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Evaluating the Accuracy and Reliability of Bicycle GPS Devices
Abstract:
Every day in the United States, an average of approximately two cyclists die in bicycle accidents. Sometimes, forensic engineers are asked to reconstruct these accidents. These cyclists may use bicycle GPS devices to record important data, which they use to monitor their riding activities. By analyzing this data, many questions can be answered regarding various parameters such as speed, position, and riding behavior of the bicyclist.
The goal of this study was to analyze the accuracy of the GPS position and speed data. For this study, four different bicycle GPS devices (one of which was paired with a magnetometer Garmin Bicycle Speed Sensor), a GoPro camera equipped with GPS, and a smartphone recording to Strava, were mounted on a bicycle. The bicycle was ridden in an approximately straight line (back and forth), and then around a building, to measure positional and speed accuracy. Additionally, the bicycle was ridden in a straight line, then decelerated to a complete stop for varied durations, and then accelerated forward. This was done to see if the retrieved data showed the bicycle coming to a complete stop, or if the GPS averaged a few data points showing that the rider never came to a stop. Furthermore, the bicycle was stopped at a specific location for a certain duration and the GPS drift of each device was studied.
Using VBOX 3i RTK DGPS positional data as the reference, test data revealed that all six bicycle test devices had relative error in positional and speed data. The Garmin Edge 530 had an average speed error of 10.83% and positional error of 21.78 ft. The Garmin Edge 1000 (BSS) had an average speed error of 4.71% and positional error of 15.2 ft. The Lezyne Mega XL had an average speed error of 3.5% and positional error of 4.82 ft. The Wahoo ELEMNT Bolt had an average speed error of 3.53% and a positional error of 10.46 ft. The Strava app had a positional error of 11.45 ft. The GoPro Hero5 had an average speed error of 5.05% and a positional error of 4.79 ft.
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