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    Re: DR navigation in the recreatiional fleet: was Role of CN at s ea
    From: UNK
    Date: 2004 Oct 13, 11:32 -0400

    On Oct 13, 2004 6:33 AM, Jim Thompson  asked about
    teaching traditional techniques to beginners with electronic-only
    David Weilacher  wisely suggested one try to
    scare one's students a bit by pointing out that GPS units (or the batteries
    they rely on) do die; waypoints can be mis-entered; rhumb lines can pass
    through nasty patches.
    I have introduced a few friends to coastal navigation since the arrival of
    easy-to-use Loran-C and GPS. Few have shown any interest in performing DR
    underway. However, I have always gotten them to agree that a non-trivial
    passage calls for non-trivial planning. I have gotten them to learn basic
    chart work, enough to be able to lay out buoy-to-buoy tracks and to measure
    the resulting courses and distances; plus the ability to take off the
    lat/lon of a charted object or plot a GPS position. I figure if they can do
    this much, they are not completely unarmed.
    The next hurdle is to get them to actually compare the GPS readout to their
    intentions. One way to do this is to get them to compare the GPS's
    bearing-and-distance-to-waypoint to the track they've laid out on the chart,
    and to ponder if they agree sufficiently -- and if not, why not.
    An alternative to plotting position from lat/lon is to take the GPS's
    distance-to-waypoint and off-track readouts to plot their position on or
    near the charted track. It doesn't require access to the chart's longitude
    scale and works better on folded charts in tight spaces.
    Finally, I try to get them to do something I always do: when plotting your
    position (GPS, DR, EP, whatever), always extend a course line from it to see
    what you're about to get into.
    The hardest part is getting them into a routine; getting them to write stuff
    down (notebook or chart); getting them to look ahead.
    (Well, actually the hardest part is making beginners understand compass
    deviation; to measure it; to correct it as much as possible; to allow for
    it. but that's another battle.)
     -- Peter

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