Calculating Speed using Video Analysis

There are many biomechanical measurements that can be made using video analysis. Described here is a simple method for measuring speed of an object that nearly anyone with a basic camera and TV can do. There are also several Video Analysis products that can do this and much more.

Make note of the video technique guidelines before collecting video footage for analysis. For speed measurements, you will need to have video footage from directly side-on, a calibration mark that can be viewed on the screen (for distance measurement), and you need to know the frame rate of the video (or have a time scale in view).

The speed of an object is a measure of how far it moves in a set time period (measured in the units meters or feet per second, km or miles per hour etc.). Therefore the first step in calculating speed of an object on screen, is to calculate the distance the object moved. Once this is determined, you will need to know what the frame rate of the video recording is. Frame rates can vary, often 24 or 25 frames per second, sometimes 30 frames/sec. For high speed filming (slow-mo) it can be 1000 frames/sec. If it is 25 frames per second, this means that there is 0.04 seconds between each frame. When you view the video frame by frame, and calculate the distance an object moves from one frame to the next, you can calculate the velocity of that object. If the object (e.g. the hand) moves 2 inches between frames, the equates to a velocity of 4.2 feet/sec.

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