Your video measures the shuttle’s movement in pixels, but speed has to be in real distance. Calibration is the step that connects the two: you mark a line in the video whose real-world length you know, and the app works out how many meters each pixel represents. Without it, a speed value would be meaningless.
How it works
You place two points on a real reference in the video — typically two known court lines — and tell the app the real distance between them. From that, Smashspeed calculates a meters-per-pixel scale and uses it for the whole measurement.
The default: 3.87 meters
The app suggests 3.87 m, the standard distance between the front service line and the doubles long service (back) line on a badminton court. These lines are clearly marked on any regulation court, which makes them an easy, reliable reference.
Where to place the two points
- Put one point on the front service line and the other on the doubles long service line.
- Place them on the lines directly under where the player is standing — not pushed forward toward the net. Points set too far forward will distort the scale.
- The two points need a bit of separation on screen; if they are nearly on top of each other the app asks you to spread them out.
Using a different distance
You can enter a custom reference length if you are measuring between different marked lines. If you do, be precise about exactly which lines you used — an inaccurate reference length scales your entire result. When in doubt, stick with the 3.87 m default.
Why this is the most important step
Because every speed is scaled by your calibration, a small mistake here multiplies through the whole measurement. Taking care to place the points on the right lines, at the right depth, is the single biggest thing you can do for an accurate result. Next, you can review and fine-tune the detection.