1. The document discusses various types of errors that can occur in marine gyrocompasses, including latitude error, course and speed error, and ballistic deflection.
2. Latitude error, also called damping or settling error, causes the gyro spin axis to settle slightly off true north due to eccentricities in the damping mechanism. This introduces a small error that can be calculated based on latitude.
3. Course and speed error, also called steaming error, occurs because the gyro senses the combined rotation of the Earth and ship's movement, not just Earth's rotation. This introduces an error that depends on latitude, course, and speed.
4. Ballistic deflection is an error caused by accelerations from changes
The document provides guidance on passage planning for ships. It discusses key terms, guidelines and components to consider when creating a passage plan. The main components are appraisal, planning, execution and monitoring. Appraisal involves considering relevant information about the ship, cargo, crew, and voyage. Planning includes plotting the intended route on charts and noting safety elements. Execution is conducting the passage according to the plan, adjusting as needed. Monitoring involves checking progress and equipment performance against the plan. The overall purpose is to ensure safe and efficient navigation while protecting the environment.
The document provides an overview of international and inland nautical rules of the road. It discusses key topics such as required navigation lights for vessels, sound signals, and right-of-way rules for different vessel encounter situations such as meeting, overtaking, and crossing. Specific lights, shapes, and whistle signals that vessels must use to identify themselves and communicate intentions are described.
GPS satellites are positioned at an altitude of 20,200 km above the Earth's surface, which falls within medium Earth orbits. This height provides global coverage with a smaller number of satellites and allows earth-based transmitters and receivers to use modest sized antennas and lower transmission powers.
Gross tonnage refers to the total enclosed volume of a ship, while net tonnage refers to the cargo-carrying capacity. Both are determined by measuring volumes and applying formulas, and are dimensionless numbers rather than units of mass.
Radar performance can be ascertained using a performance monitor. 10 cm or S-band radar is generally better for long range scanning and in heavy rain due to less clutter.
1) ROTI (Rate of Turn Indicator) is an instrument that assists ship officers in planning, executing, and monitoring a vessel's progress along curved segments of its charted course. It indicates the rate of turn (in degrees per minute) to port or starboard.
2) For large vessels, turns must be executed along curved paths rather than sharp corners due to momentum and water friction. ROTI helps determine the radius and rate of turn needed based on factors like vessel size and speed.
3) There are two main turn types - constant radius, where the radius remains fixed and rate of turn varies, and constant rate, where the rate of turn remains fixed and the radius varies. The document provides
The document provides information on various bridge equipment used on ships including:
- AIS automatically transmits ship information like identification, position, speed to other vessels and coast stations.
- Weather facsimile systems receive synoptic charts via radio signals from coastal stations.
- Auto pilots control the rudder to maintain a set course using rudder, counter-rudder and yaw controls.
- Speed logs like the EMF and Doppler logs measure the ship's speed through and over the water respectively.
- GPS uses satellite signals to determine position within 10-15 meters accuracy. DGPS improves this to 3-5 meters.
- Radar uses radio pulses to detect targets and their range
1) A marine gyrocompass uses a freely-spinning gyroscope to determine direction based on the principles of angular momentum and the earth's constant rotation.
2) A gyroscope has three degrees of freedom - it can spin about its axis and tilt or turn in horizontal and vertical planes. The earth acts like a giant free gyroscope due to its mass, high-speed rotation, and lack of friction in space.
3) The gyroscope's angular momentum and inertia cause it to resist changes to its axis of spin, allowing it to maintain a fixed direction in space independent of the ship's movements. This gyroscopic property is used to determine true north.
This document provides instructions for plotting radar targets over a 6 minute interval to determine course, speed, closest point of approach (CPA), and time to CPA (TCPA) of other vessels. It outlines the steps to mark initial bearing and range, draw target movement line, transfer own vessel movement, calculate distances traveled, and determine other vessel's course, speed, CPA and TCPA. It concludes that in this example, if no course or speed changes are made, there will be a collision at a CPA of 0.0 nautical miles at 12:09:48, and that the observer is the give-way vessel in a crossing situation.
Final report Ship Handling and Manuevering 05-13-22.pptxNieLReSpiCiO
The document provides information on proper procedures for mooring, docking, and undocking ships. It discusses topics such as mooring lines, types of mooring (e.g. Mediterranean mooring), line handling procedures, docking maneuvers, and tips for safely docking and undocking a vessel. Key points include the different types of mooring lines used to secure a ship, the importance of communication and having a plan when maneuvering near docks, and approaching docks slowly with fenders in place for protection.
The document provides guidance on passage planning for ships. It discusses key terms, guidelines and components to consider when creating a passage plan. The main components are appraisal, planning, execution and monitoring. Appraisal involves considering relevant information about the ship, cargo, crew, and voyage. Planning includes plotting the intended route on charts and noting safety elements. Execution is conducting the passage according to the plan, adjusting as needed. Monitoring involves checking progress and equipment performance against the plan. The overall purpose is to ensure safe and efficient navigation while protecting the environment.
The document provides an overview of international and inland nautical rules of the road. It discusses key topics such as required navigation lights for vessels, sound signals, and right-of-way rules for different vessel encounter situations such as meeting, overtaking, and crossing. Specific lights, shapes, and whistle signals that vessels must use to identify themselves and communicate intentions are described.
GPS satellites are positioned at an altitude of 20,200 km above the Earth's surface, which falls within medium Earth orbits. This height provides global coverage with a smaller number of satellites and allows earth-based transmitters and receivers to use modest sized antennas and lower transmission powers.
Gross tonnage refers to the total enclosed volume of a ship, while net tonnage refers to the cargo-carrying capacity. Both are determined by measuring volumes and applying formulas, and are dimensionless numbers rather than units of mass.
Radar performance can be ascertained using a performance monitor. 10 cm or S-band radar is generally better for long range scanning and in heavy rain due to less clutter.
1) ROTI (Rate of Turn Indicator) is an instrument that assists ship officers in planning, executing, and monitoring a vessel's progress along curved segments of its charted course. It indicates the rate of turn (in degrees per minute) to port or starboard.
2) For large vessels, turns must be executed along curved paths rather than sharp corners due to momentum and water friction. ROTI helps determine the radius and rate of turn needed based on factors like vessel size and speed.
3) There are two main turn types - constant radius, where the radius remains fixed and rate of turn varies, and constant rate, where the rate of turn remains fixed and the radius varies. The document provides
The document provides information on various bridge equipment used on ships including:
- AIS automatically transmits ship information like identification, position, speed to other vessels and coast stations.
- Weather facsimile systems receive synoptic charts via radio signals from coastal stations.
- Auto pilots control the rudder to maintain a set course using rudder, counter-rudder and yaw controls.
- Speed logs like the EMF and Doppler logs measure the ship's speed through and over the water respectively.
- GPS uses satellite signals to determine position within 10-15 meters accuracy. DGPS improves this to 3-5 meters.
