"dead" reckoning is NEVER dead on. It can't be. It is physically impossible.

even guessing for wind and current makes no difference.

now, over the knee, *if* you -- like jeffies before you -- wish to change the
definition to the term to include pilotage, well go ahead. At least you would
be safer should you ever find yourself on the water.

over the knee obviously does not, so let's help out a bit.

Main Entry: de·duce
Pronunciation: di-'düs, dE-; chiefly British -'dyüs
Function: transitive verb
Inflected Form(s): de·duced; de·duc·ing
Etymology: Middle English, from Latin deducere, literally, to lead away,
from
de- + ducere to lead �more at TOW
Date: 15th century
1 : to determine by deduction; specifically : to infer from a general
principle

synonym see INFER
- de·duc·ible /-'d(y)ü-s&-b&l/ adjective

You gotta make up your mind, jax. You were talking about "dead
reckoning" before, the term many use when employing time/direction/speed
only.
"deduced reckoning" applies when allowance is made for wind and current
.... something you say is impossible.
Mayhaps you should go back to the books for some further study.

otn