Precision hybrid navigation system for varied marine applications

A need has long been established to provide low cost precise inertial and integrated navigation systems for seaborne applications. The adaptation of low cost, high volume electronics and inertial sensors from Kearfott missile and land products has enabled this need to become a reality. The development of a low power navigation system for guidance of Unmanned Underwater Vehicles used in applications such as deep salvage, oil and gas well head and pipeline laying and maintenance, sea bed mining, communications cable laying and maintenance, and scientific surveys is one example of this adaptive process. High speed patrol boats, corvettes, and other medium sized surface ships are further examples of applications that could benefit from the precise navigation and dynamic attitude information available from integrated systems of this type. All have stringent positioning requirements in order to define location as well as support of autopilot functions (attitude and/or heading control). Missions for this variety of applications may last many hours or even several days in duration, and may reach depths exceeding 5 km. By combining a low-cost but accurate Inertial Navigation System (INS), a Global Positioning System (GPS) receiver for surface operation INS alignment, and an accurate sonar Doppler Velocity Log (DVL) or Electromagnetic (EM) Speed Log for an in-water reference, with a sophisticated Kalman filter to combine these data in an optimal way, both surface and underwater navigation meeting these objectives can be achieved. Long term sea bottom position error growth rates of only a few meters per hour are possible