This whole portion of this thread has come about, due to two simple post:
1. Jax took umbrage with Joe's usage of the term "DR"
2. I told jax he had one definition of the term "DR", but not the only
definition.

If you go to various source materials, you will generally find three
terms being used .... "dead reckoning", "deduced reckoning", and "ded
reckoning".
In general, you will find that all relate to a basic form of navigation
which has been in use for centuries and the differences in definition
and usage of the terms tends to vary from one source material to another
and possibly from earlier additions to newer, one group of mariners to
the next, etc.
It's not really important how *YOU* define or use these 3 terms, as they
are all closely related to the same basic navigation method. All that's
really important is that each individual in the discussion, knows how
the other is applying the 3 different/similar, terms, or if they all
mean the same.
Some people like to keep the whole process limited to
speed/direction/time, while others will introduce winds/currents and a
host of other factors, into the mix.
There is NO, one, correct definition. There are however, a number of
related and sometimes contradictory definitions and to be honest, for
me, you can use which ever one you want .... as soon as I realize yours
may be different than mine, a simple question can get me to talk about
"DR", on the same plane as you are.

EG course, trying to talk to jax on the same plane is like trying to
ride a roller coaster with no restraint mechanism.

Main message: People will use the term "DR" differently .... it's no big
deal.

otn