Match each aeronautical navigation method to its primary reference source: Navigation Methods: 1. Pilotage (Terrestrial navigation) 2. GPS 3. VOR 4. ADF/NDB Reference Sources: A. Constellation of orbiting satellites B. Magnetic radials transmitted by a ground station C. Visible landmarks and physical ground features D. Non-directional radio beacon signals

Each method relies on a different reference: visible surface features, satellite measurements, VOR radials, or NDB bearings. Recognizing the reference helps pilots understand the information displayed and its limitations. **Key takeaway:** Different navigation systems provide different kinds of position evidence. **Glossary:** **Radial**: magnetic direction outward from a VOR; **ADF**: equipment that receives NDB signals.