AUTHOR=Skålvik Astrid Marie , Saetre Camilla , Frøysa Kjell-Eivind , Bjørk Ranveig N. , Tengberg Anders 

TITLE=Challenges, limitations, and measurement strategies to ensure data quality in deep-sea sensors

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 10 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1152236

DOI=10.3389/fmars.2023.1152236

ISSN=2296-7745

ABSTRACT=In this paper we give an overview of factors and limitations impairing deep-sea sensor data, and we show how automatic tests can give sensors self-validation and self-diagnostic capabilities. This work is intended to lay a basis for sophisticated use of smart sensors in long-term autonomous operation in remote deep-sea locations.

Deep-sea observation relies on data from sensors operating in remote, harsh environments which may affect sensor output if uncorrected. In addition to the environmental impact, sensors are subject to limitations regarding power, communication and limitations on recalibration. To obtain long-term measurements of larger deep-sea areas, fixed platform sensors on the ocean floor may be deployed for several years.

Data collected by deep-sea observation equipment are of limited use if the quality or accuracy is not known. If data from a faulty sensor are used directly, this may result in an erroneous understanding of deep water conditions, or important changes or conditions may not be detected. Faulty sensor data may significantly weaken the overall quality of the combined data from several sensors or any derived model. This is particularly an issue for wireless sensor networks covering large areas, where the overall measurement performance of the network is highly dependent on the data quality from individual sensors. Existing quality control manuals and initiatives for best practice typically recommend a selection of (near) real-time automated checks. These are mostly limited to basic and straight forward verification of metadata and data format, and data value or transition checks against pre-defined thresholds. Delayed-mode inspection is often recommended before a final data quality stamp is assigned.

The goal of this paper is to:
•	Define system limitations for autonomous underwater sensors operating in deep ocean. We focus on long-term deployed stationary sensors that communicate using acoustic links.  
•	Identify factors impacting underwater sensors, focusing on sensors deployed in deep ocean, and map out the effect of relevant factors on selected measurement technologies.
•	Propose methods to extend automated real-time data quality control to cover some of the checks which are now performed in delayed mode by experienced operators.