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ATPL General Navigation (061) study materials
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ATPL General Navigation (061) practice questions

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Question 1Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

The reference surface used for defining latitude and longitude in air navigation is best described as which of the following?

  1. An oblate spheroid flattened at the poles and bulging at the equator Correct answer.
  2. A sphere whose radius equals the mean sea-level radius of the Earth
  3. A prolate spheroid elongated along the polar axis
  4. A perfect sphere passing through the highest terrain on each continent

Explanation

The Earth is modelled as an oblate spheroid: the equatorial radius is about 6 378 km and the polar radius about 6 357 km, so the surface is flattened at the poles and bulges at the equator. This figure of revolution is the basis on which geodetic latitude and longitude are defined for navigation.

Question 2Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

Which statement correctly describes the direction of the Earth's rotation and its effect on the apparent motion of the Sun?

  1. The Earth rotates west to east, so the Sun appears to move west to east
  2. The Earth rotates west to east, so the Sun appears to move east to west Correct answer.
  3. The Earth rotates east to west, so the Sun appears to move west to east
  4. The Earth rotates east to west, so the Sun appears to move east to west

Explanation

Viewed from above the North Pole the Earth turns anticlockwise, that is from west towards east. An observer on the surface therefore sees the Sun, and all other celestial bodies, rise in the east and travel towards the west.

Question 3Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

On the assumed spherical Earth used for navigation, the length of one minute of arc measured along a great circle is taken as which value?

  1. One kilometre
  2. One degree of longitude
  3. One nautical mile Correct answer.
  4. One statute mile

Explanation

The nautical mile is defined from the arc of a great circle: one minute of arc subtends one nautical mile, approximately 1 852 m. This relationship is the basis for expressing distances in minutes of latitude.

Question 4Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

The prime meridian passes through which location?

  1. The meridian of the Azores
  2. The naval observatory at Washington
  3. The Eiffel Tower in Paris
  4. The Royal Observatory at Greenwich Correct answer.

Explanation

By international agreement the zero meridian of longitude is the meridian through the Royal Observatory at Greenwich. Longitudes are measured from it both eastwards and westwards up to 180 degrees.

Question 5Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

What is the maximum possible value of geodetic latitude at any point on the Earth's surface?

  1. 45 degrees
  2. 90 degrees Correct answer.
  3. 180 degrees
  4. 360 degrees

Explanation

Latitude is measured from the equator towards each pole, so it ranges from 0 degrees at the equator to 90 degrees at the poles. Values beyond 90 degrees are impossible because the poles are the extremes of the rotation axis.

Question 6Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

A position is given as 45 degrees 30 minutes south. Which statement about this position is correct?

  1. It lies on the equator, since the minutes cancel the hemisphere
  2. It lies beyond the South Pole on the opposite meridian
  3. It lies in the northern hemisphere, between the equator and the North Pole
  4. It lies in the southern hemisphere, between the equator and the South Pole Correct answer.

Explanation

The letter S indicates a latitude measured southwards from the equator, so the point lies in the southern hemisphere. Its magnitude, 45 degrees 30 minutes, places it between the equator and the South Pole.

Question 7Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

A position is reported as 120 degrees 15 minutes west. In which hemisphere and relative to the prime meridian does this point lie?

  1. Eastern hemisphere, 59 degrees 45 minutes west of Greenwich
  2. Eastern hemisphere, 120 degrees 15 minutes east of Greenwich
  3. Western hemisphere, 120 degrees 15 minutes west of Greenwich Correct answer.
  4. Western hemisphere, 59 degrees 45 minutes east of Greenwich

Explanation

The suffix W means longitude is measured westwards from the prime meridian, so the point lies in the western hemisphere at the stated value. No conversion to an easterly value is needed when the direction is already given.

Question 8Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

What is the angular difference in longitude between the meridians 10 degrees east and 25 degrees west?

  1. 45 degrees
  2. 15 degrees
  3. 25 degrees
  4. 35 degrees Correct answer.

Explanation

When longitudes lie on opposite sides of the prime meridian their values are added to obtain the angular separation. Adding 10 degrees east and 25 degrees west gives 35 degrees.

Question 9Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

Two positions lie on the same meridian but at latitudes 20 degrees north and 50 degrees north. What is the great-circle distance between them in nautical miles?

  1. 600 NM
  2. 4 200 NM
  3. 1 200 NM
  4. 1 800 NM Correct answer.

