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43 Cards in this Set
- Front
- Back
Dead Reckoning
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the process of estimating your ships future position without taking current and wind into effect
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What does Dead Reckoning help determine (6)
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-when to adjust speed
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The 6 rules of Dead Reckoning
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1- at least every hour while in open ocean
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what to use for time-distance-speed calculations (4)
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slide ruler
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3 minute rule
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D=Speed * 100
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6 minute rule
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Distance= Speed/10
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When do you plot a running fix
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when only one nav aid is available
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the intended direction of travel with respect to the Earth
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Track
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the intended speed to be made good when planning a voyage
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Speed of Advance
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the direction from which the current is flowing
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set
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the speed of the current (knots)
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drift
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the direction of the net movement from one point to another
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Course made good
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the net speed based on the distance and time of passage from one point to another
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Speed made good
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Current Triangle
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takes into account set and drift
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To calculate SMG
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Speed= Distance/Time
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To calculate CMG
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-slide ruler between 1st and 2nd fix and see when direction on compass rose
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to calculate set
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DR to 2nd fix
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to calculate drift
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distance between DR and 2nd fix
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Purpose of estimated position
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to estimate a fix when there are no nav aids available
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the distance gained in the ORIGINAL direction the ship was traveling from the point that the rudder was put over to the point when the ship is steady on the new course
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Advance
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the distance gained PERPINDICULAR TO THE ORIGINAL course from the point where the rudder was put over to the point where the ship is steady on the new course
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Transfer
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Advance and Transfer Table
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different for every ship
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transfer during a 180 degree turn
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Tactical Diameter
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the diameter of the approximate circular path that a ship describes if the rudder is kept over indefinatly
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Final Diameter
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parallel to new course
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Slide Bar
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Purpose of the Slide bar
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assists in quickley revising a turn bearing if the vessel is off track just prior to turn
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Steps to plotting Advance and transfer
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1- transfer
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dotted line
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Turn Bearing
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final leg that the ship must follow to arrive at the center of an anchorage
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approach track
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the bearing to a prominent nav aid which is on the same bearing as the approach track (T/M)
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Head Bearing
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radius
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Distance from the hawsepipe to the pelorus
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Swing Circle
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Length of ship + amount of chain veered out
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Drag Circle
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Amount of chain veered out + distance from hawspipe to the pelorus
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A bearing that marks anchor drop point
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Letting go bearing
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If a ships fix is outside the drag circle
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the ship is...
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1200
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1500
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Pre-Anchorage Considerations (6)
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-water depth
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Accurate method for designating anchorages
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bearing and range to a nav aid
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Less accurate method for designating anchorages
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latitude and longitude
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Post-Anchorage Considerations (4)
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-enough anchor chain (5-7 times water depth)
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Is it ideal to head into the wind and current while going to anchor
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YES
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Plotting the anchorage
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1- predict wind/current
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Plotting at anchor
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1- take a fix
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