Navigation engineering: inertial, GNSS, SBAS and integrity
How aircraft know where they are, and how sure they can be: inertial sensors and drift, GNSS pseudoranges, errors and geometry, augmentation and protection levels, hybrid filtering and RNP containment, and GNSS interference as a safety hazard. Part 2 of the Avionics engineering series.
By Aerospace Garage Desk · Managing it · 50 minutes · 24 narrated pages
What you will be able to do
✓ Explain what a navigation solution contains, how dead-reckoning errors grow, and why complementary sensors are blended and cross-checked.
✓ Describe strapdown inertial sensors, alignment and Schuler behaviour, and estimate inertial drift for a given gyro grade.
✓ Explain how a GNSS receiver computes position and time from pseudoranges, and build a range error budget with dilution of precision.
✓ Compare ABAS, SBAS and GBAS integrity, and decide service availability from protection levels and alert limits.
✓ Explain hybrid inertial/GNSS filtering and coasting in words, and derive a navigation error allowance and coasting time from an RNP value.
✓ Describe how GNSS interference affects avionics and how it is detected and managed, using official FAA and ICAO safety alerts.
Course content
Session 1 · Navigation sensors and the navigation solution
1.1
Where am I? The navigation solution · free preview
Dead reckoning and the sources of error
Why we blend sensors
Worked example: how fast does dead reckoning run out?
Session 2 · Inertial navigation: sensors, alignment and drift
1.2
Gyros and accelerometers
Alignment: finding level and north
Drift and the Schuler loop
Worked example: three gyro grades over five hours
Session 3 · GNSS: pseudoranges, errors and geometry
1.3
Pseudoranges: how a receiver computes a position
Where the errors come from
Geometry, dilution of precision and the constellations
Worked example: an error budget and three geometries
Session 4 · Augmentation and integrity: ABAS, SBAS, GBAS and protection levels
1.4
Integrity inside the receiver: ABAS, RAIM and FDE
SBAS: corrections and integrity from a continental network
GBAS, alert limits and the standards behind them
Worked example: protection levels against alert limits
Session 5 · Hybrid inertial/GNSS navigation and RNP containment
1.5
The Kalman filter in words
Coasting when the satellites are lost
Accuracy and containment: the RNP error terms
Worked example: how long can we coast?
Session 6 · GNSS interference, resilience and the road to Part 3
1.6
What interference does to receivers and the systems around them
Detecting and coping: layers of protection in the avionics
Standards and what is changing
From the investigation file: two official GNSS interference alerts, 2024 and 2025
Who this course is for
Avionics and navigation systems engineers at manufacturers, suppliers and design organisations who specify, integrate or certify GNSS, inertial and multi-sensor navigation equipment
Airworthiness, continuing-airworthiness and avionics engineers at operators and MROs who assess GNSS upgrades, coasting performance and interference effects on their fleet
Flight operations engineers, PBN specialists and safety managers who need to understand what sits behind RNP alerts, protection levels and GNSS interference reports
You need: The Performance-based navigation (PBN) course or equivalent experience; Part 1 of this series (data buses and IMA) is useful; comfort with squares, square roots and simple rates.
Upskill courses are for professional development and are not approved by any aviation authority. Learner Terms