Bearings & Relative Bearings
One Line — Three Numbers
A bearing is nothing more than an angle measured CLOCKWISE from a reference direction to a line. The line between an aircraft and a ground station never changes. What changes is the reference you measure it from: True North, Magnetic North, or the aircraft's own nose. Every bearing mistake in navigation is a reference mistake.
Learning objectives
By the end of this chapter, you should be able to:
- 01Define a bearing as a clockwise angle measured from a stated reference.
- 02Distinguish True, Magnetic and Relative bearings on the same physical line.
- 03Apply signed variation to convert True ↔ Magnetic in either direction.
- 04Use RB = Bearing − Heading and Bearing = Heading + RB with confidence.
- 05Convert between bearings TO and FROM a station using the reciprocal rule.
- 06Interpret QDM and QDR correctly and relate them to relative bearing.
- 07Separate heading from track, and explain wind correction angle and drift.
- 08Plot a magnetic bearing correctly on a VFR chart and fix a position from two bearings.
Introduction and learning objectives
Bearings look trivial until a question mixes references. Build the habit now: before any calculation, name the reference.
BEARING: the angle measured CLOCKWISE from a stated reference direction to the line joining the observer to the object. Always three digits, always with its reference: 045°T, 045°M, 045°R.
A bearing without its reference is meaningless. Write 045°T, 045°M or 045°R — never just 045.
The three references
There are only three directions a bearing can be measured from in general navigation. Learn them as a set and the rest of the chapter is bookkeeping.
True bearing (°T)
True North — the direction of the geographic North Pole along the local meridian
The reference used on charts, because meridians are drawn on the chart. Everything you plot must end up in True.
Magnetic bearing (°M)
Magnetic North — the direction the compass points at that location
The reference used in the cockpit, because the compass and the VOR/ADF display work in magnetic. Related to True by variation.
Relative bearing (°R)
The aircraft's longitudinal axis — the nose
The reference used by the ADF needle. It changes whenever the aircraft turns, even if the station stays exactly where it is. Never apply variation to it.
Interactive educational diagram
The three references
Toggle each reference on and off. The aircraft and the station never move — only the reference you are measuring from.
Same station — different references
The single most important animation in this chapter. Nothing moves except the reference of the measurement.
Interactive educational diagram
Same station — different references
Watch the station line stay perfectly still while the reference of the measurement changes.
One aircraft, one station, one physical line between them. So far there is no number — only geometry.
Master bearing visualiser
Everything in one diagram: heading, variation, station position and all five readings driven by the same state.
Interactive educational diagram
Master bearing visualiser
Drag the station anywhere around the aircraft, drag the ROT handle to turn the aircraft, and move the variation slider. Every arc starts at its own reference: blue at True North, red at Magnetic North, amber at the nose.
TH (from True North)
060°T
MH (from Mag North)
055°M
RB (from nose)
060°R
TB TO station
120°T
MB TO station
115°M
TB FROM station
300°T
MB FROM station
295°M
QDM (mag TO)
115°
QDR (mag FROM)
295°
Variation (signed)
5°E
Check MH + RB
115°M
Check TH + RB
120°T
True and Magnetic — variation
Variation is the angle between True North and Magnetic North. It moves neither aircraft nor station — only the north you measure from.
True → Magnetic
Magnetic = True − Variation (East positive)
East subtract, West add
TB 090°T with VAR 6°E → MB 084°M. TB 090°T with VAR 6°W → MB 096°M.
Magnetic → True
True = Magnetic + Variation (East positive)
East add, West subtract
MB 084°M with VAR 6°E → TB 090°T. MB 096°M with VAR 6°W → TB 090°T.
Relative bearing
RB = Bearing − Heading / Bearing = Heading + RB
Same north reference on both sides of the equation
MH 030°M, RB 040°R → MB 070°M. Never convert the RB itself.
Reciprocal
FROM = TO ± 180°
Under 180 add, over 180 subtract
TB TO 070° → TB FROM 250°. QDM 250° → QDR 070°.
Relative bearing
Relative bearing is measured from the nose, so it is never corrected for variation. Turn the aircraft and it changes; the station has not moved.
