Shipboard-Relative GPS (SRGPS) is an architectural variant of the Joint Precision Approach and Landing System (JPALS) that will provide high accuracy and high integrity DGPS navigation for automatic shipboard landings. The required vertical alert limit (VAL) for the navigation system is 1.1 m, with an associated integrity risk of approximately 10 -7. Because of the stringent nature of these specifications, carrier phase DGPS (CDGPS) solutions are being pursued. This research is focused on the design of robust airborne algorithms for SRGPS terminal navigation. In this context, a processing methodology is defined to optimally combine the complementary benefits of geometry-free filtering and geometric redundancy. Specifically, when the aircraft is far from the ship (inside or outside the SRGPS service volume), geometry-free filtering is used for cycle estimation of widelane integers. For dual frequency implementations, the advantage of code/carrier divergence-free filtering prior to SRGPS service volume entry can be especially significant because long filter durations can be used. In contrast, the use of geometric redundancy for cycle resolution is restricted to the service volume (where the aircraft has access to shipboard reference measurements) and is most robust to ionospheric and tropospheric decorrelation when the displacement between the aircraft and ship is small. Thus, only when the aircraft is near the ship, can carrier phase geometric-redundancy be safely exploited for cycle estimation of any remaining widelane integers and, if needed, L1 and L2 integers. By processing this way, performance is enhanced due to the long duration of code measurement filtering, and cycle resolution is robust to spatial decorrelation error model assumptions (because geometric redundancy is used only when the baseline distance is short). In this paper, the robust navigation architecture is detailed and its performance is evaluated relative to the navigation integrity requirements for shipboard landing of aircraft.
|Original language||English (US)|
|Number of pages||9|
|State||Published - Jun 28 2004|
|Event||PLANS - 2004 Position Location and Navigation Symposium - Monterey, CA, United States|
Duration: Apr 26 2004 → Apr 29 2004
|Other||PLANS - 2004 Position Location and Navigation Symposium|
|Period||4/26/04 → 4/29/04|