1. Survey Condition

The water area to survey is a reservoir in central China, which is 830 square kilometers with capacity of about 300 million cubic meters. After construction, the reservoir had been strengthened several times. It can be used as the normal water level of around 160 meters after many times of verification. This survey is to mainly calculate the accurate storage capacity of the reservoir and observe the erosion and sedimentation of the underwater terrain, providing basic data reference for the dredging planning.

1.1. Difficulty Analysis

(1) Traditional storage capacity measurement adopts single beam echo sounder with inflatable boat or wooden boat, but the work efficiency is low and data accuracy is poor because of no correction data such as sound velocity, attitude and tide level.

(2) Single beam echo sounder is point measurement, which is to connect points to obtain full coverage of underwater terrain. So it can’t calculate the accurate storage capacity and check the detailed changes of scour and sediment situation.

2. Survey Method

We install MS400U on USV and survey vessel to survey, because the reservoir is large and underwater terrain is complicated. USV integrated with MS400U to survey shallow water on the edge of reservoir and complex terrain; Survey vessel’ s side port installeded with MS400U to survey large area rapidly. Two platforms’ combination ensure survey accuracy and greatly improve survey efficiency.

2.1. Solution Advantages

• USV integrated with MS400U

The installation of transducer, IMU and GNSS antenna is fixed, so it does not need  measure their position relationship every time and it is calibration-free in latter operation. It greatly reduce the working intensity that survoyers can start work immediately on site. The draft of USV is small, so it can survey the shallow water area by the shore, and ensure the data integrity.

• Survey vessels integrated with MS400U

It can work for whole day and won’ t be troubled by power supply and battery life. And the survey vessels are stable during sailing, they can increase the sailing speed and improve the measurement efficiency.

3. Survey Procedure

（1） With survey line planned in advance and remote control onsite, USVs integrated with MS400U sail and survey automatically.

（2） Multibeam was installed on the port side of survey vessel powered by electricity motor battery.

（3） Sound velocity profiler data acquisition. Because we survey at the reservoir, there is no much currents and obvious change of water level, but the sound velocity changes greatly at differenty depth. We need to collect the sound velocity profiling data in different areas.

4. Survey Data Analysis

4.1. Data Analysis

Cutting section across the track, we can see different survey lines match well.

4.2. Noise Analysis

The data is clean and noise is less. Most abnormal noise can be omitted through the automatic filtering function.

4.3. Main Survey Area Verification

The average depth in the survey area is 25 meters. Comparing the data of main survey line and check line to see the data accuracy. The main survey line is measured by USV. The check line (red one) is surveyed by survey vessel.

5. Survey Results

6. User Comment

‘ MS400U is lightweight and compact, suitable for shallow water survey without onsite installation. It can reduce the extra conneting and setting work of outfield surveyers. So the solution of USV installed with MS400P are perfect for reservoir and complex water environment survey.

MS400U is also suitable for small vessel to enhance survey efficiency, which will not be limited by the power supply and can survey large water area.

MS400U had been widely installed not only onto USV, but also inflatable boats, rafts, fishing boats and other small vessels. End users can choose the best survey solution according to the environment and vessel available.’