Competence 1 (Deck)

An event marker is used on an echo sounder to draw a line on the paper to mark a specific time of an occurrence. This allows the user to easily identify and analyze specific events or incidents that may have occurred during the sounder's operation. The event marker serves as a reference point for further analysis and interpretation of the echo sounder data.

Turbulence from the interaction of tidal streams with solid particles in suspension may cause false echoes in an echo sounder. When solid particles are present in the water and are disturbed by tidal streams, they can create turbulence. This turbulence can interfere with the sound waves emitted by the echo sounder, causing them to bounce back and create false echoes. This can lead to inaccurate depth readings and misinterpretation of the underwater environment.

Tidal Current Tables provide data on the direction and velocity of rotary tidal currents. These tables are specifically designed to help mariners navigate through tidal waters by providing information on the timing and strength of tidal currents. They are widely used by sailors, boaters, and other maritime professionals to plan safe and efficient routes. The data in Tidal Current Tables is based on extensive research and observations, making it a reliable source for understanding the behavior of tidal currents in a given area.

A small scale chart is a type of chart that covers a large area. It is called "small scale" because the ratio of the map distance to the actual distance on the ground is relatively small. This means that the details and features on the chart are not shown in great detail, but it provides a broad overview of a large geographic area.

Magnetostriction is an echo sounder transducer type. Magnetostriction is a phenomenon in which certain materials change their shape or dimensions when subjected to a magnetic field. This property is used in echo sounder transducers to convert electrical energy into mechanical vibrations and vice versa. These transducers emit sound waves into the water and then detect the echoes reflected back from the seabed or other objects. Therefore, the correct answer is Magnetostriction.

Tidal Current Tables would be the most appropriate source for finding data relating to the direction and velocity of rotary tidal currents. These tables provide information on the predicted times and rates of tidal currents for specific locations, including the direction and speed of the currents. The Nautical Almanac provides astronomical data, the Mariner's Guide offers general navigation information, and Tide Tables focus on tidal heights and times, making them less likely to include specific details about tidal currents.

The correct answer is "Co." In this context, "Co" most likely stands for coral. The other options, "Sh," "Cl," and "R," do not specifically indicate coral. Therefore, "Co" is the symbol that represents coral in the chart.

The Flinders bar on a magnetic compass compensates for the error caused by the vertical component of the earth's magnetic field. This error, known as dip error, occurs when the compass needle is inclined due to the vertical magnetic field. The Flinders bar is a small magnetic bar placed horizontally across the compass bowl, which helps counteract the effect of the vertical component and allows the compass to remain level and accurate. It does not necessarily reduce the deviation or correct the semi-quadrantal error at intercardinal headings.

The Flinders bar on a magnetic compass compensates for the error caused by the vertical component of the earth's magnetic field. This error, known as dip error, occurs when the compass needle is tilted due to the vertical component of the earth's magnetic field. The Flinders bar is designed to counteract this tilt and ensure that the compass needle remains level, allowing for accurate readings.

A small scale chart is a chart that covers a large area. This is because the term "scale" in cartography refers to the ratio of the map's size to the actual size of the area being represented. A small scale chart has a smaller ratio, meaning that the map covers a larger area. In contrast, a large scale chart would have a larger ratio, meaning the map covers a smaller area in greater detail. Therefore, a small scale chart is the correct answer for a chart that covers a large area.

Dead-reckoning refers to the position obtained by using only the course and speed of the vessel from a known starting point. It involves estimating the current position based on the previous known position, the course steered, and the distance traveled. This method does not consider external factors such as wind or currents, so the position obtained is a calculated estimate rather than an exact location.

A great circle is the shortest distance between any two points on Earth. It is a circle that divides the Earth into two equal halves and its center coincides with the center of the Earth. The great circle is formed by the intersection of the Earth's surface with a plane that passes through the center of the Earth and the two points. This concept is important in navigation and aviation as it helps determine the most efficient routes for travel.

The nature of the beam transmitted by an echo sounder is directional. This means that the beam is focused in a specific direction, allowing the echo sounder to accurately measure the depth of the water below the boat or ship. A directional beam helps in obtaining precise and reliable depth readings, as it avoids scattering of sound waves in different directions and provides a concentrated signal for accurate measurement.

