2D motion analysis
Only one camera is necessary for kinematic measurements when the main movement of
the body or of some parts of it is performed in a plane, such as
- gait analysis (on a treadmill)
- counter movement jumps
- high bar gymnastics
- weight lifting
Most of these movements can be analyzed from a lateral view where angles at the
ankle, knee and hip 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 from different perspectives are used to allow more detailed measurements
(e.g. both lateral views).
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2D calibration
Calibration is simple as long as the camera is perpendicular to the movement plane.
When the aspect ratio of the cameras pixels is known a simple distance with any
orientation within the movement plane can be used to scale the pixel information
to 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 within less than 60 seconds.
See also
3D motion analysis
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[2D calibration]
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