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DGCA Air Navigation · 71 questions

Chart Scale: DGCA Air Navigation Questions and Answers

71 practice questions on Chart Scale with answers and explanations, plus the key concepts and formulas, from the TrueHeading question bank.

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About this topic

Use this page to revise Chart Scale for the DGCA Air Navigation paper. Below are the key ideas first, then 12 practice questions with answers and explanations, picked from the 71 questions in the TrueHeading bank for this topic.

In short: Scale (representative fraction) is chart length divided by the real distance, both in the same unit.

Open the full set in the student zone to answer every question, track your accuracy and take timed mock tests.

Key concepts: Chart Scale

4 ideas to know cold.

How do you calculate chart scale?

Scale (representative fraction) is chart length divided by the real distance, both in the same unit.

Scale=chart lengthearth distance\text{Scale}=\frac{\text{chart length}}{\text{earth distance}}
  • 1 : 1 000 000 means 1 cm on the chart is 10 km on the ground (5.4 NM)
  • Larger denominator = smaller scale = less detail
Chart scale 1 : 1 000 00001234cm on chart05.410.816.221.6NM on the ground1 cm = 10 km ≈ 5.4 NM

On a 1 : 500 000 chart, how many NM is 1 cm?

2.7 NM (1 cm = 5 km = 5000 m ÷ 1852).

Tip: Chart length × scale denominator = ground length. Convert to NM at the end.

How does scale vary on a Mercator chart?

Scale increases with latitude. At latitude φ it equals the equatorial scale multiplied by sec φ.

Scale at ϕ=scale at equatorcos⁡ϕ\text{Scale at }\phi=\frac{\text{scale at equator}}{\cos\phi}
  • Measure distance against the latitude scale at the same latitude as the leg

How do you find chart scale from a measurement?

Scale = chart distance / earth distance (same units).

Scale=chart distanceearth distance\text{Scale}=\dfrac{\text{chart distance}}{\text{earth distance}}
  • 1:1 000 000 means 1 cm = 10 km
  • 1 NM = 1 852 m
  • Chart length (cm) = distance (NM) × 1 852 × 100 / scale denominator

Practice questions: Chart Scale

Tap “Show answer” after you have tried each one.

Q1On a chart of scale 1:1 000 000, two points are 12 cm apart. The distance between them is approximately:

  1. 81.0 NM
  2. 64.8 NM
  3. 55.1 NM
  4. 71.3 NM
Show answer

Answer: B. 64.8 NM

Distance = 12 cm × 1,000,000 = 120.0 km = 64.8 NM (1 NM = 1.852 km).

Q2On a chart of scale 1:3 000 000, two points are 12 cm apart. The distance between them is approximately:

  1. 272.1 NM
  2. 194.4 NM
  3. 116.6 NM
  4. 174.9 NM
Show answer

Answer: B. 194.4 NM

Distance = 12 cm × 3,000,000 = 360.0 km = 194.4 NM (1 NM = 1.852 km).

Q3On a chart of scale 1:250 000, two points are 6 cm apart. The distance between them is approximately:

  1. 6.9 NM
  2. 8.1 NM
  3. 4.9 NM
  4. 9.3 NM
Show answer

Answer: B. 8.1 NM

Distance = 6 cm × 250,000 = 15.0 km = 8.1 NM (1 NM = 1.852 km).

Q4On a chart of scale 1:500 000, two points are 10 cm apart. The distance between them is approximately:

  1. 27.0 NM
  2. 33.7 NM
  3. 31.0 NM
  4. 37.8 NM
Show answer

Answer: A. 27.0 NM

Distance = 10 cm × 500,000 = 50.0 km = 27.0 NM (1 NM = 1.852 km).

Q5On a chart of scale 1:2 000 000, two points are 3 cm apart. The distance between them is approximately:

  1. 24.3 NM
  2. 45.4 NM
  3. 37.3 NM
  4. 32.4 NM
Show answer

Answer: D. 32.4 NM

Distance = 3 cm × 2,000,000 = 60.0 km = 32.4 NM (1 NM = 1.852 km).

Q6A distance of 200 NM measures 9.3 cm on a chart. The scale of the chart is approximately:

  1. 1 : 4 400 000
  2. 1 : 6 400 000
  3. 1 : 4 000 000
  4. 1 : 2 400 000
Show answer

Answer: C. 1 : 4 000 000

Scale = 200 NM × 185 200 cm ÷ 9.3 cm ≈ 1 : 4,000,000.

Q7A distance of 150 NM measures 27.8 cm on a chart. The scale of the chart is approximately:

  1. 1 : 1 100 000
  2. 1 : 1 000 000
  3. 1 : 1 250 000
  4. 1 : 900 000
Show answer

Answer: B. 1 : 1 000 000

Scale = 150 NM × 185 200 cm ÷ 27.8 cm ≈ 1 : 1,000,000.

Q8A distance of 40 NM measures 3.7 cm on a chart. The scale of the chart is approximately:

  1. 1 : 1 200 000
  2. 1 : 2 800 000
  3. 1 : 1 700 000
  4. 1 : 2 000 000
Show answer

Answer: D. 1 : 2 000 000

Scale = 40 NM × 185 200 cm ÷ 3.7 cm ≈ 1 : 2,000,000.

Q9On a chart with scale 1:1 000 000 8 cm measures a ground distance of approximately (1 nm = 1.852 km):

  1. 148 nm
  2. 22 nm
  3. 80 nm
  4. 43 nm
Show answer

Answer: D. 43 nm

8 cm × 1000000 = 80.0 km; ÷ 1.852 = 43 nm.

Q10On a chart with scale 1:500 000 3 cm measures a ground distance of approximately (1 nm = 1.852 km):

  1. 4 nm
  2. 15 nm
  3. 8 nm
  4. 28 nm
Show answer

Answer: C. 8 nm

3 cm × 500000 = 15.0 km; ÷ 1.852 = 8 nm.

Q1180 nm on the ground measure 8 cm on a chart. The scale of the chart is approximately:

  1. 1:926 000
  2. 1:1 852 000
  3. 1:3 429 904
  4. 1:3 704 000
Show answer

Answer: B. 1:1 852 000

80 nm = 148 160 m = 14 816 000 cm. Scale = 14 816 000 ÷ 8 = 1:1 852 000.

Q1240 nm on the ground measure 5 cm on a chart. The scale of the chart is approximately:

  1. 1:2 743 923
  2. 1:740 800
  3. 1:2 963 200
  4. 1:1 481 600
Show answer

Answer: D. 1:1 481 600

40 nm = 74 080 m = 7 408 000 cm. Scale = 7 408 000 ÷ 5 = 1:1 481 600.

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