Acceleration can be measured along three directional axes:
• x-axis (lateral) — Sideways (left or right) acceleration, for which
positive values represent movement toward the right, and negative
values indicate movement to the left.
• y-axis (longitudinal) — Forward or backward acceleration, for which
forward acceleration, such as the device being pushed in the direction
of the top of the device, is represented by a positive value and
acceleration backwards represented by negative values.
• z-axis (vertical) — Upward or downward acceleration, for which
positive represents upward movement, such as the device being
lifted. While at rest at the device’s natural orientation, the vertical
accelerometer will register
–9.8m/s2 as a result of gravity.