- Radar uses radio pulses to detect targets and their range
1) A marine gyrocompass uses a freely-spinning gyroscope to determine direction based on the principles of angular momentum and the earth's constant rotation.
2) A gyroscope has three degrees of freedom - it can spin about its axis and tilt or turn in horizontal and vertical planes. The earth acts like a giant free gyroscope due to its mass, high-speed rotation, and lack of friction in space.
3) The gyroscope's angular momentum and inertia cause it to resist changes to its axis of spin, allowing it to maintain a fixed direction in space independent of the ship's movements. This gyroscopic property is used to determine true north.
This document provides instructions for plotting radar targets over a 6 minute interval to determine course, speed, closest point of approach (CPA), and time to CPA (TCPA) of other vessels. It outlines the steps to mark initial bearing and range, draw target movement line, transfer own vessel movement, calculate distances traveled, and determine other vessel's course, speed, CPA and TCPA. It concludes that in this example, if no course or speed changes are made, there will be a collision at a CPA of 0.0 nautical miles at 12:09:48, and that the observer is the give-way vessel in a crossing situation.
Final report Ship Handling and Manuevering 05-13-22.pptxNieLReSpiCiO
The document provides information on proper procedures for mooring, docking, and undocking ships. It discusses topics such as mooring lines, types of mooring (e.g. Mediterranean mooring), line handling procedures, docking maneuvers, and tips for safely docking and undocking a vessel. Key points include the different types of mooring lines used to secure a ship, the importance of communication and having a plan when maneuvering near docks, and approaching docks slowly with fenders in place for protection.
An ECDIS is an electronic system that can display navigational charts and position information to serve as an alternative to paper charts. It integrates data from GPS, radar, and AIS to determine a vessel's position in relation to land, hazards, and navigation aids. The IMO requires all ships to carry electronic charts and ECDIS to meet chart carriage requirements. When planning a passage using ECDIS, the navigator must ensure the vessel has up-to-date chart licenses, enter vessel parameters, set the safety contour and domain, and create a route by placing waypoints while checking for hazards. ECDIS is then used during the voyage to monitor position and trigger alarms if safety parameters are exceeded.
This document discusses navigation rules and responsibilities for vessels at sea. It covers:
1) The purpose and scope of navigation rules, which apply based on a vessel's location and have the force of law.
2) Key definitions like power-driven vessel, sailing vessel, vessel not under command, and vessel constrained by draft.
3) Requirements for lights and dayshapes on vessels to determine stand-on/give-way status and aid in identification.
4) Specific rules that govern vessel conduct in situations like meetings, crossings, and overtaking to avoid collisions. Responsibilities are placed on the stand-on and give-way vessels in each case.
This document discusses classification societies and their role in classifying ships. Classification societies set technical and safety standards for ships and ensure they are properly maintained through regular surveys. They assign ships a class rating which is valid for typically 5 years and indicates the risk level for insurers. Major classification societies around the world include Lloyd's Register, American Bureau of Shipping, Bureau Veritas, Det Norske Veritas, and others.
This document discusses ship stability and the factors that determine a vessel's stability. It defines stability as a ship's tendency to return to its original upright position after being inclined by external forces. The key factors that determine a ship's stability are the location of the metacenter (M), center of gravity (G), and center of buoyancy (B). When these points are properly aligned and the metacentric height is sufficient, the ship is in stable equilibrium. However, if the points become misaligned, such as from excessive free surface effect, the ship's stability can be compromised. Maintaining proper stability is important for safety and commercial decisions regarding cargo capacity and vessel allocation.
1. Magnetic compasses indicate magnetic north using the Earth's magnetic field, while gyro compasses indicate true north by measuring the Earth's rotation and are unaffected by magnetic fields.
2. A gyroscope maintains its orientation in space regardless of movement by relying on the principle of gyroscopic inertia. It has three degrees of freedom and its orientation remains fixed due to precession caused by external torques.
3. Errors in gyrocompasses like speed error and ballistic deflection error occur due to the Earth's rotation and changes in a ship's speed or course, but can be compensated for through electrical adjustments and a dual rotor design.
Presentation on maneuvering and collision avoidance with special focus on large tonnage vessels.
Maneuverability limits and last moment maneuver are thoroughly shown in this material.
Este documento describe varios instrumentos de navegación como el compás magnético, giroscópico y repetidores, círculo azimutal, taxímetros, corredera, sonda, ecosonda, sextante, radar, GPS, e instrumentos de trazado y misceláneos como binoculares, cronómetros y barómetro.
1. The document outlines the roles and responsibilities of the bridge watchkeeping team, including conducting regular checks of navigational equipment, compliance with collision regulations, and navigation procedures in different conditions.
2. It describes the roles of the Master, Officer of the Watch, helmsman, lookout, and pilot in ensuring safe navigation and navigation in compliance with international regulations.
3. Effective communication and coordination between all bridge team members is essential for safe navigation.
This document provides an introduction to nautical charts, including Admiralty charts. It explains that charts show water depths, shorelines, hazards, buoys and other navigational markers using standardized symbols and colors. Depths are shown in meters and refer to the chart datum, or lowest astronomical tide. The document provides examples of features found on nautical charts such as latitude and longitude lines, tidal diamonds, compass roses, buoys, wrecks, obstructions and seabed composition. It encourages further learning about charts and navigation through online courses and videos.
The document discusses the International Convention on Load Lines of 1966 which establishes uniform principles and rules regarding load lines on ships involved in international voyages. It outlines the requirements for assigning freeboards based on zones and seasons, surveying and certifying ships, marking load lines on ships, and other provisions to ensure ships are properly loaded for safety and stability in various weather conditions around the world. The convention aims to determine safe limits of load lines for ships to maintain adequate freeboard and prevent overloading.
This document provides information about ship maneuvering, including terminology, forces, and concepts. It defines key ship parts like the bow, stem, and superstructure. It describes controllable forces from propellers, rudders, and mooring lines that can maneuver a ship. Uncontrollable forces from wind, current, and water depth are also discussed. The concept of the pivot point is explained, which is the point about which a ship rotates during maneuvers and is affected by factors like headway, speed, and tugs. Basic shiphandling theory on motion and Newton's laws is presented.
The document discusses the bottom structure of ships, including the functions and types of bottoms, keels, and floors. It provides details on single bottom and double bottom construction. Single bottoms are used in smaller vessels, while larger ships generally have double bottoms for added protection against damage. Double bottoms can be of two types - watertight or dry - and provide both structural reinforcement and tank space. Floors are important transverse structural members that strengthen the bottom plate.
This document summarizes the role and services of classification societies. Classification societies develop technical standards, review ship designs, and conduct periodic surveys to certify that ships meet standards for safety and mechanical fitness. The American Bureau of Shipping is a leading classification society, with over 1500 employees and 225 offices worldwide. It develops over 60 rules and guides, reviews over 20,000 hours of engineering per month, and surveys over 7000 ships totaling over 15 million gross tons under construction. In addition to classification, the ABS can certify vessels under international conventions like ISM, ISPS, MLC, and issue certificates required by SOLAS and MARPOL for safety and pollution prevention.
