Do More Points Equal More Information? A Look Into Bathymetric LiDAR Point Densities
In recent years, technological advances have led to exponentially increasing point cloud densities. These higher resolution point clouds have enabled new applications, improved existing products, and helped to automate some manually intensive process steps. They also come with new challenges like larger data volumes, the requirement for more processing power, and in some cases, a greater amount of noise handling. End users often lack the necessary infrastructure to exploit the data and have come to expect higher density data, beyond what is required for their application. Moving from a topographic environment into a bathymetric environment, depending on the system design and scattering properties of the water columns, higher density point clouds do not necessarily contain more detail on the shape of the seafloor than lower resolution point clouds. In this presentation, we will use the sensor design parameters (pulse repetition frequency, beam divergence, aperture size, etc.) and environmental factors (water clarity, depth, etc.) to calculate the effective footprint of the LiDAR pulse on the seafloor. This enables us to quantify the overlap among adjacent laser pulses and determine at what depth the systems will report the same depth for adjacent laser pulses. We will demonstrate these theoretical results with bathymetric LiDAR datasets of varying point densities. This work informs specifications for bathymetric and topo-bathymetric LiDAR data acquisition and for design of new systems. It can also be used to identify a depth cut-off for reporting depths from higher-resolution shallow-water systems and lower resolution deep water systems when they are flown in tandem, or in hybrid systems that contain both capabilities.