2D motion analysis

Only one camera is necessary for kinematic measurements when the main movement of the body or of some of its parts are performed in a specified, unwavering plane, such as

  • gait analysis (on a treadmill)
  • counter movement jumps
  • high bar gymnastics
  • weight lifting

Most of these movements can be analysed from a lateral view at which ankle, knee and hip angles can be measured. Additionally, the position of the center of mass can be determined within the movement plane.
If the camera is far away from the movement, all segments appear to be in a single plane. Small differences in distances from the camera can be neglected for most purposes.
Often cameras positioned at different perspectives are used in order to allow more detailed measurements (e.g. both lateral views, lateral and dorsal, etc.).

2D calibration

Calibration is simple as long as the camera is perpendicular to the movement plane. When the aspect ratio of the camera's pixels is known, a simple distance with any orientation within the movement plane can be used to scale the pixel information into metric information.
More sophisticated algorithms, such as the 2D DLT, allow measurements even if the camera is not perpendicular to the movement plane.
2D calibration can be completed in less than 60 seconds.

See also
3D motion analysis

[2D calibration]
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