Unmanned Surface Vessels

Locked and Loaded for Hydrographic Missions

In recent years, the proliferation of unmanned surface vessels deployed for hydrographic missions has mushroomed as the collaborative effects of propulsion, software and sensor technologies has cumulatively made these vessels, large and small, more capable for a multitude of missions. In this edition, and on the heels of the Ocean Business exhibition last month in Southampton, Marine Technology Reporter examines recent developments.
 

The Sonobot
The Sonobot from Evologics, a  Berlin, Germany-based  manufacturer of underwater communication and positioning systems, was on hand recently at the Ocean Business 2013 exhibition in Southampton, U.K. to demonstrate its updated Sonobot Autonomous Hydrographic Survey Vehicle.
Sonobot was developed to provide surveyors, service providers and researchers with a smart lightweight solution for hydrographic surveys and other applications in harbors and inland waters, with the design objectives being usability, robustness and versatility, paired with high-performance of the onboard sensors.
“As geological mapping of the seafloor in near shore or shallow water areas presents technological challenges due to the dynamics of the environment, high volume of data collected, and the limitations of operating in very shallow water, a remotely operated or autonomous seafloor mapping USV is a great solution for the problems of shallow water settings,” said Francisco Bustamante, Senior Operations Manager, EvoLogics. “The main idea behind EvoLogics Sonobot was to present a small, simple and usable platform for planning and executing a hydrographic survey that can deliver accurate geo-referenced bathymetric measurements and high-quality imagery with minimum transport, launch and recovery efforts.”
The concept of SONOBOT is to offer the end user a modular system with several configuration options and deliver a ready-to-use vehicle with all the onboard equipment installed and ready for immediate action.
Specifically for the SONOBOT, EvoLogics used the patented S2C broadband communication technology to build an advanced single-beam echo sounder, capable of delivering precise and accurate depth measurements even in very shallow waters. The side scan sonar, a highly accurate DGPS system and other equipment options were preselected among commercial off-the-shelf products to best fit the SONOBOT platform and offer the user the best configuration for his particular requirements.
A survey USV must be convenient for day-to-day use by survey service providers, so simplicity to launch, operate and recover were recognized as essential features of the vehicle. Therefore, the SONOBOT was constructed of lightweight materials and was designed to be assembled without any tools or special skills. Larger payload capacity was given up for better transportability, so the SONOBOT system fits into a car trunk and does not require a bulky trailer or container. Designed as a turnkey solution, the Sonobot delivers precise and accurate bathymetry data in autonomous mode.
As anyone in the field knows, there exists no single solution for every hydrography scenario, and Sonobot does have its limitations. “There are compromises to be made in terms of the size of the equipment and its autonomy, or in terms of how many parameters can be measured at the same time versus the operating time,” said Bustamante. “One of the biggest limitations still is when operating in unknown areas, as there is always the possibility that the vehicle will have to be rescued if there are trees around, for example. We minimize the chances of this happening by adding sensors and the option to monitor the operation in real time even with video streams.”
While Sonobot is indeed an important system for EvoLogics, the company has a judicious investment plan to help it further penetrate this emerging market. “EvoLogics is investing in the development of modular platforms that can be deployed flexibly in different scenarios to collect a wide range of sensor data,” said Bustamante. “Our focus is on a segment that needs to operate the vehicle quickly without big logistical needs. Therefore our vehicles have a relative small size, but without compromising stability. At the same time, we aim at ease of use by having components that can be assembled easily on the field without needing tools. In addition, we are looking at alternatives in terms of autonomous navigation, in particular collision avoidance to reduce the amount of supervision that is necessary for these vehicles and increase the ability to react to different situations.”
While there are many drivers propelling the use of USVs in this sector, Bustamante said that resource monitoring and management is a big issue today. “Therefore we have continuous requests for collection of data for water reservoirs, industrial process residues an waterways, amongst others. A periodical collection of data makes it easier to identify trends and outliers. By using autonomous vessels that automate a big part of this activity, the results become more reliable. Additionally, many of these surveys happen in areas that are not necessarily accessible or safe. In this case it is better to use an autonomous vehicle than to risk somebody’s life.”

Case Study Sonobot Goes to Work
A growing metropolis, Berlin has an arsenal of big building projects, with the 2.2 km underground extension of Berlin metro in the city center an example. The construction works put the surrounding buildings and infrastructure at risk, moreover, as the line is to go underneath the river Spree, a potential flood at the site increases the risk levels and requires regular assessment. To enable early detection of a potential threat, it was important to perform geological mapping of the initial conditions of the river bottom, and proceed with regular monitoring missions to track the changes that might occur during the construction period. Hydrographic survey operations at the construction site were carried out with the EvoLogics Sonobot - a light unmanned surface vehicle for bathymetry and seafloor imaging in harbors and inland waters. Equipped with an accurate DGPS with RTK, it provided positioning data with centimeter accuracy. The Sonobot’s single-beam echo sounder, based on EvoLogics patented S2C broadband communication technology, delivered accurate depth measurements even in shallow waters at the metro line’s construction site. Sonobot offered the commissioned service provider the benefits of conducting fully-automated survey missions. It is equipped with an autopilot for waypoint-based navigation, so a once established survey grid can be repeated as often as necessary for regular monitoring of the river bottom.
Due to its flexibility and compact size, the Sonobot was chosen for the mission as a clear advantage over a survey boat. Its transportability, fast setup time and low maintenance proved valuable due to the structural and technological particularities of the construction site to be monitored.

Sonobot Key Features
-    Differential GPS for high-accuracy cartography (GPS, GLONASS and Galileo)
-    Side-scan sonar option
-    Integrated camera for operation in remote locations and surveillance
-    Fast access to points of interest, accurate maneuvers and efficient area scanning with precisely controllable hydro jet thrusters
-    Batteries for more than 10 hours of operation (at optimum operation speed)
-    Software for field operation and data processing with visual geo referenced representation
-    Autonomous and radio controlled operation modes
-    Wi-Fi communication (GPRS/UMTS)
-    On-board data logging, wireless transmission on demand
-    Carbon fiber floaters, corrosion-free materials, resistant to seawater and industrial waste water
-    Can be handled by a single person

 

(As published in the May 2013 edition of Marine Technologies - www.seadiscovery.com)