Chapter 13

Topographical Maps and Map Reading

Visual navigation · Chart symbols and legend · Lost procedure · Visual checkpoints

1. Introduction

Navigation systems are reliable but can fail or degrade. Many light aircraft lack sophisticated avionics. Pilots must develop and maintain visual navigation skills using map, compass, stopwatch, eye and brain. Aeronautical charts depict three fundamental categories:

Relief (Terrain) — elevation and high ground
Other Features — water, woods, roads, railways
Scale — ratio of chart distance to Earth distance

2. Depicting Relief (Terrain)

2.1 Contours

Lines joining all places at the same elevation above MSL. Always confirm whether contours are in feet or metres (stated in the chart margin). Close contours → steep ground; widely spaced → gentle ground.

2.2 Layer Tinting (Colour Gradient)

Different colours for different elevation bands (key given in chart margin). Both contours and layer tinting are based on elevation above MSL — effectively contours with coloured intervals.

2.3 Spot Elevations

Elevations of prominent peaks. The highest spot height is shown on a white rectangle with a black border; its position is listed in the chart margin. Others show a dot with the elevation.

2.4 MEF vs MSA — Critical Distinction

⚠ Do not confuse MEF with MSA — the difference can be fatal

Always check which figure type your chart uses. THE MEF IS NOT A SAFETY ALTITUDE.

Term	Calculation	Used On
MEF (Maximum Elevation Figure)	Highest obstacle + 300 ft for natural features (100 m in Europe); round up to next whole 100 ft. Not a safety altitude.	CAA charts, TPC, ONC
MSA / Grid MORA	MEF + 1000 ft (if <5000 ft) or MEF + 2000 ft (if ≥5000 ft)	Jeppesen charts

MEF Worked Example

TV mast at 1432 ft; hill at 1268 ft.
Hill: 1268 + 300 = 1568 ft (add 300 ft for unknown obstructions on natural features).
1568 > 1432 → dominant obstacle = 1568 ft → round up to 1600 ft.
MEF shown in grid square as 16. If shown as MSA: 1600 + 1000 = 26 (2600 ft).

3. Other Chart Features

Feature	Colour	Notes
Water (sea, lake, river)	Blue	Excellent checkpoints day and night (with moonlight)
Woods / forests	Green	Shapes change with felling/planting; use with care
Roads / motorways	Red	Motorways excellent day and night; junctions are precise checkpoints
Railways	Black	Good in open country; junctions and bridges are precise; not visible at night

4. Chart Scale

Scale = Chart Length ÷ Earth Distance (always expressed with chart length = 1).

Method	Example
Statement in Words	"One inch to ten nautical miles"
Representative Fraction (RF)	1 : 500 000 — 1 cm on chart = 500 000 cm on Earth. "One inch to 10 NM" = 1 : 729 600
Graduated Scale Line	Bar scale at chart bottom in NM, SM, or km. One degree of latitude = 60 NM, so the latitude scale acts as a graduated scale line.

Figure 1 — Graduated scale lines and latitude scale (typical aeronautical chart)

5. Map Reading

Map-to-Ground — read the chart then locate those features visually; used when confident of position near track and on time.
Ground-to-Map — see a ground arrangement, find it on the chart; used when less certain of position.

Plan thoroughly; fly planned heading and time; regain track promptly; maintain lookout; monitor fuel and systems. Do not over-concentrate on navigation.

6. Visual Checkpoints

Select checkpoints approximately every 5–10 minutes. An excellent feature close to track is better than a poor feature exactly on track. Checkpoints do not need to be on track.

6.1 The Four Selection Criteria

Criterion	Guidance
Large	Visible from a distance. Use part of a large feature for precision — e.g. a motorway junction within a city rather than the city itself.
Unique	Not confusable with similar features nearby. Disused airfields in East Anglia are too numerous to rely on alone.
Vertical Extent	Masts and mountains visible at range — very useful at low altitude. Value diminishes at higher altitudes (a 400 ft mast may be invisible at 5000 ft AGL).
Contrast	Must stand out against surroundings. Changes seasonally, by day/night, and in polar/desert regions. At night, features must be lit.

6.2 Typical Checkpoints — Merit Guide

Coastlines — excellent day and night (with moonlight). Sub-features: estuaries, headlands, ports, lighthouses.
Water — lakes, large rivers, canals. Small water features may be hidden by surrounding terrain at low level.
Mountains/Hills — good vertical extent; isolated hills best; valleys identifiable by orientation and associated roads/railways/towns.
Towns — useful position indicators; precise sub-features within town (junctions, railway stations); well-lit at night. Never overfly below 1000 ft AGL (or below safe-glide height).
Motorways/Major Roads — excellent day and night; junctions and service areas are precise; also serve as line features for track/speed checks.
Railways — good in open country; not visible at night; junctions and bridges are precise.
Woods — larger is better; shapes change seasonally (planting, felling) and in snow; use with care.
Other — power stations (range, smoke/steam for wind); quarries (check NOTAMs for blasting); airfields (check active status); lighthouses (distinctive light characteristics at night).

7. Visual Navigation Hazards

Three hazards worth memorising

7.1 Featureless / Whiteout Terrain

In deserts, jungles, tundra or snow fields, features may be absent and charts incomplete. Whiteout: uniform cloud cover + snow horizon = no visible horizon; height and distance impossible to assess visually.

7.2 "Hill-in-Front-of-the-Hill"

In poor contrast conditions, a pilot focuses on distant high ground and plans appropriate clearance, while nearer intervening terrain — masked by poor contrast — has far less clearance margin. Especially dangerous at low altitude over snow.