Interactive educational diagram
Relative bearing and the ADF needle
Change the heading and watch the compass card turn under a fixed aircraft, exactly as the instrument behaves. The needle keeps pointing at the station.
Heading
045°M
Relative bearing
060°R
Magnetic bearing
105°M
Position
ahead-right
Bearing = Heading + RB, both in the same north reference. The relative bearing itself is never corrected for variation — it is measured from the nose.
TO, FROM and reciprocals
One physical line, two legitimate readings that differ by exactly 180°. Read the question carefully: TO or FROM?
Interactive educational diagram
TO / FROM and the reciprocal rule
Only one line exists between the aircraft and the station. Switch which end you read it from and the number changes by exactly 180°.
True bearing TO
070°T
True bearing FROM
250°T
QDM (mag TO)
070°
QDR (mag FROM)
250°
QDM and QDR
The radio-navigation labels for the same two numbers: QDM is magnetic TO the station, QDR is magnetic FROM it.
QDM
The MAGNETIC bearing TO the station. Fly the QDM with no wind and you home to the station. QDM = Magnetic heading + Relative bearing.
QDR
The MAGNETIC bearing FROM the station — the VOR radial the aircraft sits on. QDR = QDM ± 180°, and it is the value you plot outwards from the station.
Heading versus track
Heading is where the nose points, track is where the aircraft actually goes. Wind, not bearing arithmetic, separates them.
Interactive educational diagram
Heading versus track
Set a required track, then apply a wind correction angle and watch the nose move away from the ground path.
Heading = Track + WCA. The aircraft points into the wind so that the resulting ground path stays on the required track. A bearing taken from this aircraft is unaffected by the wind — it still depends only on where the aircraft is and which reference you measure from.
VFR chart plotting
Plotting is where all of the above finally has to be right at the same time: convert to True, take the reciprocal, draw FROM the station.
Interactive educational diagram
Position fix from two bearings
Drag either bearing line, then toggle the two plotting rules to see how a wrong reference throws the fix out.
ALPHA QDM
050°M
ALPHA QDR
230°M
ALPHA plotted
226°T
BRAVO plotted
126°T
Plotting rule: take the magnetic bearing read in the aircraft, apply variation to make it TRUE, take the reciprocal so the line runs FROM the station, and draw it against the chart meridian. Turn either switch off and watch the fix jump to a completely different position.
Common errors
Almost every lost mark in this topic is one of the following six mistakes.
Applying variation to a relative bearing
Relative bearing is measured from the nose, not from any north. Convert the heading, add the RB afterwards.
Getting the sign of variation backwards
Work with signed variation — East positive, West negative — and use Magnetic = True − Variation. The mnemonic is only a shortcut.
Answering TO when the question asked FROM
Underline TO or FROM in the question before calculating. A perfect answer 180° out scores zero.
Plotting a magnetic bearing straight onto the chart
Charts are drawn to True North. Convert to True first, otherwise the fix is displaced by the whole variation.
Plotting the bearing TO the station instead of FROM it
A line drawn from the station must use the QDR. Drawing the QDM from the station puts the aircraft on the far side.
Confusing heading with track
With any crosswind the nose and the ground path differ by the wind correction angle. Bearings are not affected by wind — the aircraft's position is.
Knowledge check
Twenty questions covering every reference, conversion and plotting rule in this chapter.
Question 1 of 20 · Multiple choice
Definition
0/20
Chapter summary
- 1Name the reference before you calculate: True North, Magnetic North or the nose.
- 2Signed variation: East positive, West negative. Magnetic = True − Variation.
- 3RB is measured from the nose. Bearing = Heading + RB, in the heading's own reference.
- 4TO and FROM differ by exactly 180°. QDM is magnetic TO, QDR is magnetic FROM.
- 5Heading is where the nose points; track is where the aircraft goes. WCA is the difference.
- 6To plot: convert to True, take the reciprocal, draw FROM the station against the meridian.
Every bearing question is the same question: which reference, and which end of the line? Answer those two and the arithmetic is trivial.
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Work through the remaining sections and score at least 75% on the knowledge check, then mark the chapter complete.
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