The Siemens Communications and Siemens VDO Automotive Groups have jointly developed a pocket-sized navigation solution for Java-based mobile phones: Siemens Mobile Navigation is a cost-effective solution for entry into the world of navigation systems – small, light and extremely portable. State-of-the-art satellite and mobile radio technology provide the latest map material and traffic information to mobile phones via online connection, thus turning them into reliable co-pilots.
The family of permanently installed navigation systems has a new member: The mobile phone. Increasing mobility means more demand for mobile navigation devices. Having been awarded full marks for its Symbian-based navigation solution for mobile phones by the German automobile club, ADAC, Siemens now presents a solution for Java-capable mobile phones. With this latest addition, Siemens complements its product portfolio with a mobile navigation solution that is based on an open standard and can be used across all networks.
A simple, one-off activation is all that’s required and the GPS receiver, which you have in your car together with your mobile phone, automatically creates a Bluetooth connection to the mobile. The receiver determines the exact position of the vehicle within a matter of seconds via satellite signals. Even if you interrupt your journey and park in an underground carpark, the device does not have to go through complex repositioning because the memory effect of the receiver lets it find the position of your vehicle in an instant. When entering their destination, drivers can not only select the places last visited, but simply dial the contacts in the address book of their telephones. Airports, railroad stations or gas stations are preset, similar to conventional navigation systems.
Friday, May 2, 2008
Negros Navigation
Negros Navigation Co., Inc. (Nenaco) is one of the oldest domestic shipping companies in the Philippines. Its main hub is Pier 2 in Manila North Harbor.
It was organized and registered with the Securities and Exchange Commission (SEC) on 26 July 1932 for the purpose of transporting passengers and cargo at various ports of call in the Philippines.
In the 60’s Nenaco was the first among the domestic shipping companies to operate brand new, fast and luxurious air conditioned passenger ships. In 70’s , it was first to construct and operate a modern passenger terminal in Manila’s North Harbor and likewise pioneered in offering special cruises to the Philippine tourist spots using its coastwise vessels. In the 80’s , Nenaco launched its containerization program and ushered a new industry trend on the use of Roll-on Roll-off (“RORO”) vessels.
In the 90’s, it became the first Philippine shipping company to be listed in the stock exchange. Proceeds the amounting to P916.86 million from Initial Public Offering (IPO) were utilized to support the “Globalization Program” of the company that involved fleet expansion and service
It was organized and registered with the Securities and Exchange Commission (SEC) on 26 July 1932 for the purpose of transporting passengers and cargo at various ports of call in the Philippines.
In the 60’s Nenaco was the first among the domestic shipping companies to operate brand new, fast and luxurious air conditioned passenger ships. In 70’s , it was first to construct and operate a modern passenger terminal in Manila’s North Harbor and likewise pioneered in offering special cruises to the Philippine tourist spots using its coastwise vessels. In the 80’s , Nenaco launched its containerization program and ushered a new industry trend on the use of Roll-on Roll-off (“RORO”) vessels.
In the 90’s, it became the first Philippine shipping company to be listed in the stock exchange. Proceeds the amounting to P916.86 million from Initial Public Offering (IPO) were utilized to support the “Globalization Program” of the company that involved fleet expansion and service
Thursday, February 28, 2008
Classification of Global Navigation Satellite System
GNSS that provide enhanced accuracy and integrity monitoring usable for civil navigation are classified as followsGNSS-1 is the system and is the combination of existing satellite (GPS and GLONASS), with Satellite Based Augmentation Systems (SBAS) or Ground Based Augmentation Systems (GBAS). In the United States, the satellite based component is the Wide Area Augmentation System (WAAS), in is the Mulfirst generation ti-Functional Satellite Augmentation System (MSAS). Ground based augmentation is provided by systems like the Local Area Augmentation System (LAAS).
GNSS-2 is the second generation of systems that independently provides a full civilian satellite navigation system, exemplified by the European Galileo Europe it is the European Geostationary Navigation Overlay Service (EGNOS), and in Japan it positioning system. Thesnavigation systems e systems will provide the accuracy and integrity monitoring necessary for civil navigation. This system consists of L1 and L2 frequencies for civil use and L5 for system integrity. Development is also in progress to provide GPS with civil use L2 and L5 frequencies, making it a GNSS-2 system.¹
Core Satellite navigation systems, currently GPS, Galileo and GLONASS.