International convention on load lines 1968 group 2jabbar2002pk200
The document discusses the history and provisions of the International Convention on Load Lines from 1930 to 2003. Some key points:
- The 1930 Load Line Convention was the first international agreement to apply load line regulations universally based on reserve buoyancy and stability.
- Revisions were needed as ship designs evolved, leading to the 1968 Load Lines Convention which updated rules on structural strength, reserve buoyancy, crew protection and limiting deck cargo.
- The 1968 Convention set out rules for calculating and assigning freeboard based on a ship's zone, season, and cargo. It ensured watertight integrity and proper load line markings.
- Further amendments in 1971, 1975, 1979, 1983, 1995, and 2003 aimed to
The document provides an overview of key rules and definitions from the Navigation Rules for Marine Law Enforcement Officers. It defines terms like vessel, underway, power-driven and sailing vessels. It outlines lighting requirements and sound signals. It discusses rules for determining risk of collision, taking action to avoid collision, operating in narrow channels, overtaking situations, head-on encounters, and crossing situations.
The document provides guidance on properly handing over and taking over the navigational watch. It states that the officer of the watch should not hand over the watch if the relieving officer is incapable, and the relieving officer must ensure all crew members are capable of performing their duties. The relieving officer must also satisfy themselves on the safety of the vessel before taking over the watch. Proper lookout, navigation with pilots, and environmental protection are also discussed.
1. The document provides instructions for removing an anchor from the hawse pipe to enable the vessel to be moored or towed. It describes securing wires to the anchor and using the windlass to walk the anchor back while maintaining tension on wires.
2. The Mediterranean moor allows multiple vessels to berth at a single quay. It involves letting go anchors and using engines and cables to maneuver the vessel broadside to the quay.
3. Clearing a foul hawse involves various methods like using tides and wires to remove turns from an anchor chain that is fouled in the hawse pipe. Lashings and messengers are used to gradually remove half turns at a time
This document discusses regulations and procedures for safely carrying grain cargo. It covers types of grain, dangers of grain shifting, requirements of the International Code for the Safe Carriage of Grain, documents required for loading, and methods for securing grain in fully and partially filled compartments including longitudinal subdivisions, overstowing with bags, and covering surfaces with tarps and securing with lashings or wire mesh.
This document discusses Rate of Turn Indicator (ROTI), which is required on vessels over 50,000 GT per SOLAS regulations. ROTI assists the officer on watch in planning, executing, and monitoring a vessel's progress along a curved segment of its charted course. It provides the rate of turn to port and starboard in degrees per minute. The document derives the formula for ROT as the change in angle over time divided by the radius of the turn. It provides examples of using ROTI for constant radius and constant rate turns, and discusses wheel over points and planning turns.
1. The document describes how the movement of liquid in a ballistic causes errors in a gyrocompass heading reading except when on cardinal headings, due to rolling and pitching motions imparting vertical torques.
2. It explains that the inherent period of the ballistic can be matched to the ship's motion to eliminate errors, but inclination of the liquid surface still causes issues.
3. Methods for reducing errors caused by acceleration include adjusting the position of the ballistics and using multiple gyros to counteract each other's errors. Compasses without gravitational attachments have no intercardinal rolling error.
An ECDIS is an electronic system that can display navigational charts and position information to serve as an alternative to paper charts. It integrates data from GPS, radar, and AIS to determine a vessel's position in relation to land, hazards, and navigation aids. The IMO requires all ships to carry electronic charts and ECDIS to meet chart carriage requirements. When planning a passage using ECDIS, the navigator must ensure the vessel has up-to-date chart licenses, enter vessel parameters, set the safety contour and domain, and create a route by placing waypoints while checking for hazards. ECDIS is then used during the voyage to monitor position and trigger alarms if safety parameters are exceeded.
This document discusses navigation rules and responsibilities for vessels at sea. It covers:
1) The purpose and scope of navigation rules, which apply based on a vessel's location and have the force of law.
2) Key definitions like power-driven vessel, sailing vessel, vessel not under command, and vessel constrained by draft.
3) Requirements for lights and dayshapes on vessels to determine stand-on/give-way status and aid in identification.
4) Specific rules that govern vessel conduct in situations like meetings, crossings, and overtaking to avoid collisions. Responsibilities are placed on the stand-on and give-way vessels in each case.
This document discusses classification societies and their role in classifying ships. Classification societies set technical and safety standards for ships and ensure they are properly maintained through regular surveys. They assign ships a class rating which is valid for typically 5 years and indicates the risk level for insurers. Major classification societies around the world include Lloyd's Register, American Bureau of Shipping, Bureau Veritas, Det Norske Veritas, and others.
This document discusses ship stability and the factors that determine a vessel's stability. It defines stability as a ship's tendency to return to its original upright position after being inclined by external forces. The key factors that determine a ship's stability are the location of the metacenter (M), center of gravity (G), and center of buoyancy (B). When these points are properly aligned and the metacentric height is sufficient, the ship is in stable equilibrium. However, if the points become misaligned, such as from excessive free surface effect, the ship's stability can be compromised. Maintaining proper stability is important for safety and commercial decisions regarding cargo capacity and vessel allocation.
1. Magnetic compasses indicate magnetic north using the Earth's magnetic field, while gyro compasses indicate true north by measuring the Earth's rotation and are unaffected by magnetic fields.
2. A gyroscope maintains its orientation in space regardless of movement by relying on the principle of gyroscopic inertia. It has three degrees of freedom and its orientation remains fixed due to precession caused by external torques.
3. Errors in gyrocompasses like speed error and ballistic deflection error occur due to the Earth's rotation and changes in a ship's speed or course, but can be compensated for through electrical adjustments and a dual rotor design.
Presentation on maneuvering and collision avoidance with special focus on large tonnage vessels.
Maneuverability limits and last moment maneuver are thoroughly shown in this material.
Este documento describe varios instrumentos de navegación como el compás magnético, giroscópico y repetidores, círculo azimutal, taxímetros, corredera, sonda, ecosonda, sextante, radar, GPS, e instrumentos de trazado y misceláneos como binoculares, cronómetros y barómetro.
1. The document outlines the roles and responsibilities of the bridge watchkeeping team, including conducting regular checks of navigational equipment, compliance with collision regulations, and navigation procedures in different conditions.
2. It describes the roles of the Master, Officer of the Watch, helmsman, lookout, and pilot in ensuring safe navigation and navigation in compliance with international regulations.
3. Effective communication and coordination between all bridge team members is essential for safe navigation.
This document provides an introduction to nautical charts, including Admiralty charts. It explains that charts show water depths, shorelines, hazards, buoys and other navigational markers using standardized symbols and colors. Depths are shown in meters and refer to the chart datum, or lowest astronomical tide. The document provides examples of features found on nautical charts such as latitude and longitude lines, tidal diamonds, compass roses, buoys, wrecks, obstructions and seabed composition. It encourages further learning about charts and navigation through online courses and videos.
