Chapter 1. Air Navigation ▶ Section 1. Navigation Aids 1-1-1. General 1-1-2. Nondirectional Radio Beacon (NDB) 1-1-3. VHF Omni-directional Range (VOR) 1-1-4. VOR Receiver Check 1-1-5. Tactical Air Navigation (TACAN) 1-1-6. VHF Omni-directional Range/Tactical Air Navigation (VORTAC) 1-1-7. Distance Measuring Equipment (DME) 1-1-8. NAVAID Service Volumes 1-1-9. Instrument Landing System (ILS) 1-1-10. Simplified Directional Facility (SDF) 1-1-11. NAVAID Identifier Removal During Maintenance 1-1-12. NAVAIDs with Voice 1-1-13. User Reports Requested on NAVAID Outages 1-1-14. LORAN 1-1-15. Inertial Reference Unit (IRU), Inertial Navigation System (INS), and Attitude Heading Reference System (AHRS) 1-1-16. Doppler Radar 1-1-17. Global Positioning System (GPS) 1-1-18. Wide Area Augmentation System (WAAS) 1-1-19. Ground Based Augmentation System (GBAS) Landing System (GLS) 1-1-20. Precision Approach Systems other than ILS and GLS ▶ Section 2. Performance-Based Navigation (PBN) and Area Navigation (RNAV) 1-2-1. General 1-2-2. Required Navigation Performance (RNP) 1-2-3. Use of Suitable Area Navigation (RNAV) Systems on Conventional Procedures and Routes 1-2-4. Recognizing, Mitigating, and Adapting to GPS Jamming and/or Spoofing