Time-Synchronized GNSS/IMU Data Logging from Android Smartphone and its Influence on the Positioning Accuracy

Since the advancement in Smartphone GNSS positioning and the availability of GNSS observation via Android API, much of the focus have been given to bring down the Smartphone GNSS positioning accuracy from decimeter level to the centimeter level. But, considering many limitations such as Smartphone GNSS antenna, multipath and cycle slips, bringing down the accuracy to centimeter level is not an easy task. Many research work in this domain has demonstrated that the use of embedded sensors (IMU) inside the Smartphone can definitely ease the burden on GNSS. Researchers have already successfully processed the GNSS/IMU data collected from the Smartphone and highlighted some interesting results. But, when dealing with the GNSS/IMU processing, time-synchronization between GNSS and IMU data plays a vital role. Specially, in devices like Smartphone, when the GNSS and IMU data are not driven by the common clock, it becomes more important to study and analyze the effect of time-synchronizing between these two data sets. This paper gives reader an in-depth explanation about the need of time-synchronizing and the complete implementation overview. This paper will start with section I, giving an introduction to the current state of Smartphone GNSS positioning and discussing some limitations. In section II, we give an overview about our in-house GNSS/IMU logger developed at the institute. The complete time-synchronizing methodology has been implemented inside this Android Logger. In Section III, we will discuss the core of our research regarding implementation of time-synchronizing technique and their relevant equations. Further in section IV and section V, we will discuss some measurement setup and their corresponding results to validate the implementation. Finally, section VI, will focus on the conclusion and achievement related to the work.