Research Study Abstract

Time Drift Considerations When Using GPS and Accelerometers

  • Published on August 6, 2019

Purpose
To investigate potential time drift between devices when using Global Positioning Systems (GPS) and accelerometers in field-based research.

Methods
Six Qstarz BT-Q1000XT GPS trackers, activPAL3 accelerometers, and ActiGraph GT3X+ and GT3X accelerometers were tested over 1–3 waves, each lasting 9–14 days. Once per day an event marker was created on each pair of devices concurrently. The difference in seconds between the time stamps for each event marker were calculated between each pair of GPS and activPAL devices and GPS and ActiGraph devices. Mixed-effects linear regression tested time drift across days and waves and between two rooms/locations (in an inner room vs. on a windowsill in an outer room).

Results
The GPS trackers remained within one second of the computer clock across days and waves and between rooms. The activPAL devices drifted an average of 8.38 seconds behind the GPS devices over 14 days (p < .001). The ActiGraph GT3X+ devices drifted an average of 11.67 seconds ahead of the GPS devices over 14 days (p < .001). The ActiGraph GT3X devices drifted an average of 28.83 seconds behind the GPS devices over 9 days (p < .001). Time drift did not differ across waves but did differ between rooms and across devices.

Conclusions
Time drift between the GPS and accelerometer models tested was minimal and is unlikely to be problematic when addressing many common research questions. However, studies that require high levels of precision when matching short (e.g., 1-second) time intervals may benefit from consideration of time drift and potential adjustments.

Author(s)

  • Chelsea Steel 1
  • Carolina Bejarano 2
  • Jordan A. Carlson 1

Institution(s)

  • 1

    Center for Children’s Healthy Lifestyles and Nutrition, Children’s Mercy, Kansas City, MO, USA.

  • 2

    Clinical Child Psychology Program, University of Kansas, Lawrence, KS, USA


Journal

Journal for the Measurement of Physical Behaviour


Categories