Kinematic data collection Flashcards
What are the 2 types of kinematic data collection
Video analysis and Optoelectronics
What is digitisation
The process of identifying landmarks (markers) on a moving object per frame
What must happen during digitisation to gain a full data set
All markers must be tracked over all frames of the capture
What must you consider during digitisation
Sampling rate and collection time
200Hz =
200 fps
If the sampling rate was 200Hz, how many frames would you collect for 5 seconds of data
1000
What does 3D data require
2 camera views
During running my stride time is 0.25 seconds, how many frames would I have to digitise to cover the entire stride if my camera sampled at 50Hz
12.5
How do optoelectronic systems differ from video analysis
- always 3D cameras
- captures volume and environment
- calibration
- automatic digitising so more data
- the output (markers only)
Process of optoelectronics
- Infrared light emitted by camera
- Infrared light hits reflective marker, then reflects back to the camera sensor
- Positions of these light sources are computed relative to the calibrated volume
What is required for Optoelectronics
Each marker must be seen by at least 2 cameras at every instant during data recording
Average sampling rate during optoelectronics
200-500 Hz
Two types of calibration in optoelectronics
Static and dynamic
Static calibration (L frame)
Defines the axes and origin (0,0,0) of the laboratory
Dynamic calibration (wand)
Calibrates a large capture volume and is relative to position of each camera
Optoelectronic digitisation
Automatic marker tracking, marker labelling required
Optoelectronic outputs
Only outputs markers position, no image of participant or environment (benefit and limitation)
One marker =
Anatomical landmark
Two markers =
Segment/ line
Three markers =
Define a plane/ angle between two segments
