Mondays 04/19/2010 Question and boating safety tip. Answered

[CaptainScott]

Safety Tip
Know your compass.
You might ask Why? Here are two real world examples as to what has happened to me and why you need to know your compass heading.
On late evening my bride and I took Destiny to Langly to spend the night. It was dead calm so the iron lung was moving us along nicely.
We had to get back the next day early and I was curious as to what the weather would be. So on came the VHF. Hmm. Heavy fog for the AM. Bummer.
I took a compass bearing between Everett and Hat Island. Hat is a small Island directly between Everett and Langly. After rounding the island I took another compass bearing from Hat to Langly. Sure enough the next morning we were socked in in thick fog. Getting home was easy! I simply headed Destiny out 180 degrees off the Hat-Langly bearing. We motored along at 2 knots until Hat ISland came into view. After rounding the island I again headed out 180 degrees off the Hat-Everett bearing! As the fog lifted we could clearly see we were nicely on course to Everett! Simple as that!

Another time we were crossing Boundry pass between San Jaun Islands and the Canadian Gulf Islands. If you've never been there it can be extremely dissorienting! Every island looks the same as the next! I went below for about 5 minutes leaving the helm to my crew. My crew spied what they thought was whales and changed the heading to get closer. Nope no whales so the crew set the heading back on its original coarse. I came up aware of the coarse changes and asked what was up. After the explaination I started looking around and found myself very disoriented! What the . . . is going on? I quickly took a bearing off the bow and found we were 60 degrees off course! In just a few minutes of inattention we were literally headed towards submerged rocks! WOW!

The simple act of watching a compass can save you. Get used to looking at it. Do it in nice clear warm wonderfull weather! That way when you DO need it you are confident in how to use it!



Question:
Match the following terms to the defintions:


1) Magnetic Deviation
2) Magnetic Variation
3) True Heading
4) Magnetic heading



A) The error induced in a compass by local magnetic fields
B) Heading relative to true North
C) Heading with corrections for Magnetic Deviation and Magnetic Variation
D) The angle between True North and Magnetic North

[Capt. Bondo]

Wow, need to think on this one. I usually don't go this deep when teaching the Boy Scout Compass skills... their eyes glaze over

I'm going to go with...
1=A
2=D
3=C
4=B

[Alanhod]

Well lets see what I remember correctly this week.

1) Magnetic Deviation = A) The error induced in a compass by local magnetic fields
2) Magnetic Variation = D) The angle between True North and Magnetic North
3) True Heading = C) Heading with corrections for Magnetic Deviation and Magnetic Variation
4) Magnetic heading = B) Heading relative to true North


Thanks
Alan

[Banshi]

D
A
C
B

[CaptainScott]

Answer


1) Magnetic Deviation A)
The error induced in a compass by local magnetic fields.
If you have your compass swung on your boat you will get a compass deviation table. This table should be laminated and kept near your compass!


2) Magnetic Variation D)
The angle between True North and Magnetic North This can be found as a compass rose on NOAA charts
Here is an example:



3) True Heading B)
Heading relative to true North
When plotting your course on a chart you always use true.

4) Magnetic heading C)
Heading with corrections for Magnetic Deviation and Magnetic Variation
This is the heading you would steer by in your boat.