Navigation theory

Five questions on coordinates, compass and instruments.

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Concepts

Variation: between true and magnetic north. Deviation: between magnetic and compass north. Total correction: their signed sum, E positive and W negative.

Courses: NE same, SE 180 − R, SW 180 + R, NW 360 − R. True speed = log coefficient × log speed.

Activities

• Navigation calculationsTotal correction, courses, departure and dead reckoning, step by step.

Questions in this unit

• On which sharp piece of the compass does the card rest and swing?
• The angle measured between true north and the ship’s fore-and-aft line is called:
• The instrument that gives our boat’s speed is called…
• What do depth contours (veriles) show on charts?
• The arc of the equator from the Greenwich meridian to the local meridian is called:
• The instrument that measures the distance a boat has sailed is:
• The soundings on nautical charts are referred to:
• To update the magnetic variation of an area, in general we take into account:
• What is an isobar?
• A nautical mile:
• The angle between the boat’s fore-and-aft line and the line of sight to a landmark is called:
• How is the log coefficient applied?
• In a 6-metre motor boat making way ahead, in a current setting on the port side:
• The correct way to count a quadrantal bearing is:
• What is meant by “ship’s clock time” (Hora de Reloj de Bitácora)?
• What is the quadrantal course S45W as a value?
• An inset (cartucho) on a chart is:
• Mark the correct statement:
• A boat’s local meridian is:
• If the log coefficient is 1.1 and the log distance is 8 miles, what is the true distance run?
• A relative bearing (marcación) is:
• Are prohibited anchorage areas shown on navigation charts?
• Compass deviation:
• Besides describing the coast, roadsteads and hazards in detail, what other passage and arrival information do the Sailing Directions (Derroteros) include?
• On the influence of wind or current on a boat’s navigation, mark the CORRECT statement.
• The duration of the tide (rise) is the time between:
• The difference between a transit (enfilación) and an opposition (oposición) relates to:
• How should a distance between two points be measured on a nautical chart?
• The device placed on a magnetic compass to take a bearing is called:
• On nautical charts, what is the correct definition of a coastal chart?
• The central cone-shaped piece of a nautical compass, made so the support point is above the centre of gravity for stability, is called:
• Sailing, to fix our position relative to a coastal point we use the hand bearing compass on board. The reading we get directly is:
• Sailing with compass heading SW, the boat is in a 4-knot current setting NW. So the boat:
• On Mercator charts a mile is:
• On a chart, an “isobath” line is:
• Converting course N70W to circular gives:
• In a marine compass, what is the disc graduated 0º to 360º that represents the horizon called?
• A transit (enfilación):
• Ship’s clock time:
• Who publishes the lists of lights in Spain?
• What is the effect of low pressure on tides?
• The small circles parallel to the equator are called:
• The echo sounder is used to:
• When atmospheric pressure is lower than normal:
• What causes drift in a boat’s course?
• Every boat sailing in a current has its true course affected by…
• A yacht’s speed at a given moment is measured with:
• If you are in the Northern Hemisphere sailing true course SOUTH (180º), you are
• All the data you need on a given coast’s features or a port can be found in:
• When a coastal chart includes a window showing a place of interest at larger scale, it is called...
• When on course we cross the line joining two lighthouses facing each other, we are on…
• The inaccuracies measured by the log fitted on board while under way are corrected by applying the…:
• What is the great circle that passes through the poles and through the coordinates of our position called?
• A veril is a chart element that joins points having:
• The lines on navigation charts called veriles or isobaths represent
• The third quadrant of the horizon lies between…:
• The arc of meridian counted from the Equator to the observer’s parallel:
• To find the data and features of ports on the Spanish coasts, you use:
• Looking at the coast we see two tall chimneys in line, which can serve as:
• On the marine compass, the recess at the centre of the card that lets it turn horizontally is the:
• Sailing course N30E, how is it expressed as a circular course?
• In the Lisbon entrance channel, we have Bugio islet’s green light on the starboard beam and Ponta da Laje’s red on the port beam. The line of position they give is:
• In an area with variation 2W, steering compass course 030º, the deviation card gives +2º for this heading. What is the true course?
• On magnetic variation, mark the INCORRECT statement:
• On the deviation card, which statement is CORRECT?
• One degree on the latitude scale of a Mercator chart equals:
• On the deviation card:
• On nautical charts, what is the CORRECT definition of a harbour plan (portulano)?
• To work out the drift caused by a current on our boat, besides the boat’s fore-and-aft line, we use:
• If our boat has positive leeway, this means:
• A relative bearing (marcación) is:
