Lesson 14: Advanced Navigation Systems

1. Lesson 14: AdvancedNavigation Systems

2. Lesson 20: Advanced Navigation Systems • AGENDA: • NAVSTAR Global Positioning System (GPS) • Inertial Navigation Systems (INS) • Bottom Contour Navigation • Electronic Charts (Raster & Vector) • Navigation Sensor System Interface (NAVSSI) • Applicable reading: Hobbs pp. 540-555.

3. NAVSTAR Global Positioning System (GPS) • GPS = Global Positioning System • all-weather, jam resistant, continuous operation, real-time, passive, worldwide radio navigation system. • Provides: • Extremely accurate 3D position data • Extremely accurate velocity data • Precise timing services • 3 LOPs provide a Lat. & Long • 4 LOPs provide Lat., Long. & Altitude

7. Civilian Uses Marine Navigation Law Enforcement Hydrographic surveying Search and Rescue Collision avoidance Military Uses Rendezvous Close Air Support Mine Warfare Unmanned Aerial Vehicles (UAV/s) NAVSTAR GPS Uses WRN-6

8. WRN-6

9. Differential GPS (DGPS) • A receiving station located at a fixed, known location receives position data from several GPS satellites. • The data obtained from GPS is compared to the known location of the station. • Any difference between these two is due to GPS error. • This difference the applied to the individual GPS receiver and thus, increased positional accuracy is obtained

10. Standard Position Service (SPS) Position: 100 m Hor. 150 m Vert. Velocity: .5 m/sec Time: 1 milli- second Precise Position Service (PPS) - Military Position: 16 m Hor. 25 m Vert. Velocity: .1 m/sec Time: 100 nano- seconds NAVSTAR GPS Accuracy

13. Inertial Navigation System (INS) • Inertial Navigation: the process of measuring the movements of a vessel based on sensed accelerations in known spatial directions. • Gyroscopes • Accelerometers • Electronic computers

14. Inertial Navigation Systems (cont) • Integrating acceleration gives you velocity • Integrating velocity gives you position/distance traveled • Need to compare to fix, since output is an EP! • Can go up to 30 days w/out update, in theory • Typically go no longer than 7-14 days • Types • SINS • ESGN • RLGN

15. Inertial Navigation Systems Current position is inputted Xo Spinning gyro Known mass Accelerometer F=m*a Computer Through Differentiation we get velocity and position (V and Xf)

16. Bottom Contour Navigation • Establishes position by using the geographic features of the ocean floor. • An echo sounder (fathometer) is used to produce a trace of the ocean floor beneath the vessel, which can be compared to a bottom contour chart to establish the ship’s position. • Can be used as a fix source, but is only accurate when large ocean floor gradients exist

17. Bottom Contour Navigation • 2 Techniques: • Line-of-Soundings (page 567 in Hobbs) • Contour Advancement (page 568 in Hobbs)

18. Advantages no satelites required subs=> no need to go to Periscope Depth (PD) not vulnerable Disadvantages not very accurate requires a cooperative sea bottom Bottom Contour Navigation

19. Electronic Charts • Raster Chart Display Systems (RCDS) • Electronic Chart Display Systems (ECDS) • Not approved for Fleet use, but getting closer

21. Navigation Sensor System Interface (NAVSSI) • Provides/Distributes NAV data (precise position, time, velocity, pitch-roll-yaw) to multiple users. • NAVSSI has been successfully installed, interfaced, and tested with WSN-5, WRN-6, EM Log, Tomahawk, Outboard, and NTCS-A. • A similar system may be integrated into your ship’s Combat Control System (CCS)

23. Summary/Review • How does GPS work? • What is ephemeris and almanac data? • Name 3 uses of GPS. • How does differential GPS work? • How do Inertial Navigation Systems work?

24. QUESTIONS?