I've been watching international soccer and noticed several decisions involving the connected ball technology used alongside video review. In one Portugal–Croatia incident, a goal was disallowed after the system reportedly indicated that the ball had made a slight touch off a Croatian player.
That raised a few questions for me. How can the sensor distinguish a very light player touch from effects caused by rain, wet grass, or the ball bouncing on the field? What kind of data does it actually send to the officials, and how reliable is it after the ball has been kicked and struck hundreds of times?
I'm also curious about ball identification. There are usually several spare balls around the pitch, and each may contain a sensor. How do the officials know which ball is currently being used in play, especially when a ball goes into the stands and is quickly replaced? Can signals from the unused balls interfere with the tracking system, or does the system automatically identify the ball involved in the current sequence?
3 Answers
The connected-ball system is designed to associate sensor data with the ball that is involved in the current match action. The spare balls may be equipped with similar hardware, but they are not all simultaneously treated as the active ball in play. When a replacement is brought on, the system can identify that ball separately, so signals from unused balls should not be confused with the live sequence.
The sensor primarily measures the ball’s movement and contacts, rather than trying to interpret rain or grass directly. Software combines that data with optical tracking and the known positions of the players. A tiny touch might not be obvious from the change in direction alone, but the sensor can provide a timestamped contact signal that helps officials reconstruct what happened.
The technology is not simply a microphone that hears every impact. The ball contains a motion sensor that reports data at a high frequency, allowing the system to detect changes in movement and likely contact events. The match system then combines those readings with camera-based tracking and player-position data.
Rain and grass should not look like a deliberate player contact in the same way. They can affect the ball’s motion, but the system is built around movement patterns, timing, and location. Like any officiating tool, it does not independently make every judgment; it gives the video officials additional evidence. The final decision still depends on the complete sequence and the relevant laws of the game.
The technology can indicate that a contact occurred, but it may not be able to prove exactly which body part made it from sensor data alone. That is why the sensor output still needs to be matched with camera footage when deciding whether a goal should stand.
The manufacturer and governing-body explanations describe the sensor as part of a broader connected-ball system, not as a replacement for video. It can provide precise timing for ball contacts and movement, which is especially useful for offside reviews and determining whether a touch occurred before the ball reached a player.
The electronics are sealed inside the ball and tested for normal match conditions, including repeated impacts. They are not expected to be affected by ordinary rain or the playing surface. However, the system is still subject to practical limits: unclear footage, unusual collisions, equipment faults, or uncertainty about how a contact should be interpreted can all require the officials to use their judgment rather than relying on one sensor reading alone.
That makes sense for normal play, but a ball can be replaced very quickly after going into the crowd. I assume the replacement ball has to be registered or recognized before it becomes active; otherwise there would be no reliable way to connect the sensor data to the video sequence.