ES.3 RECOMMENDATIONS
The following subsections offer recommendations in three areas： GPS, WAAS/LAAS, and risk mitigation.
ES.3.1 GPS
If civil aviation is to rely on GPS, greater access, cooperation, and agreement must exist on GPS operational control segment (OCS) procedures and future system performance. Specifically, the following must be addressed：
a. GPS operational procedures that support civil aviation policy need to be defined and implemented (e.g., signal monitoring, orbit management, and end-of-life operation and replacement strategies).
b. A means to convey full knowledge of failure rates and mechanisms that are essential to intelligent system design and operations must be established.
c. A process for Department of Defense (DOD) and DOT data collection and analysis must be established and sustained to characterize system performance and resolve incident reports(including international reports).
d. GPS coverage is currently limited by prediction of receiver autonomous integrity monitoring (RAIM) availability; current approaches are overly conservative by assuming all satellite failures are soft failures; and current algorithms are limited to "snapshot" position computations. These restrictions tend to increase reliance on the number of in-view satellites.
Improvements to RAIM algorithms should be evaluated for possible cost reduction opportunities or performance improvements in the augmentation system structure.
These recommendations will allow sensible cost and performance trades between possible GPS system improvements and the implementation and operation of the augmentations supporting civil aviation. In support of these augmentations and to benefit the full domain of civil applications, a need exists to clearly define a national GPS plan that includes the following：
a. Establish a firm agreement on the size and characteristics of the satellite constellation and signal structures that will be maintained for all navigation services.
b. Specify the timetable for planned improvements (e.g., removal of selective availability and providing the second civil frequency).
