Lidar mapping is a widely acknowledged technology for generating precise and immediately georeferenced spatial information about the Earth’s shape and surface features. This article will explore lidar basics for those who are just becoming aware of this active 3D modeling technology.
From an article in Inventiva by Kritisrivastava.
The Lidar mapping systems and their underlying technologies have recently advanced, allowing scientists and mapping professionals to explore natural and constructed surroundings at scales never before possible with higher accuracy, precision, and flexibility. Several national papers published in the last five years have emphasized the importance and utility of lidar data.
Light detection and ranging (Lidar) is a composition for light detection and ranging. It is also known as LADAR or laser altimetry. It’s a type of remote sensing technology that uses intense, focused beams of light to detect reflections and measures the time it takes for the sensor to see them. This data is used to calculate object ranges or distances. In this way, Lidar is similar to radar (radio detection and content), except it uses discrete laser light pulses. The target objects’ three-dimensional coordinates (e.g., x,y,z or latitude, longitude, and elevation) are calculated from:
The time interval between when a laser pulse is emitted and when it is returned.
The angle that the beating was “fired” at.
The sensor’s absolute location on or above the Earth’s surface.
The energy source used to detect a target distinguishes two remote sensing technologies: passive and active systems. Radiation from an external source of energy, as the sun, is seen by passive methods. On the other hand, dynamic systems produce and steer pointers toward a target before detecting the radiation. The Lidar systems are active because they emit pulses (i.e., laser beams) and catch the reflected light. This property enables lidar data to be collected at night when the air is more transparent and the sky is less congested than during the day.
The Lidar technology isn’t new; it’s been around for almost 40 years and was first used to map particles in the atmosphere. This ground-based application had significantly less positional complexity than airborne mapping (i.e., the laser location did not move). The invention of GPS in the 1980s opened up new applications for moving sensors (airborne Lidar). One of the early applications of airborne Lidar was bathymetric Lidar. The water’s surface served as a “reference” that helped to de-emphasize the plane’s absolute location.
The IMU improved in the early 1990s, allowing it to achieve decimeter accuracies for the first time. The measurement of glaciers and how they were changing was one of the first non-bathymetric aerial uses. Lidar (terrestrial scanning) on the ground is also utilized to intensively map the three-dimensional nature of features and ground surfaces to an incredibly high level of accuracy (1 centimetre).
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