LiDAR FAQ: 20 Questions and Answers to Understand Everything
Everything you need to know about LiDAR in 20 technical questions: range, FoV, solid-state vs mechanical, FMCW, ROS, SLAM, pricing, accuracy, eye safety and more.
1. 2D vs 3D LiDAR
A 2D LiDAR scans a single horizontal plane producing a flat slice (x,y). Used for obstacle detection and ground robot guidance. A 3D LiDAR uses multiple beams (16 to 128 channels) or an oscillating mirror to generate a complete 3D point cloud (x,y,z).
2. Range: What to Check on a Datasheet?
Maximum range is measured on a white target at 80-90% reflectivity. In real conditions on dark targets (10% reflectivity), expect 30-50% of that value. Always check the range at 10% reflectivity — that's the relevant figure for black tires or asphalt.
3. What is FoV?
Field of View (FoV) is the total angle covered by the LiDAR, expressed in horizontal and vertical degrees. A 360° horizontal FoV is typical of mechanical spinning units. A wide vertical FoV (90° instead of 30°) improves detection of close ground and high obstacles.
4. Mechanical Spinning vs Solid-State?
Spinning uses a motorized rotor (moving parts, wear) for 360° FoV. Solid-state has no moving parts (robust, compact) but its FoV is limited to 90-120°, requiring multiple units for full coverage.
5. What is FMCW LiDAR?
FMCW uses a continuously frequency-modulated laser and measures Doppler shift to obtain both distance and velocity simultaneously. It is immune to interference from other LiDARs and sunlight, but remains more costly and less mature than ToF.
6. Which LiDARs Support ROS/ROS2?
Ouster (ouster-ros), Hesai (hesai_ros_driver), Livox (livox_ros_driver2), SICK (sick_scan_xd), RoboSense and Velodyne all provide official ROS2 drivers. Check compatibility with your distribution (Humble, Iron, Jazzy).
7. How Much Do LiDARs Cost?
Entry-level 2D: $100-300 (RPLIDAR A1). 3D solid-state: $500-1,500 (Livox Mid-360). Mid-range: $3,000-8,000 (Ouster OS0-32). High-end 128-channel: >$15,000. Automotive grade target: <$1,000 at very high volume.
8. 905 nm vs 1550 nm?
905 nm is cheaper (silicon lasers) but performs worse in rain/fog. 1550 nm uses more expensive InGaAs components but allows 40x higher power for the same eye safety, penetrating fog better with double the range (300+ m).
9. Which LiDAR for SLAM?
For 2D SLAM: RPLIDAR A2 or SICK TiM781 suffice. For 3D SLAM: favor a wide vertical FoV, such as the Livox Mid-360 (59° vertical) or Ouster OS0-32 (90° vertical). An integrated IMU improves SLAM robustness.
10. Outdoor Use?
Most modern LiDARs work outdoors. Check sunlight resistance (1550 nm preferable) and IP rating (min IP65). Range drops 30-50% in heavy rain or fog.
11. What is IP Rating?
IP rating (IEC 60529) classifies protection against solids and liquids. First digit: 6 = dust-tight. Second: 5 = water jets, 7 = temporary immersion, 8 = continuous immersion. IP67 minimum recommended for outdoor use.
12. LiDAR Accuracy?
Typical distance error: ±1 to ±3 cm for mid/high-end LiDARs. Angular error: 0.01° to 0.1°. Real-world accuracy is often 2-3 times worse than ideal conditions.
13. What is Multi-Echo?
Multi-echo detects multiple returns for a single laser pulse, enabling penetration through vegetation, glass or fog. Essential for forestry mapping, object detection behind grilles and rain filtering.
14. Do I Need an IMU/GNSS?
A LiDAR alone produces a sensor-relative cloud. For an absolute map, an IMU compensates motion distortion between scans. GNSS is essential for absolute geolocation outdoors. Some high-end LiDARs integrate IMU and GNSS.
15. ToF vs FMCW?
ToF (Time of Flight) times a laser pulse. Mature and economical but sensitive to interference. FMCW measures Doppler shift for distance + velocity. Immune to interference and sunlight, but 2-3x more expensive.
16. Ouster, Hesai or Livox?
Ouster: excellent cloud quality, well-documented SDK, ideal for research. Hesai: very broad range (Pandar128 to AT128), excellent value. Livox: non-repeating solid-state, competitive price, perfect for 3D SLAM and mobile robotics.
17. What is a Point Cloud?
A point cloud is a set of millions of 3D points (x,y,z) representing laser measurements on physical surfaces. Each point may include intensity, timestamp, echo number and sometimes RGB color. Common formats: PCD, LAS/LAZ, PLY.
18. Are LiDARs Eye-Safe?
All commercial LiDARs are Class 1 certified (IEC 60825-1), safe even with prolonged exposure. At 1550 nm, allowable power is higher because the cornea and lens absorb this wavelength before reaching the retina.
19. Required Network Bandwidth?
16-channel LiDAR: 10-30 Mbps. 32-channel: 40-80 Mbps. 128-channel: 100-300 Mbps (up to 900 Mbps for high-end models). Gigabit Ethernet is sufficient for a single sensor. For multi-LiDAR setups, prefer 2.5GbE or 10GbE.
20. How to Test a LiDAR Before Buying?
Request a sample of raw data (PCD or ROSbag) from the manufacturer. Evaluate quality on varied scenes: indoor, outdoor in sunlight, black and reflective objects. Check frame rate stability and absence of ghost points. If possible, run a comparative test.