Two modern technologies – drones and LiDAR sensors–work together to provide applications that benefit humanity. Most people think the word drone means a modern unmanned aircraft full of cameras and other devices built with the purpose of invading your airspace and privacy. In fact, drones or unmanned aerial vehicles (UAV) are not new, if we consider them as the successors of balloons. In 1849, for instance, Austria sent unmanned bomb-filled balloons to attack Venice, setting up the model for modern warfare using distance bombing.
At the beginning of this century, drones became pervasive and are used in many types of applications away from the battlefield. Drones perform peaceful activities such as mapping, surveying, transportation for goods and people, simple entertainment and other activities. The main reasons the drone market went sky-high are the FAA release of Part 107 of the Federal Aviation Regulations of June 21, 2016, and the low cost of drones. You can now buy a drone for as low as $100, for example.
LiDAR sensor, on the other hand, is a technology that uses non-visible electromagnetic radiation (infrared or ultraviolet are good choices) to locate objects and measure distance to them. LiDAR that stands for Light Detection and Ranging is similar to SONAR (sound navigation and ranging) and RADAR (radio detection and ranging). SONAR measures distance by emitting a powerful sound pulse, and measuring the time it takes to the pulse to return after impinging the object. By frequently doing this and moving the SONAR to point to different location we can “map” an entire environment. RADAR uses the same principle, but instead of sound it emits a radio (electromagnetic) wave with much higher frequency than the frequency used in SONAR. Both systems, however, give poor image resolution.
LiDAR produces high resolution images by using lasers to measure distance in a similar way. The system is designed to represent every distance measurement by one pixel. By taking millions of measurements you will create millions of pixels that can be rendered on a screen resulting in an image rich in details, similar to black-and-white photographs. Each pixel carries certain light intensity, and all the pixels together form the image. How can we produce millions of measurement? Should we use millions of lasers? The answer to this question will be covered in an upcoming article in Electronics360.
Now, we put a LiDAR sensor on a drone. In recent years LiDAR systems have been made accessible due to the fact that prices are falling abruptly. This is the reason both technologies together can be found in a wide range of industries. These systems are being used nowadays for object scanning, gesture recognition, measuring volumes, 3D photography, surveying and many others. Some industrial sectors that use the systems include: In agriculture they're used to understand the relation of crop yields respect to ground topography in order to study soil health, and in order to determine the slope of the terrain and the amount of sun exposure. In environmental conservation drone LiDARs are used to analyze rivers, lakes, climate, forest fire hazards, coastal regions, measuring biomass areas and others. In mining they're used to calculate ore volumes. In surveying drones create digital elevation models (DEM) without standard instruments. For obstacle avoidance autonomous vehicles use LiDAR for detection and avoidance of obstacle. This includes UAVs. In archeology drones are used for site surveying, planning of digs, and to locate features beneath forest canopy. In meteorology are used to measure wind speed, cloud profiles and type and quantity of atmospheric components
In 2015 the industry spent around $300 million on drones using LiDAR, and it is expected the market will reach $1 billion by 2020. Many companies, though, still use fixed wing pilot aircraft fitted with LiDAR sensors. Not only is the cost of the use of the aircraft is high, but the LiDAR trained engineer adds more, keeping the use of this technology at a minimum in the recent past. Only big-budget companies could afford to use airborne LiDAR system on a regular basis. As a historical perspective, airborne LiDAR was develop in the 1960’s with the purpose of detecting submarines during the Cold War.
An Example: Archeology Applications
One application that is helping to understand the past is in the field of archeology. Not all historical sites that archeologists and historians work on are structures that can be seen with the naked eyes; even in sites like the Pyramids of Egypt there are structures that cannot be seen unless we use special tools. Sites that have been destroyed still have some features that we would like to see or to study. This is where LiDAR comes into play. It happens that when a structure is built it disturbs the ground where it is located, making the building foundation to be either higher or lower than the original ground.
LiDAR sensors mounted on a drone can take aerial shots of the structure and produce an accurate map of either a known or an undiscovered site. An example is shown in the image where a LiDAR image of the magnificent Cambodian site Angkor Wat. After analyzing this picture the archeologist discovered unseen structures like canals and smaller building foundations in the periphery of the complex. Another example is the case of the discovery of a Roman fort previously thought to have been completely levelled by ploughing, when a LiDAR survey of the river Wharfe in Yorkshire, UK, was made. An image showing this discovery is included here.
The blow YouTube video is a short description of the technology.