nav 2b

• Mercator


  The most common projection used in navigation, distorting areas away from the equator but preserving straight lines
• Gnomonic


  Used for Great Circle charts, projecting points from the Earth onto a tangent plane
• Modified Lambert Conformal


  Used for polar charts, developing the Earth using a conic projection with two intersecting parallels
• Dead Reckoning


  Determines position by advancing a known for courses and distances
• Correcting the DR Position


  Correcting the DR position for leeway, current effects, and steering error result in an estimated position (EP)
• Methods of Position Determination


  Various methods of mathematically determining course, distance, and position
• Speed


  Rate of motion, or distance per unit of time
• Course


  Horizontal direction in which a vessel is intended to be steered
• Track Made Good


  Single resultant direction from the point of departure to point of arrival at any given time
• Speed of Advance (SOA)


  Indicates the speed to be made along the intended track
• Speed over Ground (SOG)


  Actual speed of a vessel over the surface of the Earth at any given time
• Speed Through Water (STW)


  Speed of the vessel relative to the water
• Inland Waterway Phase


  Piloting in narrow canals, channels, rivers, estuaries
• Harbor Approach Phase


  Navigating to a harbor entrance through bays and sounds, and negotiating harbor approach channels
• Coastal Phase


  Navigating within 50 miles off the Coast
• Ocean Phase


  Navigating in the Open Sea
• Types of Navigational Charts

  • General Charts
  • Coastal Charts
  • Harbor Charts
  • Routeing Charts
  • Electronic Charts
• Current


  Ocean currents result from a dynamic interplay of wind, temperature, salinity, topography, and Earth's rotation
• Tide


  Rising and falling water, caused by gravitational forces exerted by the moon and the sun
• Tidal Stream


  Horizontal movement of water caused by tidal currents
• Estimated Position


  Provides a more accurate approximation than simple dead reckoning
• Running Fix


  Combines an estimated position with bearings, making it more accurate than E.P. alone
• Dead Reckoning


  Advancing a known position for courses and distance
• VDR


  A Voyage Data Recorder is a crucial data recording system installed on vessels to comply with the IMO
• Echo Sounder


  Primarily measures water depth and provides indirect clues about the ship's position
• Doppler Log


  A vital instrument used on ships to measure the relative speed of the ship with respect to water
• Types of Nautical Chart

  • Small Scale Chart – 1:1,000,000 or 1:10,000,000
  • Large Scale Chart – 1:80,000 or even over 1:1,000,000
• Pilot Charts

  Depict winds, precipitation, temperature, wave heights, visibility, barometric pressure, and sea surface temperatures
• Wind Patterns


  • Illustrate prevailing wind directions and speeds
• Ocean Currents


  • Show information about ocean currents
  • SET - direction of the current in degrees
  • DRIFT - speed of the current, in knots
• 1 NM = 1,852 MTRS
• 1 NM = 10 CABLES
• Partially Submerged Wreck


  • Fish - Bone Symbols
• Submerged Rock


  • Plus Sign
  • Asterisk - signifies a rock that uncovers at low tide
• Coral reefs


  Indicated by the abbreviation "Co"
• Breaker


  Waves breaking over a shallow seabed, posing a danger to small boats and causing potential loss of control
• Obstruction


  Any unknown hazard lying beneath the surface, such as submerged rocks, wrecks, or debris
• Lighthouse Symbol

  A black dot with a magenta "flare," serving as a navigational aid for mariners
• Current Arrow

  Represent the speed and direction of ocean currents, providing crucial information for safe navigation
• Nominal Range


  The estimated maximum distance at which a specific navigational light or signal can be seen, aiding mariners in navigation and safety at sea