GPS Positioning:
04 satellites are the minimum required to compute a 3D position (latitude, longitude, altitude) and time.
05 satellites are required for Receiver Autonomous Integrity
Monitoring (RAIM) to detect faults. RAIM provides redundancy by allowing the system to compare the measurements from the additional satellite with the expected position.
06 satellites enable Fault Detection and Exclusion (FDE), which not only detects faults (like RAIM) but also excludes the faulty satellite and recomputes the position using the remaining satellites. This ensures the GPS receiver can continue providing reliable positioning even when one satellite's data is compromised.
This level of redundancy is critical in applications requiring high accuracy and integrity, such as aviation.
RAIM: Detecting Faults
RAIM is used to monitor the integrity of GPS signals by detecting when a satellite is providing erroneous data. The key reasons for using RAIM are:
1. Safety-Critical Navigation:
○ Ensures that the position computed by the GPS receiver is reliable, especially
for applications like aircraft navigation where errors can have serious consequences.
2. Redundancy for Error Detection:
○ By comparing the measurements from an additional satellite to the expected position, RAIM can detect inconsistencies caused by satellite malfunctions, signal interference, or multipath effects.
3. Integrity Alerts:
○ RAIM alerts the user when the GPS position cannot be trusted, preventing reliance on potentially inaccurate data.
FDE: Detecting and Resolving Faults
FDE builds on RAIM by not only detecting a faulty satellite but also excluding it from calculations to maintain a reliable position solution. Here's why it's used:
1. Continuous Operation:
○ Allows the system to continue providing accurate position data even when a fault is detected by excluding the faulty satellite.
2. Higher Reliability:
○ Especially important in environments where maintaining an uninterrupted, precise position is critical, such as in aircraft during approach and landing.
3. Fault Mitigation:
○ Ensures that a single faulty satellite does not compromise the integrity of the entire positioning system.
Aporte Piloto Nicolás Ramírez
