NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: DR vs EP vs MPP vs Fix vs Running fix
From: Ken Gebhart
Date: 2002 Feb 1, 19:00 -0600
From: Ken Gebhart
Date: 2002 Feb 1, 19:00 -0600
Gentlemen, This has been a most interesting thread of discussion. I had no idea that so many were (or had been) involved in air navigation. I was a U.S. Navy Patrol Plane pilot in the early sixties. In those days we had no navigators, so the youngest pilot had to do that chore. I had several thousand hours navigating all over the Pacific with only celestial and a drift meter. I later got an FAA Flight Navigator License. This discussion has been a wonderful recollection of all the terms and concepts of navigation with which I was intimately familiar. So, the disparity in terms got my attention. My 1966 edition of Bowditch has discussions and definitions for course, track, etc for both air and marine navigation. The book actually makes the distinction between the two, and acknowledges that some definitions are in fact different, as has been discussed here. Lastly, in reply to Sherman's poll - certainly a DR is the best possible reckoning of where a vessel will be at a given time, using all possible information. It is the position to which a rescue vessel will proceed if you need help. You would not want to omit any pertinent information in calculating it. Ken Gebhart Jared Sherman wrote: > Chuck - and all- > <"The DR position is only an approximate position because it does not allow > for the effect of leeway, current, > > Is there anyone here who would "reckon" their position without attemping to factor in ALL known effects? If one is plotting a DR position while crossing the Gulf Stream, even without knowing the current, is there anyone who would not indicate *some* offset as a best guess of the current, since they approximate current direction and speed are almost certain to exist to some extent? > > I ask this as a poll, not as an arguement. My understanding of DR, the good Mr. Bowditch aside, was that a navigator placed EVERYTHING he could into the DR position and that it was supposed to include all "guestimates" of where you actually were, not just ignoring the ones you couldn't specify to five decimal places.