GNSS-2 is the second generation of systems that independently provides a full civilian satellite navigation system, exemplified by the European Galileo Europe it is the European Geostationary Navigation Overlay Service (EGNOS), and in Japan it positioning system. Thesnavigation systems e systems will provide the accuracy and integrity monitoring necessary for civil navigation. This system consists of L1 and L2 frequencies for civil use and L5 for system integrity. Development is also in progress to provide GPS with civil use L2 and L5 frequencies, making it a GNSS-2 system.¹
Core Satellite navigation systems, currently GPS, Galileo and GLONASS.
What is Global Navigation Satellite System?
Global Navigation Satellite System (GNSS) is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage. A GNSS allows small electronic receivers to determine their location (longitude, latitude, and altitude) to within a few metres using time signals transmitted along a line of sight by radio from satellites. Receivers on the ground with a fixed position can also be used to calculate the precise time as a reference for scientific experiments.
As of 2007, the United States NAVSTAR Global Positioning System (GPS) is the only fully operational GNSS. The Russian GLONASS is a GNSS in the process of being restored to full operation. The European Union's Galileo positioning system is a next generation GNSS in the initial deployment phase, scheduled to be operational in 2010. China has indicated it may expand its regional Beidou navigation system into a global system. India's IRNSS, a next generation GNSS is in developmental phase and is scheduled to be operational around 2012
As of 2007, the United States NAVSTAR Global Positioning System (GPS) is the only fully operational GNSS. The Russian GLONASS is a GNSS in the process of being restored to full operation. The European Union's Galileo positioning system is a next generation GNSS in the initial deployment phase, scheduled to be operational in 2010. China has indicated it may expand its regional Beidou navigation system into a global system. India's IRNSS, a next generation GNSS is in developmental phase and is scheduled to be operational around 2012
Automotive Navigation system
An automotive navigation system is a satellite navigation system designed for use in automobiles. It typically uses GPS to acquire position data to locate the user on a road in the unit's map database. Using the road database, the unit can give directions to other locations along roads also in its database. Dead reckoning using distance data from sensors attached to the drivetrain, a gyroscope and an accelerometer can be used for greater reliability, as GPS signal loss and/or multipath can occur due to urban canyons or tunnels.
Astrogation
The word astrogation, used by science fiction writers beginning in the first half of the 20th century, denotes navigation of spacecraft, either in interplanetary travel or in interstellar travel. The mathematical principles governing interplanetary astrogation were derived by mathematical physicists in the 19th and 20th centuries.
Two tasks define navigation: determining present location, and planning a safe and reliable means of reaching a destination. An example of an interstellar approach to describing the location of Earth is the plaque carried by the Pioneer 10 and Pioneer 11 spacecraft, where pulsars are used as references.
Route planning is greatly affected by means of propulsion, gravitational potential, obstacles and other hazards (such as radiation), and distance or time. Since no known extrasolar star is closer than four light years away, science fiction writers commonly introduce speculative or fictional work-arounds to the awkward time problem. However, some novels such as Encounter With Tiber, co-authored by astronaut Buzz Aldrin (one of the few people to have set foot on the Moon), treat distance and time more realistically as part of the plot.
Two tasks define navigation: determining present location, and planning a safe and reliable means of reaching a destination. An example of an interstellar approach to describing the location of Earth is the plaque carried by the Pioneer 10 and Pioneer 11 spacecraft, where pulsars are used as references.
Route planning is greatly affected by means of propulsion, gravitational potential, obstacles and other hazards (such as radiation), and distance or time. Since no known extrasolar star is closer than four light years away, science fiction writers commonly introduce speculative or fictional work-arounds to the awkward time problem. However, some novels such as Encounter With Tiber, co-authored by astronaut Buzz Aldrin (one of the few people to have set foot on the Moon), treat distance and time more realistically as part of the plot.
Air Navigation
The principles of air navigation are the same for all aircraft, big or small. Air navigation involves successfully piloting an aircraft from place to place without getting lost, breaking the laws applying to aircraft, or endangering the safety of those on board or on the ground.
