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EchoBoat-160 USV with Multibeam Echosounder for Underwater Bridge Pier Condition and Scour survey

Key Points in the Case Study:

Purpose:
To demonstrate the advantages of using a portable Uncrewed Surface Vessel (USV) with high-resolution
Multibeam Sonar Technology to monitor bridge pier integrity and scour in great detail, eliminating the need to deploy divers in hazardous, high-risk environments.

Who:
Seafloor Systems, Ohio Department of Transportation (ODOT), and The Ohio State University.

Problem:
Many DOTs are using conventional survey methods such as mechanical scanning sonar, or Single Beam echosounder survey data along with diver inspections to determine the condition of bridge piers and scouring around the piers on the surrounding seafloor/river bottom. However, the resulting detail of data is not sufficient for accurate assessments while incorporating the added risk of putting divers into hazardous conditions.

Solution:
A Seafloor Systems EchoBoat-160, portable Uncrewed Surface Vehicle (USV) outfitted with a SeaRAY Multibeam Sonar System with an integrated Trimble-Applanix Inertial Navigation System, AML1 sound velocity sensor, and AML3 Sound Velocity Profiler. HYPACK, Inc. HYSWEEP software was used for multibeam data collection, calibration, and post-processing.

Trimble-Applanix POSPac software is used for post processing position and attitude data. The integrated USV is a turn-key, calibrated, ready- deployable solution that is extremely portable and easily deployed by 1-2 persons depending on the environment and conditions. The integrated SeaRay Multibeam echosounder is a wide-swath beamforming profiling sonar that simultaneously measures 256 individual soundings across its 130 degree swath, at up to 50 pings per second.

The sonar is tightly coupled with a Trimble-Applanix POS-MV inertial navigation position and orientation system that provides real-time compensation for the vessel’s attitude (heave, pitch, roll, heading, and position), enabling the system to continue to accurately navigate during loss of GPS when transiting under bridges and other structures. Additionally, the User can log associated raw POS MV data in order to post-process the navigation and attitude data and correct for errors/drift due to GNSS outages.

The Main Components of this Integrated System Include:

1. 9” moonpool through which to mount the compact SeaRAY Multibeam sona.
-Inside: The grey box is the onboard Industrial PC, withHYPACK HYSWEEP dongle installed. The green box is the theSeaRAY processor. In the middle is the Sonar head cable coming into the boat and plugging into the processor. On the panel, a single One-Button EchoBoat startup.
-Underside: SeaRAY Multibeam Sonar head, with integrated INS and SV Sensor
2. Smart Cast profiling winch to deploy Sound Velocity Profiler via remote control.
3. Long Range Remote Control for 2km line of site control of the USV in RC mode.
4. Long Rage WiFi (2km line of sight) to connect to the EchoBoat’s onboard PC from the operator’s shore-based laptop via Remote Desktop.
5. 4G Hotspot (option) for remote connection to the onboard PC via Team Viewer in areas with good Cellular coverage (no longer line of site restriction).
- Forward-looking camera for situational awareness and safe/ visual navigation.

The EchoBoat-160 with the SeaRAY fits in the back of a pickup truck or van, and can be transported via cart on site, and hand-carried into the water.

Application and Results:

From an Engineering and Safety position, there is more focus and demand for high detail, high-resolution Inspection surveys around Bridge piers.

Because the Multibeam offers wide swath coverage, you are able to collect 100% point-cloud coverage around the bridge piers to determine depth of cover over the supporting Piles. The Piles are driven into the ground, and are the fundamental foundation that supports the piers, which hold the bridge. If the river scours material away from the piers, exposing the supporting Piles, the stability of the bridge becomes compromised. Multibeam is also used to inspect for and map debris around the piers without needing to risk sending divers down with limited visibility. It’s a good tool to identify any issues or hazards that might preclude the need for divers, or better direct them to points of concern with more accuracy, knowledge, and safety.

As with hundreds and hundreds of small bridges in the United States, there had not been a true hydrographic survey of any kind conducted around this bridge in decades, if ever. The only information Bridge Engineers have access to are old engineering drawings, as-builts, with some old outdated elevations. Many sites, like this one, are not accessible via larger crewed boat. Hence the advantage of using of a portable USV platform.

With 30 minutes of setup, and 30 minutes of data collection, the combined use of the EchoBoat-160 and SeaRAY allowed for the quick and accurate collection of high-resolution multibeam data to assess the amount of scour and debris build-up around a targeted bridge. The EchoBoat was able to be hand launched right at the bridge’s bank.

Thorough, and extremely efficient. There was no need to launch a traditional crewed survey vessel, there was no transit time on the water, to the specific targeted survey site, and no humans were required to be on or in the water. Over the course of the 34-minute active data collection, the system was able to cover depths ranging from 2 to 30 feet and generated over 17.5 million soundings. The result is extremely accurate, high detail, data, with no guesswork.

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