Explanation

The angular separation along the meridian is 30 degrees, and one degree of arc equals 60 nautical miles. Thus 30 multiplied by 60 gives 1 800 NM.

Question 10Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

At the North Pole, which statement about longitude is correct?

  1. Longitude equals 180 degrees by convention
  2. Longitude changes continuously through 360 degrees
  3. All meridians converge and longitude is undefined Correct answer.
  4. Longitude equals 0 degrees by convention

Explanation

All meridians meet at the pole, so no single meridian can be identified and longitude has no meaning there. Latitude alone, 90 degrees north, defines the position.

Question 11Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

A great circle is best defined as which of the following?

  1. A circle on the Earth's surface whose plane is parallel to the equator
  2. A circle on the Earth's surface whose plane passes through the Earth's centre Correct answer.
  3. A straight line drawn between two points on a chart projection
  4. A circle on the Earth's surface centred on any point of the observer's horizon

Explanation

A great circle is formed where a plane through the Earth's centre intersects the surface, dividing the sphere into two equal hemispheres. The shortest surface path between two points always lies on a great circle.

Question 12Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

Which of the following is a small circle on the assumed spherical Earth?

  1. The meridian of 90 degrees west
  2. The prime meridian
  3. The parallel of latitude 30 degrees north Correct answer.
  4. The equator

Explanation

A parallel of latitude other than the equator has a plane that does not pass through the Earth's centre, so it is a small circle. Meridians and the equator are great circles.

Question 13Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

What is the length, in nautical miles, of the equator measured along the assumed spherical Earth?

  1. 10 800 NM
  2. 43 200 NM
  3. 5 400 NM
  4. 21 600 NM Correct answer.

Explanation

The equator is a full great circle of 360 degrees, and each degree contains 60 nautical miles. Multiplying 360 by 60 gives 21 600 NM.

Question 14Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

Two aircraft are at the same latitude of 60 degrees north, one at 0 degrees longitude and the other at 1 degree east. Which statement about the distance between them is correct?

  1. It is approximately 120 NM, because longitude spacing increases with latitude
  2. It is approximately 15 NM, because longitude spacing decreases by a quarter at 60 degrees
  3. It is approximately 30 NM, because a degree of longitude at 60 degrees latitude is about half a degree of great-circle arc Correct answer.
  4. It is approximately 60 NM, because one degree of longitude always equals one degree of great-circle arc

Explanation

The length of a degree of longitude is 60 times the cosine of the latitude in nautical miles. At 60 degrees the cosine is 0.5, so one degree of longitude corresponds to about 30 NM.

Question 15Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

A point lies at latitude 90 degrees south. Which statement is correct?

  1. It is on the prime meridian, where longitude is zero
  2. It is the North Pole, where latitude is 90 degrees north
  3. It is on the equator, where latitude is zero
  4. It is the South Pole, where all meridians meet and longitude is undefined Correct answer.

Explanation

A latitude of 90 degrees south places the point exactly at the South Pole. There all meridians converge, so longitude cannot be specified.

Question 16Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

Which statement about the relationship between latitude and the polar axis is correct?

  1. Latitude is the angle between the equatorial plane and the radius to the point Correct answer.
  2. Latitude is the angle measured along the equator from the prime meridian
  3. Latitude is the angle between the polar axis and the radius to the point
  4. Latitude is the angle between two meridians at the point

Explanation

Geocentric latitude is defined as the angle at the Earth's centre between the equatorial plane and the radius to the point. The complementary angle to the polar axis is the co-latitude.

Question 17Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

Two points lie on the equator at longitudes 20 degrees east and 80 degrees east. What is the great-circle distance between them?

  1. 1 200 NM
  2. 2 400 NM
  3. 3 600 NM Correct answer.
  4. 6 000 NM

Explanation

On the equator, which is a great circle, the angular separation equals the difference in longitude, here 60 degrees. Multiplying by 60 NM per degree gives 3 600 NM.

Question 18Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

A position is given in the form 51 degrees 28 minutes north, 000 degrees 00 minutes. What does the second element indicate?

  1. The point lies at the North Pole
  2. The point lies on the 180th meridian
  3. The point lies on the equator
  4. The point lies on the prime meridian Correct answer.

Explanation

A longitude of zero degrees zero minutes identifies the prime meridian through Greenwich. The latitude of 51 degrees 28 minutes north is independent of that and merely fixes the position along the meridian.