Air navigation differs from the navigation of surface craft in several ways:
Aircraft travel at relatively high speeds, leaving less time to calculate their position en route. Aircraft normally cannot stop in mid-air to ascertain their position at leisure. Aircraft are safety-limited by the amount of fuel they can carry; a surface vehicle can usually get lost, run out of fuel, then simply await rescue. There is no in-flight rescue for most aircraft. And collisions with obstructions are usually fatal. Therefore, constant awareness of position is critical for aircraft pilots.
The techniques used for navigation in the air will depend on whether the aircraft is flying under the visual flight rules (VFR) or the instrument flight rules (IFR). In the latter case, the pilot will navigate exclusively using instruments and radio navigation aids such as beacons, or as directed under radar control by air traffic control. In the VFR case, a pilot will largely navigate using dead reckoning combined with visual observations (known as pilotage), with reference to appropriate maps. This may be supplemented using radio navigation aids.
Air navigation differs from the navigation of surface craft in several ways:
Aircraft travel at relatively high speeds, leaving less time to calculate their position en route. Aircraft normally cannot stop in mid-air to ascertain their position at leisure. Aircraft are safety-limited by the amount of fuel they can carry; a surface vehicle can usually get lost, run out of fuel, then simply await rescue. There is no in-flight rescue for most aircraft. And collisions with obstructions are usually fatal. Therefore, constant awareness of position is critical for aircraft pilots.
The techniques used for navigation in the air will depend on whether the aircraft is flying under the visual flight rules (VFR) or the instrument flight rules (IFR). In the latter case, the pilot will navigate exclusively using instruments and radio navigation aids such as beacons, or as directed under radar control by air traffic control. In the VFR case, a pilot will largely navigate using dead reckoning combined with visual observations (known as pilotage), with reference to appropriate maps. This may be supplemented using radio navigation aids.
The American Practical Navigator
The American Practical Navigator , written by Nathaniel Bowditch, is an encyclopedia of navigation, a valuable handbook on oceanography and meteorology, and contains useful tables and a maritime glossary. In 1866 the copyright and plates were bought by the Hydrographic Office of the United States Navy, and as a U.S. Government publication, it is now available for fThe most popular navigational text of the late 18th century was The New Practical Navigator by John Hamilton Moore. Edmund M. Blunt, a Newburyport, Massachusetts publisher, decided to issue a revised copy of this work for American navigators and convinced Nathaniel Bowditch, a locally famous mariner and mathematician, to revise and update it with the help of several others. Blunt's The New Practical Navigator was published in 1799, followed by a second edition in 1800.
By 1802, when Blunt was ready to publish a third edition, Nathaniel Bowditch and others had corrected so many errors in Hamilton's work that Blunt decided to publish it as the first edition of a new work, The New American Practical Navigator. The current edition of the American Practical Navigator traces its pedigree to that 1802 edition. Edmund M. Blunt continued to published the book until 1833; upon his retirement, his sons, Edmund and George, assumed publication. The elder Blunt died in 1862; his son Edmund followed in 1866. The next year, 1867, George Blunt sold the copyright to the government for $25,000. The government has published Bowditch ever since. George Blunt died in 1878.
Nathaniel Bowditch continued to correct and revise ree online. It is not only a notable book but is considered one of America's nautical institution.
By 1802, when Blunt was ready to publish a third edition, Nathaniel Bowditch and others had corrected so many errors in Hamilton's work that Blunt decided to publish it as the first edition of a new work, The New American Practical Navigator. The current edition of the American Practical Navigator traces its pedigree to that 1802 edition. Edmund M. Blunt continued to published the book until 1833; upon his retirement, his sons, Edmund and George, assumed publication. The elder Blunt died in 1862; his son Edmund followed in 1866. The next year, 1867, George Blunt sold the copyright to the government for $25,000. The government has published Bowditch ever since. George Blunt died in 1878.
Nathaniel Bowditch continued to correct and revise ree online. It is not only a notable book but is considered one of America's nautical institution.
Satellite Navigation
Global Navigation Satellite System or GNSS is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage. A GNSS allow small electronic receivers to determine their location (longitude, latitude, and altitude) to within a few metres using time signals transmitted along a line of sight by radio from satellites. Receivers on the ground with a fixed position can also be used to calculate the precise time as a reference for scientific experiments.
