title: Step by step: reconstruction of terrestrial animal movement paths by dead-reckoning.
abstract: BACKGROUND
  Research on wild animal ecology is increasingly employing GPS telemetry in order to determine animal movement. However, GPS systems record position intermittently, providing no information on latent position or track tortuosity. High frequency GPS have high power requirements, which necessitates large batteries (often effectively precluding their use on small animals) or reduced deployment duration. Dead-reckoning is an alternative approach which has the potential to 'fill in the gaps' between less resolute forms of telemetry without incurring the power costs. However, although this method has been used in aquatic environments, no explicit demonstration of terrestrial dead-reckoning has been presented.
  
  
  RESULTS
  We perform a simple validation experiment to assess the rate of error accumulation in terrestrial dead-reckoning. In addition, examples of successful implementation of dead-reckoning are given using data from the domestic dog Canus lupus, horse Equus ferus, cow Bos taurus and wild badger Meles meles.
  
  
  CONCLUSIONS
  This study documents how terrestrial dead-reckoning can be undertaken, describing derivation of heading from tri-axial accelerometer and tri-axial magnetometer data, correction for hard and soft iron distortions on the magnetometer output, and presenting a novel correction procedure to marry dead-reckoned paths to ground-truthed positions. This study is the first explicit demonstration of terrestrial dead-reckoning, which provides a workable method of deriving the paths of animals on a step-by-step scale. The wider implications of this method for the understanding of animal movement ecology are discussed.
authors.affiliation: Institut für Terrestrische und Aquatische Wildtierforschung, Stiftung Tierärztliche Hochschule, Hannover, Werfstr. 6, 25761 Büsum, Germany.
authors.forename: O R
authors.initials: OR
authors.lastname: Bidder
authors.affiliation: Department of Computer Science, College of Science, Swansea University, Singleton Park, Swansea, SA2 8PP, Wales UK.
authors.forename: J S
authors.initials: JS
authors.lastname: Walker
authors.affiliation: Department of Computer Science, College of Science, Swansea University, Singleton Park, Swansea, SA2 8PP, Wales UK.
authors.forename: M W
authors.initials: MW
authors.lastname: Jones
authors.affiliation: College of Engineering, Swansea University, Singleton Park, Swansea, SA2 8PP Wales UK.
authors.forename: M D
authors.initials: MD
authors.lastname: Holton
authors.affiliation: Faculté des Sciences de la Vie, Master d'Ecophysiologie et Ethologie, Université de Strasbourg, 28 rue Goethe, 67083 Strasbourg Cedex, France.
authors.forename: P
authors.initials: P
authors.lastname: Urge
authors.affiliation: School of Biological Sciences, Institute for Global Food Security, Queen's University Belfast, Belfast, BT9 7BL Northern Ireland UK.
authors.forename: D M
authors.initials: DM
authors.lastname: Scantlebury
authors.affiliation: School of Biological Sciences, Institute for Global Food Security, Queen's University Belfast, Belfast, BT9 7BL Northern Ireland UK.
authors.forename: N J
authors.initials: NJ
authors.lastname: Marks
authors.affiliation: School of Biological Sciences, Institute for Global Food Security, Queen's University Belfast, Belfast, BT9 7BL Northern Ireland UK.
authors.forename: E A
authors.initials: EA
authors.lastname: Magowan
authors.affiliation: School of Biological Sciences, Institute for Global Food Security, Queen's University Belfast, Belfast, BT9 7BL Northern Ireland UK.
authors.forename: I E
authors.initials: IE
authors.lastname: Maguire
authors.affiliation: Swansea Lab for Animal Movement, Biosciences, College of Science, Swansea University, Singleton Park, Swansea, SA2 8PP Wales UK.
authors.forename: R P
authors.initials: RP
authors.lastname: Wilson
keywords: GPS; Step length; animal movement; dead reckoning; terrestrial