Question 19Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

An aircraft tracks due north from latitude 10 degrees south to latitude 10 degrees north. What distance has it covered along the meridian?

  1. 600 NM
  2. 1 200 NM Correct answer.
  3. 2 400 NM
  4. 1 800 NM

Explanation

The aircraft crosses the equator, so the total angular change is 20 degrees. At 60 NM per degree this gives 1 200 NM.

Question 20Basics of Navigation: Shape and Dimensions of the Earth, Coordinate Systems, Position

Which statement correctly describes the difference between geodetic and geocentric latitude?

  1. Geodetic latitude is measured east of Greenwich, while geocentric latitude is measured west of Greenwich
  2. Geodetic and geocentric latitude differ only by the rotation of the Earth and have the same reference
  3. Geodetic latitude is measured against the ellipsoid normal, while geocentric latitude is measured from the Earth's centre Correct answer.
  4. Geodetic latitude is measured from the Earth's centre, while geocentric latitude is measured against the ellipsoid normal

Explanation

Geodetic latitude uses the direction of the normal to the reference ellipsoid at the point, while geocentric latitude uses the radius drawn from the Earth's centre. Because of the equatorial bulge the two differ, reaching about 11.5 minutes of arc near 45 degrees latitude.

Question 21Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

In terrestrial magnetism, the angle between the magnetic meridian and the true meridian at a given position on the Earth's surface is called:

  1. Magnetic inclination
  2. Magnetic variation Correct answer.
  3. Magnetic deviation
  4. Magnetic dip

Explanation

Magnetic variation (declination) is the angular difference between the magnetic meridian and the true meridian at a place. It is a property of the location and changes slowly with time. Dip and inclination are the same thing, describing the vertical component of the field, while deviation is an aircraft-installation effect.

Question 22Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

At the magnetic poles of the Earth, the value of magnetic dip is closest to:

  1. 45 degrees
  2. 0 degrees
  3. 180 degrees
  4. 90 degrees Correct answer.

Explanation

Dip is the angle between the total magnetic field and the horizontal. At the magnetic poles the field is essentially vertical, so the horizontal component vanishes and dip reaches 90 degrees. At the magnetic equator the field is horizontal and dip is 0 degrees.

Question 23Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

A direct-reading magnetic compass is characterised by which feature?

  1. It requires a separate gyro to stabilise the card
  2. It transmits heading electrically to remote indicators
  3. It displays a digital heading derived from a flux valve
  4. The compass card is read directly against a fixed lubber line Correct answer.

Explanation

In a direct-reading compass the card, aligned with the magnetic field, is observed directly against a fixed lubber line or index. There is no electrical transmission or remote indication. Flux valves and remote indicators belong to indirect-reading (remote) compass systems.

Question 24Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

An aircraft is aligned with magnetic north on a compass base. The compass reads 358 degrees. The deviation for that heading is:

  1. 2 degrees west
  2. 358 degrees east
  3. 2 degrees east Correct answer.
  4. 18 degrees west

Explanation

Deviation is magnetic heading minus compass heading. Here 360 minus 358 gives 2 degrees, and because the compass under-reads relative to magnetic north, the deviation is east. Remember the rule that compass reads least when deviation is east.

Question 25Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

The purpose of the soft iron spheres and Flinders bar fitted near a magnetic compass is to:

  1. Reduce the effect of magnetic variation at high latitude
  2. Provide a backup heading source if the gyro fails
  3. Correct deviation caused by the aircraft's hard and soft iron effects Correct answer.
  4. Increase the sensitivity of the compass magnets

Explanation

The corrector devices, including soft iron spheres and the Flinders bar, are placed to create compensating fields that cancel the deviation produced by the aircraft's own hard and soft iron magnetism. They act on deviation only. Variation is a property of position and cannot be removed by aircraft-mounted correctors.

Question 26Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

Magnetic variation is described as easterly when the magnetic north direction lies:

  1. Exactly along true north
  2. To the west of true north
  3. To the east of true north Correct answer.
  4. Along the aircraft's longitudinal axis

Explanation

Easterly variation means magnetic north lies east of true north at that position, so true heading is magnetic heading plus easterly variation. Westerly variation means magnetic north lies west of true north. Variation is a location property independent of aircraft attitude.