As of 2007, the United States NAVSTAR Global Positioning System (GPS) is the only fully operational GNSS. The Russian GLONASS is a GNSS in the process of being restored to full operation. The European Union's Galileo positioning system is a next generation GNSS in the initial deployment phase, scheduled to be operational in 2010. China has indicated it may expand its regional Beidou navigation system into a global system.
More than two dozen GPS satellites are in medium Earth orbit, transmitting signals allowing GPS receivers to determine the receiver's location, speed and direction.
Since the first experimental satellite was launched in 1978, GPS has become an indispensable aid to navigation around the world, and an important tool for map-making and land surveying. GPS also provides a precise time reference used in many applications including scientific study of earthquakes, and synchronization of telecommunications networks.
Developed by the United States Department of Defense, GPS is officially named NAVSTAR GPS (NAVigation Satellite Timing And Ranging Global Positioning System). The satellite constellation is managed by the United States Air Force 50th Space Wing. The cost of maintaining the system is approximately US$750 million per year. including the replacement of aging satellites, and research and development. Despite this fact, GPS is free for civilian use as a public good.
As of 2007, the United States NAVSTAR Global Positioning System (GPS) is the only fully operational GNSS. The Russian GLONASS is a GNSS in the process of being restored to full operation. The European Union's Galileo positioning system is a next generation GNSS in the initial deployment phase, scheduled to be operational in 2010. China has indicated it may expand its regional Beidou navigation system into a global system.
More than two dozen GPS satellites are in medium Earth orbit, transmitting signals allowing GPS receivers to determine the receiver's location, speed and direction.
Since the first experimental satellite was launched in 1978, GPS has become an indispensable aid to navigation around the world, and an important tool for map-making and land surveying. GPS also provides a precise time reference used in many applications including scientific study of earthquakes, and synchronization of telecommunications networks.
Developed by the United States Department of Defense, GPS is officially named NAVSTAR GPS (NAVigation Satellite Timing And Ranging Global Positioning System). The satellite constellation is managed by the United States Air Force 50th Space Wing. The cost of maintaining the system is approximately US$750 million per year. including the replacement of aging satellites, and research and development. Despite this fact, GPS is free for civilian use as a public good.
Radar Navigation
Marine radar systems can provide very useful navigation information in a variety of situations. When the vessel is within radar range of land or special radar aids to navigation, the navigator can take distances and angular bearings to charted objects and use these to establish arcs of position and lines of position on a chart..A fix consisting of only radar information is called a radar fix.Some types of radar fixes include the relatively self-explanatory methods of "range and bearing to a single object"two or more bearings. "tangent bearings. and "two or more ranges.Parallel indexing is a technique defined by William Burger in the 1957 book The Radar Observer's Handbook.This technique involves creating a line on the screen that is parallel to the ship's course, but offset to the left or right by some distance. This parallel line allows the navigator to maintain a given distance away from hazards.Some techniques have been developed for special situations. One, known as the "contour method," involves marking a transparent plastic template on the radar screen and moving it to the chart to fix a position.Another special technique, known as the Franklin Continuous Radar Plot Technique, involves drawing the path a radar object should follow on the radar display if the ship stays on its planned course. During the transit, the navigator can check that the ship is on track by checking that the pip lies on the drawn line.
Electronic Navigation-Radio Navigation
Radio navigation
For more details on this topic, see Radio navigation.
A radio direction finder or RDF is a device for finding the direction to a radio source. Due to radio's ability to travel very long distances "over the horizon", it makes a particularly good navigation system for ships and aircraft that might be flying at a distance from land.
RDF's work by pointing a directional antenna in "various directions" and then listening for the direction in which the signal from a known station comes through most strongly. This sort of system was widely used in the 1930s and 1940s. RDF antennas are particularly very easy to spot on German World War II aircraft, as loops under the rear section of the fuselage, whereas most US aircraft enclosed the antenna in a small teardrop-shaped fairing.
In navigational applications, RDF signals are provided in the form of radio beacons, the radio version of a lighthouse. The signal is typically a simple AM broadcast of a morse code series of letters, which the RDF can tune in to see if the beacon is "on the air". Most modern detectors can also tune in any commercial radio stations, which is particularly useful due to their high power and location near major cities.
