All You Know About LIDAR Systems and Applications

LIDAR or 3D laser scanning was developed in the early 1960s for submarine detection from an aircraft, and early models were used successfully in the early 1970’s. Nowadays, the environmental research is hard to imagine without the use of remote-sensing techniques like Light Detection and Ranging (LIDAR) and Radio wave Detection and Ranging (RADAR). High spatial and progressive resolution of the measurements, the possibility of observing the atmosphere at ambient conditions, and the potential of covering the height range from the ground to more than 100 km altitude make up the attractiveness of LIDAR instruments.

The variety of interaction processes of the emitted radiation with the atmospheric elements can be used in the LIDAR to allow the determination of the basic environment variables of state, i.e., temperature, pressure, humidity, and wind, as well as the geographical survey, river bed elevation, study of the mines, density of forests and hills, study on underneath of the sea (Bathymetry).

How does LIDAR work?

The working principle of Light Detection and Ranging system is really quite simple. A LIDAR sensor mounted on an aircraft or helicopter. It generates Laser pulse train, which sent to the surface/target to measure the time and it takes to return to its source. The actual calculation for measuring how far a returning light photon has travelled to and from an object is calculated by

Distance = (Speed of Light x Time of Flight) / 2

Accurate distances are then calculated to the points on the ground and elevations can be determined along with the ground surface buildings, roads, and vegetation can be recorded. These elevations are combined with digital aerial photography to produce a digital elevation model of the earth.

Light Detection and Ranging Sytem
Light Detection and Ranging System

The laser instrument fires rapid pulses of laser light at a surface, some at up to 150,000 pulses per second. A sensor on the instrument measures the amount of time takes for each pulse to reflect back. Light moves at a constant and known speed so the LIDAR instrument can calculate the distance between itself and the target with high accuracy. By repeating this in quick progression the instrument builds up a complex ‘map’ of the surface it is measuring.

With airborne Light Detection and Ranging, other data must be collected to ensure accuracy. As the sensor is moving height, location and orientation of the instrument must be included to determine the position of the laser pulse at the time of sending and the time of return. This extra information is crucial to the data’s integrity. With ground-based Light Detection and Ranging a single GPS location can be added at each location where the instrument is set up.

LIDAR System Types

Based on the Platform

  • Ground-based LIDAR
  • Airborne LIDAR
  • Spaceborne LIDAR
LiDAR Systems Based On Platform
LiDAR Systems Based On Platform

Bade on Physical Process

  • Rangefinder LIDAR
  • DIAL LIDAR
  • Doppler LIDAR

Bade on Scattering Process

  • Mie
  • Rayleigh
  • Raman
  • Fluorescence

Main Components of LIDAR Systems

Most Light Detection and Ranging systems use four main components

Light Detection and Ranging Systems Components
Light Detection and Ranging Systems Components

Lasers

The Lasers are categorised by their wavelength. Airborne Light Detection and Ranging systems use 1064nm diode pumped Nd: YAG lasers whereas Bathymetric systems use 532nm double diode pumped Nd: YAG lasers which penetrate into the water with less attenuation than the airborne system (1064nm). Better resolution can be attained with shorter pulses provided the receiver detector and electronics have sufficient bandwidth to manage the increased data flow.

Scanners and Optics

The speed at which images can be developed is affected by the speed at which it can be scanned into the system. A variety of scanning methods is available for different resolutions such as azimuth and elevation, dual axis scanner, dual oscillating plane mirrors, and polygonal mirrors. The type of optic determines the range and resolution that can be detected by a system.

Photodetector And Receiver Electronics

The photodetector is a device that reads and records the backscattered signal to the system. There are two main types of photodetector technologies, solid state detectors, such as silicon avalanche photodiodes and photomultipliers.

Navigation And Positioning Systems/GPS

When a Light Detection and Ranging sensor is mounted on an aeroplane satellite or automobiles, it is necessary to determine the absolute position and the orientation of the sensor to maintain useable data. Global Positioning Systems (GPS) provide accurate geographical information regarding the position of the sensor and an Inertia Measurement Unit (IMU) records the accurate orientation of the sensor at that location. These two devices provide the method for translating sensor data into static points for use in a variety of systems.

Navigation And Positioning Systems/GPS
Navigation And Positioning Systems/GPS

LIDAR Data Processing

The Light Detection and Ranging mechanism just collect elevation data and along with the data of Inertial Measuring Unit is placed with the aircraft and a GPS unit. With the help of these systems the Light Detection And Ranging sensor collects data points, the location of the data is recorded along with the GPS sensor. Data is required to process the return time for each pulse scattered back to the sensor and calculate the variable distances from the sensor, or changes in land cover surfaces. After the survey, the data are downloaded and processed using specially designed computer software (LIDAR point Cloud Data Processing Software). The final output is accurate, geographically registered longitude (X), latitude (Y), and elevation (Z) for every data point. The LIDAR mapping data are composed of elevation measurements of the surface and are attained through aerial topographic surveys. The file format used to capture and store LIDAR data is a simple text file. By using elevation points data may be used to create detailed topographic maps. With these

data points even they also allow the generation of a digital elevation model of the ground surface.

Applications of LIDAR Systems

Oceanography

The LIDAR is used for calculation of phytoplankton fluorescence and biomass in the ocean surface. It is also used to measure the depth of the ocean (bathymetry).

LiDAR in Oceanography
LiDAR in Oceanography

DEM (Digital Elevation Model)

It has x, y, z coordinates. Elevation values can be used everywhere, in roads, building, bridge and other. It has made easy to capture the surface height, length, and width.

Atmospheric Physics

LIDAR is used to measure the density of clouds and concentration of oxygen, Co2, nitrogen, sulphur and other gas particles in the middle and upper atmosphere.

Military

LIDAR has always been used by the military people to understand the border surrounding land. It creates a high-resolution map for the military purpose.

Meteorology

LIDAR has been used for the study of the cloud and its behaviour. LIDAR uses its wavelength to strike small particles in the cloud to understand cloud density.

River Survey

Green light (532 nm) Lasar of the LIDAR is used to measure underwater information is required to understand the depth, width of the river, flow strength and more. For the river engineering, its cross section data are extracted from Light Detection And Ranging data (DEM) to create a river model, which will create a flood fringe map.

River Survey Using LIDAR
River Survey Using LIDAR

Micro-Topography

Light Detection And Ranging is very accurate and clear-cut technology, which uses Laser pulse to strike the object. Regular Photogrammetry or other survey technology cannot give the surface elevation value of forest canopy. But the LIDAR can penetrate through the object and detect the surface value.

Have you got the basic information of LIDAR and Its Applications? We acknowledge that the above-given information clarifies the basics of Light Detection and Ranging mechanism concept with related images and various real-time applications. Furthermore, any doubts regarding this concept or to implement any electronic projects, please give your suggestions and comments on this article you can write in the comment section below. Here is a question for you, What are the different types of Light Detection and Ranging?

Add Comment