AUVs:

USES

IMPORTANT NOTE: If you are unsure of what an 'AUV' is, this section probably won't make much sense. Luckily, you can find this information by visiting MARINE VEHICLES.

WHY USE AUVs?

Before the advent of AUVs, researchers used ships and submarines to explore the ocean. So why use AUVs? Perhaps one of the best reasons is in the answer to this question posed by Henry Stommel (who else?) in 1989:

"With a necessarily small fleet of research ships, how could numerous widely dispersed measurements throughout all depths of the ocean be observed on a routine basis?” [1]

There are many specific advantages that AUVs provide, so only the main benefits are provided here. Following this discussion, we'll talk about some limitations (coming soon!).

STRENGTHS

a (relatively) cheap, efficient, and safe approach

Ships and other manned vehicles are costly to operate. By comparison, AUVs have much lower operating costs; the annual cost of operating an AUV is a fraction of the cost of operating a ship for one day. Additionally, the construction cost of an AUV is roughly equivalent to the cost of a few days of ship operation. Thus, ships are often now used as AUV launching points. While the AUV is deployed, a ship may be used for other purposes as it does not need to remain with the AUV. Geographical independence also immensely reduces risk, as human operators are not required in the AUV mission area. Deployment of multiple AUVs greatly increases the amount of data collected over a single research vessel operating on its own while expanding possible areas of ocean exploration and eliminating dangers faced by manned vehicles.

a rapid and accurate method of creating 3D maps

One chief advantage of AUVs is their ability to travel both horizontally and vertically underwater, which allows a 3D map of an area to be created. Although modern satellites provide comprehensive imagery of the ocean, they are limited to 2D images and may take over a month to complete an entire scan. While many AUVs are capable of changing their path mid-mission (e.g. to avoid collision or to follow a desired phenomenon), satellites travel a predetermined path. Thus, they must be placed higher if continuous surveillance is desired; however, the price is lower image resolution and limited coverage of the higher latitudes. Since AUVs can travel less than five metres above the seafloor, they can produce very high resolution maps of the seabed.

a low-impact option for surveying vast areas

As AUVs are entirely reliant on onboard power supply, which is often provided by batteries, every aspect of the vehicle – from the hull to the propulsion to the sensor payload – is designed with a strong emphasis on energy efficiency. Long range AUVs, such as the National Oceanography Centre's (NOC) Autosub Long Range [2], can travel for up to six months between charges, collecting data over thousands of kilometres. Unlike ships, which are much larger and have engines, AUVs have a minimal impact on the environment. Even semi-submersible AUVs, which use diesel engines, create much less pollution than large, seagoing vessels.​

a 'choose your own adventure' of data collection

​Whereas the first AUVs were only capable of executing simple missions, such as travelling between two points, current AUVs have decision-making abilities that allow deviation from a pre-planned mission if necessary. For example, AUVs can avoid collisions with sensed objects in their path (e.g. iceberg, submarine volcano, or another vessel) without prior knowledge of their existence. Decision-making abilities are extremely important as most of the ocean remains relatively unknown and experiences constantly variable conditions. Regardless of how much prior knowledge is available concerning the mission, no mission can plan for every eventuality. This creates significant challenges for an AUV, which must be able to independently process inputs from an alien environment and adjust its goal(s) based on how to best fulfill the objectives set by its human operators. This is difficult even for humans (as those of you who, like me, are well-aware of from repeated failures of those 'Choose Your Own Adventure' kids' books from the 1980s-1990s). However, successful demonstrations of AUV autonomy often provide data that would be difficult, if not impossible, to capture by other means - like animal behaviour. For a really neat example of this - an AUV following sharks - see BIOGEOCHEM-GINEERING (coming soon!).

... in summary...

STRENGTH

ADVANTAGES

EXAMPLES

AUTONOMY

(independence)

  • Reduced risk to human operators

  • Missions possible in difficult/otherwise impossible conditions 

  • Searching for underwater mines

  • Surveying in bad weather or in ice-covered areas

AUTONOMY

(intelligence)

  • ​​​Decision-making abilities often prevent disasters

  • Decision-making abilities often lead to success

  • Evading an iceberg using collision avoidance 

  • Locating the origin of an oil spill through measurements and onboard calculations

AUTONOMY

(mobility)

  • Measurements in 3D space can be taken

  • Highly accurate measurements can be taken

  • Collecting samples of a Harmful Algal Bloom [3] at different depth

  • Creating a high resolution map of the seafloor 

EFFICIENCY

  • Extremely large areas can be surveyed

  • Long term phenomena can be observed

  • Searching a crash site for plane wreckage 

  • Following ocean currents [4]

  • Construction costs are low

  • Operating costs are low

  • Environmental impact is minimal

COST

ENVIRONMENTAL IMPACT

  • Cost of building one AUV = cost of operating a ship for several days

  • ​Cost of operating one AUV for one year = cost of operating a ship for less than a day

  • Sending a battery-powered AUV to track animals versus following them in a motorized boat

REFERENCES

  1. Stommel, H. (1989). The Slocum Mission. Oceanography. 22-25. ​Available from http://tos.org/oceanography/assets/docs/2-1_stommel.pdf

  2. National Oceanography Centre (NOC). 2017. Autosub Long Range. Retrieved from http://noc.ac.uk/facilities/marine-autonomous-robotic-systems/autosubs

  3. National Oceanic and Atmospheric Administration (NOAA). (2017). Harmful Algal Blooms: Tiny Organisms with a Toxic Punch. Retrieved from https://oceanservice.noaa.gov/hazards/hab/

  4. National Oceanic and Atmospheric Administration (NOAA). (2011). Ocean currents. Retrieved from http://www.noaa.gov/resource-collections/ocean-currents

Last revised: April 17, 2020​

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