Fig 1.
Hierarchy of soccer constructs.
Individual Ball Possession and its subtypes are a fundamental prerequisite for being able to discern ball actions. These actions are again the base for identifying situations. The typical behavior in these situations can be aggregated to playing styles.
Fig 2.
Relationships between the different types of ball possession.
Team ball possession (TBP) consists of an unbroken sequence of individual ball possession (IBP) phases. IBP is composed of one or more phases in which an action can be performed with the ball. These are designated individual ball actions (IBAs). It is possible for IBAs to be separated by void phases during which no ball control exists (e.g. while the ball is in the air). An IBC is an IBA where ball control is present. Team ball control (TBC) is the union of all TBC phases. Team play making (TPM) corresponds to TBC plus the intermediate void phases.
Fig 3.
Logical procedural steps for detecting different types of ball possession.
Detection is based on identifying the starting and endpoints of IBP and IBA.
Fig 4.
Illustration of IBA starting point determination according to the naive physics model, ball possession exists at time t when the separation d between player() and Ball (
is less than the threshold Tp.
Ball possession is attributed to the player closest to the ball (smallest here). With kick detection (right), the acceleration of the ball
(smoothed, norm of xy-components) must simultaneously show a local maximum of at least 4 ms-2.
Fig 5.
Detection of IBA endpoints: An endpoint exists as soon as the player is unable to interact with the ball for a period of one second.
This is the case after a shot on goal or a pass, for example, but not when the player is dribbling the ball stated formally, when using the ball prediction method, the endpoint t of an IBA phase is arrived at when the distance d between ball position () and player position (
) is no longer below the threshold value (TA) for a period of one second (t+) at the ball's current speed and direction (
). The player's position is assumed to be constant. The player prediction method additionally takes into account the player's future position
based on his direction and speed (
).
Table 1.
Quality of identification of different individual ball possession intervals.
IBPN = Starting point: Naive physical, Endpoint: /; IBPK = Starting point: Kick detection, Endpoint: /; IBAB = Starting point: Kick detection, End point: Ball prediction; IBAB = Starting point: Kick detection, End point: Player prediction.
Table 2.
Confusion matrix showing the quality of IBC classification.
Table 3.
Playing time, TPB, TPM, TBC according to game section and team status.
Table 4.
Player based metrics based on individual ball possession according to playing position.
-10 min indicates occurrences / time per 10 min net playing time. IBC (sn-1) represents mean time per interval. Playing positions are GK = Goalkeeper, FB = full back, CD = central defender, WF = wide midfielder, CM = central midfielder, CAM = central attacking midfielder, WI = Winger, CF = central forward and ALL = all positions.
Fig 6.
Heatmaps based on all positions (left) compared to positions during IBC (right).