The document discusses the International Convention on Load Lines of 1966 which establishes uniform principles and rules regarding load lines on ships involved in international voyages. It outlines the requirements for assigning freeboards based on zones and seasons, surveying and certifying ships, marking load lines on ships, and other provisions to ensure ships are properly loaded for safety and stability in various weather conditions around the world. The convention aims to determine safe limits of load lines for ships to maintain adequate freeboard and prevent overloading.
This document provides information about ship maneuvering, including terminology, forces, and concepts. It defines key ship parts like the bow, stem, and superstructure. It describes controllable forces from propellers, rudders, and mooring lines that can maneuver a ship. Uncontrollable forces from wind, current, and water depth are also discussed. The concept of the pivot point is explained, which is the point about which a ship rotates during maneuvers and is affected by factors like headway, speed, and tugs. Basic shiphandling theory on motion and Newton's laws is presented.
The document discusses the bottom structure of ships, including the functions and types of bottoms, keels, and floors. It provides details on single bottom and double bottom construction. Single bottoms are used in smaller vessels, while larger ships generally have double bottoms for added protection against damage. Double bottoms can be of two types - watertight or dry - and provide both structural reinforcement and tank space. Floors are important transverse structural members that strengthen the bottom plate.
This document summarizes the role and services of classification societies. Classification societies develop technical standards, review ship designs, and conduct periodic surveys to certify that ships meet standards for safety and mechanical fitness. The American Bureau of Shipping is a leading classification society, with over 1500 employees and 225 offices worldwide. It develops over 60 rules and guides, reviews over 20,000 hours of engineering per month, and surveys over 7000 ships totaling over 15 million gross tons under construction. In addition to classification, the ABS can certify vessels under international conventions like ISM, ISPS, MLC, and issue certificates required by SOLAS and MARPOL for safety and pollution prevention.
International convention on load lines 1968 group 2jabbar2002pk200
The document discusses the history and provisions of the International Convention on Load Lines from 1930 to 2003. Some key points:
- The 1930 Load Line Convention was the first international agreement to apply load line regulations universally based on reserve buoyancy and stability.
- Revisions were needed as ship designs evolved, leading to the 1968 Load Lines Convention which updated rules on structural strength, reserve buoyancy, crew protection and limiting deck cargo.
- The 1968 Convention set out rules for calculating and assigning freeboard based on a ship's zone, season, and cargo. It ensured watertight integrity and proper load line markings.
- Further amendments in 1971, 1975, 1979, 1983, 1995, and 2003 aimed to
The document provides an overview of key rules and definitions from the Navigation Rules for Marine Law Enforcement Officers. It defines terms like vessel, underway, power-driven and sailing vessels. It outlines lighting requirements and sound signals. It discusses rules for determining risk of collision, taking action to avoid collision, operating in narrow channels, overtaking situations, head-on encounters, and crossing situations.
The document provides guidance on properly handing over and taking over the navigational watch. It states that the officer of the watch should not hand over the watch if the relieving officer is incapable, and the relieving officer must ensure all crew members are capable of performing their duties. The relieving officer must also satisfy themselves on the safety of the vessel before taking over the watch. Proper lookout, navigation with pilots, and environmental protection are also discussed.
1. The document provides instructions for removing an anchor from the hawse pipe to enable the vessel to be moored or towed. It describes securing wires to the anchor and using the windlass to walk the anchor back while maintaining tension on wires.
2. The Mediterranean moor allows multiple vessels to berth at a single quay. It involves letting go anchors and using engines and cables to maneuver the vessel broadside to the quay.
3. Clearing a foul hawse involves various methods like using tides and wires to remove turns from an anchor chain that is fouled in the hawse pipe. Lashings and messengers are used to gradually remove half turns at a time
This document discusses regulations and procedures for safely carrying grain cargo. It covers types of grain, dangers of grain shifting, requirements of the International Code for the Safe Carriage of Grain, documents required for loading, and methods for securing grain in fully and partially filled compartments including longitudinal subdivisions, overstowing with bags, and covering surfaces with tarps and securing with lashings or wire mesh.
This document discusses Rate of Turn Indicator (ROTI), which is required on vessels over 50,000 GT per SOLAS regulations. ROTI assists the officer on watch in planning, executing, and monitoring a vessel's progress along a curved segment of its charted course. It provides the rate of turn to port and starboard in degrees per minute. The document derives the formula for ROT as the change in angle over time divided by the radius of the turn. It provides examples of using ROTI for constant radius and constant rate turns, and discusses wheel over points and planning turns.
1. The document describes how the movement of liquid in a ballistic causes errors in a gyrocompass heading reading except when on cardinal headings, due to rolling and pitching motions imparting vertical torques.
2. It explains that the inherent period of the ballistic can be matched to the ship's motion to eliminate errors, but inclination of the liquid surface still causes issues.
3. Methods for reducing errors caused by acceleration include adjusting the position of the ballistics and using multiple gyros to counteract each other's errors. Compasses without gravitational attachments have no intercardinal rolling error.
The document discusses gyrocompasses and magnetic compasses. It describes gyrocompass theory including how gyroscopes maintain orientation to true north. It also discusses gyro error determination and correction. Magnetic compass theory is explained including variation, deviation, and magnetic compass error. Methods to determine gyro error and apply corrections are provided along with examples of solving for true course from other compass readings.
Compass errors arise from two sources: variation and deviation. Variation is the difference between magnetic and true north, while deviation is caused by nearby magnetic interference. Compass error is the sum of variation and deviation, representing the angle between true and compass north. Finding transit or gyro errors allows one to determine the compass error. Regular corrections are needed since errors change with location and vessel orientation.
The document discusses relative velocity between two moving bodies. It defines relative velocity as the velocity of one body as seen from another body in motion. The relative velocity of body A with respect to body B is given by VA - VB, where VA and VB are the velocities of bodies A and B, respectively. The document provides examples of calculating relative velocity in one and two dimensions. It also discusses problems related to crossing a river and calculating velocity for different scenarios. Homework questions involving calculating relative velocities in various situations are provided at different levels.
This document discusses relative motion analysis using translating reference frames. It provides two examples of using relative motion: [1] describing the motion of a glider in a crosswind relative to the moving air mass and ground, and [2] finding the velocity and acceleration of a glider being towed by an airplane. The document explains that relative motion involves describing motion from the perspective of observers undergoing constant velocity translation, like an aircraft or particle, and combining relative and absolute motions using vector addition and subtraction.
This document discusses ship hydrostatics and stability. It begins by defining important hydrostatic curves such as displacement curves, coefficients curves, and Bonjean curves which are used to compute displacement and the position of the center of buoyancy. It then explains how to compute these curves through formulas and examples of hand calculations. The document concludes by discussing topics in stability including righting and heeling moments, upsetting forces, transverse and longitudinal equilibrium, and the calculation of initial stability values like metacentric height.
