher cost of InGaAs detectors and fiber‑laser technology means that 1550 nm sensors historically targeted high‑end applications.
• Water and snow attenuation. Water absorbs 1550 nm light strongly. MDPI reports that in rain and fog the attenuation of 1550 nm laser signals is 4–5 times higher than 905 nm; snow reduces 1550 nm reflectivity by about 60 % compared with only 15 % for 905 nm. The U.S. National Oceanic and Atmospheric Administration (NOAA) therefore does not recommend 1550 nm lidar for wet conditions.
• Heat and power consumption. 1550 nm systems operate at higher power, leading to greater heat generation.

Advantages of 1550 nm LiDAR for Aerial/UAV Mapping

Longer range enables high‑altitude flights

The ability to emit higher‑power pulses without violating eye‑safety limits allows 1550 nm systems to measure ranges of hundreds of meters. Such range means that UAVs can fly near the maximum legal altitude (e.g., 400 ft/120 m AGL in the U.S.) yet still collect high‑density data. Higher flight altitudes simplify mission planning, reduce collision risk with trees and power lines, and increase the swath width; fewer flight lines are needed, which reduces time on site and battery swaps.

Dense point clouds and multiple echoes

1550 nm sensors typically operate at high pulse repetition rates (up to 1 MHz) and, because they are eye‑safe, can deliver high pulse energy. This results in very dense point clouds. Multi‑return capability means that each emitted pulse can provide multiple distance measurements along its path. Newport explains that multi‑return systems substantially enhance the ability to map forest canopy and tree structures. With up to seven echoes per pulse, 1550 nm aerial LiDARs can penetrate dense vegetation, identify intermediate canopy layers and recover the true ground surface, even in dense conifer forests.

Improved safety and workflow flexibility

Operating at 1550 nm minimizes the risk of injuring pilots or bystanders and avoids interference with manned aircraft or night‑vision equipment. This increases operational flexibility—missions can be flown near airfields or populated areas with reduced safety concerns. High‑altitude operation also means obstacles such as power lines and tall trees are less hazardous, simplifying flight planning and training requirements.

Reduced susceptibility to ambient light and haze

Lower solar irradiance at 1550 nm provides higher signal‑to‑noise ratio in bright sunlight. The longer wavelength is less affected by Rayleigh scattering and is better at evading haze particles. These features allow UAV operators to collect consistent data throughout the day and in slightly hazy conditions.

The ROCK Ultra: A 1550 nm LiDAR System Optimized for UAVs

ROCK Robotic’s ROCK Ultra embodies the benefits of 1550 nm technology while addressing the challenges through thoughtful design and an integrated workflow. Key features include:

• High‑power 1550 nm laser with 7 returns. The Ultra uses a 1550 nm Class 1 laser capable of up to one million points per second and seven echoes per pulse. The 90° field of view (FOV) directs all points downward, concentrating the entire point rate on the area of interest and producing roughly three times the useful point density of a conventional 360° scanner.
• Long‑range mapping. With a measurement range of 500 m at 20 % reflectivity and 1000 m at 80 % reflectivity, the Ultra can fly as high as 450 m AGL, covering large areas in fewer passes. Range precision is 5 mm and post‑processed positional accuracy is 1 cm horizontal / 2 cm vertical thanks to its tactical‑grade IMU (0.006° pitch/roll, 0.03° heading) and multi‑constellation GNSS.
• Lightweight UAV integration. The sensor weighs 1.21 kg without camera and 1.40 kg with a calibrated 26 MP or 45 MP RGB camera. Compared with competing long‑range systems weighing 3.5 kg or more, the Ultra can be carried by standard drones (DJI M300/M350) without compromising flight time. A universal mount makes it adaptable to other platforms.
• Simplified mission planning – the “Easy Button.” The combination of long range and narrow FOV allows the Ultra to operate at maximum altitude, reducing the need for terrain following and complex flight plans. High‑altitude flights avoid obstacles, expand weather windows and allow less‑experienced pilots to achieve survey‑grade results. ROCK Robotic’s marketing material notes that flying high and fast enables crews to cover 2–3 times more ground per flight than standard systems while still resolving fine features such as curbs and vertical walls.
• Integrated ecosystem: After landing, users transfer data to ROCK Desktop for rapid PPK processing and QC. The processed point cloud is uploaded to ROCK Cloud, where users can visualize, measure and collaborate on the data. If desired, ROCK Pro Services converts the data into CAD‑ready deliverables (DTMs, contours, planimetrics) with a single click. This field‑to‑finish workflow eliminates complex software setups and reduces training time.

