The usage of LiDAR Technology is really becoming rampant in today’s world. This tells how helpful it has been to surveying. It’s important you learn about LiDAR Technology and how it works. In this guide, we will talk about LiDAR Technology; endeavor to read through this guide to gain knowledge on LiDAR Technology.
What Is LiDAR?
LiDAR stands for “light detection and ranging.” Generally, this technology uses infrared light or lasers to create a three-dimensional image of an environment. NASA initially developed LiDAR to monitor the positions and paths of satellites in space, but as the technology scaled down and continued to develop, new terrestrial-based applications emerged relating to automotive safety technology and autonomous vehicle systems development.
LiDAR’s central premise is to act as a vehicle’s eyes to always see in all directions. With a real-time ability to map the world in 360 degrees, LiDAR helps vehicles identify objects on or near the roadway to avoid collisions with pedestrians, cyclists, animals, and other vehicles, stationary or moving.
What does LiDAR stand for?
LiDAR is an acronym for Light Detection and Ranging. It is also known as laser scanning or 3D scanning.
What is LiDAR Technology?
According to the American Geoscience Institute, LiDAR technology uses a pulsed laser to calculate an item’s variable distances from the earth’s surface. These light pulses — put together with the information collected by the airborne system — generate accurate 3D information about the earth’s surface and the target object.
There are three primary components of a LiDAR instrument — the scanner, laser, and GPS receiver. Other elements that play a vital role in the data collection and analysis are the photodetector and optics. Most government and private organizations use helicopters, drones, and airplanes for acquiring LiDAR data.
How does LiDAR work?
A LiDAR sensor utilizes the same kind of laser used in everyday applications, such as retail barcode scanners, light shows at concerts and sporting events, and home security systems. This kind of laser technology is safe for the eye and has been in use for decades.
The LiDAR sensor on an automobile releases single units of light, this released light is known as photons, they strike nearby objects such as cars, pedestrians, and trees. The photons then bounce back to the sensor. The LiDAR system records each photon’s round-trip data, measuring the distance and time to every object in the vehicle’s vicinity.
A LiDAR sensor will fire anywhere from eight to 108 laser beams in a series of pulses. Each laser beam pulse emits billions of photons per second. With so many data points and calculations processed almost simultaneously, LiDAR accurately highlights objects, gives them shape, and shows their movement. A computer algorithm then assembles these shapes and forms a complete picture of the world around the vehicle.
A rotating or spinning LiDAR sensor located at the top of the vehicle will capture a 360-degree field of view at a rapid rate of speed to provide a complete image of the vehicle’s surroundings. Conversely, solid-state LiDAR sensors are fixed in place and point in a single direction with a 90 to 120 degrees field of view. It takes several fixed sensor units to achieve coverage comparable to a single spinning unit. LiDAR sensors can be placed in various locations, including a vehicle’s roof, within the rearview mirror housing, behind the grille, or at the rear window or tailgate of a vehicle.
LiDAR has a range of 250 to 400 meters, allowing it to identify objects and their positions well before reaching them. This allows a vehicle’s ADAS or autonomous system to process the information and react accordingly.
What can you use LiDAR systems and data for?
There aren’t many applications that wouldn’t benefit from using LiDAR. From the games industry to Formula 1 teams – simulations based on 3D models are often used to give teams the edge before setting foot on a racetrack.
- Mapping: Surveying tasks often require LiDAR systems to collect three-dimensional measurements. They can create digital terrain (DTM) and digital elevation models (DEMs) of specific landscapes.
- Architecture: Laser scanning systems are popular for surveying the built environment too. This covers buildings, road networks, and railways.
- Real Estate: Laser scanners can be used indoors to measure space and create accurate floorplans.
- Construction: The construction industry is also using LiDAR surveys increasingly. LiDAR technology tracks building projects and produces digital twins for BIM applications. It can also help produce 3D models for the conditional monitoring of structures, and Revit models for architects and structural engineers.
- The Environment: Environmental applications for LiDAR are plentiful. Laser scanning is a popular method of mapping flood risk, carbon stocks in forestry, and monitoring coastal erosion.
- Automotive: LiDAR is also seeing increased levels of adoption for automation applications. Smaller, low-range LiDAR scanners help navigate autonomous vehicles.