The speed of sound in water is 1.5 kilometers per second. Sound travels faster in water compared to air because water molecules are closer together, allowing sound waves to propagate more quickly.

The given question asks for the equivalent millibar value for a barometric pressure reading of 29.92 inches of mercury. The correct answer is 1013.25 millibars. This is because 1 inch of mercury is equivalent to 33.86 millibars, so by multiplying 29.92 by 33.86, we get the corresponding millibar value of 1013.25.

Torque-induced precession is a phenomenon in which the axis of an object wobbles when torque is applied. This means that when a force is applied to an object, causing it to rotate, the axis of rotation does not remain fixed but instead wobbles or precesses. This can be observed in various objects such as spinning tops or gyroscopes. The torque applied to the object causes a change in its angular momentum, leading to the wobbling motion known as precession.

The nature of the beam transmitted by an echo sounder is directional. This means that the beam is focused in a specific direction and travels in a straight line. The echo sounder emits a narrow beam of sound waves into the water, and when these waves encounter an object, they bounce back and are detected by the device. The directional nature of the beam allows the echo sounder to accurately determine the depth and location of underwater objects or the ocean floor.

When a vessel is dragging her anchor in a strong wind, increasing the scope of anchor cable is the correct action to take. Increasing the scope means letting out more anchor cable, which allows the anchor to have a larger radius and better holding power. This helps to prevent the vessel from dragging further and provides more resistance against the wind and current.

The mean distance between the earth and the sun is commonly measured in astronomical units (AU). An AU is defined as the average distance from the earth to the sun, which is approximately 93 million miles or 150 million kilometers. This unit is widely used in astronomy and provides a convenient scale for measuring distances within our solar system. Celestial units and parsecs are not commonly used to measure the distance between the earth and the sun, and 4.3 light years is a much larger distance that is typically used to measure distances between stars.

Polaris, also known as the North Star, is always within 1 degree of the north pole. This means that no matter where you are in the northern hemisphere, Polaris will always be within 1 degree of the true north. This makes Polaris a useful navigational tool for determining direction and finding the north.

The frequency of the low frequency pulse of the echo sounder is 24 kHz.

The standard sea level pressure of the atmosphere is 1013.25 millibars of mercury. This value is widely accepted as the average atmospheric pressure at sea level under normal conditions. It is used as a reference point in meteorology and other scientific measurements.

The standard time meridian for zone description -1 is 15deg. E. This means that the time in this zone is 1 hour ahead of Coordinated Universal Time (UTC+1). The meridian represents the imaginary line that runs from the North Pole to the South Pole and passes through the given longitude. In this case, the meridian is located at 15 degrees east of the Prime Meridian, which is the reference point for measuring longitude. Therefore, the correct answer is 15deg. E.

Taking a radar range and visual bearing would be the preferred method of position fixing for greatest accuracy and certainty of position. This is because using both radar range and visual bearing provides two independent sources of information to determine the position. Radar range provides the distance from a known point, while visual bearing provides the direction from the observer to a visible landmark. By combining these two measurements, it is possible to triangulate the exact position with greater accuracy and certainty compared to using only radar range or radar bearing.

When the water salinity increases, the speed of sound also increases. This is because saltwater is denser than freshwater, and sound waves travel faster in denser mediums. The increase in salinity leads to an increase in the density of the water, causing the speed of sound to increase.

When navigating using DGPS (Differential Global Positioning System), the system uses a network of reference stations to correct the GPS signals, resulting in improved accuracy. The given answer of 10 meters indicates that when using DGPS, one can expect their position to be accurate within a radius of 10 meters. This means that the actual position may vary by up to 10 meters in any direction from the displayed position.

The vessel is on range when she is steering a course of 243deg. T because the chart indicates that the range is 243deg. T. This means that the vessel needs to steer a course of 243 degrees True in order to stay within the narrow channel and follow the range correctly.

An East Cardinal Mark in the IALA Buoyage System is characterized by a black band above and below a yellow band. This marking is used to indicate that the safest navigable water lies to the east of the buoy. The black color provides contrast and visibility, while the yellow color signifies caution and serves as a warning to mariners. Therefore, the correct answer is "Black band above and below yellow band."