• Magnetic variation is defined as the angle between:
• True course differs from magnetic course by:
• A relative bearing is defined as:
• What is the definition of latitude?
• A relative bearing is measured:
• The angle between compass north and true north is called:
• The difference in height between consecutive high and low waters is called:
• With magnetic variation 5º NW (−) and compass deviation 1º NE (+), what is the total correction?
• What is the total correction if variation is 3º(−) and deviation 1º(+)?
• The angle between compass north and magnetic north is:
• The vertical distance between a given low and high water is:
• On the quadrantal way of giving courses, mark the CORRECT answer.
• Convert the quadrantal course S70W to circular.
• Relative bearings are measured:
• Ship’s clock time is:
• The relative bearing in circular form:
• The relative bearing of a point:
• A knot is:
• What circular course is quadrantal N50ºW?
• Why does compass course NOT match true course?
• The relation between course (R), bearing (D) and relative bearing (M) is:
• Publishing sailing directions, lists of lights and navigation charts in Spain falls to the...
• The log coefficient:
• The horizontal angle between the boat’s fore-and-aft line and the line of sight to an object is called:
• How can we find the boat’s speed?
• Mark the correct statement:
• The nautical mile is:
• The lines on a chart joining points of the same depth are called:
• The meridian through the ship’s position is called:
• The isobathic lines joining points of equal depth on a chart are called:
• On a given course our compass matches the true course. This means:
• What is the displacement a boat suffers from current called?
• One minute of latitude corresponds to:
• One minute of latitude corresponds to
• Because of the wind on the yacht’s topsides, the wake makes an angle with the fore-and-aft line called:
• The instrument giving the yacht’s speed under way is:
• The sea depths given on nautical charts are known as:
• Quadrantal course S50ºW corresponds to circular:
• The main features of the terrestrial equator are:
• The visible horizon has four quadrants like the nautical protractor. The second quadrant lies between:
• The angle between the line of sight to a coastal point and magnetic north is called:
• The effect of current on the boat’s true course is called:
• The great circle normal to the Earth’s axis, 90º from the poles, dividing the Earth into Northern and Southern Hemispheres, is the:
• Where can we find the magnetic variation for the year of issue, and its annual change for correcting later years?
• On a chart, a depth contour (veril) is…
• The arc of equator from the Greenwich meridian to the observer’s meridian is…
• Which line of position is most reliable?
• On a Mercator chart, depth contours give:
• Distances on nautical charts are measured on:
• Relative bearings are angles to an object measured from:
• Latitude at a point is defined as:
• The change to the boat’s course caused by wind is known as:
• On the chart we see a teardrop symbol with a star marked Fl(3)WRG.15s21m15-11M. It is a light:
• High-water height is the vertical distance of the water surface above:
• What is “Hora Reloj Bitácora” (ship’s clock time)?
• What is quadrantal course N64W as a circular course?
• What is quadrantal course S65E as a circular course?
• The horizontal angle between magnetic north and true north is called:
• A compass course differs from a magnetic course by:
• With wind on the bow, to correct for leeway and make good the desired water track:
• Making 5 knots with a 1-knot foul current, multiplying the log reading by the log coefficient gives:
• With magnetic variation 8º NW and deviation 6º NE, the total correction is:
• The difference between the true course and the compass course is called:
• The total correction is measured from:
• The log coefficient:
• Which statement about courses is TRUE?
• On tides, mark the INCORRECT statement:
• The angle between the ship’s head and the line of sight to an object is called:
• On a chart’s latitude scale:
• If the chart shows the abbreviation “Lo” (English “M”) for the nature of the bottom, it is:
• How should a distance be measured on a chart?
• The position line given by two charted objects in line is called:
• Sailing directions (“derroteros”) are:
• The prime meridian is:
• The nautical mile:
• The instrument that measures a yacht’s speed under way is:
• Compass deviation is an error of the magnetic compass caused by:
• The straight line along which we would see two lighthouses beyond us, one nearer and one farther, is:
• Sailing directions:
• Depth contours (“veriles”) are lines:
• We have run 20 nautical miles by the chart and the log shows 19 miles:
• The unit with which we take distances on navigation charts and measure runs or legs is…
• The great circle of the Earth that is perpendicular to the polar axis and divides the Earth into Northern and Southern Hemispheres is called…
• The value of magnetic variation changes with…
• The soundings shown on a navigation chart refer to:
• When a boat is affected by a current and its course is displaced as a result, this is known as:
• The equipment that gives us our speed and the accumulated distance run is:
