Nearly three quarters of Earth’s surface is covered by water, yet only about a quarter of that surface has been mapped in detail using modern high-resolution technology.
Marine experts worldwide work together to chart the ocean floor, ensuring the safety of ports, harbors and navigable routes. This effort is crucial for global trade, as more than 90% of goods are transported by ships. Ocean floor surveying also supports the installation of offshore infrastructure such as fiber optic cables, pipelines, drilling platforms and wind turbines.
The increasing population in coastal regions and rising sea levels due to climate change have heightened the importance of observing coastal transformations, erosion and other marine alterations. These factors are essential for understanding and protecting coastal ecosystems.
Mapping techniques
In deep waters, massive multi-beam echo sounders (MBES) operating at very low frequencies collect depth data. As water depth decreases, smaller devices with higher frequencies and resolution must be used. However, near the shore, these devices become less efficient due to the slope of the shelf interfering with sound signals.
In near-shore scenarios, collecting depth data is best done using airborne lidar sensors, which offer several advantages over sensors on surface vessels. One advantage of airborne sensors is that they can simultaneously map both the seafloor and the adjacent topography to offer seamless land-water transition data. This capability is particularly valuable in dynamic coastal environments where rapid coverage of large areas is essential.
Bathymetric lidar is specifically designed for mapping shallow coastal waters, typically effective up to depths of 50 m. It can provide high-resolution data, often achieving sub-meter positional accuracy, which is crucial for detailed coastal mapping. By combining MBES for deeper waters with lidar for near-shore areas, researchers and surveyors can create comprehensive and accurate maps of the entire coastal zone. This method offers an in-depth understanding of underwater topography, aiding various applications in marine science, coastal management and navigation.
Saildrone
Cayman Islands mapping project
The waters of the Cayman Islands are abundant in marine life, featuring coral reefs, seagrass beds and a variety of fish species. A high-resolution map of the seafloor is essential to begin exploring, identifying, characterizing, exploiting, conserving and managing ocean resources. Saildrone has begun a mission to map 29,300 square nautical miles (100,490 sq km) of the Cayman Islands’ Exclusive Economic Zone (EEZ). This mission uses autonomous technology to survey 80% of this EEZ.
The Cayman Islands EEZ, extending up to 200 nautical miles from shore, encompasses an area nearly half the size of Florida — and 380 times greater than the island itself. The mission will provide detailed and precise bathymetric data for this area, contributing to a comprehensive understanding of the seafloor topography in the region. The data collected seeks to enhance maritime navigation and support scientific research, environmental conservation efforts and marine resource management in the Cayman Islands.
“Our waters hold such great value to us for a myriad of reasons, ranging from recreational to economic. Conducting this assessment will allow our government to make data-driven decisions that will strengthen our policies and legislation as it relates to our maritime infrastructure,” said Juliana O’Connor-Connolly, premier and minister for District Administration and Lands.
The mission is philanthropically funded by the London and Amsterdam Trust Company Limited, a Cayman-based organization. Saildrone is tasked with collecting the raw bathymetry data, which will be provided to the UK Hydrographic Office to process and update the Cayman Islands’ nautical charts. The data will belong to the government of the Cayman Islands.
Autonomous seafloor exploration
The mission is being conducted using a 20-m Saildrone Surveyor uncrewed surface vehicle (USV) equipped with MBES and metocean sensors for ocean mapping and ecosystem monitoring, as well as radar, cameras and advanced machine learning. Metocean stands for meteorology and physical oceanography. Globally, only 26% of the ocean has been mapped, a result of the lack of survey ship capacity. While a survey ship takes years to build, Saildrone can produce one Surveyor in as little as six weeks.
Saildrone USVs have demonstrated a reduction of more than 97% in operational carbon emissions when compared to survey ships to accomplish the same task. Additionally, they lower the risk to personnel. This information is highlighted in Saildrone’s Carbon Impact Report, which provides a comprehensive evaluation of the carbon emissions associated with maritime data collection and the emissions mitigated by using Saildrone’s USVs.
Saildrone’s ocean mapping solutions support storm surge modeling efforts and emergency response, as well as coastal resiliency and hazard studies, resource management, restoration projects, habitat mapping and infrastructure for renewable energy generation. USVs equipped with deep ocean mapping sonars now serve as a reliable option for data collection in large areas such as EEZs.
Trimble
Emerging trends in Bathymetry
Bathymetry is crucial to understanding Earth’s aquatic environments. Its importance has evolved significantly since the early days of navigation, when mariners relied on lead lines and poles to gauge water depths. The field of bathymetry continues to advance with emerging trends that enhance data collection capabilities. Autonomous platforms such as USVs and autonomous underwater vehicles are increasingly utilized for bathymetric surveys, allowing for more extensive and detailed mapping. Additionally, as the industry grapples with challenges such as workforce shortages and the need for more efficient data collection methods, autonomous systems are proving to be a valuable solution.
“Autonomous and uncrewed platforms have become a real force multiplier, and the trend continues,” said Peter Stewart, director of marine products at Trimble Applanix. “Companies such as XOcean and Saildrone are showing what is possible, leveraging cloud processing and enabling data collection in remote areas while maintaining a work-life balance for their staff. Since finding qualified engineers and surveyors to fill these roles offshore is an industry-wide concern, more flexible working conditions are needed to hire and retain talent.”
Another emerging trend is the development of sensors capable of penetrating murky waters, which can significantly enhance surveyors’ ability to gather data in challenging environments. Advanced sonar systems, innovative light-and-sound combinations and newly developed sensors allow research teams to collect detailed data. Post-processing technology for bathymetry has also significantly advanced, making data acquisition, processing and presentation more efficient and accessible. This allows researchers to map and study underwater terrains that were previously inaccessible or poorly understood.
“Ease of use and installation are key trends toward ensuring valuable hydrographic data can be acquired, processed and presented efficiently,” Stewart said. Trimble works with users and third parties to offer an optimal workflow, making technology and the data it creates more accessible and operations more efficient, he added.
The IN-Fusion+ PP-RTX2 processing mode in Trimble’s POSPac MMS software is designed to improve post-processed GNSS-inertial trajectory generation. This mode uses Trimble’s CenterPoint RTX technology to deliver centimeter-level positioning accuracy without the need for local base stations. Stewart shared how this technology can be particularly useful when surveying around offshore windfarms, where shore-based RTK infrastructure is often too distant to be useable.