Captain Quinn of the sinking yacht Kestrel needs to determine his position to direct rescuers to his location. The chapter will cover navigation techniques to accurately describe positions on Earth using lines of latitude and longitude. It will also discuss compass use, fixing positions on charts, and how lighthouses and GPS can assist navigators. The ability to rapidly communicate one's position in an emergency could mean the difference between life and death.
1. The document discusses conservation of angular momentum and properties of vectors related to rotation. It contains 17 multiple choice or calculation problems regarding topics like vector products, torque, angular momentum, and circular motion.
2. Key concepts covered include the perpendicular relationship between torque and force vectors, conditions for maximum vector products, calculations of angular momentum for particles moving in circles or along straight lines, and the relationship between angular momentum, moment of inertia, and angular velocity.
3. The problems are solved by applying definitions of angular momentum, torque, and vector products and utilizing relationships like the perpendicular nature of the cross product to find missing vector components or calculate angular quantities.
1. The document discusses gyroscopic couple, which acts on a spinning object that is rotating about another axis.
2. It provides examples of gyroscopic couple in naval ships, where the spinning of propeller shafts affects steering, pitching, and rolling.
3. The document also examines the gyroscopic couple and centrifugal couple in vehicles like cars and motorcycles taking turns, and how this affects their stability.
This document outlines the steps to compute the closure, accuracy, and area of a traverse survey. It discusses key terms, sources of error, and a 9-step process to calculate closure, precision ratio, and area using the double meridian distance method. As an example, it works through the calculations for a 5-sided closed traverse, determining the closure is 0.49 feet, precision ratio is 1:4200, and total area is 6.126 acres.
This document provides information on theodolite surveying. It discusses how to measure the magnetic bearing of a line, prolong and range a line, measure deflection angles, vertical angles, and includes steps for closed and open traverse surveys using the included angle and deflection angle methods. It also covers topics like observation tables, consecutive and independent coordinates, and balancing a traverse using Bowditch's rule and the transit rule.
Curvature is inevitably provided on railway tracks to bypass obstacles, provide longer gradients, and pass lines through desirable locations. Horizontal curves change track direction, while vertical curves connect gradients or gradients to level ground. Curvature restricts speed and train length, increases maintenance costs, and risks accidents. Degree and radius describe curves, with smaller radii indicating sharper curves. Super-elevation/cant counters centrifugal force on curves, and is calculated using speed, weight, radius, and gauge. Cant deficiency occurs where full cant cannot be provided, like where lines branch, requiring speed restrictions.
Cam mechanisms use cams to provide unusual motions to followers. Cams can create different types of motions but are expensive to manufacture and wear down over time. Cams are classified based on their shape and type of contact. Common cam motion curves include linear, simple harmonic, parabolic, and cycloidal motions. The cycloidal motion curve provides the smoothest motion in terms of finite acceleration. Cam size is determined by considering the pressure angle and minimum radius of curvature to minimize size while ensuring proper force transmission and strength.
A gyroscope is a device that uses angular momentum to detect orientation and maintain stability. It consists of a spinning wheel or disk whose axis is free to orient in any direction. Gyroscopes are used for navigation and stabilization in ships, airplanes, drones, and other vehicles. They work by producing a gyroscopic effect - as the spinning axis rotates about another axis, conservation of angular momentum causes a reactive torque perpendicular to the plane of rotation. This effect counters external forces and helps maintain the orientation of the device.
This document summarizes key concepts about uniform circular motion including:
- Radians are the SI unit for measuring angles where 1 radian is the central angle that spans an arc equal to the circle's radius.
- Formulas relate angular quantities like speed (ω) and displacement (θ) to linear quantities like speed (v) and arc length (s) using the radius (R).
- Centripetal force (Fc) is required to cause circular motion and is given by Fc = Mv2/R, where M is the object's mass and v is its speed.
- Banked roads allow vehicles to safely take curved portions faster by providing tilt that replaces needed friction with
This document provides an introduction to physics concepts related to kinematics including vectors, scalars, units, displacement, velocity, acceleration, and graphing motion. Key topics covered include the definitions and differences between scalars and vectors, common physics units, the relationship between mass and weight, how to represent vectors with arrows, definitions of distance, displacement, speed, velocity, and acceleration, and how to graph position, velocity, and acceleration as functions of time for objects undergoing constant acceleration. Examples and practice problems are also provided.
This document provides an introduction to physics concepts related to kinematics including vectors, scalars, units, displacement, velocity, acceleration, and graphing motion. Key topics covered include the definitions and differences between scalars and vectors, SI units used in physics, mass versus weight, and the definitions and relationships between distance, displacement, speed, velocity, and acceleration. Formulas for kinematics including the kinematics equations are also presented along with examples of how to graph position, velocity, and acceleration versus time.
"How to Study Circular Motion (Physics) for JEE Main?"Ednexa
This document defines and explains circular motion. It begins by defining circular motion as the motion of a particle along the circumference of a circle. It describes uniform circular motion as when the magnitude of linear velocity remains constant. It defines important terms like position vector, angular displacement, angular velocity, angular acceleration, and their relationships. It provides examples of using the right hand rule and vector methods to determine acceleration in circular motion. It concludes by providing sample homework problems.
1. The document outlines 23 performance standards that autopilot and heading control systems installed on ships must meet according to the International Maritime Organization (IMO).
2. The standards require systems to reliably maintain a preset heading under various operating conditions, incorporate controls to adjust for weather and steering performance, and allow for easy and safe operation.
3. Systems must also ensure the ship's heading can only be altered intentionally by crew, integrate properly with navigation systems, and include alarms and indications for failures or off-heading situations.
1. The purpose of a simplified voyage data recorder (S-VDR) is to securely store information about a vessel's position, movement, status, and command in the event of an incident for use in subsequent investigations.
2. Ships defined in SOLAS Chapter V must be fitted with an S-VDR that continuously records preselected data items relating to ship status, equipment output, and command/control. The data must be time-correlated and stored in a tamper-proof capsule for at least 2 years.
3. An S-VDR must record data items including date, time, position, speed, heading, bridge audio, communications audio, radar data, and AIS data
The document provides information on the International Aeronautical and Maritime Search and Rescue (IAMSAR) Manual. It discusses that IAMSAR is a joint publication of ICAO and IMO that assists states in meeting SAR needs and obligations under international conventions. It has three volumes that deal with specific SAR system duties and can be used independently or together. The document then provides definitions and explanations of key terms related to SAR operations, structures, and coordination.
This document outlines the International Maritime Organization's (IMO) performance standards for rate of turn indicators (ROTI) installed on ships. The ROTI must be capable of indicating port and starboard turns, have a means to verify operation, and use a center-zero analog dial indicator with positive indications for port and starboard turns. The scale must allow measurement of turns between -30 and 30 degrees per minute and meet accuracy standards for deviations from the actual turn rate under various ship motions and speeds.
The document outlines 17 performance standards that GPS receiver equipment installed on ships must meet in order to be compliant. The standards require the equipment to:
1) Be capable of receiving and processing GPS signals to provide position, latitude and longitude, in the WGS-84 coordinate system and UTC time within specified accuracies and update rates.
