I. Introduction
In recent years, we observed an exponential increase of wireless signals being used in today’s busy urban areas. This change is supported by technological innovations made available for everyone. The device that comes quickly to mind is everyone’s favorite, our smartphone. The increasing need of Location Based Services (LBS) provoked the rapid evolution of smartphones’ embedded low-cost Global Navigation Satellite System (GNSS) chipsets within the last few years. Most Android devices are now equipped with multi-constellation and multi-frequency positioning units.