What is LiDAR? An overview of LiDAR Sensor, its types, and advantages

LiDAR is the latest buzzword in the world of autonomous vehicles, but how exactly does the technology work? How many types are there? Why use LiDAR sensor instead of any other tech?
What is LiDAR? An overview of LiDAR Sensor, its types, and advantages

What is LiDAR?

LiDAR is a popular remote sensing method that employs light in the form of a pulsed laser to detect and categorize objects. LiDAR sensors generate precise, 3-dimensional information about the shape of surrounding objects and their surface characteristics.The technology uses laser beams within the eye-safe range to create a 3D representation of the surveyed environment.

Typical applications of LiDAR sensor comprise surveying, geography, atmospheric physics, and archeology, but today it is used in many state-of-the-art applications as well as robotics, smart cities, and autonomous vehicles.

What is the definition of LiDAR?

LiDAR is an acronym of Light Detection and Ranging. It is also known as laser scanning or 3D scanning.

Key components of a LiDAR Sensor

A LiDAR sensor that scans the surroundings and illustrates them in a virtual 3D format primarily consists of a laser source for shooting out laser pulses, a scanner for deflecting the light upon the scene, and a detector for collecting the reflected light. Other supporting elements are, for example, optical lenses.

How does LiDAR technology work?

A typical LiDAR sensor follows a simple principle, also known as the time of flight principle. It sends out pulsed light waves into the surrounding environment, and these pulses reflect or bounce off objects and return to the sensor’s detector. The time taken for each pulse to return can be used to calculate the distance it traveled.

The diagrams below succinctly explains the time of flight principle:

Laser emits light pulses and detects the light reflected by the objects. The sensor measures the time between the emission and return of the laser pulse (echo). The distance is then calculated using the velocity of light using the formula shown in the figure below.

How LiDAR calculates the distance from objects. D = distance, C = speed of light, t = time taken for pulse to travel to the object and back to the receiver.

LiDARs repeat this process a million time per second and summarize the results in a high-definition 3D point cloud. Repeat this process millions of times per second, and a precise, real-time 3D map of the environment is generated. This 3D map contains data that is easy to analyze and utilize, for example, for autonomous driving decisions.

What is LiDAR Sensor used for?

LiDAR sensor has made its way into almost all walks of life and has a wide variety of applications

Security: LiDAR based security systems are safer thanks to the real-time data processing ability and high accuracy of LiDARs. The applications can range from perimeter protection to façade detection and even crowd surveillance.   

Mapping: Surveying often requires LiDAR systems to collect 3D measurements. LiDARs are used to generate digital terrain (DTM) and digital elevation models (DEMs) for the required landscapes.

Architecture: LiDARs are also useful for surveying the built environment. This covers buildings, road networks, and railways and is incredibly vital for smart city applications.

Automotive: LiDAR have regained popularity thanks to automotive applications. LiDAR sensors are an integral part in making autonomous vehicles a reality. Here’s an overview of why is LiDAR is essential for autonomous vehicles.

Real Estate: Laser scanners can be used to measure indoor space and create digital floorplans for virtual tours.

Construction: The construction industry is also using LiDAR to track building projects and produces digital twins for Building Information Modeling (BIM) applications. LiDARs can also help produce 3D models for restoration of buildings such as the Notre Dame, predictive maintenance and monitoring of structures, and revit models for architects and engineers. LiDAR can also be helpful in volume measurement of building materials such as log decks or the bulk volume measurement of cement or sand.  

The Environment: LiDAR is a popular method for mapping flood risk, tree density in a forest, and monitoring coastal erosion. Space Travel: And if your mind isn’t blown yet, LiDAR even has extra-terrestrial applications. NASA and Elon Musk’s SpaceX have used LiDARs to assist in the landing and operations of rockets and extra-terrestrial vehicle.

What are the main types of LiDAR?

LiDAR sensors can be categorized into different types based on their platforms, underlying technologies, and modus operandi. The diagram below illustrates the main categories with respect to platforms.

LiDAR Sensor types flowchart

On a high level, LiDAR systems can be divided into two types — Airborne and Terrestrial.

Airborne LiDAR Sensor

These were the first LiDAR systems, developed in the 1960s, predominantly for aeronautics and aerospace applications. Airborne LiDARsare usually installed on planes, helicopters, or sometimes even satellites to collect data. LiDAR sends out pulsed light waves towards the ground surface, which returns to the sensor after hitting the object. It gives an exact distance measurement and crucial information on the characteristics of the surface. Naturally, these LiDARs require very high-power emitters to cover such long distances, making them highly complicated and expensive technologies.

Airborne LiDARs can be further divided into two main categories: Topological LiDARs, used for monitoring and mapping topography of a region, and Bathymetric LiDARs, used for measuring the depth of water bodies. Read about the complete evolution of the LiDAR technology here.

Terrestrial LiDAR Sensor

In comparison, terrestrial LiDARs operate from the ground level and can scan objects in several directions using mirrors instead of just scanning down. This allows them to scan and reach areas inaccessible to airborne LiDARs.

