Aerial Lidar is an aerial mapping technology that uses calibrated laser returns from the earth’s surface. The laser then reflects an overflying GPS monitored aircraft equipped with on-board positional and IMU sensors. There are many factors to consider when deciding which type of mapping drone to combine with the Lidar surveying and mapping equipment. The primary consideration is the ability of the drone to lift the weight of the LiDAR equipment comfortably and fly for a required amount of time.
Here are some tips when considering which drone to choose for the Lidar survey projects.
Table of Contents
Payload
The weight of the payload is often directly correlated to the mapping drone’s size and the possible fly time. Some unmanned aerial vehicle (UAV) LiDAR systems can fly on an aerial platform that can carry a payload of 3.3kg, depending on the selected options.
Flight Performance
The flight speed and time are the key considerations and impact on the efficiency of the survey and the results. The duration of the mapping drone flight has a direct effect on the efficiency of the study. With the short-duration drones that last at least 15 to 20 minutes, the number of flights, take-off, and landings needed to cover a survey area will be much more than a long-endurance drone. The drones with long endurance capacity like the Aeries LiDAR by Aeva have more than 12 hours of data storage capacity, low power consumption, and the telemetry system can, under the right conditions and setup, achieve a range of 10km.
The flying speed of the UAV significantly impacts the resolution and the quality of the final results. The slower the flying process, the higher the point cloud resolution is achieved between individual scans. The flying speed is also dependent on the application that is in use. The nominal flying rate recommended to achieve an excellent data intensity, and vegetation penetration is 5-7m/s. The maximum speed expected is 15m/s to ensure the data resolution and quality are not compromised too much.
Fuel
The type of fuel or energy used to power the mapping drone is essential. The primary type of energy used to control Aeries LiDAR by Aeva drone is electrical power, typically using lithium polymer (Li-Po) batteries. The Li-Po batteries have a high energy density and a high power density; hence they are ideal for UAV drone use. Drones will always need batteries that will provide increased power to the props during take-off. In addition, the batteries need to be as light as possible to increase the UAV’s endurance. Recharging batteries in the fields is another essential consideration to take note of, either by using a generator or battery power pack.
Hybrid power sources are also becoming quite common. Some drones use the gas (petrol) powered generator to create electrical energy, which powers the props. The power source has a very high energy density which enables the UAV to have a long duration. The fuel is readily available around the world, making logistics a lot easier.
The hydrogen fuel cells are still under investigation, and there are a few on the market. The fuel, in this case, is renewable and environment friendly (since it only emits water and air as by-products). The energy density of a hydrogen fuel cell is significant and can be up to 150 times that of a Li-PO battery. Hydrogen fuel is much heavier than Li-Po batteries; hence it is used in larger UAVs. The availability and ability to transport this fuel type across the globe might be a factor to consider, especially since the energy source is not widely available. The power density will always equal the amount of power the head can provide in an instance, while the energy density equals the amount of energy stored in the power source.
Beyond Visual Line Of Sight (BVLOS)
The UAV industry is working towards longer endurance and BVLOS operations. The BVLOS enables the UAV to fly beyond the sight of the pilot. However, the BVLOS flying requires more onerous operational procedures. Application of the waiver for each sortie is necessary to start using the BVLOS flying. In addition, a method to detect other aircraft in the vicinity needs to be employed. A long-range telemetry system is required to ensure reliable communications.
Unmanned/ Unscrewed Aerial System Type (UAS) Type
The type of UAS (E.G., helicopter, VTOL, multi-copter, or fixed-wing) to be used is essential. This decision will impact the duration, the practicality of take-off and landing, flying altitude, and the minimum airspeed. These factors will, in turn, influence the ability of the LiDAR system to penetrate vegetation quickly and effectively. The accuracy of the results is proportional to the flying height. That is, the higher the fly above the survey site, the lower the accuracy.
The most common type of UAS type for the LiDAR surveys is the multi-copter. These types of drones can fly slowly, and they don’t need a high safety margin since the pilot has a high level of control. These drones can fly relatively low over the area of interest and take off vertically in a small clearing due to their maneuverability.
The VTOL (Vertical Take-Off and Landing) UAS is increasing in popularity. It provides the best in vertical take-off from the small clearings and aerodynamic flight (only achieved when the plane is in airplane mode). The VTOL uses its wings to create lift, enabling them to fly much longer than the multi-copters. The flying speed affects the flying attitude required above the survey site. The higher the rate, the higher the required altitude. This allows a more significant safety margin in height to ensure sufficient reaction time to avoid any unexpected objects in its flight path (e.g., tall trees).
Helicopters are increasing in popularity for long-range and BVLOS operations. Because of their payload capacity (higher than that of multi-copters and the VTOL), their endurance is longer. The ability to take off from small areas, hover, and move slower means that the helicopters are more agile than the VTOL aircraft. The aircraft is suited for LiDAR survey operations, particularly those where long range is required.