Intra- and Inter-Device Reliability of the Change-of-Direction Angles Using a Smartphone Application for Sailing.

Jacek Tarnas,Rafał Stemplewski,Nina Schaffert,Leszek Kostański,Helena Elegańczyk-Kot

doi:10.3390/ijerph17103494

Abstract

The smartphone has recently become a commonly used tool for satellite navigation. The reliability of built-in smartphone Global Navigation Satellite Systems receivers was analyzed in terms of distance, velocity/speed and acceleration, but little is known about the accuracy of angular change-of-direction measurements. This might be important in the assessment of usefulness in sailing navigation. The aim of the study was to assess the reliability of the calculated change-of-direction angles, measured with the built-in smartphone Global Navigation Satellite Systems technology using the SoniSailing application. One individual completed five trials in an urban open space (sports ground), wearing six identical Samsung Galaxy J5 smartphones. The trials simulated an upwind sailing race (127 m), including two consecutive courses at 45° angle to the line of the tacking leg. To assess the reliability of change-of-direction angle measures the intra- and inter-device correlation coefficients were calculated. The analysis showed excellent reliability in change-of-direction angle measures—no less than 0.95 and 0.93 in case of correlation coefficients for inter- and intra-device, respectively. Correlation coefficients for average measures were no less than 0.99 in both cases. The study confirmed high reliability of the calculated change-of-direction angles, measured with the Global Navigation Satellite Systems technology using the SoniSailing application for smartphones.

Highlights

In recent years, the smartphone has become a commonly used tool mainly due to its new functions thanks to built-in sensors, such as multi-axis accelerometers and gyroscopes, magnetometers or GlobalNavigation Satellite Systems (GNSS) receivers
The reliability of COD angle measurement estimated by smartphones with the use of the SoniSailing application was checked
Retest depicts variability depending on implemented procedures and reflects the stability of the phenomena [11]—in this particular case, it reflects the consistency in COD given by the same device across multiple trials

Summary

Introduction

The smartphone has become a commonly used tool mainly due to its new functions thanks to built-in sensors, such as multi-axis accelerometers and gyroscopes, magnetometers or Global. Smartphones are useful in monitoring and supporting physical activity [1,2] and sports training [3]; locating the user with the GNSS (the term includes e.g., Global Positioning System—GPS, GLONASS, Galileo, Beidou and other regional systems) appears to be one of its significant functions. Beside the weather conditions, the presence of buildings, etc., the accuracy of GNSS receivers depends generally on the sampling rate. Commercially available, sport-specific GPS units with a sampling rate of 10 Hz are capable of athlete tracking for distance and velocity in team games [4], Int. J. Public Health 2020, 17, 3494; doi:10.3390/ijerph17103494 www.mdpi.com/journal/ijerph

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