Hydrographic Lidar Processing Moves into the Next Dimension

Lidar hydrography has been in use world-wide since the mid-1980s, with current systems proving to have unique capabilities, particularly in shallow, hazardous and remote areas. The systems have also demonstrated their flexibility and mobility to respond rapidly to evolving requirements in both the coastal management and defense scenarios. As a result, the Lidar systems have found application across a wide variety of coastal mapping including navigation hazard identification, nautical charting, storm damage assessment, beach nourishment and design, navigation channel inspections and erosion monitoring. As the technology has evolved the data rates have increased and algorithms are being developed to extract more information from the data. The airborne platform allows the use of a number of sensors to build on the efficiency of the Lidar system and its general mobility. This can include the addition of a digital still or video camera, a topographic Lidar and a multispectral scanner. To complement the higher volumes and variety of data there has been a parallel evolution of the approaches to processing, driven particularly by the massive amounts of data from shallow water multibeam systems. The original line by line based systems that required the inspection of every data observation are a thing of the past and cannot be supported with current data rates and resources. The whole data workflow of acquisition and processing is being automated and based on an area approach. However, this approach requires suitable tools to ensure that the automatic processes are validated and to guarantee the quality of the final products meets the required standards. An effective area based approach needs to satisfy three important elements: a data structure designed for area processing; rigorous automated filtering techniques; and the integration of these capabilities within an intuitive and efficient 3D area based view of the data that allows rapid and accurate analysis as well as validation of the automated processing. The data structure must allow direct access from the area view to the full-resolution data stored in its native format, and occasionally during the validation this may require access to the Lidar waveform. Quality Control must be implemented throughout the workflow from planning flight lines through to automated processing and area based filtering to produce the accepted products. The 3D area based analysis and editing tools must be directly integrated with the unique Lidar processes from flight line planning and management to detailed Lidar point investigation and manipulation. The 3D application provides the benefit in a single interface of allowing integration and processing of all the acquired and other available data such as chart, aerial photograph and existing topographic and bathymetric models. This paper describes the development of the latest generation Ground Control System (GCS) software for the SHOALS-1000 Airborne Lidar Hydrography (ALH) system. One unit has recently been delivered to the Japan Coast Guard and a second system with integrated 10 kHz topographic capability is scheduled for delivery to the US Naval Oceanographic Office this summer.