RT Journal Article SR Electronic T1 Deriving Accurate Time from Assisted GNSS Using Extended Ambiguity Resolution JF NAVIGATION: Journal of the Institute of Navigation JO NAVIGATION FD Institute of Navigation SP 217 OP 229 DO 10.1002/navi.412 VO 68 IS 1 A1 Blay, Ryan A1 Wang, Boyi A1 Akos, Dennis M. YR 2021 UL https://navi.ion.org/content/68/1/217.abstract AB The advent of assisted GPS/GNSS can reduce the time to first fix (TTFF) dramatically and still provide sufficient positioning accuracy. However, many applications utilize GNSS for timing and assisted GPS/GNSS does not always provide the accurate nanosecond synchronization. Accurate timing is challenging for assisted GNSS due to the lack of diversity in the solution over short time periods. The relatively short ambiguities of the GPS L1 C/A code signal, one millisecond and twenty milliseconds, are too coarse to resolve accurate time reliably. In this paper, the impact of different ambiguity times has been derived/computed and validated. Experimental results show that when the ambiguity time is 200 milliseconds or longer, the least squares process will reliably converge and the typical nanosecond-level timing can be achieved. An example shows how the GPS L1 C/A data parity word (provided every 600 milliseconds) can be used, demonstrating nanosecond-level timing from assisted GPS.