What are the components of a drone lidar system?
A drone LiDAR system has four primary components:
- A LiDAR module.
- An inertial measurement unit (IMU).
- A global navigation satellite system (GNSS) component.
- A drone.
Each of these components plays a critical role in the accuracy of the final product.
LiDAR modules and sensors
A LiDAR sensor measures distances with light from a pulsed radar. The time it takes for each pulse to return to the LiDAR module is used to measure the distance between the module and the object or landscape being mapped.
LiDAR modules differ based on a few specifications, including:
- How many pulses are sent out—or how many measurements are taken—in a given timeframe, such as 240,000 points per second.
- The range at which the LiDAR module can capture accurate data.
- The lidar module’s maximum altitude (though this is also determined by geography; in the United States, very few drones are allowed to fly above 400 feet, and only under very special circumstances).
- The number of returns. A greater number of returns typically provides better vegetation penetration.
- Beam divergence - the smaller the number the better.
These specifications help to determine the final system accuracy. A strong LiDAR module is important, as are the other components such as the IMU and GNSS receiver.
E38 Survey Solutions offers LiDAR modules from two highly reputable brands: DJI and RESEPI. We deliberately chose LiDAR modules at a wide range of price points, precision levels, and other specifications to help our customers find the LiDAR system that works best for them. Our best sellers include:
- DJI Zenmuse L2. The L2 is a budget-friendly LiDAR module made by the unmatched drone experts at DJI. The Zenmuse L2 LiDAR module performs well in a number of these categories. The small beam divergence and 5 returns are the key points that categorize their LiDAR module.
- RESEPI Hesai XT-32. The Hesai XT-32 is the industry standard for survey-grade drone LiDAR. The most impressive part of the XT32 is in the results. The LiDAR provides clean and accurate data, without any manipulation needed.
Global Navigation Satellite System (GNSS)
Every LiDAR drone needs a GNSS receiver for global positioning purposes. The GNSS receiver leverages the International Multi-Constellation Satellite System to determine the LiDAR drone’s exact global location. GNSS data is used to geotag every piece of data captured by the LiDAR sensor for a more accurate final product.
While the GNSS receivers are critical, it is also a fairly old technology, and simple to provide consistent results in this case. RTK receivers require good satellite visibility. Given good visibility, most any RTK receiver will provide results that are equivalent. In this case we will have a base station that we can set up anywhere, so we will choose to set it up in an area with good visibility. The LiDAR receiver will be in the air, giving it ideal satellite visibility. Because of this, every multi-band RTK setup on a drone LiDAR should perform about the same.
DJI Zenmuse L2 - The L2 utilizes the RTK receiver built into the M350 RTK itself. The RTK receiver is well suited for this application.
RESEPI Hesai XT 32 - E38 Survey Solutions is proud to offer GNSS receivers from NovAtel, a highly reputable positioning technology provider and a pioneer in the GNSS space. NovAtel was acquired by Hexagon, a multinational technology group for metrology and geoanalytics, in 2007.
E38 also offers Emlid RTK GNSS receivers in order to be used as a base station, or for ground truthing as a base and rover.
Inertial Measurement unit (IMU)
An inertial measurement unit (IMU) captures extremely precise data about the orientation of the LiDAR system, including specific force and angular rate. LiDAR, IMU, and GNSS data all play a role in determining total system accuracy, but the accuracy of the IMU is absolutely critical to the quality of the final product.
Because IMU data is so important, E38 Survey Solutions has done significant research to find the best IMU on the market, and we chose Inertial Labs, an American company and a trailblazer in positioning, navigation solutions, and orienting technologies with over twenty years of experience. Inertial Labs makes truly exceptional IMUs that guarantee survey-grade results.
DJI Zenmuse L2 - The IMU is the first major difference between the Hesai XT-32. This is a driving factor towards the Zenmuse L2 published system accuracy of 4 cm horizontally and 5 cm vertically. The Yaw accuracy is 0.05 degrees. The Pitch/Roll accuracy is 0.025 degrees.
RESEPI Hesai XT 32 - RESEPI uses their own industry leading IMU with a Yaw accuracy of 0.03 degrees and a Pitch/Roll accuracy of 0.006 degrees. This high level of accuracy, combined with a strong LiDAR module provide clean and accurate data without any manipulation, or estimations. The system accuracy of the XT32 is 2-3 cm.
LiDAR drones
The LiDAR drone is the vehicle that transports all the other components skyward. There are many different lidar drones on the market, but the gold standard is DJI. DJI has extensive drone manufacturing experience, is compatible with many leading LiDAR brands, and offers a competitive price point.
Two excellent options are the DJI Matrice 300 RTK and the DJI Matrice 350 RTK.
DJI Matrice 300 RTK
The DJI M300 RTK can handle a payload of up to 2.7kg or 6lb. With batteries, it weighs about 6.3kg, just under 14lb. The DJI M300’s max flight time is 55 minutes on a single charge.
DJI Matrice 350 RTK
The DJI M350 RTK has many of the same specs as the M300, with a few minor improvements, including:
- Enhanced dust protection and a higher ingress protection (IP) rating.
- A first-person view (FPV) night vision camera with higher resolution.
- An improved transmission system with greater range.
- A new integrated arm lock indicator for better flight safety.
The DJI M350 RTK also uses the RC Plus, a newer remote controller from DJI with a seven-inch screen.
Both the DJI M300 RTK and the DJI M350 RTK are compatible with DJI Zenmuse payloads, as well as a range of RESEPI lidar modules and other third-party payloads. If you are using the M300RTK, you will have to upgrade the controller to the RC Plus if you are using the Zenmuse L2.