Position Uncertainty of Consumer GNSS Smart Devices: A GUM-Based Analysis

Smartphones and wearable devices are in most cases equipped with a large number of sensors able to support different features and services. Applications, such as navigation or sports activity monitoring, are very popular among users and they implement services that exploit the position revealed by the onboard integrated Global Navigation Satellite System (GNSS) receiver. For these applications to perform well, the detected position must be as accurate and precise as possible. As the GNSS receiver performance is closely related to device design and its implementation, evaluating the uncertainty is of interest to understand how powerful these devices are in detecting the user's position. Therefore, in this article, an assessment of the uncertainty of the geographical position measured by GNSS receivers onboard consumer electronics devices is proposed. A comparative analysis is carried out on four different devices, two commercial smartphones and two commercial smartwatches, by resorting to using the recommendations of the Guide to the Expression of Uncertainty in Measurement and exploiting Type A estimation method.