Background
Conventional lidar terrain mapping will not penetrate water by more than a few centimeters. Bathymetric lidar systems use a different and more complex technology to measure seabed topography in shallow waters. Such surveys are typically performed for beach replenishment studies, near-shore surveys, seafloor mapping, nautical chart updates, and coastal zone erosion monitoring. They are used in fields like oceanography, marine biology, oil and gas exploration, and coastal and reef management, as well as by the Coast Guard and the Armed Forces.
Airborne bathymetric lidar surveys use the interaction of different laser wavelengths with the seafloor to perform seabed profiling. But the lasers also interact with particles or sediments in suspension in the water column between the surface and the seabed. These interactions need to be considered when mapping the seabed, failing which errors in topographic elevations and hydrographic depths may occur.
Solution
INO has developed a submarine lidar to measure the reflectance of the seafloor and water column. The system is used to determine the reflectance of sea bottom so that their composition can be correlated with relative intensity data from aerial surveys. INO’s lidar system helps to calibrate the results of airborne bathymetric surveys, increasing their accuracy and enhancing our understanding of the results. Use of bathymetric lidar systems is likely to increase in the future due to improvements in their functionality, so calibration of those systems is important to ensure accurate seabed topography data.
INO is working closely with INRS-ETE to test the maximum depth achievable and calibrate the system in the water. This lidar prototype has the potential to cover a range of 3 to 50 m underwater. The lidar submarine enclosure is currently carried by a zodiac and submerged while following airplanes doing aerial surveys. Future development of the lidar submarine system will include putting it in an Unmanned Underwater Vehicle (UUV) for independent measurements.