Catapult Proximity Project: Incursion Validation Trials

This report is an attempt to better understand the incursion detection process. It provides detailed results from a controlled protocol involving two athletes.

Catapult Sport & Data Science Teams (Catapult Sports)

Table of Contents

Background and Introduction

The overarching goal of the Proximity Project is to provide information about physical distance between players that may be used to better understand the possibility of viral transmission during the course of a game or training session.

For this report, a radius of specified distance around each athlete is referred to as the close proximity zone. Any instance in which another athlete enters the close proximity zone is referred to as an incursion. Incursions may vary in duration, and overlapping incursions are possible when more than 2 athletes are positioned together. If Athlete A breaches the close proximity zone of Athlete B, the inverse is also true. Therefore, each incursion is essentially doubled in order to achieve an accurate count for each athlete.

The overall objective is to assess the quality of the detection of any incursion and the related accumulated total duration within a 2m radius around an athlete.

For this investigation, a simplified environment consisting of only 2 athletes is considered. Real-world results will likely be more complex, involving interactions between many pairs of athletes, but the protocol followed for this report allows for a focused understanding unencumbered by the complexities of a typical training session.

The Validation Protocol

A primary objective of the Proximity Testing Protocol was to assess the effect of the close proximity zone radius on incursion detection and total duration of incursions detected. The effect of dwell-time is also assessed, although it should be noted that dwell-time considerations were not a primary concern when designing the protocol, and insights concerning dwell-time likely require further analysis.

The Proximity Testing Protocol consisted of 8 drills (listed below). Two trials of the Proximity Testing Protocol were completed for a total of 4 athletes and two locations. In this document, it is implied that a single incursion involves 2 athletes.

A schematic diagram of the validation protocol is included below.

Data Collection and Brief Error Discussion

Wearable Device and Satellite Positional Information

The data for this investigation was measured using Catapult Vector S7 devices which rely on GPS and GLONASS satellite constellations for 10 Hz positional information. As stated in the introduction, the objective of detecting all incursions within a 2m threshold around an athlete is used as a baseline for which to assess the dwell-time and close proximity zone radius parameters. Due to measurement error associated with satellite-derived positional information, close proximity is regarded as 2m (±1m).

The following table contains positional quality information for each portion of the protocol.

Video Verification of Expected Results

Expected incursion duration data was verified after completing the protocol using Vision video analysis software.

Participants followed strict adherence to the protocol described above, but some of the expected durations drifted slightly from those described in the protocol. The video-verified durations were used in the following analysis.

Even after manual video verification of expected results by an experienced video analyst, accuracy of these expected results is still subject to human error.


Summary Tables and Graphs

Data Summary By Period

The table below contains the complete set of data collected for each trial, drill, close proximity zone radius, and dwell-time. The table illustrates the effect of manipulating dwell-time and close proximity zone radius for each drill. Expected incursion durations and counts can be compared with measured incursion duration and count for each period, radius, and dwell-time combination. Durations have been rounded to the nearest second. Percentage errors have been selected as an evaluation metric*.

High-Level Overview by Close Proximity Zone Radius and Dwell-Time

To simplify the table above, all periods can be combined and grouped by dwell-time and Close Proximity Zone radius only. This provides a high-level overview of overall incursion count and duration that might be more suitable for quick comparisons.

A plot of the data in the table above may be easier to interpret. The data in the table directly above is summarized in the following plot.