RE: [Paddlewise] Dead Reckoning Accuracy

Since visibility may be poor due to fog or just your closeness to shore, #6
is extremely valuable. I've used for hiking off trail in relatively thick
woods, and several times in a kayak as well, including thick fog. Its very
frustrating to arrive at a "line" (shoreline, reef line, trail, etc) and not
know which way to turn.
In some visibility and/or terrain situations, if you are off by as little as
a few hundred meters you'll be forced to make a guess with only a 50:50
chance of getting it right. A few hundred meters could turn into miles.
The key to working it out in advance is deliberately plotting a course to
one side of your destination, such that with reasonably expected errors you
are guaranteed to miss in that direction ONLY. This all depends on having
some "line" that you know you have reached, so that you can turn in the
proper direction. If it's a shoreline or some other "line" that can't be
missed it's a piece of cake. 
Obviously, it's also important that the consequences of a miss to one side
are tolerable. If you're shooting for a very small island in the middle of a
very big ocean after a very long leg, this may not be the case.
I have read of using time, estimated paddling speed, current, and wind
effect to make a stopping point (Standard dedrec waypoint). Then paddling
increasing diameter circles until dryland is spotted. That may work well in
an environment with little wind or current, but I'd probably turn on my GPS
anyway if I couldn't spot land by reaching the waypoint.
I'm sure there are some salty island hoppers on the list that have actually
worked this scenario out for real without benefit of GPS. Any island I have
paddled to in low visibility was too close and too big to miss entirely.

Steve Brown
 

-----Original Message-----

G'Day Steve,

........
1. Select bearings which were likely to be clearly defined i.e large objects
such as points, light houses, water towers,  with high contrast in the line
of sight. A point covered in trees against a backdrop of a coast covered in
trees was one of the poor selections I made, it was almost invisible in
fact.
2. Take a hard surface on which to put the map for plotting bearings, if
possible do most of the plotting in advance at home
3. Use a portland square rather than protractor and setsquare.
4. If using laminated maps take a fine water proof pen (and some alcohol as
an erasor).
5. The theory looked easy, putting it into practice on the water was hard.
6. Work out in advance which direction to paddle if bearings aren't quite
right.
......

All the best, Peter
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