• A harbour plan inset in a chart like a window, enlarging a port, anchorage or place of interest for navigation, is called in cartography:
• The nautical publication that gives the features of the coast and of ports is called:
• The relation between the unit “one knot” and the unit “one nautical mile” is:
• Magnetic variation (“declinación magnética”) is the:
• Which of these angles can be plotted on the chart to get our position?
• On course, to fix our position by charted lights or landmarks, we should preferably use:
• The chart used for arrival or approach to port when only a few miles remain is called:
• Leeway (“abatimiento”) is known as:
• Convert quadrantal course S50W to circular.
• All the data you need on lights of aids to navigation is found in:
• Sailing in a given area, the local magnetic variation affects:
• The books describing the coast, its features, ports and so on are:
• If we are unsure about details of the coastal area we are sailing, we consult:
• Under way, prevailing beam winds can alter our true course. This alteration is called:
• Under way, to fix our position by charted landmarks, we preferably use:
• Compass deviation varies with:
• The lines on charts joining points of equal depth are called:
• The term “cartucho” (inset) on a chart refers to:
• Compass deviation:
• A course is the angle between the ship’s head and:
• How are relative bearings measured?
• Which instrument measures distance run and speed on a boat?
• Which three characteristics, combined, do navigation lights have?
• Where can we find the deviation card?
• The time shown by the clock aboard is called:
• For calculations, leeway is the angle between:
• What is deviation?
• On how courses are measured:
• By the meridian used to measure it, which three kinds of course are there?
• Converting S60E to a circular course gives:
• The change in a boat’s course caused by the movement of the water on her underwater body is called:
• If we have a chart where latitudes increase downwards and longitudes increase to the left, it shows an area in:
• To find the latitude of any point on the Earth we measure:
• Among the characteristics of maritime lights are:
• In a given place, magnetic variation:
• Relative bearing (marcación) is measured:
• Relative bearings are counted:
• Magnetic variation:
• Applying the formula linking bearing, course and relative bearing, if sailing on true course S53W we take a relative bearing of 30º to port on a prominent point on the coast, what is the true bearing to that point?
• What is the total correction?
• What is the angle between the direction of the compass needle and the magnetic meridian called?
• A bearing (demora) is:
• Tidal range:
• The action of the wind on the sides and superstructure makes the boat:
• The difference between the true bearing and the compass bearing is:
• Two vessels with the same latitude, not on the Equator:
• The value of one minute of arc of meridian is:
• The angle between the boat’s true course and the course made good, or the angle between the boat’s movement relative to the water and to the seabed, with no other disturbing cause, is called:
• Drift (deriva) is produced by:
• How can the value of magnetic variation be updated?
• What is the correct definition of a parallel?
• Regarding the Total Correction, choose the INCORRECT statement.
• The influence of high pressure on the height of the tide is to:
• Tides are mainly caused by the gravitational pull of:
• What characterises a lighthouse with an occulting light?:
• According to the log on board, we have run 10.4 miles in one hour. What real distance have we run if the log coefficient is 0.97? (round to a tenth of a mile):
• Choose the correct statement:
• Leeway is:
• The angle counted from North to the boat’s centreline is called:
• What conditions must be met for a transit to be reliable?:
• Deviation on the boat’s different courses can be found from:
• Latitude scales on a nautical chart:
• On nautical charts, what is the line joining seabed points of equal depth called?
• An inset at larger scale of a particular area on some charts is called:
• Relative bearing (marcación) is counted:
• Soundings on nautical charts correspond to:
• To work properly, nautical compasses need two essential qualities:
• What does the echo sounder on a boat measure?
• On a nautical chart, a cartucho is:
• To measure distance on the chart, we set the dividers on the distance and then:
• Mark the correct statement:
• The drift a boat suffers:
• Charts giving the fullest detail of a small stretch of coast, inlets, ports and anchorages are called:
• The meridian passing through the observer or boat is called:
• On a chart, “FW” appears beside a light symbol. It is:
• The unit of speed equal to one nautical mile per hour is:
• Soundings on official Spanish charts show:
• On installing the compass, which answer is correct?
• Sailing directions (derroteros) are:
• Magnetic variation affects:
• The pivot cap (chapitel) is a part
• A lighthouse seen at night is identified by:
• Ship's clock time (Hora Reloj Bitácora):
• If we know the log coefficient we can calculate:
• The angle between true North (Nv) and magnetic North (Nm) is called:
• The quadrantal course N80ºW corresponds to the circular course ...:
• If you sail for some hours along the same meridian on a northerly course:
• Spanish navigation charts are published by…