Ball
Calibrate the court
Mark the court once per video, in about a minute, so the ball is measured in real metres. Step by step, and how to read the fit.
To measure the ball in metres (how far over the net, where it lands, how fast it leaves the racket), the app needs to know where the court is in your video. You tell it once per video by clicking a few points on the lines. It takes about a minute.
Step by step#
- Open Tools → Ball and press Calibrate the court.
- Say where the camera is. Camera: Behind (behind the player), Side (on the side fence) or Front. If the diagram doesn’t look like your video, press Turn until it does.
- Click where it asks. The tab tells you what to mark, e.g. “Click on the video: where your baseline meets the singles sideline”. A magnifier shows the pixels under the pointer. If that point isn’t visible, press Can't see it to move on.
- Add references until you have at least 4. The counter says … of the 4 references needed. You can pick any dot or line on the diagram: corners count most; a point anywhere along a line counts half.
- Check the fit and press Done. The fitted court is drawn on the video as you mark, with a verdict (below).
Reading the fit#
| Verdict | What it means | What to do |
|---|---|---|
| Good fit | The marks match a real court, a few pixels off | Nothing: you can measure |
| Fair fit | They match, with a bit more error | Usable; add one or two more references if you can |
| Check the points | A mark isn’t where the diagram says | The tab says which one is furthest off: move it or remove it |
Below it reads, for example, “8 references · they miss the fitted court by 3 px on average”: the fewer pixels, the better.
Depending on where the camera is#
- Behind: the easiest. Mark the corners of your baseline and service line, the T and, if visible, those on the far side.
- Side: long lines run off the picture. Use points along the lines (click the line on the diagram) and the top of the net at the post.
- Front: mark the lines on your side of the court and the net; remember the ball is measured only roughly from this angle.
After calibrating#
The tab shows Court calibrated with its fit. From there you can:
- Show the court on the video to check it matches throughout the video.
- Adjust the marks or Remove the calibration.
- Tick Slow-motion video (unknown speed) when the video is slow motion and you don’t know the frame rate it was filmed at (if you do, enter it in Video → Filmed at).
Now you can analyse the ball. If you scan the session with the court calibrated, the scan follows the ball of a few strokes too.