How Your Phone Calculates Steps

cell-phone-walking

Timothy R. Primrose, Mobile Forensic Analyst

Modern day smartphones have health applications that monitor and document many aspects of the user’s daily events. This data can be collected by the phone, synced from a wearable device such as a Fitbit, or input directly by the user. These datatypes include steps, distance, hearing, heart rate, mobility, menstrual cycle tracking, mindfulness, nutrition, respiratory, sleep, vitals, and other user input data such as blood glucose and inhaler usage.

Different methods are used by health applications to document this data. Health applications utilize the cell phone’s accelerometer and a gyroscope to calculate steps. Every time the user’s foot makes contact with the ground, a ping to the acceleration sensor signal will occur. Health applications also compute distances by multiplying the number of steps by an estimate of stride length. Registered distances are not as accurate as steps because their calculations are also impacted by a range of different factors that affect the stride length:

  • Carrying location (in hand, pants pocket, jacket pocket, chest pocket)
  • Walking speed
  • Arm movement
  • Height (leg length)

Larger distances are registered when the user performs a larger forward-backward movement with their arms while holding their phone and walking or running. Any inaccurate step results will also affect the distance. Checkout your health application to see what other data your phone tracks.

Cell Phone Downloads | Cell Phone Forensics | Mobile Forensics

 

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