2) Have static and dynamic position accuracy of 100m or less depending on whether differential GPS corrections are applied.
3) Generate and output position, course, speed, and time data at least once per second and interface with other navigation equipment.
4) Provide warnings if performance standards for position dilution or update rates are not met.
This document outlines the performance standards for echo-sounding equipment set by the International Maritime Organization (IMO). The equipment is intended to provide reliable depth readings between 2-200 meters to aid navigation, especially in shallow waters. It must have at least two depth ranges (20m and 200m scales), record soundings for 15 minutes, and be able to record depth and time for 12 hours. The display must show depth marks no more than 1/10 the range and time marks at most every 5 minutes. Alarms are required for shallow water and any failure affecting safe operation.
This document discusses an inclining test performed on a ship to determine its metacentric height (GM). It provides details of the test, including five shifts of weights totaling 216 tonnes that caused deflections of the ship ranging from 12 to 110 mm. It also shows the calculations to determine that the ship's GM as inclined is 1.68 m. Precautions for an accurate inclining test are noted, such as having a calm environment, securing loose weights, and restricting crew movement during the test.
The document discusses the relationships between a ship's speed, displacement, distance traveled, and fuel consumption. It states that daily fuel consumption varies as the cube of ship speed, as the 2/3 power of displacement, and as the square of speed multiplied by distance for a voyage. Examples are provided to demonstrate calculating new fuel consumption with changes in speed, displacement or distance. Specific fuel consumption is also defined as the fuel used per kilowatt hour of power.
An integrated bridge system (IBS) combines systems like the integrated navigation system (INS) to allow centralized monitoring and control of operations from the bridge like navigation, machinery control, safety, and security. An IBS provides benefits like enhanced decision making and workload reduction. Key components of an IBS include the navigation management system, alarm system, and conning display. Passage planning, position fixing, and track keeping can be automated if principles are followed, but overreliance on automation without watchkeeping can be dangerous. An IBS interconnects INS and other systems, while INS specifically combines navigational data and systems.
The document discusses autopilot systems and steering gear controls on ships. It provides details on:
- How autopilots work to automatically steer the ship and reduce workload in heavy weather by learning a ship's handling characteristics.
- The different control modes and settings used on autopilot control units, including proportional, integral, derivative controls and weather compensation settings.
- Limitations of autopilot use in rough conditions, tight spaces, slow speeds, or during maneuvers.
- Procedures for changing between manual and autopilot steering, testing equipment, and emergency steering protocols.
VDR is a marine recording device that functions like an aircraft's black box, recording critical ship data and communications to help investigators determine the cause of accidents. A VDR continuously records data from navigational equipment, alarms, and communications for at least 12 hours. This data is stored in a protective capsule that can withstand fire and deep water immersion. Accessing and analyzing VDR data after an incident allows for faster, more accurate investigations that help improve safety. VDR recordings have also assisted ship owners in assessing bridge team performance and identifying areas for improvement.
The document contains several numerical problems related to marine gyrocompasses. It provides solutions to problems involving calculating the tilt and direction of a gyroscope's spin axis (SA) given its initial position and the latitude, passage of time, or a later observed position. One question calculates the percentage change in the moment of inertia (MOI) of a gyroscope rotor if its mass increases by 20% and radius of gyration decreases by 20%.
This document contains checklists for various emergency situations that may occur on ships, such as general emergencies, abandoning ship, search and rescue, rescuing crew from a disabled vessel, flooding, fire, stranding or grounding, collision, main engine failure, steering failure, rudder failure, and checklists for navigation in coastal and ocean waters. The checklists provide step-by-step instructions for crew to follow to ensure passenger and crew safety, assess damage, send distress signals, and follow proper emergency procedures in a variety of emergency situations at sea.
1. Atmospheric pressure is the pressure exerted by the weight of the earth's atmosphere. It is measured in hectopascals (hPa), with 1 hPa equal to 1 millibar.
2. Pressure gradient refers to the rate of change of pressure over distance and indicates how strongly winds will blow between areas of high and low pressure.
3. Dew point temperature is the temperature at which air becomes saturated with water vapor and fog can form. It is an important measurement for mariners to consider when deciding whether to ventilate cargo holds.
1. The document outlines International Maritime Organization performance standards for Bridge Navigational Watch Alarm Systems (BNWAS).
2. BNWAS monitors bridge activity and detects if the Officer of the Watch becomes incapacitated, alerting others. It has automatic, manual on, and manual off operational modes.
3. The system remains dormant for 3-12 minutes before initiating visual alerts. If not reset, it issues audible alarms to the bridge and then remotely to summon help. Resetting cancels alerts and restarts the dormant period.
1. An electromagnetic (EM) log works by inducing an electromotive force in sea water moving through the Earth's magnetic field using a solenoid, with the induced voltage proportional to water velocity.
2. The solenoid is housed in a streamlined flow sensor that extends below the ship's hull. Electrodes on either side of the sensor measure the voltage induced in the strip of sea water moving across the magnetic field.
3. This voltage corresponds to ship speed and is amplified and used to drive indicators showing speed in the wheelhouse. The EM log thus non-intrusively measures ship speed through water.
AIS aims to automatically identify vessels using electronic communication without human intervention. It works by having each vessel broadcast its identification and position using a transponder. Vessels are assigned time slots to transmit this data to avoid interference on the shared VHF channel. The time slots are precisely synchronized using GPS time signals. This allows many vessels to broadcast on the same frequency without interfering with each other. Vessels can then receive the identification and position of all other vessels within range, aiding navigation safety.
1. The document outlines performance standards for route planning, monitoring, and voyage recording functions of Electronic Chart Display and Information Systems (ECDIS).
2. It describes that ECDIS should allow for simple and reliable route planning including straight and curved segments as well as adjustments to planned routes. It should monitor the ship's position along the selected route and provide alarms if deviations occur.
3. For voyage recording, ECDIS should store minimum navigation elements from the past 12 hours including ship track, time, position and headings as well as the ENC database information used for reconstruction and verification purposes. It should also record the complete voyage track with time marks not exceeding 4 hours.
1. The document outlines performance standards for Electronic Chart Display and Information Systems (ECDIS) as set by the International Maritime Organization (IMO).
2. The primary function of ECDIS is to contribute to safe navigation by displaying all necessary chart information and facilitating simple chart updating. ECDIS should reduce navigational workload compared to paper charts.
3. ECDIS must have reliability and availability equal to or better than paper charts, and provide alarms for information errors or equipment malfunctions. It must support on-board testing and back-up arrangements to ensure safe navigation if ECDIS fails.
This document outlines performance standards for electronic chart display and information systems (ECDIS) regarding displays. It includes standards for the display of electronic navigational chart (SENC) information such as displaying the standard display at the largest scale by a single operator action. It also covers displaying navigational information like radar in a way that does not degrade the SENC information. Additional standards address display mode in north-up orientation, true motion mode, and the generation of neighboring areas. Minimum display requirements like an effective chart size of 270mm by 270mm are also specified.
