Drone LiDAR - 3 Keys to Successful Canopy Penetration
Summer is finally here! For the surveying, engineering, and land management professionals out in the field, this means more amenable working conditions and longer hours of daylight. However, many challenges remain, including the need to safely collect accurate project data in remote and difficult areas while permeating summer’s abundant foliage and vegetation.
RedTail LiDAR System’s RTL-400 could be your answer!
The adoption of drone-based, 3D laser scanning (LiDAR) is emerging as the preferred remote sensing technique to rapidly and cost effectively produce highly accurate, high-resolution point clouds despite the presence of tree foliage and vegetation.
How LiDAR penetrates foliage:
Just how does LiDAR capture data beneath foliage? If you are hiking through a forest, or heavily wooded area, and you can see the sky through the trees, then LiDAR can also see through the foliage to get light returns from the ground.
Fundamentally a distance measuring technology, LiDAR’s foliage penetrating capabilities are founded in the laser’s ability to send hundreds of thousands of laser light pulses per second, from the drone, to peer through the gaps between the leaves and branches of the trees. Each laser pulse sends multiple returns back to the sensor, with the last return being the ground, making LiDAR ideal for under canopy topographic mapping.
As the LiDAR optical sensor collects returns, the data is used to generate point cloud images made up of millions of data points. Collectively, these points create a high-density, highly accurate 3D image of your project that can be used for data analytics.
How to use the LiDAR data:
There are many uses for LiDAR data across industry sectors. While it can be used to produce topographic estimates, it can also be used to estimate canopy height, tree volume, and other measurements with unprecedented accuracy and resolution.
The point clouds can be exported as common .las files and then imported into any number of commercial, industry specific, software packages for use in planning, design, mapping, monitoring, and documenting your projects.
The point cloud images created by a LiDAR system can be used to create multiple types of models for analysis. One of the most common models created is the Digital Elevation Model (DEM) for use in creating topographic maps. DEM’s can also be used to analyze slope (rise or fall expressed in degrees or percent), aspect (slope direction), hill-shade (shaded relief considering illumination angle), and various other morphological changes.
LiDAR data can also be used to create Digital Terrain Models (DTM), Digital Surface Models (DSM) and Canopy Height Models (CHM).
Why use the RedTail LiDAR System:
Designed specifically for use on small drones, the RTL-400 was developed with technology licensed from the U.S. Army Research Laboratory (ARL) and designed to provide high-resolution 3D images of objects on the ground, flying at an altitude of up to 400 ft.
There are 3 keys to getting LiDAR returns from beneath the canopy and the RTL-400 excels at all three. These keys include; 1) a laser pulse that has small beam divergence, 2) the ability to process multiple returns from each transmitted pulse, and 3) a high pulse density in the area being scanned.
Here’s how it works:
- Minimizing beam divergence ensures that the size of the laser spot is small as it reaches the canopy. A laser pulse with a small spot size has a higher probability of reaching the ground since the transmitted light can effectively pass through small openings in the canopy. The RTL-400 has an exceptionally small beam divergence of 0.5 milliradians (.03 degrees).
- The ability to process multiple returns provides increased detail of an area being mapped. A pulse might reflect off of leaves and several branches before it finally reaches the ground. The ability to analyze up to 5 returns for every transmitted pulse provides the best chance possible to get returns needed to create DEMs and DTMs.
- The RTL-400 incorporates an innovative microelectromechanical system (MEMS) mirror-based laser scanner that rapidly and evenly distributes laser pulses. The mirror moves side-to-side 400 times per second; when the rapid side-to-side scan rate is combined with a laser pulse rate of up to 400,000 pulses per second and an optimized scan angle of 40 degrees, the point density is extremely high. A high point density increases the likelihood that pulses will see through the small gaps between the leaves.
Weighing in at 4.5 lbs., the RTL-400 is easy-to-use and easy-to-operate and offers the unique capability of 2 scanning modes, the 3D line scan mode and a 40 x 40 raster scan mode for “stand and stare” missions, providing unmatched operational flexibility.
RedTail LiDAR Systems demonstrated the exceptional performance capabilities of the RTL-400 in a mapping flight performed for the West Virginia Department of Environmental Protection (WVDEP).
The WVDEP was faced with the problem of obtaining time critical data for evaluating mine reclamation to ensure the natural environment is being properly restored by mining companies. Using their existing point cloud generation method (photogrammetry), they were unable to create accurate DTMs beneath canopy. In addition, they were concerned that a low-cost LiDAR system would be unable to provide the data density needed to create accurate DTMs.
The demonstration flight showed that the RTL-400 could be used to create accurate DTMs even in the presence of dense leaf cover. The ability to collect and analyze DTMs in summer, as well as winter, provides the ability to work and analyze reclamation efforts throughout the year versus only in the winter.
See images to the right.
Benefits of the RTL-400 to user:
Utilizing the RTL-400 3D LiDAR mapping system for your foliage penetration project provides several benefits over traditional surveying methods, including:
- Collecting high-resolution, highly accurate, under-canopy data in one deployment
- Reducing risk for manned survey crews
- Reducing man hours for site assessment
- Reduction in cost associated with data processing time
- Reduced cost in man-hours and travel time for face-to-face meetings by presenting electronic data and findings to clients via web meetings
- Improved overall ROI
Designed specifically for use on small drones, the RedTail LiDAR System is the optimal remote sensing tool to rapidly and cost effectively penetrate tree foliage and vegetation, collecting the accurate, high-resolution images that you need!
Contact us today to learn more about the RedTail LiDAR System’s RTL-400.