Written by 2:25 pm Wilderness Navigation Masters

15) Three north & bearings

(Last Updated On: June 7, 2021)

Hello and welcome to this light information lesson of the online course Wilderness Navigation Masters, where you will be introduced to some little information that will be useful in the next lessons.

You will learn:

There are three things that I want you to learn in this lesson :

  • The first thing, what are these three north (geographic north, magnetic north, and the grid north)?
  • What is bearing?
  • How to measure a bearing?

Yes, just this little three pieces of information.

 

Geographic north vs magnetic north:

So, first thing first, what are these three north?

When we were little, they teach us that the magnetic needle of a compass points to the north of the map, which is not always true.

Why?

Because there are 2 north, the geographic north, and the magnetic north.

The difference between the two is that the magnetic north is what our compass magnetic needlepoint to, and the geographic north is what we will found if we follow one of the meridian lines going up.

And they are not in the same spot.

This is an illustration that will help you to understand that.

So, when we have a compass on our hand and the magnetic need point to the north, this is really where he points. 

Credit: sofar.co.za

Magnetic declination:

And if you see, between the two norths there is an angle, this angle is what we call, the magnetic declination.

 

Because the magnetic north always keeps changing position due to the changes in the earth’s magnetic field, the magnetic declination also changes.

For that, the map makers put date on maps.

And every place on earth has a different magnetic declination, that is printed also on the topographic map.   

Grid north:

But what about the grid north?

The grid north is the north of the grid that we see on a topographic map.

Even the grid north looks like it’s in the same direction as the geographic north, it’s not exactly the same.

The difference exists because the correspondence between a flat map and the round Earth is imperfect.

But, because it’s a very small difference, people ignore that and use the grid north as if it’s the geographic north.

Like I’ve said before, this lesson is just an introduction to different things that we will see in more detail later, there is too much to say but I want to keep things simple.

What is bearing?

In wilderness navigation, a bearing is just an angle between the direction of an object and another object. It’s what helps us to know in which direction something is.

Before I go on to show you how to measure a bearing, I want you to know that a bearing on a map is always measured clockwise from the geographic north.

Now that we’ve seen what is the geographic north, the magnetic north, the grid north, and the magnetic declination, let’s see how to measure a bearing on a map.

 

How to measure a bearing (skip to 3:04):

Show video transcript
  • In this example, we will measure the bearing from this point A to this point B.
  • As I’ve said before, we start measuring a bearing always from the geographic north, and to do that, we have to mark a north line on at the first point, which is A.
  • The second thing we have to do is to draw the line connecting point A to point B.
  • Then, measure the angle clockwise from the north line to point B.
  • To do that, put your protractor over the north line with 0° at the top, and measure the angle to point B.
  • And remember to always give the answer in the correct order.
  • In this case, it’s a bearing from point A to point B, and not from point B to point A. Because, the bearing of the opposite order, is totally different.
  • Now you know how to measure a bearing on a topographic map.

 

Question #1

You are at point A, and you want to go to point B then C. You will be going :

  • A– North, then Northeast.
  • B– South, then Southwest.
  • C– South, then Northeast.
  • D– None of the above.
Show answers

The correct answer is the answer “C” because from point A to B, I think it’s clear that we will be going south. And from point B to C, we will be going Nouth and at the same time East, so it’s Northeast.

 

Question #2

You are at point A, the Pierson Mountain peak is at :

  • A: between 40° and 60°
  • B: exactly at 45°
  • C: exactly at 135°
  • D: exactly at 315°
Show answers

In this question I’ve wanted you to remember that we always measure a bearing clockwise, so even the short bearing between point A and B is anticlockwise, we measure clockwise.

And when you go this way, you will found that from point A, point B, it’s a bearing of 315°.

That’s all for this lesson, I hope you start seeing how we measure a bearing on a map.

Don’t forget to let us know in the comments section below if you get question #2 correct easily.

Thank you and see you in the next lesson.

Last modified: June 7, 2021

Close