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Old 10-15-2006
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Reciprocal Bearings

Thank you all for your responses. My question has been answered, specially by the notion where, if you had to give someone your position, you would indicate the direction FROM a particular object.
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Old 10-15-2006
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Reciprocal bearings

Do you always contribute nothing? It's easy to be critical, but not so easy to contribute with valid thoughts. If you read my question, I did say I understood the reciprocal bearings. I simply asked for valid reasons for them from other people. It was not an idle thought or something not thunk (sic) through, as you imply.

Originally Posted by btrayfors
I find the whole discussion silly (notwithstanding the serious and excellent responses).

Asking why reciprocals are important is like asking, "Gee, if I know my way TO the grocery store, why should I be concerned with the way FROM the grocery store?".


Or, maybe just an idle thought, not thunk thru :-)

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Old 10-19-2006
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Interestingly I had the same question as you. I have taught land navigation in a military environment, but I haven't "plotted" on a chart in a long time. So I was walking around wondering why the need for a reciprocal; and then the proverbial light bulb went off.

In land navigation using map and compass, you don't have those nifty rolling rulers, walking rulers, or what have you to carry the course from the compass rose over to the sighted bearing. Usually you are just using a standard ruler so you need the reciprocal from the church steeple. With boating charts, you can carry the the steeple angle over from the compass rose to the the church steeple and with at least one other bearing your good to go. If you have radar, you may not need another bearing if you can get a hit off the church; the church will give you distance down your bearing line, and that is all you need.

A reciprocal on a course is handy if you go out into an area that is fog prone, like BC Coastal areas in the fall. So if you are leaving an area, you might take reciprocals so you can get back if fog should roll in at an inopportune time. Remember the reciprocal bearing isn't enough as you might have to take wind, current and tide into account as well.
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Old 10-19-2006
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Much less silly

I can imagine a situation where knowing a reciprocal bearing could be very useful. You're sailing along happily one night and suddenly the radio crackles: "Vessel bearing 095 degrees True, vessel bearing 095 degrees True. This is the USS Delaney. You are standing into danger. Repeat: You are standing into danger. Alter course immediately to avoid collision."

You would know to take the reciprocal of 95 degrees -- 275 degrees -- and look in THAT direction to see if the Delaney was closing in on you at 45 or 50 knots. Hopefully, you'd also be aware of what the local variation was between Magnetic and True headings and take that into account too. If there's nothing coming at you from that direction, the Delany is talking to someone else. Hope they know their reciprocals. It wouldn't have to be something moving four times as fast as you to warrant attention, either. If I got the same message from a freighter or a Tug & barge, knowing I'd checked the right reciprocal bearing would help me feel a lot calmer as I continued along. Not to say I wouldn't try calling up the boat that was announcing the warning as well, to get a better idea of where they actually were, but you don't always get an answer back.
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