Characterization of dual frequency GNSS observations from Xiaomi Mi 8 smartphone in absence of duty cycle

Beginning in May 2016 after Google announced that the GNSS raw measures (Global Navigation Satellite System) acquired by smartphones equipped with Android would be freely accessible, a real race began for scientists to achieve of centimeter accuracy using smartphone. A further acceleration took place in May 2018 with the appearance of the first dual-frequency GNSS chip-set the Broadcom BCM47755. The manufacturer Xiaomi marketed the first mobile phone equipped with this chip-set; for the first time smartphone users had access to raw double-frequency GNSS measurements from more than one satellite system. Unfortunately, the duty cycle technique, necessary to safeguard battery life, degraded the quality of the measurements acquired by the smartphone. The last milestone reached came with the release of the Android Pie operating system which makes it possible to switch off the duty cycle. Thus the use of high-precision techniques such as Real Time Kinematic (RTK) or Precise Point Positioning with the measurements acquired by the smartphone became possible. However, in order to use these techniques, it is necessary that the quality of the measurements is not too low. Therefore, it is very important to conduct an analysis to assess their quality. The results obtained show that the second frequency offers measurements that are much less sensitive to multipath, while the signal to noise ratio of the measurements is on average above 30 dB/Hz, guaranteeing a good quality. The results of the analysis conducted show that the quality of the measurements acquired by the smartphone has reached a quality sufficient to be able to use PPP or RTK techniques.