Networked GPS Approach to Tracking Marine Animal Schools

L. Heng, G.X. Gao

Abstract:	For marine species, being in the right place at the right time may mean surviving instead of dying, being able to grow instead of going hungry, or reproducing instead of having no off-spring [1]. Where a marine animal swims determines the rich ocean environment that it experiences, including such features as temperature, pressure, salinity, oxygen levels, and the marine vegetation or animals it encounters. There is a great need to track the movements of the marine animals in order to study their seasonal movement patterns, regional habitat use, and location of foraging and breeding. Being able to monitor their locations is critical to protect marine animals, especially endangered species against hash nature or human encroachment. Tracking and localizing marine animals will enable further scientific research on species diversity, population structure, migrations, and gene flow of these animal species. In addition, better understanding of the ecosystem in pelagic environments will lead to more accurate study of global climate change. There has been a field program using GPS to track individual marine animals. The program is called Tagging of Pacific Predator (TOPP), which has tracked more than 19 species of marine vertebrates [2]. This program only tracks individual marine animals, not animal schools. The challenges in using GPS to track marine animal schools are the following. 1) Since GPS signals do not penetrate underwater, measurements are limited to times when the marine animals swim to the surface of the ocean; 2) Traditional GPS receivers require long exposure to GPS satellites for positioning, while most marine animals’ surfacing is brief; 3) Traditional GPS receivers for marine animals lack confidence in accuracy by creating a considerable number of outliers and suspicious measurements; 4) Traditional GPS receivers for marine animals are not accurate enough to study schooling behaviors. This paper presents a networked GPS approach to tracking marine animal schools. The marine animals are tagged with GPS receivers. The GPS receivers in a marine animal school are networked via acoustic links and cooperatively calculate their positions. First, we develop statistical models to character the noise associated with range measurements. The noise among different nodes is partially correlated, since the GPS receivers within a school share the same set of satellites in view. The satellite signals also penetrate the same area of ionosphere, which is a major error source to GPS. Second, we design network protocols for cooperative positioning. In other words, how the nodes within a school communicate and help each other. We conduct theoretical analysis on trade-offs among power consumption, localizability, positioning accuracy and robustness under appropriate noise models. The minimum number of required links is calculated. Positioning accuracy and robustness are then improved by adding redundancy in connectivity. The degree of added redundancy is further calculated to ensure desired school positioning accuracy and robustness. Third, we develop localization algorithms for a dynamic marine animal school in a cooperative setting where each sensor only communicates to very few other sensors. The algorithms are based on multidimensional scaling (MDS) and high-dimensional matrix completion. To address the computational challenges of having to process enormous amount of data collected from a large number of sensors over a long period of time, distributed version of the proposed algorithms are also investigated. [1]. Payne, John, et al. "Tracking Fish Movements and Survivalon the Northeast Pacific Shelf." Life in the World's Oceans: Diversity, Distribution, and Abundance (2010): 269. [2]. Block, Barbara A., Daniel P. Costa, and Steven J. Bograd. "A view of the ocean from Pacific predators." Life in the world’s oceans: diversity, distribution and abundance. Oxford: Wiley-Blackwell (2010): 291-311.
Published in:	Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013) September 16 - 20, 2013 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	612 - 619
Cite this article:	Heng, L., Gao, G.X., "Networked GPS Approach to Tracking Marine Animal Schools," Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013), Nashville, TN, September 2013, pp. 612-619.
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