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OPERATIONAL ERRORS OF THE GYRO:
1. Latitude error (Damping Error or Settling Error)
2. Course, Latitude & Speed Error (Steaming Error)
3. Ballistic Deflection
4. Ballistic Tilt
5. Rolling Error
6. Inter cardinal Rolling Error
Latitude Error (Damping Error or Settling Error):
This error is due to the eccentricity of the damping weight (i.e. offset of the
mercury ballistic cone bearing).
The spin axis reaches equilibrium and settles in a position at which drifting is
counteracted by control precession & the damping precession counteracts tilting.
Since for any latitude except the equator there will always be a drifting given by
15o
Sin (Lat) per hour. This Dg is counteracted by control precession (Pc) which
comes into action only with tilt. In a given proportion damping precession (Pd)
also accompanies, which counteracts the tilting (Tg). This results in tilt being
reduced which in turn will reduce the Pc. This means that some sustained increase
in Tg is required which compensates for this. But Tg can occur only when spin
axis is off the meridian, as Tg at meridian is nil.
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Therefore the spin axis of the gyro settles off the meridian & slightly tilted, where
all the forces balance out. That is Dg = Pc and Tg = Pd
In N lat this position is slightly above the horizon and east of the meridian and in S
lat the spin axis settles slightly below the horizon and west of meridian.
This error can be calculated for given latitude and applied manually. In Sperry
compass this error is allowed for by moving lubber line by means of auxiliary
latitude corrector. Tilt is very slight and can be ignored.
This error occurs only in gyro compasses damped in tilt and not in compasses
damped in azimuth
Formula for Latitude error:
At the settling position:
Drifting (Dg) = Control precession (Pc)
Tilting (Tg) = Damping precession (Pd)
Or, 15 Sin lat = Pc and, ---------------- (1)
15 Cos lat. Sin Az. = Pd -------------- (2)
Dividing (2) by (1), we have:
Cos lat. Sin Az = Pd = Pc (In Sperry compass, Pd = Pc/40)
Sin lat Pc 40 Pc
Or, Sin Az = K Tan lat (Where, K = 1/40, in Sperry compass)
Thus: Sin Az = Tan lat/40 (in Sperry compass eccentricity = 1/40)
Since azimuth is very small, we have: Az (radians) = Tan lat/40
Or, Az (degrees) = 57.3 Tan lat/40 = 1.43 Tan lat
Thus Azimuth (DE or SE or LE in degrees) = K Tan Lat (where K=constant, about
1.43 in Sperry Compass)
Thus students can use either of the two formulas:
1. Sin Az = 1/40.Tan lat.
2. Az in degrees = 1.43 Tan lat.
Where Az is Damping error (or Settling error or Latitude error)
Course & Speed error (Steaming error):
Gyrocompass is basically a fast spinning gyrosphere which is controlled and
damped so as to make it point and keep pointing true north. We know that all
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meridians, which represent true north, are perpendicular to equator and all
parallels of latitudes. This means that the gyro spin axis points at right angle to the
direction of rotation of the earth. This is alright as long as gyro is placed on a
stationary vessel. But on a moving vessel, gyro senses the resultant of earth’s E-W
motion and vessel’s own motion as the actual direction of rotation of the earth and
aligns the axis along the perpendicular to this resultant. This is called gyro north
and its displacement from true north is called gyro error.
A little imagination will tell straightaway that no error would be caused on
easterly or westerly course and maximum error would be caused on northerly or
southerly course. On other courses, error will lie between zero and the maximum
value. Error is also dependent on latitude (i.e. length of earth’s motion vector) and
speed of vessel (length of ship’s motion vector).
Further, error is high or west on northerly courses and low or east on southerly
courses.
This error is independent of the design of the compass and is the same for all types
of compasses for a given course & speed for a particular Latitude.
Tan (Error) = V Cos co .
(900 Cos lat ± V Sin co)
The Course, Latitude & Speed errors are corrected by various means as per the
design:
1. To be allowed for by the navigator from the supplied tables or by
calculation.
2. This error can be allowed for by a corrector mechanism which can be
adjusted for ship’s speed and latitude. The correction is made to the
position of the LL and is made to vary as the cosine of ship’s course by
means of a cam which runs in a cosine grove cut beneath the compass
card.
3. In Arma Brown compasses this error is eliminated by injecting a signal
into the azimuth servo motor system so that the twist is produced in the
vertical torsion wires. The resultant tilt of the gyro ball in tilt is equal
and opposite to the rate of tilting due to N-S component of ship’s speed
and the tilting sensed by the pendulum is that due to earth’s rotation
only. The strength of the signal injected into the azimuth servo motor is
determined by setting a speed control and by an input from the
transmitter, which varies the signal as the cosine of ship’s course.
Derivation of the formula:
Derivation for vessel’s course in each quarter is given separately.
In each of the following cases, following notations are used:
AD = BC = E = 900 Cos lat (vector representing earth’s west to east rotation). At
equator, E =900 (as Cos 0 = 1) and it reduces as lat. Increases.
AB = DC = V (vector representing vessel’s motion)
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AC = R (vector representing resultant of E and V)
CP is perpendicular drawn to vector E
TN is true north (perpendicular to E)
GN is gyro north (perpendicular to R)
Angle ‘a’ is gyro error. It is high (or west), if GN is west of TN. It is low (or east),
if GN is east of TN
Angle ‘b’ is the acute angle which V makes with E
Angle ‘co’ is the vessel’s quadrantal course. In all cases ‘co’ = 90 ─ ‘b’
Courses in NE quarter:
Tan a = V Sin b .
900 Cos lat + V Cos b
Or, Tan a = V Sin (90-co) .
900 Cos lat + V Cos (90-co)
Or, Tan a = V Cos co .
900 Cos lat + V Sin co
Note: Course has northerly component. GN is west of TN. Hence error is high
(west)
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Courses in SE quarter:
Tan a = V Sin b .
900 Cos lat + V Cos b
Or, Tan a = V Sin (90-co) .
900 Cos lat + V Cos (90-co)
Or, Tan a = V Cos co .
900 Cos lat + V Sin co
Note: Course has southerly component. GN is east of TN. Hence error is low
(east).
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Courses in SW quarter:
Tan a = V Sin b .
900 Cos lat ─ V Cos b
Or, Tan a = V Sin (90-co) .
900 Cos lat ─ V Cos (90-co)
Or, Tan a = V Cos co .
900 Cos lat ─ V Sin co
Note: Course has southerly component. GN is east of TN. Hence error is low
(east).
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Courses in NW quarter:
Tan a = V Sin b .
900 Cos lat ─ V Cos b
Or, Tan a = V Sin (90-co) .
900 Cos lat ─ V Cos (90-co)
Or, Tan a = V Cos co .
