Lidar System & Lidar Scan
LIDAR is an acronym for light detection and ranging.
Lidar is a remote sensing method that uses a laser to measure elevation like ground forests and buildings. Lidar uses ultraviolet-visible or near-infrared sources to sense objects. Light energy emitted by the lidar system is known as pulse, light reflected from the ground or object is known as a return. This means the lidar system sends a pulse of light and it waits for the pulse to return it measures how long it takes for the emitted pulse to return back to the sensor in the end it gets a variable distance of the objects. Actually, this is how lidar got its name: light detection and ranging.
Like sonar uses sound waves to map things, radar uses radio waves , a lidar on the other hand uses light sent out from a laser a lidar unit scans the ground from side to side as the plane flies because of this it covers a larger area. While some pulses will be directly at nadir or a straight line most pulses travel at an angle airplanes unmanned aerial vehicles and helicopters are the most commonly used platforms for acquiring lidar data over broad areas.
The different ways to collect data using lidar are from ground, from flame or from satellite.
Types of Lidar
There are two types of Lidar
With airborne lidar, the system is installed in either a fixed-wing aircraft or helicopter. The infrared laser light is emitted toward the ground and returned to the moving airborne lidar sensor. There are two types of airborne sensors: topographic and bathymetric.
- Topographic Lidar
Topographic lidar can be used to derive surface models for use in many applications, such as forestry, hydrology, geomorphology, urban planning, landscape ecology, coastal engineering, survey assessments, and volumetric calculations.
- Bathymetric Lidar
Bathymetric lidar is a type of airborne acquisition that is water penetrating. Most bathymetric lidar systems collect elevation and water depth simultaneously, which provides an airborne lidar survey of the land-water interface. With a bathymetric lidar survey, the infrared light (traditional laser system) is reflected back to the aircraft from the land and water surface, while the additional green laser travels through the water column. Analyses of the two distinct pulses are used to establish water depths and shoreline elevations. Bathymetric information is very important near coastlines, in harbors, and near shores and banks. Bathymetric information is also used to locate objects on the ocean floor.
There are two main types of terrestrial lidar: mobile and static. In the case of mobile acquisition, the lidar system is mounted on a moving vehicle. In the case of static acquisition, the lidar system is typically mounted on a tripod or stationary device. Both lidar sensors consist of eye-safe lasers. Terrestrial lidar collects very dense and highly accurate points, which allows precise identification of objects. These dense point clouds can be used to manage facilities, conduct highway and rail surveys, and even create 3D city models for exterior and interior spaces, to name a few examples.
Mobile lidar is the collection of lidar point clouds from a moving platform. Mobile lidar systems can include any number of lidar sensors mounted on a moving vehicle. These systems can be mounted on vehicles, trains, and even boats. Mobile systems typically consist of a lidar sensor, cameras, GPS (Global Positioning System), and an INS (inertial navigation system), just as with airborne lidar systems. Mobile lidar data can be used to analyze road infrastructure and locate encroaching overhead wires, light poles, and road signs near roadways or rail lines.
Static lidar is the collection of lidar point clouds from a static location. Typically, the lidar sensor is mounted on a tripod mount and is a fully portable, laser-based ranging and imaging system. These systems can collect lidar point clouds inside buildings as well as exteriors. Common applications for this type of lidar are engineering, mining, surveying, and archaeology.
How Does Lidar Work
There are four parts of an Airborne Lidar.
Lidar sensors scan the ground from side to side with a pulsed laser beam as the plane flies the sensor has a detector for sensing the returns from objects.
GPS receivers track the altitude and location of the airplane these variables are important in attaining accurate terrain elevation values.
Inertial measurement units (IMU) track the orientation and speed of the airplane as it flies elevation calculation use orientation to accurately determine the actual position of the pulse on the ground.
Computers record all of the height information as the lidar scans the surface these four parts of lidar system work together to produce highly accurate and usable result.
These four parts of Lidar system work together to produce highly accurate and usable results.
Components of Lidar System
- LASER : The most of the lasers which are used for this LIDAR system are in the range of near-infrared but in some applications like in underwater applications even green lasers are also used.
- DETECTOR : It consists of the photodiode circuit to measure the reflected or the scattered light which is coming from the object.
- OPTICS AND THE ROTATING MECHANISM : To scan the object
- GPS & IMU : to measure the difference between the transmitted pulse and received pulse.
- COMPUTER : Lidar system used to generate the enormous amount of data points in real-time, so to compute that data, we also require the computer.
- GPS & IMU: This stands for the inertial measurement unit is also part of this LIDAR system. So, this GPS and IMU are particularly useful when we have Air Borne LIDARs, which means the LIDAR system is being fitted either in the helicopter or Airplane or maybe even drone and sometimes maybe even in the satellites. And this Airborne LIDARs are particularly useful to scan the particular terrain.
Applications of Lidar System
- Agricultural Research : This LIDAR system can be used for agriculture Research and using this we can help the farmers to find the area which can give them maximum yield
- Police Trafficking : The LIDAR system can be used for police trafficking for the measurement of vehicle speed. Now so far the radar guns were used for the measurement of vehicle speed but because of its higher accuracy nowadays the radar guns have been replaced by LIDAR guns.
- Autonomous Vehicles : You might see the LIDAR system in your upcoming self-driving Cars, where it can be used to scan the object in front of it in real-time, and using that it can make the decision accordingly.
- Video Games : The LIDAR system is also used in designing the video games. For example, the company EA Sports is using LIDAR point clouds to create the most realistic three-dimensional environment of golf, basketball as well as football stadiums.
- Flood mapping of River
- Study of Atmosphere
So, LIDAR system can be used in almost all every field, and if we count the applications then list will go on.