- Space Travel: If that wasn’t enough, LiDAR data isn’t only useful on earth! It has been identified by NASA as key in enabling them to land lunar vehicles safely.
Types of LiDAR by Functionality
Let us take a brief look at the different types of LiDAR classified by the way they are set up and the way they function.
As the name suggests, terrestrial LiDAR is a system that works on the ground. It can be either mounted on a moving vehicle or implanted at a static location. Either way, terrestrial LiDAR data is beneficial for applications that require a detailed survey of the ground or “a closer look” at objects.
Some applications of terrestrial LiDAR include construction, self-driving vehicles, road surveys, city surveys, and so on. Terrestrial LiDAR can be further classified into Mobile and Static versions. Here is how these two differ.
A mobile LiDAR setup typically comprises a sensor, a global positioning system (GPS), an inertial navigation system (INS), and a few cameras. It is mobile because the unit is placed on top of a moving vehicle, such as a car or a train.
From this moving vehicle, the LiDAR unit continues to send out laser pulses in all directions and read the reflections. These valuable point clouds (data points) and then processed to understand the conditions of roads and railway tracks, identify unwanted obstacles on the road, and so on.
In self-driven cars, an advanced rotating LiDAR sensor is mounted on top of the car that detects the presence of pedestrians/other vehicles on the road.
In some applications, it is advantageous to have the LiDAR unit fixed at one point rather than have it move around. Such applications use static LiDAR.
In this setup, the LiDAR unit is mounted on a static object, which is usually a tripod. If needed, the entire unit can be moved to another location along with the tripod. In essence, even though this unit is not mobile, it is fully portable.
A static LiDAR unit continues to send laser pulses to the surrounding area from a fixed point. The data is then used to understand the characteristics of the surrounding. This functionality is highly useful in applications such as building construction, mining, engineering, etc.
When the LiDAR unit is airborne, it means that the system is placed either in an aircraft or a helicopter that continues to hover above the surface of the earth, sending laser pulses downward as it moves.
Airborne LiDAR can scan vast areas in a shorter time as compared to terrestrial LiDAR. This makes airborne LiDAR systems suitable for those applications that require a bird’s eye view of an area spanning multiple acres.
Based on what kind of area the LiDAR unit scans, airborne systems can be further classified into topographic LiDAR and bathymetric LiDAR. Read on for more information on these types.
Topographic LiDAR is used to scan any kind of land, wherein the laser pulses sent down to the surface of the earth provide an estimate of the various characteristics of the area. The rise and the fall of the surface are mapped out based on the altitude of the structures that reflect the laser beams.
In short, topographic LiDAR is used to chalk out the topographic map of a particular piece of land. Applications of topographic LiDAR include forestry, urban planning, ecology, infrastructure mapping, geomorphology, and so on.
While topographic LiDAR can remotely sense any kind of land, it does not work very well when water bodies have to be scanned. To accomplish this task, another type of airborne LiDAR system called the bathymetric LiDAR is used.
A bathymetric LiDAR sensor consists of all the components of a topographic LiDAR plus an extra characteristic that allow the unit to send green laser pulses. These pulses can penetrate the water surface and return to the airborne vehicle.
Data collected in this manner gives an estimation of the depth of the water bodies. When used in conjunction with the topographic sensors, these units can identify shorelines and elevations more distinctly.
Disadvantages of LiDAR
Although LiDAR is considered a game-changer for those developing ADAS systems and autonomous vehicles, some are skeptical of its potential. The downsides of LiDAR include:
- Sensors can have difficulty differentiating between objects that are similar in size and shape, which means threats and non-threats can be confused with one another.
- LiDAR images are recreations rather than photos, so a vehicle system is susceptible to tampering and manipulation; LiDAR has a decreased level of security as compared to actual images from a camera.
- Artificial Intelligence (AI) and machine learning are not inherent to LiDAR; camera-based systems are more aligned with ADAS technology that learns over time.
- LiDAR sensors are significantly more expensive than camera and radar systems.
Lastly, LiDAR systems will continue to advance ADAS, and autonomous driving in the future is yet to be seen. But there is no doubt this technology helps cars “see” the surrounding world better. Which, for many, means improved roadway safety and a more confident driving experience? So expect to see more of this technology.