Archeological Survey of the Qian Dao Lake

Introduction

A survey was performed at Qian Dao Lake on June 18, 2024, using the NORBIT WINGHEAD i77h.

The ancient underwater city of Shī Chéng (Chinese: 狮城, literally ‘Lion City’) is located in the lake. The city of Shī Chéng is believed to have been built during the Tang Dynasty in 621 AD, making it nearly 1,400 years old. Based on records of the region’s history, it is thought to have been quite large, possibly over 60 football fields. Due to the modernisation of Zhejiang province, a hydroelectric dam was built in 1959, flooding the valley where the ancient city was located.

Map of Qian Dao Lake with highlighted survey area.

Multibeam Echo Sounder

A case study was conducted at Qian Dao Lake using the NORBIT WINGHEAD i77h. The NORBIT WINGHEAD i77h is a compact ultra-high resolution curved array broadband multibeam sonar. It offers tight integration with GNSS/INS (Applanix OceanMaster) and is designed for use in demanding operational environments.

The WINGHEAD i77h was the first cylindrical ultra-high resolution bathymetry sonar on the market.

0.5 x 0.9°beam width at 400kHz
HD beamformer providing 1024 beams per ping
High-performance integrated GNSS/INS systems
Integrated sound velocity probe
Small form factor and low power consumption
Designed for rapid mobilisation on any platform
Available with optional LiDAR

NORBIT WINGHEAD i77h multibeam sonar device.

Installation and survey info

Survey location: Qian Dao Lake, China
Frequency: Auto Mode
Speed: 3-4 knots
Survey depth: 45m-70m

The Sonar was mounted on the starboard side of the vessel, with both antenna 1 and antenna 2 set up on the upper deck.

[PLACEHOLDER] Four images showing survey vessel and sonar equipment. — The survey vessel and sonar equipment.

Ad Hoc Vessel

The survey vessel used on the Qian Dao Lake.

Survey Area

Results

In Areas B and C, a river creek with high riverbanks was observed. In Area C, likely ponds or rectangular depressions next to a steep riverbank were observed.

The high-performance integrated POSMV OceanMaster GNSS/INS system, with its precision, significantly reduced the chance of installation errors compared to a traditional setup with standalone sensors, ensuring the accuracy of our survey.

3D sonar scan of Area A showing terrace-like formations. — The results at Area A, observed likely terrace paddy fields.

3D sonar scan of Area B showing terraces beside a steep slope. — Results at Area B, observed terrace paddy fields next to a steep riverbank.

3D sonar scan of Area C showing ponds or rectangular depressions. — Results at Area C, observed likely ponds or rectangular depression next to a steep riverbank.

Summary

The ultra-high-resolution WINGHEAD i77h bathymetry sonar insonified the underwater city structures in high-resolution details, with observed terrace paddy fields around the city structures.

The WINGHEAD Sonar is designed for rapid mobilisation anywhere in the world. Thus, we were able to commence our survey within an hour of installation.

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