How does Lidar work?

Lidar, LIDAR, LiDAR, LADAR... They're all names for the same thing. Okay, technically Lidar stands for 'Light Detection And Ranging' while LADAR stands for 'Laser Detection And Ranging'. But they work the same way.

Key highlights: 

• Very similar to radar and sonar
• Scanning from as big as a landscape down to as small as a particle
• Handheld, or vehicle-based
• Expect more Lidar in everyday life

If you break it down to the basics, it works the same as radar or sonar. Radar (Radio Detection And Ranging) works by pulsing inaudible radio waves, which the radar machine then detects upon return after it has collided with an object. The angle that the pulse was cast in, plus the time it took for that reflected wave to return, equals a coordinate of where the object that reflected the radio wave is located. Sending out a constant pulse of waves means that you can locate objects more accurately, as well as update the location of any object if it's moving, such as an aircraft. Radar is also useful because it's generally used as a 360-degree system, mapping anything within range of the machine in all directions. Sonar (Sound detection And Ranging) works exactly the same way, but substitutes radio waves for sound waves. These sound waves penetrate water particularly well when compared to radio waves, hence why they are famous for being used in underwater detection, whether that is for the detection of terrain, debris, mines or submarines. 

Lidar works almost exactly the same way: the machine sends out light/lasers, then detects how long it takes for these pulses to return after they've been reflected and the built-in computer calculates the precise coordinates of where objects are located. The types of light that are sent out can be visible light, invisible/near-visible, infrared and ultraviolet.

What is it used for? 

The speed at which Lidar works is a major advantage: up to hundreds of thousands of pulses can be sent out per second, meaning even a fast moving platform such as an aircraft can carry a Lidar system without compromising the accuracy of the scan. Of course the speed of light is a major bonus here, and this also means that the range of Lidar can be immense. These scans are not just limited to handheld scans of individual components, or even buildings, but entire landscapes can be scanned.

It's even possible to scan through water, down to a certain depth at least. Light can only penetrate water for a finite amount, so for accurately mapping the ocean floor, sonar is a more reliable solution. However, using green light, Lidar can scan deeper than other types of light and this is particularly useful in the analysis of flooding risk. For instance, when scanning a landscape surrounding a river, knowing not only the height of the banks and the surrounding land, but also the depth of the river in multiple places can provide insightful knowledge on what areas are more at risk from flooding. 

Even particles can be scanned with Lidar. When scanning cities, for instance, it's possible to scan the levels of air pollution. Particles like methane or carbon dioxide will show up and this can be used for analysis on how to reduce air pollution. 

Will we see more Lidar systems in the future, or will it be replaced by something else?

A lot of autonomous vehicles that are being developed use Lidar. It's a fast and accurate system to measure distance, especially while moving. However, Tesla founder Elon Musk famously said that Lidar is not the way of the future. Tesla cars use radar as a back up navigation tool, with their main navigation coming from visual analysis. The theory here is that an autonomous vehicle would be better suited for navigating human traffic if it analysed situations the same way as humans do: visually. So a 'normal' camera is used to observe the environment, while a computer analyses and interprets the information, in order to safely navigate the vehicle. Another big reason for this is that Lidar has, historically, been limited to very expensive equipment. However, in recent years Lidar systems have become lighter, cheaper and much, much smaller: they can even be mounted on Boston Dynamics' robot dog, Spot. 

What we can expect from the future is that Lidar will likely become more accurate, with an even longer working range from a cheaper, smaller and faster machine. The most recent iPhone already has some Lidar technology, foreshadowing that this is a technology that will be all around us in the near future.