900 Cos lat ─ V Sin co
Note: Course has northerly component. GN is west of TN. Hence error is high
(west)
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IMPORTANT NOTES REGARDING STEAMING ERROR:
1. Error is directly proportional to vessel’s speed (Vector V).
2. Error is directly proportional to north/south component of course; i.e. closer
the course to north/south greater the error. (Cos 0=1, Cos 180= -1)
3. Error is inversely proportional to earth’s speed of rotation. At equator the
speed is maximum (900 nm/hr) and the error is the least. At higher latitudes
speed is less (given by 900 Cos lat) resulting in smaller denominator and
thus greater error.
4. On courses having easterly component (NE and SE) perpendicular CP falls
outside on extended vector E. The vector V Cos b is thus added to vector E.
5. On courses having westerly component (SW and NW) perpendicular CP
lies inside, on vector E. The vector V Cos b is thus deducted from vector E
6. Error is independent of the name of latitude i.e. independent of which
hemisphere vessel is in.
7. In the final formula, term V Sin co is quite small compared to 900 Cos lat.
Hence this term can be ignored and the formula is further simplified as
below:
Tan a = V Cos co .
900 Cos lat
For small values of ‘a’, Tan a = ‘a’ radians
Thus, a (in radians) = V Cos co .
900 Cos lat
Thus a (in degrees) = V Cos co . x 180
900 Cos lat π
= V Cos co . (Approximate formula)
5 π Cos lat
However, in case of high speed crafts and in higher latitudes, V Sin co will
become significant and 900 Cos lat will become smaller. In such a case V Sin co
will not be small enough to be ignored and it would be advisable to use the main
formula and not the approximate one.
Ballistic Deflection:
BD is a precession which results from accelerations imparted to compass by
change in speed and/or course of the vessel, It is an error caused by the precession
imparted to the compass by a N-S change in speed and / or course of the vessel. If
vessel going on North course alters course to 090, there will be surge of Hg from S
pots to N pots, as governed by Newton’s first law of motion. As the rotor is
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spinning ACW, precession will be caused towards East, which is opposite of
westerly CLSE when the vessel was initially going on Northerly course. On
settling on new course the Hg level regains its natural level, but as long as the
acceleration exists the error also exists. This is known as BD and depends on free
surface of Hg and the amount of change in the N-S component of vessel’s motion.
It is independent of the latitude and thus can be made exactly equal to “change in
CSLE”. But CSLE varies with latitude. Hence BD is usually made equal to
“change in CSLE” for standard latitude, usually 45. It is found that for making BD
= change in CSLE, the time period of undamped gyroscope i.e. the ellipse (given
by T = 2π√ R/g (where R is radius of earth) T has to be 84.7 minutes.
R= 6378388 m, g =9.81 m/s2
BD is a product of BP and the time it operates for. Thus for a given compass the
BD produced will be same in all latitudes. But speed error increases with lat, so
the amount of CLSE for a given change of northerly speed increases with lat. Thus
BD can be made = CLSE in one lat. Lat chosen is 45 deg. For other latitudes the
difference is small enough to be tolerable.BD is independent of the name of
latitude.
Alteration of course towards N or increase in northerly speed or decrease in
southerly speed means: Northerly (positive) acceleration (means Hg flows to S
pots) produces a westerly (negative) change in azimuth.
Alteration of course towards S or increase in southerly speed or decrease in
northerly speed means: Southerly (negative) acceleration (means Hg flows to N
pots) produces an easterly (positive) change in azimuth.
These accelerations cause a false vertical and hence false horizontal. The false
vertical is the resultant of the acceleration due to gravity and that due to vessel’s
change of motion. The control element remains in the true horizontal due to
gyroscopic inertia, but the liquid senses false horizontal and flows to cause N or S
heaviness. The control element remains in the true vertical due gyroscopic inertia
but liquid associates itself with false vertical and flows to produce N or S
heaviness. N heaviness gives easterly precession and vice versa. The rate of P is
proportional to acceleration causing it. The P continues for as long as the
acceleration continues, so that for a given acceleration of speed and/or course the
total change in azimuth will be constant, irrespective of the rate at which the
maneuver is carried out.
This problem does not exist in Arma Brown compass.
Ballistic Tilt:
BT is result of BD. BD is precession in azimuth and BT is precession in tilt.
Surge of Hg also causes a torque about vertical axis because of the eccentricity of
the damping weight (offset of MB cone bearing).
A southerly acceleration causes north end to precess upwards.
A northerly acceleration causes north end to precess downwards.
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Thus the axis arrives at the new settling azimuth slightly displaced in tilt from the
settling position. The compass thus executes a small damped spiral until the axis
finally settles.
Damping Error and BT are both due to the eccentricity of the pivot of the MB. By
reducing eccentricity both DE and wander due to BT can be reduced. For this
reason damping %age is kept within limits so as to reduce BT. Damping %age of
66.67% is chosen with this in mind. This keeps BT within tolerable limits and no
further attempt is made to tackle it.
ROLLING ERROR:
If an unsymmetrical pendulum ( e.g. a ring) is tied as a bob and set oscillating, it
would be found that it tends to align so as to have the maximum MOI lying in the
plane of the swing. The MOI of a ring is greater about an axis than about a
diameter. Thus when vessel is rolling and the gyroscope is swinging like a
pendulum in gimbals, a torque is produced about the vertical axis tending to turn
the plane of the plane of the vertical ring into the plane of the swing. This T will
cause P in tilt and a subsequent wander of the compass.
In Sperry compasses this is prevented by compensator weights, called quadrantal
weights attached on each side of the vertical ring so that the MOI of the rotor is
same in all directions about the vertical axis.
In AB compasses control and damping is by electrical signals and torsion wires
and no gravitational controls are attached to the gyroscope. A further source of
rolling error can develop if sensitive element has unequal MOIs about N-S and E-
W axes. This is prevented by spherical shape of the gyro ball.
INTERCARDINAL ROLLING ERROR:
It is a combination of two effects. When vessel rolls on an E-W course, gyroscope
swings in N-S plane in its gimbals and vice versa. Swing in N-S plane causes Hg
to surge to and fro between the Hg pots, though inertia keeps the rotor and pots
stable with respect to the horizontal. Since the surge is equal and opposite with the
alternate N and S swing, horizontal P produced are also equal and opposite on
each successive swing and no error is allowed to accumulate.
When on N-S course the swing is in E-W plane. There is no surge of Hg but the
link attachment (between rotor casing and MB) shifts alternately between
eastwards and westwards. We know that the link is deliberately offset to provide
the damping T about the vertical axis. The alternate E and W swing thus results in
the DT being alternately greater than and less than the desired value. Here also, the
average value is not affected and the settling position is not disturbed.
Now consider vessel rolling in NE course. The swing will be in NW and SE plane.
Both the effects will be seen now. Hg will surge and the link also will be shifted.
On NW swing Hg will surge to N pots and link will be carried westwards and vice
versa on SE swing.
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This error is approximately corrected by restricting the bore of the tubes
connecting the Hg bottles, so that the surge of Hg lags about a quarter of period
behind the roll.