Lidar

Several companies produce small, lightweight Lidar units for sUAS. They are usually at a lower price point as well. The disadvantage of the sUAS Lidar units is that they have shorter range than those in manned planes. Lidar in manned planes can operate at high altitudes which it must to be safe with pilots on board. The sUAS versions of Lidar are typically flown as close to the ground as possible yet still avoid trees and other tall obstacles in the area. This works out to be 20 – 50 feet above the highest object be it a tree or a tower. No manned aircraft be it a plane or a helicopter would like to operate at this altitude long term for safety reasons. Of course, manned aircraft does fly low where necessary though the costs are high due to the risk involved. The Lidar systems installed in manned aircraft are very sophisticated and cost upwards of $1,000,000. Of course, in many instances the Lidar system in a manned plane is justifiable. However, Lidar in a sUAS is less expensive, can fly low to the ground and not endanger the pilot, and get a dense point cloud. Point cloud density can be precisely tuned which using an unmanned helicopter or multirotor. These can fly as low and as slow as necessary to obtain the point cloud which is required by the customer. Installation onto a fixed wing aircraft will extend the endurance, but the higher minimum speed required to avoid stalling a fixed wing doesn’t allow as high a density of the point cloud as a rotary wing. One sUAS data collection company uses fixed wing for forestry because the lower point cloud density is adequate for its needs. For surveying, depending on the vegetation of the area to be surveyed, a fixed wing aircraft may provide adequate cloud density. There are several companies providing Lidar today. A couple of the more popular today which mount onto sUAS are Velodyne and Riegl. The Velodyne being less expensive it sells more units annually than the Riegl into the sUAS market. However, there are advantages to the more expensive Riegl Vux-1 which justifies its higher price point.

The laser has three distinct components, often times they come from different manufacturers. The laser scanner works together with an INS and an onboard computer. The INS is the inertial navigation system which is made up of an IMU (inertial measurement unit) and a GPS. This is often a very high portion of the cost. It is also a very critical piece of the component which provides location to the points in the cloud. Accuracy of the data is highly dependent on the accuracy of the INS. The aircraft is flying along, bobbing and weaving to stay on course, and if the requested accuracy of the data is 2 cm, then the INS has to know where it is within 2cm at all times. This is not an easy feat with traditional GPS which is accurate only to a couple of meters.

The prices of Lidar are coming down, and companies like Lidar USA are putting together packages which make getting into the Lidar business easier and more affordable. Lidar has a lot of advantages over EO photogrammetry, and with the cost coming down, it is becoming much more prevalent. At this time most of the Lidar airborne units are put onto rotary wing aircraft. The Pulse Aerospace Vapor 55 helicopter or the Gryphon Dynamics GD-1000 multirotor and a couple of the dozens of available aircraft suitable to carry Lidar. These can also carry small EO cameras to get RBG info simultaneously.

This technology, though it has been available for many years, is changing rapidly. With the advent of drones capable of lifting more weight and being very reliable a lot of money in going into R&D to miniaturize Lidar and the associated components. Again, it is difficult to recommend a particular system because different Lidar have different specific purposes, and new entries to the market happen regularly. For instance, a LIDAR system for mapping roadways only is not the same LIDAR system used to map roadways if signs and railings are included.