Quantifying the uncertainty in bicycle-computer speed measurements

The goal of this study is to quantify the uncertainty in bicycle computer measurements of speed. We acquired 100+ hours of data at 1-second intervals simultaneously from three Garmin Edge 530 computers mounted to the same handlebars during road cycling in rural and urban environments. Each computer recorded speed data using a different method: One unit was paired to a Garmin GSC 10 speed-and-cadence sensor (wheel rotation based), a second unit was paired to Garmin Speed Sensor 2 and Cadence Sensor 2 (accelerometer based), and a third unit was not paired to any remote sensors and relied on the device’s GPS position to calculate speed (GPS based). Based on these data, we generated probability distributions that quantify the uncertainty in the accelerometer based and GPS based speed measurements. This study provides foundational information regarding the appropriate methods to quantify the uncertainty in bicycle-computer speed data and to probabilistically interpret these data for collision reconstruction purposes.