Product specifications at a glance

Parameter / Feature	ROCK Ultra specification	Benefit
Laser wavelength	1550 nm, Class 1 eye‑safe	Allows high power, long range and safe operations near manned aircraft
Measurement range	500 m @ 20 % reflectivity; 1000 m @ 80 % reflectivity	Enables high‑altitude flights (up to ~450 m AGL), larger swath widths and reduced flight lines
Point rate and FOV	Up to 1 million points/s, 90° FOV	Concentrated point density on target area; 3× useful point density compared with 360° scanners
Echoes per pulse	7 returns	Excellent vegetation penetration and bare‑earth recovery
Range precision	5 mm	Produces high‑resolution DEMs and accurate volume calculations
IMU accuracy	0.006° pitch/roll, 0.03° heading	Minimises strip misalignment; ensures clean point clouds
GNSS & positioning	Multi‑constellation GNSS with PPK; 1 cm horizontal, 2 cm vertical accuracy	Survey‑grade geolocation for professional mapping
Weight	1.21 kg (sensor only); 1.40 kg with 26 MP camera	Allows mounting on common UAVs; long flight times
Camera options	26 MP or 45 MP calibrated RGB	Provides colorized point clouds and high‑resolution orthomosaics
Software ecosystem	ROCK Desktop, ROCK Cloud, ROCK Pro Services	Field‑to‑finish workflow simplifies data processing and deliverable creation

Applications and Use‑Case Fit

The ROCK Ultra and similar 1550 nm UAV lidars are ideal for professionals who need to map large or vegetated areas quickly and accurately. Typical use cases include:

• Land surveying and civil engineering: Rapidly survey thousands of acres for corridors, highways or large infrastructure; multi‑return capability identifies bare‑earth elevations for design; high‑altitude flights reduce time and risk.
• Forestry and environmental management: Derive accurate digital terrain models (DTMs) beneath dense canopy; estimate biomass, canopy height and wildfire fuel loads. Phoenix LiDAR notes that multi‑return 1550 nm systems penetrate dense vegetation at high speeds and altitudes.
• Utility corridor inspection: Inspect power‑line corridors from a safe altitude; 1000 m range allows single‑pass coverage of wide corridors; multiple returns highlight vegetation encroachment.
• Mining and construction: Measure open‑pit volumes, track stockpiles and monitor haul roads; high‑altitude flights improve safety by keeping drones clear of heavy equipment.
• Emergency response and disaster mapping: Quickly generate accurate terrain models after floods or landslides; high power and eye‑safety allow operations near rescue helicopters.

Conclusion

1550 nm LiDAR technology offers compelling benefits for aerial and UAV mapping. Its inherent eye‑safety permits higher transmitted power, enabling long‑range operation, high resolution and dense multi‑echo point clouds. These systems are less affected by solar radiation and haze, penetrate vegetation effectively and simplify mission planning by allowing drones to fly higher and faster. Trade‑offs include higher equipment costs, greater power consumption and reduced performance in heavy rain or snow. When these factors are balanced against mission requirements, 1550 nm lidar is often the best choice for professional surveying, large‑area mapping and canopy‑penetrating applications.

ROCK Robotic’s ROCK Ultra captures the advantages of 1550 nm technology in a compact, lightweight UAV package. With up to seven returns, one million points per second, a 90° downward FOV and centimeter‑level accuracy, the Ultra delivers high‑quality data while simplifying flight planning and processing through its integrated software ecosystem. Surveyors and mapping professionals seeking to maximize efficiency, penetrate dense vegetation and reduce operational complexity will find the ROCK Ultra to be a highly capable “easy button” for field‑to‑finish LiDAR workflows.