Light Detection and Ranging (LiDAR) refers to a remote sensing technology that measures the distance to an item using light pulses reflected from it. Lidar is used in various applications, including surveying, mapping, and navigation.
LiDAR sensors are classified by the type of light they measure, distance, and reflectivity. These include laser diodes, avalanche photodiodes, and time-of-flight (TOF) sensors.
The main difference between these sensors is their wavelength range, which determines their resolution and accuracy. The most common LiDAR sensors use ultraviolet (UV) or near-infrared (IR) wavelengths, but versions operate at visible wavelengths such as green or red.
In addition to measuring distance, lidar can also provide information about other features of an object, such as its shape or material composition. This is achieved by combining multiple measurements taken over time with a single scan using triangulation techniques or by adding up all the data collected during multiple scans to create a 3D model of an object’s surface geometry.
What are the Lidar Specifications?
LiDAR Imaging Range
The LiDAR imaging range is the maximum distance a LiDAR can accurately image objects. The two are typically not the same, as they depend on how many lasers are used and how much power they deliver to each target point in the field of view.
LiDAR Detection Range
The LiDAR detection range is the maximum distance at which a laser beam can be detected. It is the minimum horizontal separation between two points at which the sensor will still detect the laser beam. The distance between two points can be found with a straight edge, a ruler, and a calculator. The speed of sound in air is about 340 m/s, and it takes about 4 seconds for a laser to travel that distance.
Range Precision and Accuracy
The range of the LiDAR sensor is the distance between the laser beam source and the LiDAR sensor. The range of a laser beam source can be extremely precise or be designed with a wide range, defined as the maximum distance at which 50% of points on a ground plane will be detected.
The maximum resolution for a laser beam source is defined by its wavelength (λ) and its pulse duration (T). A shorter wavelength gives a better resolution but also causes more power to be absorbed by air molecules, resulting in reduced range accuracy. A longer wavelength allows for greater power output without incurring this loss in range accuracy. However, longer wavelengths cause more heat generation because they have a longer path length through air molecules, resulting in increased aperture size requirements for cooling systems.
Field-of-View (FoV)
The LiDAR specifications include the field-of-view (FOV) of the LiDAR sensors, which is a measurement that describes the area around the scanner. The larger the FoV, the more detailed your mapping will be. For example, if you are building a 3D model of a city, you would want a large FoV to capture as many buildings as possible in one pass.
Scan Patterns
The process of creating a LiDAR model involves creating a scan pattern. It is about aligning the laser scanner to a specific point on the ground, known as the target point. The laser scanner then captures images of this area from many different angles and distances, and these scans are combined into one dataset. The more points used in the scan pattern, the better it will be for estimating terrain height and slope.
Crosstalk Immunity
Crosstalk is the interference between the different wavelengths of light pulses. It is measured in decibels (dB). It is also called intermodulation distortion, which is caused by mixing two or more beams at different wavelengths. This mixture can be intentional or unintentional, but it can only be rejected if the user sets an appropriate filter for that specific wavelength. The filter should be set to a maximum value so that it does not affect other wavelengths and prevents them from interfering with each other. The measurement of this parameter requires a special spectrometer that has high precision and can distinguish between different wavelengths.
Key Takeaway
A LiDAR specification is an essential tool for any recent LiDAR user. This is because LiDAR specifications can provide users with valuable information about the capabilities of a given LiDAR system. Specifications that consist of range, resolution, millisecond returns, and spot size are all crucial factors in determining a particular LiDAR’s suitability for a specific purpose.