AUVs or Gliders? Integrating Hydrophones for Underwater Monitoring

By: Mark S Wood , CEO and Founder, Ocean Sonics?

Recently, I had the pleasure of attending the International Underwater Glider Conference in Sweden, where I engaged with some incredible leaders in marine science and technology. This experience highlighted the growing importance of gliders in underwater monitoring, particularly for acoustic data collection. However, I noticed that there are significant differences between AUVs and Gliders that are worth noting. In this article I will go into detail about what those differences are and why they are important.??

Understanding AUVs and Gliders?

AUVs and gliders are both essential tools for underwater exploration and monitoring, but they have distinct differences, which were underscored at the conference.?

AUVs are self-propelled, battery-powered robots that navigate through the water column. Designed for a wide range of missions, from seafloor mapping to water sampling, AUVs are known for their speed, maneuverability, and ability to carry a variety of sensors. This makes them ideal for short, targeted missions where rapid data collection is essential.?

Gliders, by contrast, use buoyancy to move through the water in a sawtooth pattern. By adjusting their buoyancy, they convert vertical movement into forward motion. They “glide” by sinking to the ocean floor and then rising to the surface, with wings and fins guiding them along a predetermined path. A buoyancy engine controls their ascent and descent, enabling them to move efficiently through the water. Gliders are highly energy-efficient heir slower, more deliberate movements make them perfect for long-term monitoring and data collection over vast areas, particularly in remote or hard-to-reach locations like the Arctic.?

Why Gliders are Great for Certain Missions?

Gliders excel in several areas, making them particularly valuable for specific types of underwater monitoring:?

• Climate Change Studies: Gliders are ideal for long-term monitoring, which is crucial for observing and understanding climate change impacts over time.?

• Surveys of Remote Areas: Their ability to operate in the most remote parts of the ocean makes gliders indispensable for exploring uncharted waters.?

• Long Time Series Data Collection: Gliders can collect data continuously over extended periods, providing a more comprehensive view of ocean conditions.?

• Year-Round Studies in Inaccessible Areas: Gliders can be deployed year-round in areas that are typically inaccessible, such as the Arctic, enabling continuous data collection.?

• Stealth Operations: Their low profile and quiet operation make gliders ideal for missions that require minimal disturbance to the environment.?

• Long-Term Weather Monitoring: Gliders can monitor oceanic conditions for extended periods, providing valuable data for weather prediction models.?

• Smart Sensor Deployment: Gliders can be equipped with smart sensors that pre-process and pre-package data, reducing the need for frequent data retrieval and making long-term missions more feasible.?

However, gliders also come with some disadvantages:?

• Slower Speed: Gliders are slower than AUVs, which can be a drawback for missions requiring rapid data collection.?

• Risk of Loss: If a glider fails while diving, it may be lost, unlike AUVs, which are slightly buoyant and can return to the surface.?

• Restricted Power Budget: Gliders have a limited power supply, which restricts the types and number of sensors they can carry.?

Why AUVs are great for certain missions?

AUVs also excel in certain areas, occasionally making them a key tool in underwater monitoring:?

• Flexibility in dynamic environments?

• Adaptable to changing conditions?

• High-resolution data over specific areas for targeted acoustic studies??

Hydrophones, like the icListen, are critical for capturing the acoustic environment of the ocean.?

?When integrating hydrophones on AUVs and Gliders, several factors must be considered:?

• Noise Reduction: Minimizing noise from the AUV itself is crucial for capturing clear acoustic data.?

• Power Consumption: Hydrophones must be integrated in a way that does not excessively drain the AUV’s power supply.?

• Data Storage and Transmission: AUVs must be equipped with sufficient data storage and robust transmission capabilities to handle the large amounts of data generated by hydrophones.?

Enabling Smart Hydrophones such as the icListen to process the data and select events helps mitigate the quantity of data stored and transmitted. This removes the burden from the Glider computer at the same time from having to interpret raw acoustic data.?

Conclusion: Complementary Tools for Comprehensive Monitoring?

AUVs and gliders each offer unique advantages for integrating hydrophones and conducting underwater acoustic monitoring. AUVs provide flexibility and high-resolution data for targeted missions, while gliders excel in long-duration, low-noise monitoring over large areas.?

At Ocean Sonics, we recognize the importance of both platforms in advancing our understanding of the underwater world. By integrating hydrophones with AUVs and gliders, we can leverage their complementary strengths to create a comprehensive acoustic monitoring network.?

Attending the International Underwater Glider Conference in Sweden has reinforced my belief in the power of collaboration and innovation in our field. As we continue to develop and refine our hydrophone technologies, I look forward to exploring new possibilities and pushing the boundaries of what we can achieve in underwater monitoring.?