Written by 3:52 pm Wilderness Navigation Masters

24) Match your map to the terrain using bearings

Reading Time: 6 minutes(Last Updated On: June 7, 2021)

Let’s imagine this scenario.

You are hiking following a trail on your map, and unexpectedly you found a trail intersection in front of you that you don’t have on your map.

This can happen to you even if your map is just 2 years old.

So, which one of the trails is the one that you see on your map?

After you finish watching this lesson, you know how to answer this question.

Hello and welcome this lesson of the online course Wilderness Navigation Masters, where you will learn how to match your map to the terrain using bearings.

Saying that, means if I see a landmark in the real world I can pinpoint it on my map and vise versa.

Why should I match my map to the terrain using bearings:

You may ask me, but why should I match my map to the terrain using bearings, if I already know how to do it without bearings.

This is a good question.

You have to know how to do it using bearings because it’s more accurate.

Now that you see the importance of knowing how to match your map to the terrain using bearings, let’s start with how to take a bearing of a point landmark from your map and sight it on the terrain.

 

Take a bearing on your map and sight it on the terrain :

Taking a bearing from your map and sight it on the terrain is useful when we see a landmark on our map, but we don’t know in which direction he is in the real world.

To take a bearing from your map, you should have a north-south line to measure the angle between the geographic north and your point.

If you have a map like this, where the UTM grid north is the same as the geographic north, because the declination diagram doesn’t mention that there is an angle between the two, 

you can use the UTM grid to get this north-south line.

If you don’t, I mean, there is an angle between the UTM grid north and the geographic north, you can draw a parallel line to the edge of your map.

[Skip the video below to 1:58]

SHOW TRANSCRIPT

Now that you have your north-south line. In my case, I will use this blue UTM grid. Let’s say that I am here, at this point of the CDT, and I want to take the bearing to this trail intersection.

Step 1: draw a line that intersects with both, your place, and this landmark point.

Step 2: align the edge of your compass with this line, making sure that the direction of the travel arrow point to this landmark and not this opposite.

Step 3: turn the housing till the orienting lines are up and parallel to one of the north-south lines on your map.

Step 4: you can read the bearing to this landmark at the intersection of the dial with graduations and the direction of the travel arrow. And in this case, it’s a bearing of around 80°.

Now, you can sight this landmark by shooting this bearing of 80°.

If you have a negligible declination, take your compass at your waist to keep it level, and turn yourself till the magnetic needle sits in the orienting arrow.

And, if you have a declination of 20° like me, adjust for it by sitting the magnetic needle in the new black mark and not the orienting arrow.

So, from this bearing, I know that this trail intersection in the map is in this direction.

If you didn’t understand what we’ve just done.

  • We measured this angle between geographic north and this trail intersection on our map.
  • And because when we align our map compass edge to the line that intersects with both our position and the landmark, this north-south line is parallel to these orienting arrows, and this line to our landmark is parallel to the direction of the travel arrow.
  • So this angle equals this angle.
  • And, because this angle is between the geographic north line and the landmark and not the magnetic north and the landmark, when you sight this bearing you should adjust the declination.

I hope it’s clear for you.

Take a bearing on the terrain and sight it on the map

Taking a bearing on the terrain and sight it on your mao is helpful when you see a landmark in front of you but you want to know where is it on your map.

[Skip video to 4:23]

SHOW TRANSCRIPT

To do that :

Step 1: Aim at your landmark with the direction of the travel arrow.

Step 2: if you have a negligible declination, turn the housing till the magnetic needle sits in the orienting arrow, if you have a declination of 20° marked on the back of your compass like me, turn the housing till the magnetic needle sits in this declination new black mark.

Step 3: read the bearing value on the graduations at the intersection with the direction-of-travel arrow.

Let’s say you get a bearing of 200°.

Go on your map and draw a north-south line as we’ve seen before.

Align the edge of your compass with the point of your position on the map, and turn your compass base plate and not the housing, till the orienting lines are parallel to one of your north-south lines.

After that, your landmark should be on this line.

First question:

Till now, I still didn’t show you how to answer our first question of, if we are walking following a trail on your map, and suddenly you found a trail intersection in front of you that you don’t have on your map, how to know which one of them is the one on your map?

To answer this question, I should show you how to match your map to the terrain using bearings for linear landmarks.

  • Step 1: try to pinpoint exactly where you are on your map.
  • Step 2: Measure the angle between the geographic north and the general direction of this trail to get a bearing.
  • Step 3: Shoot this bearing on the field, and now the direction of travel arrow point at one of your two trails in front of you, and this trail is the one on your map.

This technique of matching your map to the terrain using bearings can also help you to pinpoint exactly your location on your trail when you know that you may found two intermittent creeks on your way.

Because the bearing of this intermittent creek will be something below 90°, and the bearing for the other intermittent creek audience between 30° and 40°, when you arrive at an intermittent creek and you want to know which one of them you are at to locate yourself exactly on your map, take a bearing of the intermittent creek you found, and from the bearing, you can know if you are here or here.

Now let’s go to see the exercise of this lesson.

 

EXERCISE

Exercise

In this exercise, I want you to go outdoor to an area you are familiar with, with a topo map of this place.

Locate yourself on your map.

Take the bearing of a landmark on your map.

Shoot the bearing of this landmark and try to found it on the field.

 

Besides the exercise, I want you to practice what you learned in this lesson because it’s the base for what we gonna see in the next ones.

If you didn’t understand something, do not forget that you can leave me a comment in the comments section below.

Thank you and see you in the next lesson.

Last modified: June 7, 2021

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