GPS navigation
How it works, RAIM, WAAS, and the traps of moving-map complacency.
14 min read · Navigation
After this lesson you can
- Explain how a GPS receiver computes a position, and how many satellites that requires.
- Interpret RAIM status and know its limits, especially on VFR-only receivers.
- Explain what WAAS adds to plain GPS, and what LPV means.
- Apply the FAA's specific cautions for VFR GPS use: database currency, antenna limits, and cross-checking.
GPS has changed navigation more than any technology since the VOR. It gives an absolute position, an accurate groundspeed, and a reliable arrival time, without a single ground station or a hand-drawn triangle.
It has also introduced a new failure mode: confidence. A pilot who only follows a magenta line loses all situational awareness the moment the screen goes dark, and has no way to notice a typed-in waypoint that quietly sends the flight toward a similarly-named point 200 miles away.
The rest of this lesson
- 1.How a GPS position is computed
- 2.RAIM: watching itself
- 3.WAAS: a stronger, guaranteed signal
- 4.Selective Availability: a discontinued threat receivers still plan for
- 5.Cautions for VFR use
- 6.VFR waypoints
- 7.Good habits with a moving map
- 8.The box will hold your attention as long as you let it
These 8 sections, their figures, the checks along the way and the end-of-lesson quiz come with the PPL track. Paid once, yours for good.
Key terms
Try to recall each definition before turning the card.