LiDAR Sensors & LiDAR Scanners for UAVs, Drones and Autonomous Vehicles
Top LiDAR sensor manufacturers include: Teledyne Optech, Riegl, Yellowscan and PolyExplore. Their LiDAR sensor systems are designed for use on drone platforms for aerial mapping, surveys and inspections
What is LiDAR Technology and how does it work?
YellowScan Vx-20 Precision LiDAR Technology
Lidar, or LiDAR (a portmanteau of light and radar, also interpreted as an acronym for “Light Detection And Ranging”), is a distance-measuring and imaging technology that uses pulses of light in the form of a laser beam from the ultraviolet, visible and infrared portions of the electromagnetic spectrum.
These pulses of light are reflected, typically via backscattering, by the object under measurement. The LiDAR sensor measures the time taken for the pulse reflection to return and can thus calculate the distance from the object.
Drones and LiDAR Applications
LiDAR sensors are often mounted to UAVs and other unmanned vehicles for mapping and surveying applications. Unmanned LiDAR systems offer significant time and cost savings over traditional manned mapping and surveying methods.
Methods of LiDAR Scanning
There are two general methods of detection – incoherent or direct energy detection, which is used for amplitude measurements, and coherent detection, for phase-sensitive measurements. LiDAR can be used to scan a wide variety of materials and the wavelength of the emitted laser is varied to suit the target.
How LiDAR Systems are used on Drones and Airborne Unmanned Vehicles
Teledyne Optech Drone Mounted LiDAR System
When combined with a GPS receiver, inertial measurement unit and onboard computer, a LiDAR sensor can be installed on a drone or UAV and used to scan a large area, with tens of thousands of points per second being measured.
The reflection time interval data is post-processed, converted to distance and correlated with data from the GPS receiver and IMU, which provide highly accurate information on the unmanned aircraft’s position and attitude respectively. The resulting 3D point cloud can be used to build up a detailed image of the surveyed area and provide vital insights to decision-makers.
UAV LiDAR Mapping and Survey Applications
Teledyne Optech Survey-Grade-UAV-Lidar-Sensor
LiDAR technology has many applications and is especially ideal when high-accuracy measurements are required, or when the area under survey or inspection is dangerous or physically difficult to reach. Drone LiDAR mapping provides many additional benefits, including reduced mission time and manpower requirements, and the ability to obtain quicker results by gathering all required data in a single pass.
Modern LiDAR scanners are capable of achieving a wide field of view (FOV) and offer 360 degree visibility and very high data rates. LiDAR mapping has been used in surveying, cartography, agriculture, forestry, meteorology, mining, environmental management, inspection of utility lines and transport networks, and many other fields.
LiDAR Technology for Obstacle Detection and Collision Avoidance
In addition to mapping, UAVs and other unmanned systems may also utilise LiDAR technology for obstacle detection and collision avoidance, and for safe automatic landing. LiDAR is one of the leading technologies currently being utilised in the development of autonomous driving vehicles and self-driving cars.
Topographic and Bathymetric LiDAR
Riegl VQ-840-G for Topographic and Bathymetric LiDAR Scanning
Bathymetric LiDAR, which is used for hydrographic applications to survey coastlines and shallow waters, operates on a different wavelength to topographic LiDAR, which uses laser pulses that are absorbed too rapidly by water to be of use. Bathymetric LiDAR sensors output laser light using the green wavelength of 532 nm, requiring a higher power which means a lower pulse rate and fewer measurements per second.
Bathymetric LiDAR drones fly lower than topographical LiDAR UAVs due to the differing laser powers and attenuations in water and air. Bathymetric LiDAR systems are typically heavier than topographical LiDAR, and so require heavy-lift multirotor drones to carry them.
UAV LiDAR bathymetry is used in coastal surveys to characterise the land and seafloor, for environmental monitoring and coastal reef mapping, to gather data for flood simulations, and in a wide variety of other applications.
MEMS (micro-electromechanical system) LiDAR technologies are currently being developed for use in autonomous driving as well as unmanned systems such as UGVS and UAVs. These use tiny MEMS mirrors, etched onto silicon wafers, to accurately deflect the laser beam. The MEMS mirror arrays can be used to replace traditional beam deflection units, which are usually spinning devices that are mechanically complex and prone to friction and wear.
Pulses of light from an ultraviolet, visible or infrared laser beam are reflected, typically via backscattering, by an object under measurement. The LiDAR sensor measures the time taken between emission of the pulse and the detection of the pulse reflection, and can thus calculate the distance from the object.
The term LiDAR originated as a portmanteau of light and radar. It has also come to be interpreted as an acronym for “Light Detection And Ranging” or “Laser Imaging, Detection And Ranging”, following the reasoning that radar was originally an acronym for “Radio Detection And Ranging”.
LiDAR mapping and surveying is used to gather accurate, precise data on both manmade and natural environments. Applications include cartography, agriculture, forestry, meteorology, mining, environmental management, inspection of utility lines and transport networks, and many other fields.
LiDAR is also used in UAVs and other unmanned systems for obstacle detection, collision avoidance and safe automatic landing. It is currently one of the leading technologies being utilised in the development of autonomous driving vehicles and self-driving cars.
LiDAR mapping uses measurements of reflected laser pulses to produce highly accurate maps and elevation models of terrain and buildings. LiDAR mapping payloads may be fitted to UAVs, USVs and ground robots.
LiDAR using green wavelength lasers provides maximum penetration of water – many other wavelengths will be rapidly absorbed within a few centimetres of water depth. Bathymetric LiDAR sensors can be used to measure river beds, the seafloor and other underwater features.
Doppler LiDAR uses the frequency shift of moving objects (caused by the Doppler effect) to directly measure velocity. The reflected backscatter signal is recorded and mixed with a reference laser beam of known frequency. The frequency shift of the mixed signal is used to calculate the velocity.