LiAir V: What is It?
LiAir V (“Lie-Air Vee”) is a lightweight UAV LiDAR data collection system for 3D surveying and mapping. Designed and manufactured by GreenValley International (GVI), LiAir V has been labeled “everyone’s drone LiDAR system” by its users. With an unprecedented price for a package that includes full access to all hardware and software needed, the LiAir V offers a UAV LiDAR solution to those who have never been able to access the technology before. The system’s one-button operation makes it exceptionally easy to use and an ideal entry point for those that are new to LiDAR data collection or just not interested in dealing with overly-complicated workflows, equipment, or software any longer.
GVI has developed a streamlined data processing routine that can be completed within a single firmware/software ecosystem. In well under an hour, a trained LiAir V operator can collect and generate thirty or more acres of high-quality 3D point cloud data. Production rates can be even higher for advanced LiAir V operators or when UAV piloting portions of the operation are handled by someone other than the person in charge of processing collected LiAir V data.
The high-accuracy point cloud data captured by the LiAir offers valuable information to user groups in surveying, civil engineering, architecture, design, natural resource management, forestry, vegetation management, power line inspection, construction, and other important revenue-generating industries. Public safety and emergency response sectors also benefit from the LiAir V’s ability to generate high-fidelity 3D models and accurate measurement data in a short amount of time from an aerial platform. As a source of time-, location-, and (laser pulse return) intensity-stamped range measurements, LiDAR data acquired with the LiAir V can also be of great worth to scientific researchers, NGOs, and agencies who need correct and timely answers to fine-scale geospatial questions.
While not being overly difficult to achieve, a mastery of LiAir V operations from end to end requires an understanding of the concepts that underline each stage of a successful LiDAR survey. The remainder of this article offers an overview of the integrated LiAir V technology stack which allows for easy capture and generation of quality 3D point clouds. Additional LiAir V Product Articles covering important concepts such as Fundamentals of Operation, Data Processing, and Point Cloud Coloration.
A UAV-LiDAR Solution for Everyone
LiAir V is a remote sensing instrument comprised of multiple technologies integrated by GVI into a single system. Its compact design weighs in at 1.0 kilogram (2.2 lbs.), allowing it to be safely carried by many commercially available unmanned, multi-rotor aerial platforms. This hardware integration, along with its accompanying software programs, allow for collection, storage, and georeferencing (global positioning) of 3D LiDAR measurements. LiDAR technologies exploit the relationship between light’s constant velocity and time to produce highly accurate and precise measurements of variable distances or ranges. The LiAir V emits a specific infrared wavelength (905 nm) of electromagnetic energy in short bursts, sometime referred to as pulses, that are then returned to the broadcasting unit’s integrated photon sensors by signal-reflecting objects falling within its circular 38.4 degree field-of-view. The photo sensors detected laser pulse returns, also called echoes, are used to calculate distance measurements (ranges) and save them to the LiAir V’s internal storage device. The return laser signal intensity value for each data point (distance measurement) will also be recorded.
The LiAir V features a LiVox Mid-40 LiDAR sensor which can collect up to to 100,000 returns (LiDAR measurements) per second. Range measurement scanning patterns for the Mid-40 are non-repetitive and resemble the pedals of a flower when viewed in short bursts. The sensor features a maximum target detecting range limit of 260 meters for objects that are highly reflective. At the core of the LiAir V technology stack sits a Position Orientation System (POS) used to determine velocity, position, and attitude values for the integrated Mid-40 LiDAR unit throughout each data acquisition period. Accurate and precise localization of the LiAir’s ranging component allows for the creation of crisp (high-resolution) 3D point cloud models.
LiAir V’s POS system is comprised of a Micro Electromechanical System (MEMS) Inertial Measurement Unit (IMU). The IMU/GNSS POS system is OEM'd by GVI supplier’s from NovAtel. This non-ITAR inertial sensor contains a three-axis gyroscope as well as a threeaxis accelerometer. The high-frequency and high-precision data collected by the IMU serve as inputs to an estimation process which integrates the accelerometer measurements (external specific force) and the gyroscope measurements (angular velocity), to predict instrument position and orientation. This IMU data can be used as inputs to a navigation and location prediction method known as “dead reckoning”. Errors in location and position estimates, also known as 6D pose estimates, made via dead-reckoning techniques alone accumulate bias and estimation accuracies tend to decrease as data collection times increase.
To improve the accuracy of 6D pose estimates (longitude, latitude, elevation, heading, pitch and roll) that document LiAir V paths of travel during data collection (trajectories), IMU measurements are fused with GNSS data that has been differentially corrected using information collected by an auxiliary GNSS base station. The LiAir V’s IMU interface allows it to connect directly with a Global Navigation Satellite System (GNSS) receiver. GPS, GLONASS, and BeiDou broadcast positioning as well as timing data from space-borne satellites that LiAir V’s dual-antenna input, multi-frequency GNSS receivers gather. No GNSS or IMU data from the UAV itself is needed to process LiAir V data.
The fusion of the IMU and GNSS data takes place in LiGeoreference’s LiNav module. This user-friendly software developed by GVI generates 6D pose estimates with latitude (Y) and longitude (X) coordinates that, by default, reference the World Geodetic System 1984 (WGS84, EPSG: 4326) standard. Elevation (Z) values for individual LiDAR measurement points captured by the LiAir V are also made relative to the WGS84 ellipsoid. A tightly-coupled pose finding technique is used to create the georeferenced POS data. The method also allows for the updating of the hybrid GNSS/IMU navigation solution in situations where poor GNSS signal quality or limited coverage exists. Assuming there are no blackouts in sufficient GNSS data, at one-sigma LiNav processed POS system attitude measurements for the LiAir V are accurate within 0.008 degrees and azimuth (heading) values are within 0.038 degrees. Using the tightly-coupled GNSS/IMU 6D pose estimation data output by LiNav, LiGeoreference registers individual 3D LiDAR measurements from the corresponding LiVox sensor data to a target (global) coordinate system and thereby produces a georeferenced point cloud with high absolute and relative accuracies.
UAV LiDAR data does not have to be difficult to obtain. The LiAir V may be comprised of very advanced technologies but GVI has developed an end-to-end solution that make them integrate seamlessly with each other. Please visit GVI’s LiAir V product website for more information or email info@greenvalleyintl.com with comments and questions.