Improved GNSS navigation with chip-scale atomic clocks [article]

Thomas Krawinkel, University, My, University, My
2019
The determination of position and time as well as navigation by means of a Global Navigation Satellite System (GNSS) is always based on one-way range measurements between satellites and receiver. Synchronization of their time scales is carried out by introducing so-called clock biases with respect to GNSS time. Satellite clock corrections are either provided by the system operator via the navigation message or calculated using clock products of the International GNSS Service. On the receiver
more » ... e, the clock bias has to be corrected by the user. Due to the poor accuracy and limited long-term stability of the built-in quartz oscillator of a GNSS receiver, the clock bias must be estimated together with the coordinates at each measurement epoch. That is why GNSS-based three-dimensional position determination always requires at least four satellites in view. In addition, high mathematical correlations arise between the up-coordinate and clock bias of the receiver as well as other elevation-dependent error sources. As a consequence, the vertical coordinate can only be determined approximately two to three times less precisely than the horizontal coordinates. If the internal oscillator of the receiver is replaced by a more stable external one, the behavior of the latter can be modeled thanks to its higher frequency stability. An epochwise estimation is not necessary anymore. The physically meaningful prediction of the clock behavior is possible over intervals in which the integrated clock noise is smaller than that of the GNSS observations in use. This approach is referred to as receiver clock modeling (RCM). The development of so-called chip-scale atomic clocks (CSACs) makes the use of a highly stable oscillator in kinematic GNSS applications possible. Thus, connecting a CSAC to a GNSS receiver enables physically meaningful RCM in GNSS navigation based on code observations. In this thesis, the requirements regarding the frequency stability of an oscillator for RCM are investigated by means of two different CSACs. The r [...]
doi:10.15488/4684 fatcat:ixtm2etxa5fnbc547zskgmsshu