LiDAR sensors unlock highly accurate data-enabling detailed three-dimensional mapping and model building with remarkable precision.
But understanding the technology for drones is not as easy, and it's essential to cover the main elements and their various applications.
Let's start with the history of LiDAR and why it's such a tremendous tool in drone technology. Let's jump right into it.
The History of LiDAR
LiDAR technology, short for "Light Detection and Ranging," was first developed in the 1930s to measure distances.
In 1930, EH Synge used searchlights to study the atmosphere, tracing back to early LiDAR concepts, while in 1938, light pulses measured cloud heights.
Advances in both hardware and software recently made the technology applicable in an airborne capacity, even though it was primarily limited to terrestrial use.
LiDAR, RADAR's cousin, found uses in meteorology, mapping, defense, and space exploration. NASA even used lidar data for spacecraft development and planetary mapping. The integration of GPS and IMUs in the late 1980s propelled LiDAR's maturation, enabling it to provide highly accurate measurements for topographic mapping.
As drones have become popular, LiDAR sensors have become widely used for mapping purposes as well as inflight navigation and spatial awareness
LiDAR can collect highly detailed data at an unprecedented speed, allowing drone operators to acquire valuable insight into their target environments quickly.
LiDAR's affordability and ease of implementation make it an excellent choice for different industries, from agriculture to construction.
Read the full history of LiDAR here to know more.
How LiDAR sensor work?
LiDAR mapping involves using laser pulses to measure the time it takes for them to bounce back off a surface, as it can accurately measure distances and create detailed 3D maps.
This makes LiDAR an excellent tool for different applications, like land surveying, monitoring crops, and digital elevation models, to name only a few.
It can also be used to detect elevation or terrain changes, adding an advantage compared to traditional aerial photography. To learn more about how they work, check out the “Mechanics of LiDAR Sensors” section below.
LiDAR vs RADAR: A comparative analysis
In some ways, LiDAR and RADAR are similar technologies.
Both are used to detect and measure objects from a distance. However, there are several key differences between the two that make them better suited for certain applications than others:
- LiDAR's laser pulse is more precise than RADAR
- LiDAR sensors aren't sensitive to rain or fog
- RADAR isn't as accurate for smaller objects
The primary distinction is that RADAR uses radio waves to detect its targets, while LiDAR uses laser pulses. This difference is significant, as LiDAR's laser pulse allows far greater precision than radio waves.
Additionally, radar signals are affected by rain and fog, which makes them unreliable in some cases. On the other hand, LiDAR sensors are not as prone to these factors due to their narrow beam of light.
That's not all - LiDAR also offers a greater range and resolution than its counterpart, allowing it to detect and accurately measure even the smallest of objects.
This makes LiDAR the preferred choice for mapping and surveying applications.
Last but not least, while radar is typically used in military operations due to its capability to track moving targets from long distances, Lidar is more suited for stationary or slow-moving objects.
Uses for LiDAR in Drones
Drones use LiDAR for several reasons, primarily revolving around its capability to generate accurate, high-resolution, three-dimensional information about the terrain and structures below. Here are some reasons why drones might be equipped with LiDAR systems:
High-Resolution Mapping: LiDAR can create highly detailed and accurate elevation models, which are particularly useful for industries such as mining, forestry, and civil engineering. These models help in volume calculations, slope analysis, and site planning.
Vegetation Analysis: In forestry, LiDAR can penetrate dense foliage to measure ground elevation accurately. This is difficult for traditional photogrammetry methods that rely on visible imagery. As a result, forest managers can determine tree heights, canopy density, and even biomass estimation.
Infrastructure Inspection: LiDAR-equipped drones can scan infrastructure such as power lines, bridges, dams, and railways, providing engineers with detailed data without requiring human access to potentially dangerous sites.
Archaeology: Hidden ruins and geological features can be revealed by LiDAR as it can uncover differences in terrain that might be obscured by vegetation or sediment.
