As a Scout Leader, being able to confidently use a compass is table-stakes. I’m currently working on my T1 permit and using a compass is a fundamental part. This post will cover the major aspects of being able to use one:

1. Baseplate compass
2. Orient a map (“Setting the map”)
3. Getting the bearing between two points
   1. On an oriented/set map
   2. On an unoriented map
4. Using Bearings
   1. Taking a bearing and using it
   2. Heading for a bearing
   3. On a map, from a location, head towards a bearing
5. Compensating for difference between magnetic north and grid north
6. Resection/Triangulation to locate yourself on a map

This YouTube video explains a lot of how you can use a baseplate compass to navigate:

Baseplate compass

This guide is based on the versatile baseplate compass, which has a number of features that make navigation easier:

• The compass itself, within a rotating dial (the “bezel”)
• Within the compass, a means of aligning and maintaining a northern bearing represented by an arrow outline (the “orienting arrow”).
• A means of shifting readings to compensate for the difference between grid and true north.
• Measurements to allow gauging of distances on maps of standard scales (eg. 1:25 or 1:50)

This video has some good guidance on various baseplate compasses:

In order to use a compass, it must be held correctly:

• Hold it at waist level, with the Direction of Travel Arrow pointing away from you.
• Keep the baseplate as flat as possible to allow the needle ample opportunity to “track” magnetic north.
• Keep it away from metal and electronic objects, which may interfere with the magnetic reading provided by the needle.

Orient a map (“Setting the map”)

Being confident that your map relates to what you see and, importantly, the direction you’re going is a simple process.

1. Move the bezel to 0°, or magnetic North (assuming no compensation).
2. Place the compass on the map so its straight edges align with the north-south gridlines (“Eastings”)
3. Rotate the map (and compass) until “red” is in its “bed”. The map is now pointing to magnetic north.

Getting the bearing between two points

On an oriented/set map

With a “set map” (that is correctly oriented so Grid North is pointing to Magnetic North), it is possible to take a bearing from Point A to Point B.

1. Set the bezel to 0 degrees (North)
2. On the set map, line up between Points A and B with the edge of the compass or one of the “Parallax lines” (lines on the baseplate) on the baseplate of the compass.
3. Twist the rotary dial so that the red needle is directly above the outline of the needle (known as “putting red in its shed” or “red in its bed”)
4. The number immediately by the Direction of Travel arrow is the bearing required.

On an unoriented map

If the map is not “set” (Grid North is not pointing to Magnetic North), the lines within the bezel are used:

1. Assuming the map has Eastings (the lines running vertically), place the compass baseplate or Parallax lines between two points on the map, making sure that the direction of travel points in the way you’d like to go..
2. Rotate the bezel to line-up the lines within the bezel with the Eastings with the red arrow within the bezel pointing to the top.
3. The number immediately by the Direction of Travel arrow is the bearing required.

This video has an example of two methods, including these two methods:

Using Bearings

Taking a bearing and using it

Useful when you need to head towards a point in the distance such as a landmark but know that you may not be able to see it throughout the journey.

1. With the compass at waist height, point the Direction of Travel Arrow to the item you can see, to which you want to head.
2. Twist the rotary dial so that the red needle is directly above the outline of the needle (known as “putting red in its shed” or “red in its bed”).
3. Take the degrees value immediately by the Direction of Travel Arrow. This is your bearing.
4. Occasionally re-read your compass and ensure that you are still heading into the direction of your Direction of Travel Arrow (which should still be set to your bearing from step 2)

Heading for a bearing

If you already know your bearing or are told to go to a cardinal compass point (eg. “head west”), you can use a slightly modified version of taking a bearing, above.

1. Line up the Direction of Travel Arrow with the bearing or cardinal point on the rotary dial by twisting the dial.
2. Maintaining the compass’ position at waist height, rotate your body until the red needle is in its “bed”.
3. Follow the Direction of Travel Arrow.
4. Periodically stop and ensure “red” is still in its “bed” to make sure you haven’t drifted.

On a map, from a location, head towards a bearing

From a known point on a map, it is possible to head towards a location by getting its bearing from the map and transferring that to “real world” and heading to that bearing.

1. Set the bezel to the bearing or cardinal point required.
2. Align a straight line on the baseplate of the compass (not within the bezel) with your starting point. The starting point can be anywhere in this line. This line is known as a “Parralax line”. (If using the edge of the compass, use the edge that is closest to you to avoid “parallax errors”.)
3. Rotate the baseplate to ensure the lines within the bezel align with the North-South (“Eastings”) gridlines on the map.
4. Head in the direction of the Direction of Travel Arrow.
5. You’ve now got your bearing and no longer need your map, just head for the bearing. Repeat, making sure “red is in its bed”.

Compensating for difference between magnetic north and grid north

Maps are aligned with “grid north”, that is how we understand North to be: the top of the map. Compasses track “magnetic north”, that is the north pole. The north pole of The Earth moves. Ordnance Survey maps identify this difference and if meaningful (more than 5 degrees over a mile), baseplate compasses have declination modifiers within the bezel.

In order to compensate for magnetic vs grid north, locate the declinations on the map. These will typically be in the legend area and be identified by their position on the map (remember the direction of magnetic north changes over distance) and will be identified by the direction of declination, eg. “2° 21′ (41 mils) E” meaning a declination of 2° 21 minutes over 41 miles to the East.

1. Perform the bearing operation as per usual.
2. Using the declination identified on the map, move the entire baseplate to align the compass needle with the declination in the bezel (typically in red)
   • If the direction is East, this subtracts degrees (“East is least”)
   • If the direction is West, this adds degrees (“West is best”)
3. Move the Orienting Arrow to the “new” north position so “red” as back its “bed”

Resection/Triangulation to locate yourself on a map

Knowing your location on a map is imperative to be able to find your way around and out of trouble, but sometimes you lose track. In this case, by creating a virtual triangle, you can find your position on the map.

1. Try and get to a high vantage point from which you can identify landmarks.
2. Orient the map to north.
3. Look at the first landmark, to the east. Then take its bearing (point the compass Direction of Travel Arrow to the landmark, put “red in its bed” and read the bearing)
4. Place the compass on the map and line up the orientation lines by rotating the entire compass (not the bezel) within the bezel to the north-south gridlines and “red” must be in its bed. The edge of the compass gives you your first vertex, which should be drawn on the map.
5. Look at the second landmark, to the west. Take its bearing.
6. Place the compass on the map and line up the orientation lines by rotating the entire compass (not the bezel) within the bezel to the north-south gridlines and “red” must be in its bed. The edge of the compass gives you your second vertex, which should be drawn on the map.
7. Where the two lines intersect is your current position. It is possible to get even more accurate and confident by taking a third bearing and drawing another vertex.