7.3 Scattered Lights / Night Disorientation

Over dark sea or land with scattered pinpoints of light (ships, rigs, settlements), it is easy to confuse lights below with stars above, especially after manoeuvres. Smooth surfaces (water, snow, desert) also make accurate height judgement extremely difficult.

8. Lost Procedure

Do not carry on regardless — act immediately on uncertainty

Check compass and ASI — confirm planned heading and speed.
Climb to increase visual and radio horizon (weather and airspace permitting).
Fix position: VOR/DME, VDF, radar or visual fix.
If visual only: calculate DR position from last known fix (track, GS, time).
Draw circle of uncertainty (radius ≈ 10% of distance since last fix). Map-read ground-to-map to identify a large feature.
If still uncertain: turn towards a line feature outside the circle (coastline, motorway, main railway). Follow it to a definite checkpoint.
Avoid high ground, controlled airspace, and low fuel. Monitor all systems throughout.
Use 121.5 MHz (PAN call) for emergency fixing if needed.

9. Chart Symbol Legend

Aeronautical charts use standardised symbols for navigation aids, airfields, obstacles and airspace. Study these carefully — examination questions require identification of specific symbols by number.

Questions

Questions 2 and 5–8 refer to the chart symbol legend above. Questions 3 and 4 refer to a low-level enroute chart. Tap any question to reveal the answer.

Figure 7 — Appendix A — chart symbols 16–21

Q1 Flying VFR, you are uncertain of position. Best course of action?

a — Set heading towards a line feature (coastline, river or motorway)

b — Reverse flight plan tracks until recognising something

c — Fly ever-expanding circles from present position

d — Return to base along the reverse flight plan

Answer: a — The lost procedure requires turning toward a good line feature outside the circle of uncertainty, following it to a definite checkpoint. Expanding circles waste time and fuel. Reversing the full flight plan risks re-entering the same uncertainty.

Q2 What is the symbol for an unlighted obstacle? (Refer to legend)

a — Symbol 9

b — Symbol 10

c — Symbol 12

d — Symbol 15

Answer: d (Symbol 15) — Unlighted obstacle. Symbol 10 is the exceptionally high (>1000 ft AGL) lighted obstruction; symbol 9 is a high lighted obstruction (<1000 ft AGL).

Q3 On a low-level enroute chart, position 5211N 00931W — which denotes all the symbols?

a — Military airport, ILS, NDB

b — Civil airport, VOR, ILS

c — Military airport, VOR, ILS

d — Civil airport, ILS, NDB

Answer: d — Civil airport with ILS and NDB at position 5211N 00931W.

⚑ Instructor Note: This question requires the physical enroute chart for verification. The answer is taken verbatim from the answer key. Ensure students use the correct current chart edition when practising chart-reading questions.

Q4 On a low-level enroute chart, symbols at Galway Carnmore (5318.1N 00856.5W)?

a — VOR, NDB, DME, compulsory reporting point

b — Civil airport, NDB, DME, non-compulsory reporting point

c — Civil airport, VOR, DME, non-compulsory reporting point

d — VOR, NDB, DME, non-compulsory reporting point

Answer: b — Galway Carnmore: civil airport with NDB and DME; reporting point is non-compulsory.

⚑ Instructor Note: Chart-dependent question. Answer per the answer key. Verify against current chart edition in practical study.

Q5 Symbol for an exceptionally high (>1000 ft AGL) lighted obstruction? (Refer to legend)

a — Symbol 6

b — Symbol 9

c — Symbol 10

d — Symbol 15

Answer: c (Symbol 10) — Exceptionally high lighted obstruction (>1000 ft AGL). Symbol 9 = high lighted obstruction (<1000 ft AGL). Symbol 15 = unlighted obstacle.

Q6 What symbol shows a VORTAC? (Refer to legend)

a — Symbol 5

b — Symbol 7

c — Symbol 13

d — Symbol 14

Answer: d (Symbol 14) — VORTAC (combined VOR and TACAN). Symbol 13 = VOR or VOR/DME.

Q7 Which is the symbol for a VOR? (Refer to legend)

a — Symbol 4

b — Symbol 5

c — Symbol 13

d — Symbol 14

Answer: c (Symbol 13) — VOR (and VOR/DME) is represented by the hexagon symbol 13. Symbol 14 = VORTAC; Symbol 5 = NDB.

Q8 What does symbol 3 represent? (Refer to legend)

a — Lit obstacle

b — Lighthouse

c — VRP (Visual Reporting Point)

d — Aeronautical ground light

Answer: d — Symbol 3 = aeronautical ground light. Used as a night visual navigation reference.

Q9 VFR, visual navigation. Aircraft crosses two parallel roads at right angles to track. What can this information be used for?

a — Tracking check

b — Ground speed check

c — Heading check

d — Deviation check

Answer: b (Ground speed check) — The known distance between two parallel roads, combined with the timed crossing, gives ground speed (GS = distance ÷ time). A tracking check requires a line feature parallel to track; a heading check requires compass and reference.

Q10 Most useful visual checkpoint when planning a VFR flight?

a — A small copse

b — A large wood

c — A large motorway junction

d — A bend in a river

Answer: c — A large motorway junction satisfies all four criteria: Large (visible from a distance), Unique (each junction has a distinct shape and number), good Contrast, and provides a precise fix point. A large wood has variable shape, seasonal changes, and lacks precision. A river bend is small-scale and easily confused with others.

Answers Summary

Q	Answer	Q	Answer
1	a	6	d
2	d	7	c
3	d ⚑	8	d
4	b ⚑	9	b
5	c	10	c

⚑ = answer requires physical chart for verification; taken verbatim from the answer key.

Capt. Pankaj Pahil