Flood Modeling: Accurate elevation data is crucial for hydrological modeling, which can help in predicting flood paths and determining flood-prone areas.
Night or Low-Light Operations: Unlike traditional cameras that require good lighting conditions, LiDAR uses its own light source (laser) and can operate day or night, making it versatile for various applications.
Consistency Across Different Conditions: While photogrammetry (the use of photographs to measure distances and make maps) might be affected by shadows, varying light conditions, or reflections, LiDAR data remains consistent as it isn't reliant on ambient light.
Speed of Data Collection: LiDAR-equipped drones can cover large areas quickly, capturing vast amounts of data in a short period.
Integration with Other Data: LiDAR data can be combined with RGB (Red, Green, Blue) imagery or multispectral data, allowing for more comprehensive analysis. This is often done to provide context to the 3D models produced by LiDAR.
While LiDAR offers many advantages, it's worth noting that it might not always be the best tool for every application. Photogrammetry, for example, may be more suitable for tasks where visual detail and color are essential. Nonetheless, the integration of LiDAR with drones has opened a range of possibilities for various industries, pushing the boundaries of what aerial surveying and mapping can achieve.
Do all drones come with LiDAR?
No, not all drones come equipped with LiDAR. While LiDAR technology is highly sought after for drone applications, it can be expensive and limited in availability.
For this reason, buying a separate LiDAR sensor and integrating it into your drone system (or attaching it to your drone) is an affordable and practical solution.
You will still be able to get precise measurements, 3D mapping, and obstacle avoid but without spending thousands of dollars.
Affordable LiDAR Drone Sensors
A good, affordable LiDAR sensor is the LightWare SF23/B Low-power 50m.
If you want to add LiDAR to your drone setup, Lighware currently makes a range of entry-level LiDAR sensors. See our selection here.
The Mechanics of LiDAR Sensors
LiDAR sensors are an essential technology for modern-day mapping, autonomous vehicles, and even firefighting. But apart from their extensive use cases, aerial LiDAR sensors are also remarkably precise.
They can detect objects as small as a few centimeters wide, making them extremely accurate.
How Do LiDAR Sensors Work?
LiDAR (Light Detection and Ranging) is a remote sensing method that uses light in the form of a pulsed laser to measure distances to the Earth or other objects. Here's a basic breakdown of how a typical LiDAR system operates:
Emission of Light: The LiDAR system emits a pulsed laser beam toward the target object or surface.
Reflection of Light: The light beam reflects off the target object or surface and travels back to the LiDAR sensor.
Detection: The sensor has a detector, typically a photodiode or avalanche photodiode, that captures the reflected light beam.
Time Measurement: The system calculates the time it took for the emitted light beam to travel to the target and return to the sensor. Given that the speed of light is constant and known, the time measurement can be used to calculate the distance between the LiDAR system and the target.
The division by 2 accounts for the round trip (to the target and back) of the light pulse.
Multiple Pulses and Scan: LiDAR systems can emit many thousands of pulses per second, scanning the environment in a systematic manner. In airborne LiDAR, the system also often employs a rotating or oscillating mirror to spread the laser pulses over a field of view, capturing a wider area.
Position and Orientation Data: In order to make accurate measurements and models, the LiDAR system must know its precise position and orientation. This is typically achieved using a combination of GPS (Global Positioning System) for positioning and IMU (Inertial Measurement Unit) for orientation.
Data Processing: The raw LiDAR data typically consists of a point cloud, with each point having X, Y, Z coordinates (and often intensity values, which represent the strength of the returned signal). This data can then be processed and analyzed using specialized software to create digital elevation models, contours, 3D reconstructions, and other outputs.
Multiple Returns: One unique feature of LiDAR is its ability to record multiple returns. This is especially important in environments like forests. When a laser pulse hits a tree canopy, some of the light reflects back from the leaves, but some continue downward, reflecting off lower branches or the ground. By recording these multiple return signals, LiDAR systems can map both the canopy and the ground surface.
