Lidar is a method used to determine variable distances, targeting an object with a laser and measuring the period it takes the reflected light to return to the receiver. Due to the different laser return times and varying laser wavelengths, you can use it to make digital 3-D representations of ocean bottoms and areas of the Earth’s surface.
This article looks at developing 3D lidar systems, applications, and modern 3D laser scanning systems. The development of 3D lidar started in the 1980s and has continued till the emergence of versatile modern scanners.
In addition, the article discusses the two main types of 3D lidar systems – airborne and terrestrial lidar systems, and their use situations.
So, what is 3D lidar? Lidar is a unique combination of laser scanning and 3-D scanning and is sometimes called 3-D laser scanning. The technology is predominantly used to make high-resolution maps, with geomatics, geography, surveying, geology, atmospheric physics, seismology, laser altimetry, forestry, archeology, and airborne laser swath mapping (ALSM), among other applications.
Development of Lidar Systems
The development of non-scanning airborne lidar systems began in the early 1980s, and surveyors used topographic mapping. For instance, Krabill et al. (1984) mapped the topography of a watershed near Memphis in Tennessee using an airborne lidar system. In the mid-1980s, researchers used 3D lidar systems to determine vegetation canopy heights and changes in canopy densities.
However, these systems were non-scanning, and you can obtain only a single line of data. The data obtained was a cross-sectional profile beneath the aircraft. There were, therefore, more limitations, especially where vast areas needed to be covered.
Airborne scanning lidar became available in the mid-1990s. The technology was first used for topographic mapping terrains and carrying out forest measurements. This is because the scanning systems can sweep a band of landscapes through lateral deflection of the emitted laser beams occurring when the aircraft moves forward. As a result, the airborne 3D lidar scanner can scan a large area in a series of bands. This is due to the laser beam’s relatively small footprint diameter ranging between 10 to 30 cm on the ground.
Generally, lidar viewer applications are divided into airborne and terrestrial types. These types both require scanners with varying specifications. The specifications required were selected depending on the purpose of data needed, size of the area to be covered, cost of equipment, range of measurements to be taken, among other requirements.
Airborne Lidar Applications
This is where a laser scanner is used to create 3-D point cloud models of a landscape while attached to an aircraft during the flight. It is currently the most precise and accurate method of developing digital elevation models. Compared to photogrammetry, this system can filter out reflections from vegetations to create digital terrain models representing ground surfaces such as cultural heritage sites and rivers in a much better way.
Large-footprint scanning lidar systems are used in large-scale forest remote sensing from satellites. They have a larger footprint covering between 10 to 25 meters in diameter. Besides, they are obtained from a higher altitude resulting in wider image swaths.
The main components of airborne lidar viewer are digital surface models and digital elevation models. Where an interpretation of tension cracks, erosion or landslides under cover of vegetation is needed, airborne lidar is used. This is because they can easily see through forest canopies.
Terrestrial Application of Lidar
These are terrestrial laser scanning processes on the Earth’s surface and can be mobile or stationary. However, static scanning is expected to monitor, forensics, and document cultural heritage as a survey method.
Mobile 3D lidar is when two or more scanners attached to a moving vehicle are used to collect data along a path.
Range Of Light
Lidar uses near-infrared, ultraviolet, and visible light to image a wide range of objects such as rocks, chemical compounds, clouds, rain, aerosols, rain, single molecules, and even non-metallic objects.
Laser beams are potent and can image objects with very high resolutions. Aircraft, for instance, can map terrains at a resolution of 30-centimeter or even higher.
Static Lidar Scanning
One standard modern 3D-lidar scanning device is the ScanX3D. It utilizes 3D laser scanning to obtain 3-D data products. It also uses a RIEGL VZ400i scanner which produces full 1000×3600 survey-grade point clouds. Besides, it captures high-definition images for true colorization.
The laser scan data is quite accessible and can be georeferenced and downloaded anytime in real-time. Also, the data is tied to vertical or horizontal site-specific datum for easy access.
In addition to RIEGL VZ400i, ScanX3D uses a 3D camera to measure 3D spaces while also capturing ultra-high-definition 4K imagery. This tool is handy in creating 3D models and schematic floor plans.