Question 27Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

An aircraft flies a true heading of 090 degrees in an area where variation is 6 degrees west. The magnetic heading is:

  1. 096 degrees Correct answer.
  2. 084 degrees
  3. 090 degrees
  4. 102 degrees

Explanation

With westerly variation, magnetic heading equals true heading plus variation: 090 plus 6 gives 096 degrees. The memory aid is that westerly variation is added when converting from true to magnetic. Easterly variation would be subtracted.

Question 28Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

A magnetic compass reads 214 degrees. Variation at the position is 8 degrees east and deviation is 3 degrees west. The true heading is:

  1. 209 degrees
  2. 203 degrees
  3. 225 degrees
  4. 219 degrees Correct answer.

Explanation

First convert compass to magnetic: magnetic equals compass plus easterly deviation or minus westerly deviation, giving 214 minus 3 = 211 degrees. Then magnetic to true with easterly variation means adding: 211 plus 8 = 219 degrees. Combining the corrections gives a net 5 degrees added to the compass reading.

Question 29Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

A remote-reading (indirect) compass system typically obtains its directional signal from:

  1. A vertical gyro only, with no magnetic reference
  2. A direct-reading card viewed through a magnifier
  3. A static pressure sensor in the pitot system
  4. A flux valve or flux gate sensing the Earth's field Correct answer.

Explanation

Indirect-reading systems use a flux valve or flux gate detector that senses the horizontal component of the Earth's magnetic field and transmits the signal to indicators. The gyro in such systems provides short-term stability, not the primary magnetic reference. Direct-reading cards are a separate class of compass.

Question 30Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

The main advantage of a gyro-stabilised remote-reading compass over a simple direct-reading compass is that it:

  1. Removes all magnetic variation from the displayed heading
  2. Requires no correction for installation error
  3. Provides a steady indication during turns and acceleration Correct answer.
  4. Eliminates the need for any magnetic sensing element

Explanation

The gyro stabilises the indication so that turning and acceleration errors, which affect a simple magnetic compass, are largely suppressed. The system is still slaved to a magnetic detector, so variation remains a real-world effect on the heading reference. Installation effects are handled by the detector and correctors, not removed by the gyro.

Question 31Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

In the Northern Hemisphere, when an aircraft accelerates on an easterly heading, the direct-reading magnetic compass typically indicates:

  1. No change at all
  2. A turn toward north Correct answer.
  3. A continuous rotation of the card
  4. A turn toward south

Explanation

Acceleration and turning errors arise because the compass card pivots on a point above its centre of gravity. In the Northern Hemisphere, acceleration on an easterly or westerly heading produces an apparent turn toward north. Deceleration on the same headings produces an apparent turn toward south.

Question 32Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

In the Northern Hemisphere, on a northerly heading during a turn, the direct-reading magnetic compass tends to:

  1. Lag the turn, indicating less turn than has been made Correct answer.
  2. Show the correct heading immediately
  3. Lead the turn, indicating more turn than has been made
  4. Reverse direction and indicate south

Explanation

Turning error causes the compass to lag the turn when turning through north in the Northern Hemisphere, so the indicated heading shows less turn than actually achieved. When turning through south the compass leads the turn. The error is greatest on north and south headings.

Question 33Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

The line on a chart joining points of zero magnetic variation is called the:

  1. Isogonic line
  2. Aclinic line
  3. Agonic line Correct answer.
  4. Isogonal grid line

Explanation

The agonic line is the locus of zero variation, where magnetic and true meridians coincide. Isogonic lines join points of equal variation but not necessarily zero. The aclinic line is the magnetic equator, where dip is zero.

Question 34Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

The magnetic equator (aclinic line) is the locus of points where:

  1. Magnetic dip is 90 degrees
  2. The horizontal field component is maximum at the poles
  3. Magnetic dip is zero Correct answer.
  4. Magnetic variation is zero

Explanation

On the aclinic line the Earth's magnetic field is horizontal, so dip is zero and the horizontal component is at its strongest. This line does not generally coincide with the geographic equator or with the zero-variation line. Dip reaches 90 degrees at the magnetic poles.

Question 35Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

An aircraft is on a compass heading of 275 degrees. Deviation is 4 degrees east and variation is 9 degrees west. The true heading is:

  1. 288 degrees
  2. 270 degrees Correct answer.
  3. 280 degrees
  4. 262 degrees

Explanation

Compass to magnetic: easterly deviation is subtracted, giving 275 minus 4 = 271 degrees. Magnetic to true: westerly variation is subtracted, giving 271 minus 9 = 262 degrees. Wait, rechecking the arithmetic, the correct combined result is 262 degrees.

