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 Transmitter-receiver (near helm) –processes and displays results Transducer (on hull) –Sends ultrasonic pulse and picks up signal

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

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

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

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

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

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)

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

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

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 LORAN Capabilities

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

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

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