LiDAR can be classified based on platforms (e.g., airborne, terrestrial, mobile) and its operational principle (e.g., topographic, bathymetric). The exact workings might differ slightly based on these classifications, but the core principle of distance measurement using the speed of light remains consistent.
Choosing the Right LiDAR Sensor
In this section, we will delve into the key considerations when selecting the perfect Lidar sensor for your drone operations and why Acroname's Lightware products are a superior choice.
How to choose a LiDAR sensor?
First-time buyers can find it challenging to choose the right LiDAR sensor. There are several considerations to take into account, such as:
- Data density
It's essential to determine what your specific application requires and what your budget is. Are you looking for a sensor that can accurately map large areas or a more compact sensor for mobile applications? Do you need a sensor that can penetrate through vegetation or has a high-resolution capability?
The range of the sensor will determine how far you can gather data from and thus affects the overall accuracy of your mapping operations. Additionally, the higher the resolution of a LiDAR sensor, the more precise data you can obtain.
Let's discuss a few options to make it clearer and make an informed decision before buying.
Short and Close Range Vs. Long-Range
A long-range LiDAR sensor is perfect for faster-moving vehicles, detecting objects within mid to long ranges, and has a range beyond 300 ft. On the other hand, short-range LiDARs have a range of up to ~82 ft and are ideal for slower-moving vehicles.
But when it comes to quickly identifying objects in close vicinity, close-range LiDARs are the way to go.
You'll get better results when combining a long or short-range LiDAR with a close-range one, and that is something you want to keep in mind.
3D vs. 2D
2D LiDARs excel at detecting objects within a certain range with a drone, but they provide limited additional information beyond that.
3D LiDARs, however, provide specific details that can help understand the object's shape, size, and depth.
Simply put, the main difference is that you'll get more information with a 3D LIDAR and know the object located at the location, while a 2D sensor won't provide such details.
Number of Channels
Another important consideration when selecting a lidar system is the number of channels. This factor determines the density and level of detail in the point cloud, with a higher number of channels delivering a denser yet more comprehensive view of the environment scanned.
Factors such as budget, object size, and relative distance will determine your choice regarding the number of channels in your LIDAR system.
Points Per Second (PPS)
PPS is one of the critical factors to consider when choosing a Lidar system, which is the number of laser measurements taken per second.
The PPS value indicates the detail, density, and accuracy of raw data LiDAR point clouds generated by the system. This value can then define the number of data points recorded to understand objects' position, shape, size, and distance in the environment.
Needless to say, the higher the PPS, the higher the accuracy and details you'll get, and that's surely something you want to consider.
The Remission Levels
Remission measures the reflectivity of an object in percentage. It affects the accuracy and range of LiDAR systems as they rely on light pulses to measure distances.
A white drywall's remission rate is approximately 90%, meaning most of the light reflecting back to the sensor is captured.
In contrast, a piece of coal would have a remission rate of only 5 percent, making it challenging for LiDAR systems to capture accurate data. Understanding Remission levels is vital to selecting the right LiDAR technology for your drone.
Lightware LiDAR Sensors
Acroname's Lightware products provide some of the most advanced Lidar solutions on the market.
Our accurate LiDAR sensor solutions come with different ranges, resolutions, and accuracy rates for all your needs, and our best sellers include:
- LightWare SF45/B 50m Scanning LiDAR Range Sensor
- LightWare SF30D 200m LIDAR Laser Range Sensor
- LightWare LW20 100m LIDAR Laser Range Sensor
Of course, each of these and our sensors is efficient and corresponds better to certain situations than others, and you'll want to check them out for the best results. From multispectral and imaging sensors to a compact lidar laser scanner, we're confident you'll get the right drone LiDAR sensors for your needs. With their cutting-edge technology and optimal power consumption, these sensors provide unparalleled performance.