Question 36Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

A pilot observes that a direct-reading compass is unusable during a prolonged coordinated turn through east or west in the Southern Hemisphere. The most likely cause is:

  1. Dip-induced turning error, whose sense is reversed in the Southern Hemisphere Correct answer.
  2. Failure of the flux valve
  3. Loss of the gyro vacuum supply
  4. Excessive variation at that latitude

Explanation

Turning error results from the vertical component of the Earth's field tilting the compass assembly, and its sense depends on the hemisphere. In the Southern Hemisphere the leading and lagging behaviour is reversed compared with the Northern Hemisphere. A direct-reading compass has no flux valve or gyro, so those failures cannot apply.

Question 37Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

The compass swing procedure is carried out primarily to:

  1. Determine and record the deviation on various headings Correct answer.
  2. Align the flux valve with the aircraft axis
  3. Measure the local magnetic variation
  4. Calibrate the gyro horizon

Explanation

A compass swing compares compass readings with known magnetic headings and produces a deviation card for the aircraft. Variation is obtained from charts, not from the swing. The procedure addresses aircraft-induced deviation, which is unique to each installation.

Question 38Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

If the deviation on a particular heading is 5 degrees east, the relationship between compass heading and magnetic heading is:

  1. Magnetic heading equals compass heading minus 5 degrees
  2. Magnetic heading equals compass heading plus 5 degrees Correct answer.
  3. Magnetic heading equals compass heading
  4. Compass heading equals true heading plus 5 degrees

Explanation

Easterly deviation means the compass reads less than the magnetic heading, so magnetic heading equals compass heading plus 5 degrees. The mnemonic is compass least, deviation east. Westerly deviation would require subtracting the value.

Question 39Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

An aircraft's magnetic compass indicates 090 degrees while the true heading is known to be 096 degrees. If deviation on that heading is 2 degrees west, the variation is:

  1. 4 degrees east Correct answer.
  2. 8 degrees east
  3. 4 degrees west
  4. 8 degrees west

Explanation

Convert compass to magnetic first: westerly deviation is added, so magnetic heading is 090 plus 2 = 092 degrees. The difference between true 096 and magnetic 092 is 4 degrees, and since magnetic is less than true, magnetic north lies east of true north, giving easterly variation.

Question 40Magnetism and Compasses: Terrestrial Magnetism, Variation, Deviation, Direct and Indirect Reading Compasses

During a turn in the Northern Hemisphere, a direct-reading compass is most reliable and least affected by turning error when the aircraft is turning through:

  1. North
  2. East or west Correct answer.
  3. Any heading equally
  4. South

Explanation

Turning error is greatest when turning through north or south and is least when turning through east or west. At east and west headings the dip-induced error is minimal because the card's pivot tilt has least effect on the indicated heading. This is why pilots time turns using the compass near east or west.

Question 41Charts: Projections, Scale, Relief, Chart Properties and Use

On a Lambert conformal conic chart covering mid-latitudes, a straight line drawn between two points is best described as which of the following?

  1. A rhumb line that plots as a straight line
  2. A line of constant bearing that is slightly curved
  3. A great circle that plots as a straight line
  4. A great circle that is approximately straight but not exactly so Correct answer.

Explanation

On a Lambert conformal conic the meridians converge and the cone touches the standard parallels, so a great circle plots as a gently curved line concave to the pole. Over short distances it is nearly straight, which is why it is used for practical plotting. Only the Mercator makes a rhumb line exactly straight.

Question 42Charts: Projections, Scale, Relief, Chart Properties and Use

A Mercator chart is described as conformal. What does this mean for the navigator?

  1. Great circles plot as straight lines
  2. Distances can be measured with a single scale anywhere on the chart
  3. Areas are shown in true proportion at all latitudes
  4. Angles measured on the chart equal the corresponding angles on the Earth Correct answer.

Explanation

Conformality means the shape of small features and the angles between lines are preserved, so a bearing measured on the chart can be used as a true bearing. Scale varies with latitude, so a single distance scale is not valid over large latitude changes. Great circles plot as curves on a conformal Mercator.

Question 43Charts: Projections, Scale, Relief, Chart Properties and Use

On a chart with a representative fraction of 1:500 000, a measured chart distance of 8 cm represents what ground distance?

  1. 400 km
  2. 4 km
  3. 0.4 km
  4. 40 km Correct answer.

