Evaluating Movement Initiation Timing in Ultimate Frisbee via Temporal Counterfactuals

TL;DR

This paper introduces a novel quantitative method to evaluate the timing of movement initiation in Ultimate Frisbee, using drone footage, positional data, and space evaluation metrics to objectively assess play strategies.

Contribution

It presents a new approach combining drone-based data collection, temporal counterfactual analysis, and space evaluation metrics tailored for Ultimate Frisbee to quantify movement initiation timing.

Findings

Sequences with actual disc throws scored higher in evaluation metrics.

Higher-skill players show more varied timing offsets from the optimal.

The proposed metric objectively assesses movement initiation timing in unlabeled team sports.

Abstract

Ultimate is a sport where points are scored by passing a disc and catching it in the opposing team's end zone. In Ultimate, the player holding the disc cannot move, making field dynamics primarily driven by other players' movements. However, current literature in team sports has ignored quantitative evaluations of when players initiate such unlabeled movements in game situations. In this paper, we propose a quantitative evaluation method for movement initiation timing in Ultimate Frisbee. First, game footage was recorded using a drone camera, and players' positional data was obtained, which will be published as UltimateTrack dataset. Next, players' movement initiations were detected, and temporal counterfactual scenarios were generated by shifting the timing of movements using rule-based approaches. These scenarios were analyzed using a space evaluation metric based on soccer's pitch control reflecting the unique rules of Ultimate. By comparing the spatial evaluation values across scenarios, the difference between actual play and the most favorable counterfactual scenario was used to quantitatively assess the impact of movement timing. We validated our method and show that sequences in which the disc was actually thrown to the receiver received higher evaluation scores than the sequences without a throw. In practical verifications, the higher-skill group displays a broader distribution of time offsets from the model's optimal initiation point. These findings demonstrate that the proposed metric provides an objective means of assessing movement initiation timing, which has been difficult to quantify in unlabeled team sport plays.