ASV C-Worker 5 USBL Demonstration
By
Brandon A. Mattox, Applied Science Group, NCS SubSea
 
NCS recently had the opportunity to partner with Autonomous Surface Vehicles (ASV) to help demonstrate the survey capabilities of the C-Worker 5. The C-Worker 5 is a five meter long unmanned vessel intended for hydrographic survey work. In our case, the vessel acted as a USBL or ultra-short baseline acoustic platform that would typically be installed on a larger vessel for ocean bottom seismic (OBS) work.


Figure 1. A brief video of the C-Worker 5 in action on Lake Conroe followed by a timelapse of the demonstration day.

Installation of the USBL system was accomplished while the C-Worker was on a trailer near the test area on Lake Conroe. The large air conditioned rack space inside the vessel provided plenty of room for our survey equipment. The Sonardyne USBL transceiver was bolted directly to the bottom of the vessel (Figure 2).


Figure 2. Sonardyne USBL transceiver installed on the C-Worker 5.

The onboard equipment sent comms back to base via the existing ASV radios installed on the C-Worker 5. The comms were then piped into the navigation computer for use in our software. The base station setup was relatively simple and a single network connection was all that was required for navigation.


Figure 3. NCS and ASV base station at Papa’s on the Lake, Lake Conroe.

Prior to launching the C-Worker 5 we deployed a test line of USBL transponders using a support vessel. The 200 meter weighted line had 9 transponders attached at 25 meter intervals and a pop-up buoy on the end. Using only dead reckoning, we managed to deploy a line that made for good USBL results (Figure 4).


Figure 4. The results of the line layout and our base.

The USBL results started coming in when the C-Worker 5 began its pre-plotted pattern around the deployed stations. The results we received were typical of a normal USBL acquisition on an OBS crew, and the line keeping was more precise. The noise results are encouraging for the C-Worker 5 as a USBL platform (Figures 5, 6, and 7).


Figure 5. Sonardyne Scout noise profile while C-Worker 5 at idle speed.


Figure 6. Sonardyne Scout noise profile while C-Worker 5 at 3.3 knots.


Figure 7. Sonardyne Scout noise profile while C-Worker 5 at 5.0 knots.

Overall, it was a very good test and demonstration of the C-Worker 5’s capabilities in the seismic survey realm. The use of unmanned vessels will likely become a standard part of any geophysical survey company’s set of tools when the benefits of efficiency are realized. For more information about the C-Worker 5 be sure to visit ASV's website and don’t hesitate to contact NCS SubSea for more information about integrating a survey solution on any platform you have.


Figure 8. The ASV C-Worker 5 on Lake Conroe.