Lasergrammetry by drone
A virtual rendering process in 3D
Lasergrammetry is a 3D topographic survey mode. It allows precise measurements using a scanning rangefinder device also called laser scanner or LiDAR. This technology allows the acquisition of 3D data of large complex scenes and the direct exploitation of distances and angles. Lasergrammetry is a true technological evolution in the topographic world since it brings a real time saving and proposes new perspectives of result with a real precision of the renderings.
The functioning of lasergrammetry
Lasergrammetry uses a laser type sensor and is based on the principle of echolocation. The sensor measures the time between the emission of the wave and its receipt. This calculates the distance between the source and the target. Then knowing the angle of emission of the laser, it is possible to calculate the position of the points. Thanks to the position of each point, we can perform precise measurements.
LiDAR: laser remote sensing
The acronym “LiDAR” stands for “Light detection and ranging” or “Laser detection and ranging”. This innovative technology is based on the analysis of the properties of a laser beam. Using a pulsed laser, the distance between a point A and a point B is measured by calculating the time elapsed between the emission of the pulse and the detection of the reflected pulse. Today, LiDAR can be embedded on a drone for surveying. This involves the integration of a GNSS receiver which will determine the x, y, and z position to within a few centimeters and an Inertial Measurement Unit (IMU) to measure the precise orientation of the drone for each point statement.
From photogrammetry to lasergrammetry
In the case of some applications, photogrammetry is not suitable and requires the use of lasergrammetry. For example, this is the case for smooth and homogeneous surfaces such as steel or concrete, but also for complex geometries such as vegetation or utility networks.
Lasergrammetry can be used in many fields such as precision agriculture, forest management, power line survey, inspection, maintenance, construction and infrastructure monitoring. This remote measurement technique makes it possible to control the quality of a site but also to evaluate its damage by mapping it in real time using a drone equipped with LiDAR technology.
The benefits of lasergrammetry
Lasergrammetry is a technology that has multiple advantages in performing topographic surveys. Above all, it guarantees the safety and efficiency of the work while bringing considerable time saving to the operator. The special feature of LiDAR is the quick acquisition of real-time data. Indeed, a drone equipped with LiDAR can raise up to 300 000 points per second and can collect several echoes for the same beam. Thus, LiDAR makes it possible to generate DTMs (digital terrain model) despite the density of the vegetation. The measurement is direct and doesn’t require post-processing. It also allows to benefit from a high centimeter precision.