Decca, OMEGA, and LORAN-C are three similar hyperbolic navigation systems. Decca was a hyperbolic low frequency radio navigation system (also known as multilateration) that was first deployed during World War II when the Allied forces needed a system which could be used to achieve accurate landings. As was the case with Loran C, its primary use was for ship navigation in coastal waters. Fishing vessels were major post-war users, but it was also used on aircraft, including a very early (1949) application of moving-map displays. The system was deployed extensively in the North Sea and was used by helicopters operating to oil platforms. After being shut down in the spring of 2000, it has been superseded by systems such as the American GPS and the planned European Galileo positioning system.
The OMEGA Navigation System was the first truly global radio navigation system for aircraft, operated by the United States in cooperation with six partner nations. OMEGA was originally developed by the United States Navy for military aviation users. It was approved for development in 1968 and promised a true worldwide oceanic coverage capability with only eight transmitters and the ability to achieve a four mile accuracy when fixing a position. Initially, the system was to be used for navigating nuclear bombers across the North Pole to Russia. Later, it was found useful for submarines.[1] Due to the success of the Global Positioning System the use of Omega declined during the 1990s, to a point where the cost of operating Omega could no longer be justified. Omega was permanently terminated on September 30, 1997 and all stations ceased operation.
LORAN is a terrestrial navigation system using low frequency radio transmitters that use the time interval between radio signals received from three or more stations to determine the position of a ship or aircraft. The current version of LORAN in common use is LORAN-C, which operates in the low frequency portion of the EM spectrum from 90 to 110 kHz. Many nations are users of the system, including the United States, Japan, and several European countries. Russia uses a nearly exact system in the same frequency range, called CHAYKA. LORAN use is in steep decline, with GPS being the primary replacement. However, there are current attempts to enhance and re-popularize LORAN.
For more details on this topic, see Radio navigation.
A radio direction finder or RDF is a device for finding the direction to a radio source. Due to radio's ability to travel very long distances "over the horizon", it makes a particularly good navigation system for ships and aircraft that might be flying at a distance from land.
RDF's work by pointing a directional antenna in "various directions" and then listening for the direction in which the signal from a known station comes through most strongly. This sort of system was widely used in the 1930s and 1940s. RDF antennas are particularly very easy to spot on German World War II aircraft, as loops under the rear section of the fuselage, whereas most US aircraft enclosed the antenna in a small teardrop-shaped fairing.
In navigational applications, RDF signals are provided in the form of radio beacons, the radio version of a lighthouse. The signal is typically a simple AM broadcast of a morse code series of letters, which the RDF can tune in to see if the beacon is "on the air". Most modern detectors can also tune in any commercial radio stations, which is particularly useful due to their high power and location near major cities.
Decca, OMEGA, and LORAN-C are three similar hyperbolic navigation systems. Decca was a hyperbolic low frequency radio navigation system (also known as multilateration) that was first deployed during World War II when the Allied forces needed a system which could be used to achieve accurate landings. As was the case with Loran C, its primary use was for ship navigation in coastal waters. Fishing vessels were major post-war users, but it was also used on aircraft, including a very early (1949) application of moving-map displays. The system was deployed extensively in the North Sea and was used by helicopters operating to oil platforms. After being shut down in the spring of 2000, it has been superseded by systems such as the American GPS and the planned European Galileo positioning system.
The OMEGA Navigation System was the first truly global radio navigation system for aircraft, operated by the United States in cooperation with six partner nations. OMEGA was originally developed by the United States Navy for military aviation users. It was approved for development in 1968 and promised a true worldwide oceanic coverage capability with only eight transmitters and the ability to achieve a four mile accuracy when fixing a position. Initially, the system was to be used for navigating nuclear bombers across the North Pole to Russia. Later, it was found useful for submarines.[1] Due to the success of the Global Positioning System the use of Omega declined during the 1990s, to a point where the cost of operating Omega could no longer be justified. Omega was permanently terminated on September 30, 1997 and all stations ceased operation.
LORAN is a terrestrial navigation system using low frequency radio transmitters that use the time interval between radio signals received from three or more stations to determine the position of a ship or aircraft. The current version of LORAN in common use is LORAN-C, which operates in the low frequency portion of the EM spectrum from 90 to 110 kHz. Many nations are users of the system, including the United States, Japan, and several European countries. Russia uses a nearly exact system in the same frequency range, called CHAYKA. LORAN use is in steep decline, with GPS being the primary replacement. However, there are current attempts to enhance and re-popularize LORAN.
