Seamanship_Secrets_185_Tips_-_Techniques_for_Better_Navigation-_Cruise_Planning-_and_Boat_Handling_Under_Power_or_Sail_(Re)_e..

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88 seamanship secrets


squiggles. To find the depth of any curve, look along the line or circle for a
bold number. This indicates the depth anywhere along the curve.
Plot your trackline across these contour lines. For circular contours, plot
dead reckoning positions at the entry and exit points. Set up waypoints in the
GPS or chart plotter at both positions. Correct your fathometer reading to mean
lower low water (MLLW) and compare it with the GPS. Do they agree?


Magic Boat Markers for Distance Off


Th e bow-beam bearing gives great position information using just one object.
Sight a charted object when it’s 45 degrees off your bow to port or starboard.
Note the time of the bearing, then hold a steady course and speed until the
object draws abeam, or 90 degrees off your bow. Your distance off the object
when it’s abeam equals the distance run between the two bearings, and that
distance run is equal to speed multiplied by elapsed time (see Chapter 3).
Before you leave the dock, set up your boat to do most of the work for
you. Follow these two simple steps:



  1. Sit or stand at your normal helm position. Using your handbearing compass,
    sight directly down the centerline of your boat, aiming at the headstay or
    bow pulpit. Write down that centerline bearing, then calculate the bearings
    45 degrees on either side of it. Write down both of these bearings.

  2. Now sight over the handbearing compass at the bow once again, making
    sure it’s aligned to the original centerline bearing. Th en slowly rotate the
    compass to each of the bearings 45 degrees from the bow. What part of
    your boat do you see superimposed in the compass sight at each of these
    bearings? Th e upper shroud? A lifeline stanchion? An aft corner of the
    coachroof? Mark those points port and starboard and you’re done!


When crossing a circular contour curve, set up a GPS waypoint at the entry and exit points.

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