{"id":731,"date":"2024-08-11T10:39:01","date_gmt":"2024-08-11T08:39:01","guid":{"rendered":"https:\/\/demo.athemes.com\/sydney-main\/?p=731"},"modified":"2026-05-03T10:43:13","modified_gmt":"2026-05-03T08:43:13","slug":"comment-fonctionne-un-lidar-bathymetrique-aerien","status":"publish","type":"post","link":"https:\/\/www.lidar-bathymetrique.fr\/en\/bathymetrie-lidar\/fonctionnement\/comment-fonctionne-un-lidar-bathymetrique-aerien\/","title":{"rendered":"How Does Airborne Bathymetric LiDAR Work?"},"content":{"rendered":"

How Does Airborne Bathymetric LiDAR Work?<\/strong><\/h1>\r\n

LiDAR technology (Light Detection and Ranging) uses light pulses in the green spectrum to penetrate water and measure the depth of the seabed.<\/p>\r\n

Unlike traditional methods, this technology relies on the use of laser (light beam ) to measure the depth of water.<\/p>\r\n

In this article, we will detail the operation of an aerial bathymetric LiDAR<\/strong> system, covering its laser<\/strong>, wavelength<\/strong>, interaction with water<\/strong>, as well as GPS<\/strong> and INS<\/strong> (inertial navigation system) positioning technologies, which are essential for obtaining centimetre-accurate georeferenced surveys.<\/p>\r\n

1. The Laser: The Primary Tool of LiDAR<\/strong><\/h2>\r\n

The core of a LiDAR system is the laser<\/strong>. In the case of aerial bathymetric LiDAR, a specific laser is used: the green LiDAR<\/strong>, which operates at a wavelength of 532 nm<\/strong> (nanometres). This particular wavelength belongs to the visible light spectrum and is especially suited for underwater surveys because it can penetrate the water's surface.<\/p>\r\n

Why green light ?<\/strong><\/h3>\r\n

Unlike other wavelengths (such as red or blue), green light has the ability to penetrate the upper layers of water<\/strong> before being absorbed, while remaining strong enough to return to the sensor after reaching the seabed. This property makes it the ideal wavelength for bathymetric surveys in shallow waters<\/strong> (up to approximately 15 to 20 metres), where other technologies, such as sonar, are not suitable (e.g., rivers or coastlines).<\/p>\r\n

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\"bathym\u00e9trie
Absorption Spectrum of Visible Light in Water<\/figcaption><\/figure>\r\n

The Principle of Reflection and Refraction<\/strong><\/h3>\r\n

When a laser beam passes through the water's surface, it undergoes a phenomenon of refraction<\/strong>. This means that the direction of the beam changes depending on the angle of incidence and the density of the water. Part of the beam's energy is reflected back towards the airborne sensor, while the rest continues to penetrate deeper before being reflected by the seabed.<\/p>\r\n

Diagram\u00a0<\/strong><\/h4>\r\n
\"shema
Shema r\u00e9fl\u00e9xion \/ r\u00e9fraction d’un lidar bathym\u00e9trique<\/figcaption><\/figure>\r\n
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2. The Inertial Navigation System (INS) and GPS: Centimetric Accuracy<\/strong><\/h2>\r\n