Underwater Altimeters

An underwater altimeter uses acoustic- or pressure-based methods to measure the distance between the instrument and the seafloor or other submerged objects, for precise depth measurements. Underwater altimeters allow scientists to map the topography of the ocean floor, monitor changes in seabed elevation, and assess underwater features.
Overview Underwater Altimeters
By Staff Writer Last updated: June 26th, 2024

Underwater altimeters are key in modern subsea operations, providing precise depth and distance measurements. These devices can be used in a range of applications, including bathymetric surveys, underwater navigation, and subsea mapping. The accuracy and reliability of these devices is pivotal due to the challenging conditions they operate in.

Types of Underwater Altimeter

  • Acoustic altimeters emit sound pulses and measure the time it takes for the echo to return from the seabed. The distance is then calculated using the speed of sound in water. Modern acoustic altimeters are equipped with advanced signal processing algorithms to enhance accuracy and filter out noise.
  • Multi-Frequency operation – some acoustic altimeters operate on multiple frequencies to improve precision and reliability. This allows them to adapt to varying seabed conditions and water column properties, making them versatile tools for subsea mapping.
  • Laser-based altimeters offer high-resolution measurements and are particularly effective in clear water conditions. They use laser pulses to determine distances, providing superior resolution and accuracy.
  • Blue-Green wavelengths laser altimeters often utilize blue-green wavelengths, which penetrate water more effectively than other wavelengths. This technology is particularly useful in environments with high turbidity, where visibility is limited.

Subsea Altimeter Design

VA500 Underwater Altimeter for ROV and AUV by Valeport

VA500 Underwater Altimeter for ROV and AUV by Valeport

Underwater altimeters utilize sonar technology to measure the distance from the ocean floor to a vessel or underwater vehicle. These altimeters typically include a transducer to send and receive sound signals, signal processing units, and often a display or data logging system. They are designed to be robust and resistant to high pressure, corrosion, and other harsh subsea conditions and are often manufactured using materials such as titanium, stainless steel, and advanced composites for these reasons.

Designed to ensure they can withstand extreme pressures at depth, they encorporate robust housing materials and pressure-compensating mechanisms to protect sensitive electronic components.

Using enhanced signal processing algorithms helps to distinguish between true echoes and noise. Doppler shift correction and beamforming techniques isolate the relevant signals for accurate distance measurement.


Bathymetric Mapping
Underwater altimeters are integral to bathymetric surveys, providing detailed maps of the seafloor. These maps are essential for navigation, resource exploration, and environmental monitoring.

Subsea Vehicle Navigation
Autonomous underwater vehicles (AUVs) and remotely operated vehicles (ROVs) rely on altimeters for precise navigation and obstacle avoidance. Accurate distance measurements enable these vehicles to perform complex tasks with high precision.

Subsea Construction and Maintenance
In subsea construction, altimeters facilitate the installation and maintenance of underwater infrastructure such as pipelines, cables, and offshore platforms. They ensure accurate positioning and alignment, which is critical for the integrity and safety of these structures.