What Is Lidar?

What Is Lidar?

LIDAR stands for Light Detection & Ranging. It is a technology that was discovered in 1961 but came into focus in recent years. Lidar is three dimensional mapping method which is worldwide accepted to generate Geo-referenced spatial information about surface characteristics and shape of the earth. As the Lidar is a mapping method, there is a continuous improvement in the field which allows the mapping professionals and scientists to examine natural and built environment across a wide range of scales with greater flexibility, accuracy and precision than even before.

Advancement in lidar technology has become an established method for collecting very dense and accurate elevation data. This includes great range across landscape, shallow areas and project sites. This active remote sensing is similar to RADAR but it uses LASER pulses instead of radio waves. Lidar data is collected from planes where it can rapidly collect points over large scale. The data for lidar can also be collected from ground based stationary or mobile platforms. The lidar technology is popular among surveying and engineering community.

How Does LIDAR Works?

Lidar or LiDAR or LADAR or Laser Altimetry refers to the technology that deals with remote sensing. Lidar system emits full focused and intense beam of light and measures the time it takes for reflection to be detected by the lidar sensor. The information obtained by the sensor is used to compute ranges that are desired. In this manner working of LADAR is analogues to RADAR except that it works on laser light pulses (discrete laser pulses). The computation of elevation, latitude and longitude involves following:

1. The time difference between laser pulse being emitted and return.

2. Impact angle at which pulse is emitted (the angle is also called scan angle)

3. Absolute location of sensor on or above the surface of the earth.

 If you have gone through basic physics in your higher secondary. You can easily understand the working by the figure representing below:

Image Credit : Wikipedia

Classification of the technology

There are two classes or types of remote sensing technology and both are differentiated on the basis of source of energy used to detect the target. They are passive remote sensing technique and active remote sensing technique. 


Passive Remote Sensing Technology: This technology of remote sensing detects the target on the basis of radiation emitted by the target. This includes the mapping of objects like sun, moon etc.


Active Remote Sensing Technology: This technology of remote sensing detects the target on basis of radiation reflected by the target when radiation is emitted towards it and subsequently detects the target and maps it according to data obtained (in this case reflected data).



Schematic diagram of airborne lidar performing line scanning resulting in parallel lines of measured points (other scan patterns exist, but this one is fairly common

Lidar Technology comes under the category of active systems because it uses pulses of laser and this characteristic allows it to collect data in night also. In fact most lidar data is collected during night time. The main drawback of lidar technology is that the EM spectrum used cannot penetrate through clouds, rain and dense haze.

General Technological Specifications:

a. Lidar instruments traces earth surface at 150 KHz (i.e. 150000 pulses/sec) which results in highly accurate geo-referenced elevation points (called point cloud) that are used to generate 3D representation of earth surface.

b. Lidar system operates in infrared region of electromagnetic spectrum and also some sensors operates in green band that can penetrate through water and can detect bottom features.

c. Many corporate are using lidar based technological systems in following areas

01. Laser guidance

02. Airborne laser swath mapping

03. Atmospheric physics

04. Agricultures

05. Automobiles

06. Military

07. Mining

08. Robotics

09. Mobile phones

10. Virtual reality/Augmented reality

11. Video games

12. Geomorphology

13. Geodesy

Research in this field is going on and scientists across the world are trying to enhance the technology. This technology is capable of changing world. 

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