Magnetic Compass Alignment

[Bill Roosa]

True, magnetic bearing, heading, and course

True and magnetic we all get
bearing is the direction to an object from where you are now can be either T or M
heading is the direction you are pointed in. Can also be either T or M
Course is the direction you are traveling and can be either T or M.

So my BTW (bearing to waypoint) is, say, 100 deg M no mater which way I'm going or pointing
my course needs to be 100 deg M too for me to get to my WPT
I adjust my heading so that current, sideslip etc are accounted for till my course (via GPS no doubt) is 100 deg M

Course this is a motorboat solution as I have NEVER been able to point (for long) at my WPT due to the wind

 

[Witzend]

Scott, the fluxgate from my Raymarine auto pilot provides the heading info for my C90w chart plotter w/gps and represents where the bow is pointed. Even most handhelds have compass functions and will provide heading by where it is pointed.

 

[Ross]

My Garmin 72 gives me direction of travel or distance off course left or right. I can call it up in true or magnetic. The only time my compass agrees with the gps is at slack water at flood or ebb.

 

[Stu Jackson]

http://www.boatus.com/husick/n_hsensor.asp

 

[Witzend]

So what is your point?
Fact "Heading" is where the bow is pointed. Both the compass and the flux gate should be in close agreement if calibrated properly. The flux gate signal is sent to the auto pilot which in turn creates a heading number This number is sent to the chart plotter and displayed as "heading". While this data does not technically coming from the GPS satellite calculations which provide speed and COG, it does get displayed with this other data. My hand held has a compass built in, point it in the direction you want to go and it will tell you your heading.

 

[Stu Jackson]

So what is your point?
Fact "Heading" is where the bow is pointed. Both the compass and the flux gate should be in close agreement if calibrated properly...provide speed and COG, it does get displayed with this other data.

Sorry, just ain't so.

Try reading my earlier post about the river situation.

Where your bow is pointed ain't nothin' like your heading in a sailboat, especially when beating into the wind with leeway.

 

[Todd Smith]

You guys gotta agree on terminology or you will never have a useful discussion.

There seems to be two conflicting definitions of heading here.

1) The direction parallel to the keel of a vessel.
2) The direction in which a ship is moving.

Stu seems to use #2 ( which everybody else calls course ), everybody else seems to use #1.

 

[Ross]

If I am walking sideways down the side walk but facing the street am I on a heading for crossing the street or for continuing down the side walk? I believe that direction of travel and heading are the same.
I can be on a heading that will take me to turkey point but I may have to steer for Red Point to account for the set of the curent.
If I am not underway then the direction that I am pointed may be my heading but since I have no steerage stating my heading is meaningless.

 

[Ross]

Thinking about this a little more if I am on a heading for Red Point but arrive at Turkey Point was my heading in error or was my course in error? I think in this case my heading is my wish but my course is reality. I am confused. Maybe in order to sail to Red Point I have to head for Carpenter point and the set wil take me to Red Point.

 

[Witzend]

The definition of Heading right out of Dutton"s

"Heading of a ship is the direction in which the ship actually points or heads at any particular moment. It is the instantaneous angle which the ship's keel makes with the meridian. Heading is not to be confused with course. A ship is off the course but never off the heading."

We had this argument before Stu.

 

[NancyD]

A sailor with one compass always knows his heading.

A sailor with two compasses is never sure.

 

[Witzend]

Good point, better make sure that one is calibrated.