The Marine sextant
The second critical component of modern celestial navigation is to measure the angle formed at the observer's eye between the celestial body and the sensible horizon. The sextant, a clever optical instrument, is used to perform this function. The sextant consists of two primary assemblies. The frame is a rigid triangular structure with a pivot at the top and a graduated segment of a circle, referred to as the "arc", at the bottom. The second component is the index arm, which is attached to the pivot at the top of the frame. At the bottom is an endless vernier which clamps into teeth on the bottom of the "arc". The optical system consists of two mirrors and, generally, a low power telescope. One mirror, referred to as the "index mirror" is fixed to the top of the index arm, over the pivot. As the index arm is moved, this mirror rotates, and the graduated scale on the arc indicates the measured angle ("altitude"). The second mirror, referred to as the "horizon glass", is fixed to the front of the frame. One half of the horizon glass is silvered and the other half is clear. Light from the celestial body strikes the index mirror and is reflected to the silvered portion of the horizon glass, then back to the observer's eye through the telescope. The observer manipulates the index arm so the reflected image of the body in the horizon glass is just resting on the visual horizon, seen through the clear side of the horizon glass.
Adjustment of the sextant consists of checking and aligning all the optical elements to eliminate "index correction". Index correction should be checked, using the horizon or more preferably a star, each time the sextant is used. The practice of taking celestial observations from the deck of a rolling ship, often through cloud cover and with a hazy horizon, is by far the most challenging part of celestial navigation. The mechanics of celestial navigation can be mastered in the classroom, but proficiency with a sextant at sea is a matter for expert instruction and extensive practice.
Adjustment of the sextant consists of checking and aligning all the optical elements to eliminate "index correction". Index correction should be checked, using the horizon or more preferably a star, each time the sextant is used. The practice of taking celestial observations from the deck of a rolling ship, often through cloud cover and with a hazy horizon, is by far the most challenging part of celestial navigation. The mechanics of celestial navigation can be mastered in the classroom, but proficiency with a sextant at sea is a matter for expert instruction and extensive practice.
Marine Chronometer
In order to accurately measure longitude, one must record the precise time of a sextant sighting (down to the second, if possible). Various types of chronometers are widely used.
The spring-driven marine chronometer is a precision timepiece used aboard ship to provide accurate time for celestial observations.A chronometer differs from a spring-driven watch principally in that it contains a variable lever device to maintain even pressure on the mainspring, and a special balance designed to compensate for temperature variations.A spring-driven chronometer is set approximately to Greenwich mean time (GMT) and is not reset until the instrument is overhauled and cleaned, usually at three-year intervals. The difference between GMT and chronometer time is carefully determined and applied as a correction to all chronometer readings..Spring-driven chronometers must be wound at about the same time each day.. At maximum intervals of about three years, a spring-driven chronometer should be sent to a chronometer repair shop for cleaning and overhaul.Quartz crystal marine chronometers have replaced spring-driven chronometers aboard many ships because of their greater accuracy.They are maintained on GMT directly from radio time signals.This eliminates chronometer error and watch error corrections.. Should the second hand be in error by a readable amount, it can be reset electrically.The basic element for time generation is a quartz crystal oscillator. The quartz crystal is temperature compensated and is hermetically sealed in an evacuated envelope.. A calibrated adjustment capability is provided to adjust for the aging of the crystal.The chronometer is designed to operate for a minimum of 1 year on a single set of batteries..A good marine chronometer has a built-in push button battery test meter. The meter face is marked to indicate when the battery should be replaced. The chronometer continues to operate and keep the correct time for at least 5 minutes while the batteries are changed. The chronometer is designed to accommodate the gradual voltage drop during the life of the batteries while maintaining accuracy requirements..A chronometer should not be removed from its case to time sights.. Observations may be timed and ship’s clocks set with a comparing watch, which is set to chronometer time and taken to the bridge wing for recording sight times..In practice, a wrist watch coordinated to the nearest second with the chronometer will be adequate..A stop watch, either spring wound or digital, may also be used for celestial observations.. In this case, the watch is started at a known GMT by chronometer, and the elapsed time of each sight added to Navthis to obtain GMT of the sight.All chronometers and watches should be checked regularly with a radio time signal.. Times and frequencies of radio time signals are listed in publications such as Radio igational Aids.
