Editorial Feature

What is a LiDAR Sensor?

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Introduction

Technology is continuously advancing – there are home assistants you can almost have a conversation with, mobile phones more powerful than a decade-old computer and even self-driving cars.

The car has come a long way since the mid-1880s, when Karl Benz built what was considered the first true automobile. But how does a self-driving car work – how does it know when to stop, or determine if someone is about to cross the road. The answer is a remote sensing technology called LIDAR.

The Origins of the LIDAR Sensor

LIDAR - or Light Detection And Ranging - originated in the 1960s, shortly after the advent of lasers and was first used by the American National Center for Atmospheric Research in meteorology to measure clouds. Since then, the technique - also known as laser scanning or 3D scanning - has been used in applications from geography to forestry, and from atmospheric physics to laser altimetry.

It has been widely used in archaeology to map dig-sites and large areas of land, identifying things that couldn’t be seen from the ground. The National Oceanic and Atmospheric Administration in America has used it to map shorelines and the surface of the Earth, and NASA utilized the technology in 1971 when Apollo 15 astronauts mapped the surface of the moon using a laser altimeter.

How Do They Work?

The technique employs ultraviolet (UV), visible or near infrared (IR) light to image objects and map their physical features. Several measurements are taken in quick succession to yield a complex map of the surface at high resolution.

LIDAR measures the distance to a target using active sensors which emit an energy source for illumination, instead of relying on sunlight. It fires rapid pulses of laser light at a surface – anything up to 150,000 pulses a second – usually IR to map land, or water-penetrating green light to measure the seafloor or riverbed.

When the light hits the target object, it is reflected back to a sensor which measures the time taken for the pulse to bounce back from the target. The distance to the object is deduced by using the speed of light to calculate the distance traveled accurately. The result is precise three-dimensional information about the target object and its surface characteristics.

Applications

LIDAR was first used in vehicles in the early 2000s, mostly in the Grand DARPA Challenge – it is only in the last five years, or so that progress has been made concerning self-driving cars. Google and Uber are just a two of many names developing self-driving vehicles; their cars feature a bulky box on top of the roof which spins continuously giving 360° visibility and precise, in-depth information about the exact distance to an object to an accuracy of ±2cm. This box is the LIDAR system; it consists of a laser, scanner and optics and a specialized GPS receiver, especially important if the system is moving.

In the case of self-driving cars, LIDAR is used to generate huge 3D maps – which was its intended original use - that the car can then navigate through. It is also used – particularly by Google – to detect pedestrians and cyclists, traffic signs and other nearby obstacles.

Of course, such autonomous technology isn’t without its pitfalls – take the recent fatality in Arizona where the technology failed to pick up a pedestrian crossing the road, for example. However, as LIDAR becomes more sophisticated, it will be increasingly capable of detecting and tracking objects. Improvements will mean higher resolution imagery will be possible and it will be able to operate at longer ranges so that the technology is capable of differentiating between someone walking, or someone on a bike, their speed, and direction.

References and Further Reading

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Kerry Taylor-Smith

Written by

Kerry Taylor-Smith

Kerry has been a freelance writer, editor, and proofreader since 2016, specializing in science and health-related subjects. She has a degree in Natural Sciences at the University of Bath and is based in the UK.

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