Bias correction and uncertainty characterization of Dead-Reckoned paths of marine mammals

Abstract Background Biologgers incorporating triaxial magnetometers and accelerometers can record animal movements at infra-second frequencies. Such data allow the Dead-Reckoned (DR) path of an animal to be reconstructed at high resolution. However, poor measures of speed, undocumented movements cau...

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Main Authors: Liu, Yang, Battaile, Brian, Trites, Andrew, Zidek, James
Format: Other/Unknown Material
Language:English
Published: BioMed Central Ltd. 2015
Subjects:
Online Access:http://www.animalbiotelemetry.com/content/3/1/51
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spelling ftbiomed:oai:biomedcentral.com:s40317-015-0080-5 2023-05-15T15:44:00+02:00 Bias correction and uncertainty characterization of Dead-Reckoned paths of marine mammals Liu, Yang Battaile, Brian Trites, Andrew Zidek, James 2015-10-21 http://www.animalbiotelemetry.com/content/3/1/51 en eng BioMed Central Ltd. http://www.animalbiotelemetry.com/content/3/1/51 Copyright 2015 Liu et al. Biologging Dead-Reckoning High-resolution animal tracking Bayesian Melding Energy expenditure Global Positioning System Uncertainty statement Brownian Bridge Research 2015 ftbiomed 2015-10-25T00:09:06Z Abstract Background Biologgers incorporating triaxial magnetometers and accelerometers can record animal movements at infra-second frequencies. Such data allow the Dead-Reckoned (DR) path of an animal to be reconstructed at high resolution. However, poor measures of speed, undocumented movements caused by ocean currents, confounding between movement and gravitational acceleration and measurement error in the sensors, limits the accuracy and precision of DR paths. The conventional method for calculating DR paths attempts to reduce random errors and systematic biases using GPS observations without rigorous statistical justification or quantification of uncertainty in the derived swimming paths. Methods We developed a Bayesian Melding (BM) approach to characterize uncertainty and correct for bias of DR paths. Our method used a Brownian Bridge process to combine the fine-resolution (but seriously biased) DR path and the sparse (but precise and accurate) GPS measurements in a statistically rigorous way. We also exploited the properties of underlying processes and some approximations to the likelihood to dramatically reduce the computational burden of handling large, high-resolution data sets. We implemented this approach in an R package “BayesianAnimalTracker”, and applied it to bio-logging data obtained from northern fur seals ( Callorhinus ursinus ) foraging in the Bering Sea. We also tested the accuracy of our method using cross-validation analysis and compared it to the conventional bias correction of DR and linear interpolation between GPS observations (connecting two consecutive GPS observations by a straight line). Results Our BM approach yielded accurate, high-resolution estimated paths with uncertainty quantified as credible intervals. Cross-validation analysis demonstrated the greater prediction accuracy of the BM method to reconstruct movements versus the conventional and linear interpolation methods. Moreover, the credible intervals covered the true path points albeit with probabilities somewhat higher than 95 %. The GPS corrected high-resolution path also revealed that the total distance traveled by the northern fur seals we tracked was 40–50 % further than that calculated by linear interpolation of the GPS observations. Other/Unknown Material Bering Sea Callorhinus ursinus BioMed Central Bering Sea
institution Open Polar
collection BioMed Central
op_collection_id ftbiomed
language English
topic Biologging
Dead-Reckoning
High-resolution animal tracking
Bayesian Melding
Energy expenditure
Global Positioning System
Uncertainty statement
Brownian Bridge
spellingShingle Biologging
Dead-Reckoning
High-resolution animal tracking
Bayesian Melding
Energy expenditure
Global Positioning System
Uncertainty statement
Brownian Bridge
Liu, Yang
Battaile, Brian
Trites, Andrew
Zidek, James
Bias correction and uncertainty characterization of Dead-Reckoned paths of marine mammals
topic_facet Biologging
Dead-Reckoning
High-resolution animal tracking
Bayesian Melding
Energy expenditure
Global Positioning System
Uncertainty statement
Brownian Bridge
description Abstract Background Biologgers incorporating triaxial magnetometers and accelerometers can record animal movements at infra-second frequencies. Such data allow the Dead-Reckoned (DR) path of an animal to be reconstructed at high resolution. However, poor measures of speed, undocumented movements caused by ocean currents, confounding between movement and gravitational acceleration and measurement error in the sensors, limits the accuracy and precision of DR paths. The conventional method for calculating DR paths attempts to reduce random errors and systematic biases using GPS observations without rigorous statistical justification or quantification of uncertainty in the derived swimming paths. Methods We developed a Bayesian Melding (BM) approach to characterize uncertainty and correct for bias of DR paths. Our method used a Brownian Bridge process to combine the fine-resolution (but seriously biased) DR path and the sparse (but precise and accurate) GPS measurements in a statistically rigorous way. We also exploited the properties of underlying processes and some approximations to the likelihood to dramatically reduce the computational burden of handling large, high-resolution data sets. We implemented this approach in an R package “BayesianAnimalTracker”, and applied it to bio-logging data obtained from northern fur seals ( Callorhinus ursinus ) foraging in the Bering Sea. We also tested the accuracy of our method using cross-validation analysis and compared it to the conventional bias correction of DR and linear interpolation between GPS observations (connecting two consecutive GPS observations by a straight line). Results Our BM approach yielded accurate, high-resolution estimated paths with uncertainty quantified as credible intervals. Cross-validation analysis demonstrated the greater prediction accuracy of the BM method to reconstruct movements versus the conventional and linear interpolation methods. Moreover, the credible intervals covered the true path points albeit with probabilities somewhat higher than 95 %. The GPS corrected high-resolution path also revealed that the total distance traveled by the northern fur seals we tracked was 40–50 % further than that calculated by linear interpolation of the GPS observations.
format Other/Unknown Material
author Liu, Yang
Battaile, Brian
Trites, Andrew
Zidek, James
author_facet Liu, Yang
Battaile, Brian
Trites, Andrew
Zidek, James
author_sort Liu, Yang
title Bias correction and uncertainty characterization of Dead-Reckoned paths of marine mammals
title_short Bias correction and uncertainty characterization of Dead-Reckoned paths of marine mammals
title_full Bias correction and uncertainty characterization of Dead-Reckoned paths of marine mammals
title_fullStr Bias correction and uncertainty characterization of Dead-Reckoned paths of marine mammals
title_full_unstemmed Bias correction and uncertainty characterization of Dead-Reckoned paths of marine mammals
title_sort bias correction and uncertainty characterization of dead-reckoned paths of marine mammals
publisher BioMed Central Ltd.
publishDate 2015
url http://www.animalbiotelemetry.com/content/3/1/51
geographic Bering Sea
geographic_facet Bering Sea
genre Bering Sea
Callorhinus ursinus
genre_facet Bering Sea
Callorhinus ursinus
op_relation http://www.animalbiotelemetry.com/content/3/1/51
op_rights Copyright 2015 Liu et al.
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