Abstract
Zero offset correction of diving depth measured by time-depth recorders is required to remove artifacts arising from temporal changes in accuracy of pressure transducers. Currently used methods for this procedure are in the proprietary software domain, where researchers cannot study it in sufficient detail, so they have little or no control over how their data were changed. GNU R package diveMove implements a procedure in the Free Software domain that consists of recursively smoothing and filtering the input time series using moving quantiles. This paper describes, demonstrates, and evaluates the proposed method by using a “perfect” data set, which is subsequently corrupted to provide input for the proposed procedure. The method is evaluated by comparing the corrected time series to the original, uncorrupted, data set from an Antarctic fur seal (Arctocephalus gazella Peters, 1875). The Root Mean Square Error of the corrected data set, relative to the “perfect” data set, was nearly identical to the magnitude of noise introduced into the latter. The method, thus, provides a flexible, reliable, and efficient mechanism to perform zero offset correction for analyses of diving behaviour. We illustrate applications of the method to data sets from four species with large differences in diving behaviour, measured using different sampling protocols and instrument characteristics.
Highlights
Zero offset correction of depth is one of the first considerations in analyses of diving behaviour data from time-depth recorders (TDRs)
Ethics Statement Research on Antarctic fur seals was carried out in accordance with the ethical guidelines set by Institut Polaire Francais Paul Emile Victor (IPEV) for Terres Australes et Antarctiques Francaises (French Antarctic and Austral Territories)
Demonstration First, we load diveMove and a TDR object that is free of any pressure transducer errors, except for a few brief periods that are of no interest and a 2 m offset that we correct for
Summary
Zero offset correction of depth is one of the first considerations in analyses of diving behaviour data from time-depth recorders (TDRs). It is crucial to calibrate depth measurements if valid biological interpretations of diving behaviour are to be made For diving animals, such as marine mammals and seabirds, the problem of zero offset correction is simplified by the cyclical return to or from the surface as study animals perform their dives throughout the deployment period, thereby providing a reference for calibration. This adjustment is typically done via proprietary software provided by instrument manufacturers which implement methods that are, not fully documented for users, so researchers have little or no control over this procedure and cannot know how their data were corrected e.g. This adjustment is typically done via proprietary software provided by instrument manufacturers which implement methods that are, not fully documented for users, so researchers have little or no control over this procedure and cannot know how their data were corrected e.g. [1,2,3,4]
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