LiDAR and How It’s Used With Drones
When it comes to UAV payloads, thermal and Red Green Blue (RGB) cameras get a great deal of attention.
With low price points, the technology is easily accessible to just about everyone. Several standard drone missions, such as three-dimensional mapping, are effortlessly carried out using it. There are, however, limitations to using only these two types of payloads on drones.
Thermal cameras are ideally suited for inspections where temperature variations are the primary data points. Beyond this function they are, by design, limited.
RGB cameras are excellent tools for photogrammetry. While this survey method is accurate and useful in a wide range of applications, it is also not without its limitations. For example, drones with RGB cameras can survey vacant land in preparation for development. In most cases, the images collected can produce precise three-dimensional models and topographic maps that planners will find useful.
However, if this same land were covered in thick, dense vegetation, the RGB camera would fail to give planners any information on the actual earth’s surface. For this type of analysis, RGB and thermal cameras are not the best tools for the job.
What is LiDAR and how does it work?
Invented in 1961 by the Hughes Aircraft Company, LiDAR (Light Detection and Ranging) is ideal for the type of analysis mentioned above. LiDAR systems consist primarily of three components: a laser, scanner, and a specialized GPS receiver.
LiDAR works by accurately measuring the distance from the drone to the ground. A laser is fired millions of times from the LiDAR scanner towards the ground as the drone flies a predetermined pattern. As each pulse of light is emitted, the exact time the light is fired is recorded. As the light pulse is reflected, the scanner detects the return and again marks the exact time the light returned.
The specialized GPS receiver records the exact position of the sensor throughout this process. An equation that utilizes the constant speed of light generates a slant range for each beam of light fired. When all the data is compiled, millions of points on the ground produce an accurate representation of the earth’s surface and features above it.
The data points are so numerous and so precise that layers of vegetation or other obstacles can be removed to show the topography of the region. One light pulse can generate multiple returns and thus, layer the area being surveyed. The technology has seen successful use in many fields such as disaster response, high precision infrastructure monitoring, and topographic/hydrographic survey.
Types of LiDAR for UAS, and the industries that benefit
UAVs use two types of lidar.
For measuring the earth’s surface, topographic LiDAR is ideal. It utilizes a near-infrared laser for mapping land.
The second type — bathymetric LiDAR — is designed for surveying the seafloor and riverbeds. It uses a green laser to penetrate water, but operates on the same principles as described above.
LiDAR systems on UAS provide professionals across many industries the ability to map the earth’s most challenging environments. The level of accuracy spread across millions of data points is particularly beneficial to construction planners, as well as those monitoring utility infrastructures. Hard-to-see features, such as powerlines, are easily identified by LiDAR. These features can also be isolated from other features, aiding in in-depth analysis.
There is perhaps a no better example of the power of LiDAR than in archeology. The incredibly dense jungles of Central America were home to one of the ancient world’s greatest civilizations, the Mayan. The Mayans built vast cities with massive structures.
After a mysterious decline and disappearance in 900 A. D., many of their cities were swallowed up by the jungle. Dense jungle canopies all but erased many locations. Traditional investigation methods, such as aerial surveys in aircraft, see only vast expanses of the jungle.
However, LiDAR systems on crewed aircraft and drones are revolutionizing what researchers know about the Mayans. LiDAR can remove the vegetation and show what lies underneath. In some cases, its identified previously unknown locations with tens of thousands of structures. LiDAR is helping to expand this ancient civilization’s study in ways that seemed unimaginable just a few years ago.
Bringing it all together
Drones carrying LiDAR payloads are a power tool.
With only a few years of UAV technology and lidar working together, impossible topographic challenges are becoming increasingly simple tasks. For decision makers in construction, utilities, survey, and research, the advantages of UAVs carrying LiDAR are worth further investigation.
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