This document provides an overview of several advanced navigation systems: - The NAVSTAR GPS system uses satellites to provide extremely accurate global positioning with errors less than 100 meters. Differential GPS can further improve accuracy to 2-5 meters. - Ship's inertial navigation systems (SINS) use gyroscopes and accelerometers to continuously calculate position via known accelerations, but require periodic resets. Newer electrostatic systems can operate for 30 days without reset. - Bottom contour navigation relies on echo sounding to determine position based on comparisons to ocean floor contour charts. - LORAN is a ground-based hyperbolic navigation system using time differences between signal transmissions, providing accuracy within 200-500 yards.

1. Lesson 16: Advanced
Navigation Systems

2. • AGENDA:
– NAVSTAR Global Positioning System
– Ship’s Inertial Navigation Systems (SINS)
– Bottom Contour Navigation
– LORAN-C
– Electronic Charts (Raster & Vector)
– Navigation Sensor System Interface (NAVSSI)
• Applicable reading: Hobbs pp. 540-572.
Lesson 20: Advanced
Navigation Systems

3. NAVSTAR Global
Positioning System (GPS)
• GPS = Global Positioning System
– A space based, all-weather, jam resistant,
continuous operation, worldwide radio
navigation system.
• Provides extremely accurate 3D location
data as well as velocity and time.
• 3 LOPs provide a Lat. & Long.
• 4 LOPs provide Lat., Long. & Altitude

7. NAVSTAR GPS Specifications
• Frequency: 1227 MHz, 1575 MHz
• Range: Worldwide
• Accuracy: next slide
• 3 Types:
– SPS- Standard Positioning Service
– PPS-Precise Positioning Service
– Differential GPS- for military only

8. NAVSTAR GPS Accuracy
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

9. NAVSTAR GPS Uses
Civilian Uses
• Marine Navigation
• Law Enforcement
• Hydrographic
surveying
• Search and Rescue
• Collision avoidance
Military Uses
• Marine Navigation
• Air Navigation
• Rendezvous
• Close Air Support
• Mine Warfare
• Unmanned Aerial
Vehicles (UAVs)

10. Differential GPS
• A receiving station located at a fixed,
known location receives fix information
from GPS.
• The fix obtained from GPS is compared
to the known location of the station.
• Any difference between these two is due
to GPS error.

11. Differential GPS
• GPS error information is then
transmitted to vessels operating in the
area.
• The resulting fix accuracy is 2-5 meters
using the differential technique
• Requires more than 1 receiver

12. GPS
Advantages
• Continuous Coverage
(regardless of weather)
• worldwide coverage
• 3-D locator
• Precise Timing Standard
Disadvantages
• Vulnerable to Attack

13. Inertial Navigation Systems
• Inertial Navigation: the process of
directing the movements of a vessel based
on sensed accelerations in known spatial
directions.
• System uses:
– Gyroscopes
– Accelerometers
– Electronic computers

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

15. Inertial Navigation Systems
• Two types:
– SINS (Ship’s Inertial Navigation System)
• first used in 1960s
• getting phased out
• must be reset periodically
– ESGN (Electrostatic Gyroscopic Navigation)
• operates in a near perfect vacuum
• rotor is solely supported by an electrostatic field
• essentially frictionless
• resets only required once every 30 days

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.

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

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

19. LORAN
(Long Range Navigation)
• Over the years, many ground based
electronic navigation systems were
developed prior to satellite based systems
becoming possible.
• Most of these have been taken out of
service, but LORAN still enjoys
popularity and is still widely used.

20. LORAN (cont)
• The operating principles of the system
are similar to those now used by GPS.
• Ground stations, at known locations,
transmit signals at a predetermined time.
• These signals are received by vessels at
sea, and the time delay is used to form a
range LOP.

21. LORAN (cont)
• First established in 1957.
• Theory-hyperbolic LOPs based on time
differences between master and
secondary stations.
• Run by the Coast Guard
• Frequency: 100 kHz (LF)
• Range: 1200 nm
• Accuracy: 200-500 yds

22. Electronic Charts
• Electronic Chart Display Systems (ECDS)
• Raster Chart Display Systems (RCDS)

23. 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.

25. Homework
• Ch. 30
– Section 1: 1
– Section 2: 1, 5, 6, 9
• Ch. 31
– #4c, 5, 6