## Using your Compass with a Map - North Reference Exercises

A few north reference conversions for you to try.

This video presents 5 north reference conversion problems for you to solve. Each problem will state the conversion to be preformed and provide a declination digram to use. If you want to solve the problem on your own, pause the video, do the conversion, and then continue playing the video to see the solution. The problems will explore different combinations of Grid and Magnetic North on either side of True North. They will also get a bit trickier as they progress. Once you feel that you have the hang of this, I’d suggest you dig out a map of your local area and try a few north reference conversions using your declination values.

Problem 1

Convert a bearing of 285° Grid to a Magnetic bearing.

Remember, when you are working with the declination diagram, bearings increase in a clockwise direction.

Magnetic North is 16 degrees East of True North. Grid North is 1.5 degrees East of True North.

The angle between Grid North and Magnetic North is the 16 degrees from Magnetic to True, less the 1.5 degrees from True to Grid, or 14 and a half degrees. Let’s round that up to 15 degrees.

Now draw the 285° Grid bearing onto the diagram. Start at Grid North and go in a clockwise direction.

The answer we are seeking is the angle from Magnetic North to the target.

In this case the Magnetic bearing we are seeking is smaller than the Grid bearing we were given.

So we subtract 15° from the 285° Grid value to get the answer of 270° Magnetic.

Now lets make our short cut rules for this situation.

Problem 2

Convert a bearing of 67° Magnetic to a True bearing.

Magnetic North is 12 degrees West of True North. Grid North is 1 degree 42 minutes West of True North.

The angle between True North and Magnetic North is 12 degrees.

Draw the 67° Magnetic bearing onto the diagram.

The answer we are seeking is the angle from True North to the target.

In this case the True bearing we are seeking is smaller than the Magnetic bearing we were given.

So we subtract the 12° difference from the 67° Magnetic value to get the answer of 55° True.

Problem 3

Convert a bearing of 108° Grid to a Magnetic bearing.

Magnetic North is 9 degrees East of True North. Grid North is 25 minutes East of True North.

The angle between Grid North and Magnetic North is the 9 degrees from Magnetic to True, less the 25’ minutes from True to Grid. That would be 8 degrees 35 minutes, which we’ll round up to 9°.

Draw the 108° Grid bearing onto the diagram.

The answer we are seeking is the angle from Magnetic North to the target.

In this case the Magnetic bearing we are seeking is smaller than the Grid bearing we were given.

So we subtract the 9° from the 108° Grid value to get the answer of 99° Magnetic.

Problem 4

Convert a bearing of 11° Grid to a Magnetic bearing.

Magnetic North is 18 degrees East of True North. Grid North is 1 degree 15 minutes East of True North.

The angle between Grid North and Magnetic North is the 18 degrees from Magnetic to True, less the 1° 15’ from True to Grid. That would be 16° 45’, which we’ll round up to 17°.

Draw the 11° Grid bearing onto the diagram.

The answer we are seeking is the angle from Magnetic North to the target. Remember the angle need to go clockwise from Magnetic North to the target bering.

In this case the Magnetic bearing we are seeking is smaller than the Grid bearing we were given.

So we subtract the 17° from the 11° Grid value. This gives us a result of minus 6 degrees. Bearings need to be given in terms of a 0 to 360 degree circle. So add 360° to the -6° to get the answer of 354° Magnetic.

Problem 5

Convert a bearing of 350° Magnetic to a Grid bearing.

Magnetic North is 14 degrees East of True North. Grid North is 1 degree 45 minutes West of True North.

The angle between Grid North and Magnetic North is the 14 degrees from Magnetic to True, plus the 1° 45’ from True to Grid. That would be 15° 45’, which we’ll round up to 16°.

Draw the 350° Magnetic bearing onto the diagram.

The answer we are seeking is the angle from Grid North to the target.

In this case the Grid bearing we are seeking is larger than the Magnetic bearing we were given.

So we add the 16° to the 350° Grid value. This gives us a result of 366 degrees. Bearings need to be given in terms of a 0 to 360 degree circle. So subtract 360° from the 366° to get the answer of 6° Magnetic.