Location:  The dangerous section of Longwan bridge in Foshan city and the harbors of Taishan power station in Tangshan bay, Taishan city

Date: April 25-28, 2018

Instrument: Oceanalpha M40 multi-purpose unmanned boat

Beijing Anderson Changchun 3DSS-DX-450 3D side scan sonar

Beijing Zhuhai Putonghua MS-400 multibeam sounding system

User: Guangdong Banting Survey Technology Co., Ltd.

Instruments overview:

In this mission, the M40 unmanned boat is deployed with a 3DSS-DX-450 3D side scan sonar, an MS-400 multibeam sounding system, a wave master navigation system and a wireless broadband antenna. Receiving mission commands from the base station, the unmanned boat controls the above instruments to conduct the bathymetric survey and submerged geomorphology detection automatically.

Case details

Survey area

The mission includes watercourse survey and harbor basin survey.

  1. Watercoursecircumstance
    Survey area around Longwan bridge, Foshan city(The red frame area)

    The survey area includes both the upper and lower reach of the Longwan bridge and is of approximately 1 square kilometer and the water depth ranges from 2 to 5 meter.

  2. Harbor basincircumstance
    Survey areas in Taishan harbor (The red frame area)

     

    The basin is within in the Taishan power station harbor, which is divided into two parts: a smaller one of 2-6m depth, and a bigger one of 9-15m depth. Due to the dredging work carried out in the large basin, which would has huge impact on the acoustic equipment, the survey is mainly conducted in the smaller basin.

Main process

Two

M40 boats are transported and launched by an integrated crane.

When surveying the watercourse in Foshan, the base station and communication antenna are set up under the Longwan bridge to ensure the signal coverage of both reaches. After simple tests, the unmanned boats receive commends from the base station and start working. It took the boats five hours to complete the task at an average speed of four knots.

As the unmanned boats docked, they’re collected by hooking the hanging point to the hook of the crane.

Operators working under the bridge

The survey line of the unmanned boat set on the base station

Ping 3D side scan sonar performance analysis

As can be seen from the real-time data, the data points of the 3D side scan sonar have high density and the output image is clear and delicate. The sonar with a span widths of up to 10 times the water depth greatly improves the survey efficiency and accuracy.

Dock piles in Taishan harbor

The breakwater and waste immersed pipes in Taishan harbor

Bridge pier of Longwan bridge

MS400 multibeam performance analysis

  1. Cross-section matching analysis

After correcting and calibrating the sensor data, we check the matching situation of the cross-section of Foshan watercourse and Taishan harbor respectively and get satisfying results.

data matching output of Taishan harbour

data matching ouput of Foshan watercourse
  1. Multi-beam precision analysis of Foshan watercourse

Using the quality control function that comes with the CARIS software, we analyze the accuracy of the data of overlapping area based on the IHO super-accuracy standard.

The terrain of Foshan watercourse is complex and the topography changes frequently, to demonstrate the survey result accurately, we process the statistical analysis with a square mesh size of 0.1 m. The result is as followed:

The analysis result with mesh size of 0.1 m

From the above table, we can see that all data within the measuring area meet the accuracy standard.

 

  1. Multi-beam precision analysis of Taishan harbor

Since the underwater topography of the Taishan harbor is relatively flat, we establish the statistical analysis of mesh size of 0.1m*0.1m and 1m*1m respectively. The results greatly excel the IHO measurement accuracy standards.

The analysis result of the 1m*1m mesh size

The analysis result of the 0.1m*0.1m mesh size

Through the field-work modeling function of the CARIS software, a 3D surface model of the survey area is generated as shown below.

The 3D mapl of Taishan harbor

The 3D map of Foshan watercourse

The mission shows that the M40 unmanned boat is easy to be launched and retrieved, and it can conduct underwater multibeam survey and geomorphology side scan detection in complex river and harbour environment. Its sailing noise impacting the acoustic equipment is low due to the excellent engineering design. The output data is in excellent quality, meeting the IHO44 premium standard and China’s Hydrographic Measurement Norms.

 

Conclusion

  1. Strong capacity. The dual-system hull and equipment cabin ensure a strong loading capabilityof the M40 unmanned boat. The hull platform and the parallel dual-system design are completely modulared thus improves ease of use, maintainability and serviceability. The boat can to be equipped with multiple equipment such as multibeam, side scan sonar, ADCP, water quality online monitor, etc.

 

  1. High accuracy. The survey is conducted within the level 2 sea condition. Under the influence of passing ships, berthing ships and river water flow, the deviation of navigation can still maintainswithin 1 meter, effectively improve the accuracy of output image.Output data quality meets the IHO44 premium standard.

 

Perfect for shallow water survey. M40 provides the ultimate solution for near-shore shallow water survey. With a draft less than 0.5m, M40 can access to shallow area compared to manned vessels, which makes full coverage hydrographic survey possible.

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