Autonomous onboard hydrographic data processing

During a traditional hydrographic survey, data can be acquired, accessed and processed by personnel working on the vessel or launch. Improved data processing tools have reduced the ratio of acquisition to processing time significantly in the past 10 years, despite an increase in the quantity and quality of data points available from modern sonars and sensors. The improved performance of the bathymetric sonars and their associated ancillary sensors (motion, position etc.) has allowed surveyors to identify smaller targets with higher resolution than ever before. In addition, the physical size of these sensors has decreased, allowing deployment on platforms previously inaccessible by survey teams. The platforms used for acquisition have improved autonomy with Autonomous Underwater Vehicles (AUVs) and Autonomous Surface Vessels (ASVs), along with extended mission times driven by improved battery technology. Hydrographic survey platforms are increasingly becoming autonomous or semi-autonomous due to the benefits that these platforms offer. Lower capital and operating costs, the ability to work undetected and closer to the intended target and multiple unit operation are just some of the benefits that can be exploited by the operator. AUV technology has allowed for the development of smaller vehicles that are able to work in the shallow waters of the littoral, with a lower build cost allowing the deployment of several units for a single mission. AUVs have also been improved by battery power technology, allowing for extended mission times. A good example of a current program is the US Navy´s Large Displacement Underwater Vehicle (LDUUV) which is anticipated to have an endurance measured in weeks rather than hours. ASV development has been significant, with the challenges associated with navigating a surface vessel autonomously being addressed as a priority in the maritime community. The advantages of the ASV is the improved bandwidth that above water communications offers, allowing for real time transmission of data to the unit controlling the vehicle. Improvements in renewable energy sources such as solar, wind and wave power have meant that it is possible to operate an ASV for extended periods of time, and the decrease in platform cost has allowed for several units to be used in unison to gather intelligence over a large area.The increased use of autonomous survey platforms has resulted in the ratio of acquisition to processing time has becoming a mission limiting factor again. Without human interaction in the real-time feedback loop, the platform must gather the data and await post-processing when it is recovered. This method has significant disadvantages, most notably a lack of assurance that the data collected is within the required specification and an increased turnaround time before the platform can be re-deployed. On manned survey platforms significant time is often spent at the end of the survey conducting batch processing tasks such as conversion of data and running automated data cleaning algorithms. By performing these tasks at the end of the survey on a complete and large dataset, the processing times can be lengthy and this impedes the surveyor-in-charge´s ability to make decisions for the subsequent survey plan. This paper will describe a new software based method of acquiring and processing data autonomously in near real time whilst the survey is underway and look at the benefits that can be gained from using this method.