Terrestrial LiDARs can collect data points with high precision and density, which allows very accurate identification of objects. These dense point clouds are then utilized to identify vehicles, conduct highway and rail surveys, or create 3D city models, to name a few examples.

Terrestrial LiDAR systems again have two types — Static LiDAR and Mobile LiDAR.

Blickfeld LiDAR Qb2

Static LiDAR Sensor

Static LiDAR collects point clouds from a static location. They can scan in every direction, including upwards. The sensor can be transported to different locations after completing one scan, so the static system — although fixed during scans — is fully portable. Static LiDARs are generally used in mining, surveying, and archaeology applications.

Mobile LiDAR Sensor

Mobile LiDAR is leading the way for modern mapping and autonomous driving solutions and incorporates top of the line LiDAR technology to collect quality data points. The method can be employed to acquire millions of 3D design points per minute. The mobile laser can offer a data density of up to 150 points per square foot, making it the fastest way to acquire coordinates compared to all other LiDAR methods.

Mechanical vs Solid-state LiDAR Sensor

Within the mobile LiDARs, there are yet two more types, namely mechanical or rotating LiDARs and solid-state LiDARs. 

The rotating or mechanical LiDARs rely on gears and motors to mechanically steer the laser diodes. Although this allows them to offer a 360-degree view of the surroundings and therefore have made them popular in R&D and Autonomous Driving system prototyping, the moving mechanical components are prone to technical failures. They are also more sensitive to vibrations, and expensive (i.e., several-to-tens of thousands of dollars) due to their intricate design, set-up, large dimensions, and manual construction. This makes them not very cost-effective, even when produced in large quantities.

In comparison, MEMS-based LiDAR systems are based on semiconductor technology and therefore are built without motorized mechanical scanning. This makes the entire systems less complicated, more compact, and longer-lasting. They are also less expensive and can be produced reliably, providing a path to high-volume manufacturing and commercial viability. Therefore, the solid-state LiDAR systems act as a breakthrough for many applications, especially the next level of autonomous driving. 

What is the difference between LiDAR Sensors and Other Sensing Technologies?

LiDAR sensors have already phased out several other technologies and sensors, such as Radars or infra-red in many applications, as they were not precise enough in their detection and data encapsulation. For many challenges, such as scanning between trees, LiDAR proves to be a valuable technology as it offers a fast, precise, and direct method of 3D mapping while producing accurate and easy-to-analyze data.

Also in mobility applications, where high precision and reliability is required, the LiDAR technology is gaining popularity, quickly.

These features make LiDAR stand out from most of the alternatives, e.g., photogrammetric techniques that faced difficulties in interpreting ground elevations. Modern LiDARs are also mostly independent of environmental factors, and can work 24/7, giving them a significant edge on sensors like cameras, which are nearly useless in the dark or rain.

LiDAR is capable of providing high-resolution 3D vision by generating millions of data points in real-time. This creates a precise map of the ever-changing surroundings that allow the objects to be recognized and categorized. For instance, a car can easily be distinguished from a cyclist, which is not possible using just radars or ultra-sonic sensors.

LiDAR’s robust performance, an extended range of up to 200 meters, and distance accuracy of a few centimeters allows it to detect objects quickly.  And thanks to the advent and adoption of solid-state technology, the cost of these high-resolution 3D sensors has also been considerably reduced, making them a perfect fit for a wide range of technologies.

Here is a figure showing some LiDAR sensor parameters in comparison with other sensors such as Radars and Cameras.

Performance Comparison of LiDAR Sensor vs Radar and Camera
Performance Comparison of LiDAR Sensor vs Radar and Camera

What are the benefits of LiDAR?

Resolution & Accuracy: LiDAR generates instantaneous, massive amounts of measurements, and can be accurate to a millimeter.

3D Mapping: LiDAR data can be easily converted into 3D maps to interpret the environment.

Low Light Performance: LiDAR is unaffected by ambient light variations, and performs well in low light conditions.

Speed: LiDAR data are direct distance measurements that don’t need to be deciphered or interpreted– thus enabling faster performance and reducing processing requirement.

Anonymous detection: LiDAR can accurately detect the type of objects, but it cannot detect faces or identities due to the very nature of the point-cloud, making it perfect for compliance with privacy requirements when used in public applications.

LiDAR sensors are the future:

Standing out in its ability to provide reliable detection and ranging over short to long distances, LiDAR sensors are fit for use in multiple industries and applications. Most applications, such as Autonomous driving and smart cities, require LiDAR to be part of a sensor fusion and complete the existing sensor suite (i.e., Camera vision, Radar, and Ultrasonic technologies), which creates a unique and fast-growing opportunity for the proliferation of LiDAR in the emerging markets. And with MEMS-based LiDAR sensors, such as offered by Blickfeld, it is only a matter of time when they become the go-to sensors for most industries.

Visit our website if you want to learn more about our LiDAR sensor range.

 

What is LiDAR? An overview of LiDAR Sensor, its types, and advantages

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