Explanation

A representative fraction of 1:500 000 means one unit on the chart equals 500 000 of the same units on the ground. Eight centimetres therefore equals 8 x 500 000 cm, which is 4 000 000 cm or 40 km. Converting centimetres to kilometres requires dividing by 100 000.

Question 44Charts: Projections, Scale, Relief, Chart Properties and Use

Which statement correctly describes a rhumb line on a Mercator projection?

  1. It plots as a curve concave to the equator
  2. It plots as a straight line only when it runs north-south
  3. It plots as a straight line crossing all meridians at the same angle Correct answer.
  4. It plots as a straight line but does not represent a constant bearing

Explanation

The Mercator is constructed so that the track of constant bearing, the rhumb line, appears as a straight line. Because meridians are parallel vertical lines, a straight line cuts them all at the same angle, matching the constant bearing. This is the principal navigational advantage of the projection.

Question 45Charts: Projections, Scale, Relief, Chart Properties and Use

What is the main purpose of relief shading on a topographical chart?

  1. To indicate the scale of the chart at different latitudes
  2. To show the shape of the terrain by simulating illumination from a nominated direction Correct answer.
  3. To indicate the magnetic variation over the area
  4. To show airspace boundaries and controlled zones

Explanation

Relief shading uses graded tones to give an impression of terrain shape, as if lit from a stated direction, helping the reader visualise slopes and ridges. It is supplementary to contours and spot heights, not a substitute for them. It carries no magnetic or airspace information.

Question 46Charts: Projections, Scale, Relief, Chart Properties and Use

Contour lines that are closely spaced on a topographical chart indicate what about the terrain?

  1. A depression
  2. A steep slope Correct answer.
  3. A flat plateau
  4. A gentle slope

Explanation

Contour spacing is inversely related to slope: closely packed contours mean the height changes rapidly over a short horizontal distance, which is a steep slope. Widely spaced contours indicate gentle gradients. Depression is shown by hachures or by contour values, not by spacing alone.

Question 47Charts: Projections, Scale, Relief, Chart Properties and Use

A conical projection is produced by projecting the Earth's surface onto what shape?

  1. A cylinder wrapped around the equator
  2. A sphere concentric with the Earth
  3. A plane tangent to the Earth at a single point
  4. A cone placed over the Earth with its apex above a pole Correct answer.

Explanation

A conical projection uses a cone whose axis coincides with the Earth's polar axis and whose apex lies above a pole, touching or cutting the globe at one or two standard parallels. The cylinder is the basis of Mercator and transverse Mercator, while the tangent plane gives azimuthal projections.

Question 48Charts: Projections, Scale, Relief, Chart Properties and Use

On a polar stereographic chart used for high-latitude navigation, which property makes it particularly suitable for plotting?

  1. Bearings from the pole are true and meridians are straight lines radiating from the centre Correct answer.
  2. Great circles plot as straight lines through the pole
  3. Distance scale is constant over the whole chart
  4. It is the only projection on which rhumb lines are straight

Explanation

On a polar stereographic chart all meridians are straight lines converging at the pole and the angle around the pole equals the difference in longitude, so bearings from the pole are true. It is also conformal. Great circles do not generally plot as straight lines and scale varies away from the standard parallel.

Question 49Charts: Projections, Scale, Relief, Chart Properties and Use

A chart has a scale of 1:250 000. A line measures 12 cm on the chart. On a second chart of the same area at 1:500 000, what length would the same line measure?

  1. 48 cm
  2. 3 cm
  3. 6 cm Correct answer.
  4. 24 cm

Explanation

Doubling the denominator halves the chart length for the same ground distance. Twelve centimetres at 1:250 000 becomes six centimetres at 1:500 000. The ground distance is 30 km in both cases.

Question 50Charts: Projections, Scale, Relief, Chart Properties and Use

What is the significance of the standard parallel on a conic projection?

  1. It is the latitude at which the scale is exactly correct and from which scale error grows with distance Correct answer.
  2. It is the latitude beyond which the projection cannot be used
  3. It is the latitude at which magnetic variation is zero
  4. It is the equator, where all conic projections are tangent

Explanation

The standard parallel is where the cone touches or intersects the globe, so chart scale matches the stated scale there. Away from it the scale factor departs from unity, increasing the distortion of distance. Charts are normally specified with one or two standard parallels chosen to suit the area of use.