By Taxiya Wang

Waterways are critical for global maritime transport, and ensuring their safety is vital for vessel operations, crew welfare, and maintaining economic flow. The underwater terrain is constantly reshaped by natural forces, such as sediment buildup, shifting seabed, and geological hazards, which introduce uncertainty and risk, especially in busy or remote navigation channels.

Traditionally, these areas have been monitored using manned survey vessels equipped with multibeam echosounders (MBES). While effective, these operations are costly and require complex deployment procedures. They also have limited access to shallow or constrained zones.

To overcome these challenges, the maritime industry is increasingly turning to intelligent, unmanned systems that provide accurate, efficient and adaptable solutions, especially for high-resolution hydrographic mapping in dynamic aquatic environments.

Breaking the Boundaries of Traditional Hydrographic Surveys

Manned survey vessels encounter operational limitations in confined or shallow environments. In narrow channels, ports, and complex river junctions, submerged structures, limited space, and other vessel traffic often hinder their maneuverability.

More critically, traditional vessels have difficulty accessing nearshore and ultrashallow zones, which are essential for assessing sedimentation, scouring, and potential navigational hazards. Without data from these areas, effective waterway management becomes difficult, resulting in reactive rather than proactive dredging or infrastructure reinforcement.

 

A Modern Solution to Complex Hydrographic Conditions

In a recent survey of a Yangtze River tributary, CHCNAV overcame the challenges posed by the environment with a fully integrated system: the Apache 4 USV paired with the HQ-400 compact multibeam echosounder. This combination provided a compelling alternative to traditional vessel-based methods by delivering high-quality data with exceptional deployment flexibility.

In just 3 hr., the system mapped 0.7 km2 of complex underwater terrain and produced detailed contour maps, terrain point clouds, and digital elevation models. Compared to conventional approaches, the integrated solution tripled operational efficiency while maintaining centimeter-level accuracy across the entire data set.

Accurate Positioning in Remote Environments

Remote and topographically challenging waterways often result in communication and GNSS correction disruptions. During the Yangtze River project, network limitations and terrain interference disrupted real-time kinematic (RTK) corrections, jeopardizing the reliability of live data.

To address these issues, CHCNAV used post-processed kinematic (PPK) positioning technology. The HQ-400 MBES and the Apache 4 USV captured high-quality raw GNSS and IMU data that were later corrected using post-processing software. This approach bypassed the need for real-time RTK corrections, ensuring precise positioning even in environments with limited connectivity.

The result was a dependable, uninterrupted workflow capable of capturing dense, high-accuracy bathymetric data in real-world conditions.

 

 

Streamlined Surveying with Intelligent Automation

CHCNAV’s EasySail control software is an Android-based platform that simplifies mission setup. It allows users to import CAD files (.DXF) to define survey boundaries. Operators can configure route plans, set line spacing, swath overlap (typically greater than 20 percent), and course direction with a few taps for full area coverage.

During operation, the system dynamically adjusts to environmental changes. Parameters such as beam angle, ping rate, and depth gates automatically adjust to match depth and bottom conditions. This smart automation reduces the operator’s workload, ensures optimal sensor performance, and enhances data integrity without requiring constant manual adjustments.

Thanks to its ultrashallow 0.15-m draft, the Apache 4 excels in narrow and nearshore environments. Meanwhile, the HQ-400’s 150-m depth range and 120° swath angle provide comprehensive coverage at various depths, ideally suited for high-resolution bathymetric surveys.

Efficient Post-Processing for Reliable Deliverables

After data collection, it is essential to transform raw sonar returns into actionable insights. CHCNAV’s Multibeam Suite (CMS) software offers an intuitive interface for efficiently managing extensive bathymetric data sets.

Built-in automated filters quickly remove noise, outliers, and false echoes caused by environmental or sensor interference. This reduces the need for manual cleaning and ensures that only soundings with a high degree of confidence are kept, speeding up post-processing while ensuring data quality.

 

 

Proven, Accurate Results

The integration of CHCNAV’s Apache 4 USV and HQ-400 MBES yielded impressive results during the Yangtze River tributary survey. The team mapped 0.7 km² of the riverbed in just 3 hr., which is three times more efficient than traditional survey methods. The accuracy was equally impressive: 99.96 percent of the recorded depth points met the International Hydrographic Organization’s stringent standards.

The resulting data set supported the creation of detailed contour maps, dense underwater point clouds, and accurate digital elevation models. These deliverables revealed valuable information about shoreline sedimentation and scour dynamics. This information aided in the development of targeted plans for dredging, bank stabilization and long-term waterway management.

Even under fluctuating water levels, the data remained consistent with satellite imagery, confirming the system’s reliability and resilience in the field.

The Future of Waterway Monitoring

The Yangtze River tributary project highlights the potential of unmanned hydrographic solutions. Replacing traditional manned surveys with a high-resolution, agile USV-MBES platform substantially improved the project’s data quality, efficiency and operational safety. The ability to capture centimeter-accurate underwater terrain data in shallow, restricted areas while meeting international standards demonstrates the real-world value of the integrated unmanned USV-MBES approach. As waterways continue to shift due to natural forces and human impact, advanced unmanned systems are poised to become essential tools for managing, maintaining, and protecting these vital infrastructure lifelines.

 

Taxiya Wang is the product manager for USV solutions in bathymetry and unmanned water exploration for CHCNAV.