LIDAR, or light detection and ranging, is a remote sensing technique that measures the range to the Earth using light as a pulsed laser. The light pulses yield accurate info on the shape of the Earth and its surface features when paired with other information taken by the aerial system.
LiDAR technology is a well-liked remote sensing technique for determining the precise relative distance of objects on the earth’s surface. Since its conception in the 1960s, the technology has seen many advancements. LiDARs have found extensive usage in mapping, surveying, and forestry. But as of late, they have developed into a well-liked device for robotic applications, mining, and infrastructure inspection.
Choosing the best LiDAR sensor for a particular application might be difficult because there are so many LiDAR sensors on the market, each with a different set of capabilities and characteristics.
To choose the best LiDAR sensor for your application, read on to learn about key factors to consider. You can even speak with your preferred LiDAR company about these features.
1. Long-Range Versus Short-Range
Long-range LiDARs are costly and have a range greater than 100 meters. They are appropriate for faster-moving navigational vehicles and object detection at mid- to long ranges.
Slow-moving vehicles can benefit from the 25-meter detection range of a short-range LiDAR. Close-range LiDARs can swiftly identify items that are nearby. For example, a close-range LiDAR can find obstructions near a car’s doors. Combining a close-range LiDAR with a long- or short-range one will produce better results.
2. 2D vs. 3D
2D LiDARs will find an object. Instead of just informing the robot or vehicle that “there’s something there,” 3D LiDARs will generate a more detailed point cloud that may be utilized to assess the object’s shape, depth, and nature. Because 3D gives you a greater sense of your surroundings, your robot or car can distinguish between an approaching truck, a tree, and a road sign.
The knowledge that they may glean is what makes a difference. When used in a building, for instance, 2D LiDARs can only provide a floor plan, whereas 3D LiDARs can provide a 3D map and the location and height of every object. Therefore, the choice depends on the task at hand.
A 2D LiDAR may be sufficient if you are traveling in flat terrain and your robot is not tall. However, you need 3D perception for 3D outdoor settings with impediments like hanging tree branches or pipes. Other uses for 3D LiDARs include the segmentation and classification of topography.
3. Field of view (FoV)
Any LiDAR must have a field of view (FoV), a crucial component. Both the horizontal axis and the vertical axis are measured individually. A 360° horizontal FOV LiDAR or a greater number of directional LiDARs are typically installed on an autonomous vehicle to ensure 360° vision is available. However, it might only need to gaze at the road and possibly 30 to 40 degrees above the surface; thus, it might not require a wide vertical FoV.
If your application involves obstacle avoidance within a small area, a 360-degree LiDAR may not be necessary. In some situations, the 360-degree surround capability is not advantageous. A 360-degree LiDAR would provide you with extra and unneeded data if you only needed to look straight ahead, which would add excessive processing load to the system.
4. Number of channels
The point cloud’s density and specifics depend on the number of channels. A point cloud will be thicker but more complete if more channels exist, and vice versa. Your choice of the number of channels depends on your processing power, your financial situation, the size of the objects, and their distances from one another.
5. The remission levels
Since LiDAR uses light pulses, an object’s reflectivity (the quantity of light being reflected from it), also known as remission, significantly impacts the accuracy and range of the technique. It is stated as a percentage. White drywall, for instance, would have a remission rate of about 90%, whereas coal would have a remission rate of 5%.
6. Points Per Second
Another useful specification to consider is PPS or points per second. It displays the number of laser measurements made per second. A point cloud with more points will be more accurate, dense, and detailed.
PPS largely depends on the number of channels, returns, and Hz frequency of the LiDAR. A LiDAR in dual return mode would output twice as many points per second. Similar to this, a higher frequency LiDAR would produce a higher PPS.
7. Safety vs. non-safety rated
It is crucial to base your decision on the sensor’s safety ratings when selecting LiDAR sensors. Safety-rated sensors are required for applications where there may be a risk to people. Standards and guidelines have been published by the International Electrotechnical Commission (IEC) and the American National Standard Institute (ANSI) to govern the security of LiDAR sensors. For example, the IEC61496 standard outlines the requirements for designing and testing electro-sensitive protective equipment (ESPE).
The risk connected to the equipment or procedure employed within the industry determines the ESPE levels. Similarly, a standard called ISO 13849-1 or Safety Integrity Level 2 (SIL2) describes the functional safety of LiDAR sensors. For instance, the UAM-05LP sensor from Hokuyo is approved for personnel safety applications and complies with IEC61496-1/3, Type 3 IEC61508, SIL2 ISO13849-1, and PL d Category 3. In addition, these sensors feature data output capabilities that can be used by automated guided vehicles (AGVs) and autonomous mobile robots (AMRs) for obstacle localization and detection.
Non-safety-rated sensors can be used in processes with less human engagement. Despite having comparable capabilities, these sensors do not fully comply with CAT 3 and Sil2 safety regulations.
Wrapping it up
For your needs, a complete mapping solution might be better than a LiDAR sensor. Although a LiDAR company can offer you a point cloud, you might require additional information, such as time stamping and localization, to interpret it properly.
In such circumstances, you would wish to consider all-inclusive sensor technology solutions that incorporate LiDARs, IMUs, GPS, software, cameras, and Inertial Measurement Units (IMUs).
