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Electronic Navigation Chapter 23

Electronic Navigation Chapter 23. Many Toys. Speed up and make easier many tasks Tools are better with knowledge Common: VHF Depth Sounder RADAR LORAN GPS EPIRPBS. Depth Sounders. Echo sounders Time from sound emission and receiving its echo Rate sound travels through water is known

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Electronic Navigation Chapter 23

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  1. Electronic NavigationChapter 23

  2. Many Toys • Speed up and make easier many tasks • Tools are better with knowledge • Common: • VHF • Depth Sounder • RADAR • LORAN • GPS • EPIRPBS

  3. Depth Sounders • Echo sounders • Time from sound emission and receiving its echo • Rate sound travels through water is known • Transmitter-receiver (near helm) • processes and displays results • Transducer (on hull) • Sends ultrasonic pulse and picks up signal ATTENTION TO DEPTHS

  4. RADAR • Radio Detection and Ranging • Transmits microwave which bounces off metal • Determines distance to and direction of object • Useful at night and poor visibility • Not shielded – stay out of beam

  5. RADAR • 5 parts: • Transmitter: produces radio waves • Modulator: sends waves in pulses • Rotating antenna • Receiver: picks up weak incoming signal and processes it • Display unit

  6. RADAR • Pro’s • One object fix (RB and distance) • Greater distances to objects than visual • Magnetic anomalies • Con’s • Training and experience for proper interpretation • Two people needed • No small boats if near other objects or shore • Subject to mechanical or electric failure

  7. Radar Reflectors • 3 flat, metallic plates set at right angles to each other • Enhance the strength of transmitted RADAR beam • Big ships can better see smaller vessels and non-metallic objects • Used on some buoys and other aids to navigation

  8. RADAR Beacon • Transmits a coded signal when it detects a RADAR beacon (stronger signal) • “Racon” or “Raymark” on charts

  9. Land-Based Radio Navigation • Land-based radio transmitter and shipboard receiver • Measure time differential between arrival of signals from 2 different stations (master and secondary) • Charts printed with a lattice of lines (each line same time difference)

  10. LORAN • Long Range Navigation • LORAN-C current version • Covers all navigable waters of North America – See Canadian Aids to Navigation booklet for map

  11. How LORAN-C Works • Receiver measures time difference between 2 stations (LOP) • Using 2 sets of MASTER/secondary pairs gives a FIX (microprocessor gives the Lat/Long) • Problems: • Traveling over a lot of land distorts data • Grids not on large-scale charts

  12. LORAN Capabilities • LORAN’s with microprocessors can store waypoints and calculate: • Speed over Ground • Velocities of Currents • ETA’s • Cross Track Error • Some can interface with autopilots and maintain anchor watch Power failure, etc.

  13. LORAN Selection Criteria • Portable? • Interfacing capabilities • Antenna installation • Wiring, grounding, interfacing technicalities • Daylight readability • Accuracy

  14. GPS • Global Positioning System • 24+ polar-orbiting satellites emit position and time signals in a network covering all earth • Receiver interprets and displays position (FIX) • Also displays: • Course over Ground, Speed over Ground

  15. EPIRB • Emergency Position Indication Radio Beacon • Safety Equipment at Sea • Needs activating when in distress and sinking • Signal picked up by 1 of 4 orbiting satellites • Transmitted to nearest Search and Rescue • Must register with Coast Guard upon purchase Replace Battery

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