1. C. Ryan Tang ICS 280 UbiComp Winter 2006
Global Positioning System (GPS) for Submersibles By Marvin B. May Rodney A. Martin Bereket Tanju Robert A. Lopez, CAPT USN
C. Ryan Tang
ICS 280 UbiComp
Winter 2006
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2. Introduction
Motivation for TRANSIT satellite navigation system came submarine community
Periodic updates used to augment inertial navigation system
GPS faces unique technical challenges in submarine environment
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3. Challenges Attenuation of the GPS Signal Effect of Residual Seawater
Reflection at air/water interface
Attenuation due to lossy nature of seawater
Effect of Residual Seawater
Increases voltage standing wave ratio
Alters phi/theta components of the radiated far field
Ducting
Atmospheric phenomenon
Extends transmission of radio waves
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4. Challenges Time RMS Navigation Error
Lack of sensitivity to GPS error
Can store ephemeris data on sub
Receiver Initialization-Time to First Fix
Want to minimize exposure time
Need to search many phase/frequency bins to get P/Y code
Antenna Considerations
Separate antenna from antenna electronics
Interference from transmission antennas
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5. Proposed Solutions Covert GPS Navigation Capability (COGNaC)
Storage GPS receiver recirculates signal in non real-time
Minimizes exposure time at the cost of post exposure processing
Trailing Wire GPS Antenna
Provides GPS at depth
Submarine tied to GPS buoy
Severe space constraints
Can be towed or stationary
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6. Proposed Solutions Submersible Underwater GPS Aided Receiver (SUGAR)
Use GPS buoy with avionics grade inertial navigator
Keeps track of submarines relative distance from the buoy
GPS Acoustic Ranging Net (GARN)
Deploy multiple GPS buoys
Use SONAR to determine submersible position relative to the net
Provides precise and continuous location while within range
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7. Questions?
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