[Rhodes22-list] Magnetic or True? By a famous nautical author... Other th...

[Brad Haslett]

Dave,

Yup, that's about right.  It doesn't matter what electronic device you are
using for guidance, if you are following an electronically generated lubber
line you only need to steer relative to the track.  It doesn't matter what
the variation is at your location or the deviation for your craft, or how
the compass is marked.  It could be a Russian compass and marked in
'potatoes' - if it takes 10 potatoes to the left to hold course it takes 10
potatoes to the left to hold course.  Now when the electronics go kaput, all
bets are off.

Brad

On 4/10/07, DCLewis1 at aol.com <DCLewis1 at aol.com> wrote:
>
>
> Bill and Ed,
>
> I don't think it matters much if I were to try to sail a true heading as
> magnetic, my chart plotting GPS  would straighten me out  quickly.  With a
> chart
> plotting GPS I enter  my destination/way points on the electronic charts
> in
> the GPS unit and  then  I  watch my track evolve in real time as I
> sail.  Of
> course, I always try to start on the right magnetic bearing, since I steer
> via
> compass, but it's not critical at all.  If I'm not headed where I want
> to  be
> headed relative to my desired way point, the plot on my chart plotting GPS
> will tell me immediately and quantitatively.   I can look at the  track
> display
> that's automatically displayed (no transferring plot points)  and
> instantly
> know if my course is too high or low and with that crude info  I can make
> a
> steering adjustment, note the new reading on the compass,  and then hold
> that new
> compass reading.  I  never make the  calculation to go from degT to degM,
> instead I just note I'm off  track and adapt.
>
> As to deviation and variance, I'm not sure it matters when   a compass is
> used with a chart plotting GPS.  The compass becomes a  relative
> instrument that
> is used to hold a heading appropriate to keep on,  or near,  the desired
> trip
> track, that's it.  The numbers on the dial  are just a way to help you
> keep a
> heading - whatever that heading  really is, and that heading is ultimately
> determined by your chart plotting  GPS.  Making progress to the next way
> point is
> what's important, and you  can see that evolve (or not evolve) on the GPS
> display.  Steering  accurately by compass, as per John Vigor, is now
> besides the
> point - I use  the compass to hold a bearing that will keep me on my
> desired
> track (or get me  back to my desired track) and that track is monitored
> accurately in real time by  my chart plotting GPS.
>
> And all of the above is accomplished without keeping my head
> down  navigating
> via GPS because the chart plotting GPS unit does all of the  calculations
> and
> plotting.  All I have to do is glance at the display  to see that I'm on
> track or off track and if I'm off track what I have to do to  get back on
> track.
> If I want to know quantitatively how far off-track I  am, speed, or
> whatever,
> I have to change the display page - but that's pretty  quick & simple.
>
> And with GPS I always know where I am (Lat/Lon) much better than the
> paper-plotters.  I don't think there's any question about that.
>
> Of course we should always know how to fall back to paper and pencil,  but
> I
> think that fall back is a long ways back.  I think a chart plotting  GPS
> can
> really be a very useful asset - and it can be an especially useful  asset
> at
> night or in inclement weather (low vs).
>
> Dave
>
>
>
> ************************************** See what's free at
> http://www.aol.com.
> __________________________________________________
> Use Rhodes22-list at rhodes22.org, Help? www.rhodes22.org/list
>