The apparent altitude is the sextant altitude corrected for inaccuracies in the reading and reference level. This means that when using a sextant to measure the altitude of a celestial body, there may be errors in the reading due to factors such as parallax or imperfect calibration of the instrument. The reference level, which is used as a baseline for the measurement, may also have inaccuracies. Therefore, to obtain the true altitude, these inaccuracies need to be corrected.

The vessel's heading is given as 330°pgc and 345°psc, with a 2°E gyro error. The gyro error means that the gyrocompass is reading 2° more than the true heading. The variation is given as 6°W, which means that the magnetic heading is 6° less than the true heading. To find the deviation, we need to subtract the magnetic heading from the gyrocompass reading. Since the gyrocompass reading is already 2° more than the true heading, and the magnetic heading is 6° less than the true heading, the deviation would be the sum of these two values, which is 2°+6°=8°W. However, since the options only include 7°W, the correct answer is 7°W.

Isogonic lines are lines on a chart that represent points of equal variation. Variation refers to the difference between true north and magnetic north, which can vary depending on the location on the Earth's surface. Isogonic lines help navigators determine the magnetic declination at different locations, allowing them to accurately adjust their compasses for navigation purposes.

A general chart typically has a scale that represents the range of values being depicted. In this case, the correct answer is 1. 200,000. This means that the chart's scale can go up to a maximum value of 200,000. The other options provided (50,000, 25,000, and 1,000,000) either represent lower or higher values that would exceed the scale of a general chart.

The correct answer is 3 mins and 56 secs. This is because the Earth not only rotates on its axis but also revolves around the Sun. This revolution causes a slight discrepancy between the time it takes for the Earth to complete one rotation (sidereal day) and the time it takes for the Sun to appear at the same position in the sky (solar day). The Earth needs to rotate a little further to catch up with the Sun's apparent motion, resulting in a longer solar day compared to a sidereal day. This difference amounts to approximately 3 mins and 56 secs.

The standard atmospheric pressure is a measurement of the pressure exerted by the Earth's atmosphere at sea level. It is commonly expressed in millimeters of mercury (mmHg) or in units of pressure such as pounds per square inch (psi). The correct answer is 760 mmHg, which is the most commonly used value for standard atmospheric pressure.

Stream error refers to an error in a gyrocompass caused by rapid changes in course, speed, and latitude. These rapid changes create a deviation before the gyro can adjust itself, leading to inaccuracies in the compass reading. This error is known as a stream error.

Nautical twilight is the correct answer because it refers to the interval between the sun's upper limb being in the horizon and its center being 12 degrees below the horizon. During this time, there is still enough light for maritime navigation at sea. This period is characterized by a dimmer sky and the visibility of certain navigational stars. It is distinct from civil twilight and astronomical twilight, which have different degrees of darkness and visibility.

The vessel's heading is given as 330○pgc and 345○psc. PGC stands for True Course and PSC stands for Compass Course. The gyro error is 2○E, which means the gyrocompass is reading 2 degrees to the east of the true course. Variation is the angular difference between true north and magnetic north, and in this case, it is given as 10○W, meaning magnetic north is 10 degrees west of true north. To find the deviation, we need to subtract the gyro error from the variation. Therefore, the deviation on this heading is 3○W.

The vessel's heading is given as 330○pgc and 345○psc with a 2○E gyro error. The gyro error is East, which means that the actual heading is 2○ more than what is indicated by the gyro. The variation is given as 13○W, which means that the magnetic heading is 13○ less than the true heading. Since the gyro error is in the opposite direction of the variation, they cancel each other out. Therefore, the deviation on this heading is 0.

The "night effect" refers to the phenomenon where radio signals are affected during nighttime due to changes in the ionosphere. The ionosphere is a layer of the Earth's atmosphere that contains charged particles, and it plays a crucial role in reflecting radio waves back to the Earth's surface. During nighttime, the ionosphere undergoes rapid changes, such as the recombination of ions and the disappearance of certain layers, which can cause fluctuations in the reception of radio signals. Therefore, the correct answer is that the "night effect" is caused by rapid changes in the ionosphere.

When the apparent wind is zero, it means that there is no relative wind felt by an observer on a moving object. In this case, the apparent wind can be zero when the true wind is astern (coming from behind) and equal to the ship's speed. This means that the ship is moving at the same speed as the wind, causing the apparent wind to be zero.