The spring-driven marine chronometer is a precision timepiece used aboard ship to provide accurate time for celestial observations.A chronometer differs from a spring-driven watch principally in that it contains a variable lever device to maintain even pressure on the mainspring, and a special balance designed to compensate for temperature variations.A spring-driven chronometer is set approximately to Greenwich mean time (GMT) and is not reset until the instrument is overhauled and cleaned, usually at three-year intervals. The difference between GMT and chronometer time is carefully determined and applied as a correction to all chronometer readings..Spring-driven chronometers must be wound at about the same time each day.. At maximum intervals of about three years, a spring-driven chronometer should be sent to a chronometer repair shop for cleaning and overhaul.Quartz crystal marine chronometers have replaced spring-driven chronometers aboard many ships because of their greater accuracy.They are maintained on GMT directly from radio time signals.This eliminates chronometer error and watch error corrections.. Should the second hand be in error by a readable amount, it can be reset electrically.The basic element for time generation is a quartz crystal oscillator. The quartz crystal is temperature compensated and is hermetically sealed in an evacuated envelope.. A calibrated adjustment capability is provided to adjust for the aging of the crystal.The chronometer is designed to operate for a minimum of 1 year on a single set of batteries..A good marine chronometer has a built-in push button battery test meter. The meter face is marked to indicate when the battery should be replaced. The chronometer continues to operate and keep the correct time for at least 5 minutes while the batteries are changed. The chronometer is designed to accommodate the gradual voltage drop during the life of the batteries while maintaining accuracy requirements..A chronometer should not be removed from its case to time sights.. Observations may be timed and ship’s clocks set with a comparing watch, which is set to chronometer time and taken to the bridge wing for recording sight times..In practice, a wrist watch coordinated to the nearest second with the chronometer will be adequate..A stop watch, either spring wound or digital, may also be used for celestial observations.. In this case, the watch is started at a known GMT by chronometer, and the elapsed time of each sight added to Navthis to obtain GMT of the sight.All chronometers and watches should be checked regularly with a radio time signal.. Times and frequencies of radio time signals are listed in publications such as Radio igational Aids.
Celestial Navigation
Celestial navigation systems are based on observation of the positions of the Sun, Moon and stars. By knowing which point on the rotating earth a celestial object is currently above and measuring its height above the observer's horizon, the navigator can determine his distance from that subpoint. A Nautical almanac and a chronometer are used to compute the subpoint on earth a celestial body is over, and a sextant is used to measure the body's angular height above the horizon. That height can then be used to compute ones distance from the subpoint to create a circular line of position. A navigator shoots a number of stars in succession to give a series of overlapping lines of position. Where they intersect is his celestial fix. The moon and sun may also be used. The sun can also be used by itself to shoot a succession of lines of position (best done around local noon) to determine a position as well.
Piloting
Piloting (also called pilotage) involves navigating a vessel in restricted waters and fixing its position as precisely as possible at frequent intervals. More so than in other phases of navigation, proper preparation and attention to detail are important. Procedures vary from vessel to vessel, and between military, commercial, and private vessels.. It is the responsibility of the navigator to choose the procedures applicable to his own situation, to train the piloting team in their execution, and to ensure that duties are carried out properly..A military navigation team will nearly always consist of several people. A military navigator might have bearing takers stationed at the gyro repeaters on the bridge wings for taking simultaneous bearings, while the civilian navigator must often take and plot them himself..While the military navigator will have a bearing book and someone to record entries for each fix, the civilian navigator will simply plot the bearings on the chart as they are taken and not record them at all.If the ship is equipped with an ECDIS, it is reasonable for the navigator to simply monitor the progress of the ship along the chosen track, visually ensuring that the ship is proceeding as desired, checking the compass, sounder and other indicators only occasionally..If a pilot is aboard, as is often the case in the most restricted of waters, his judgement can generally be relied upon explicitly, further easing the workload. But should the ECDIS fail, the navigator will have to rely on his skill in the manual and time-tested procedures discussed in this chapter.
Dead Reckoning
Dead reckoning is the process of estimating one’s present position by projecting course and speed from a known past position.It is also used to predict a future position by projecting course and speed from a known present position. The DR position is only an approximate position because it does not allow for the effect of leeway, current, helmsman error, compass error, or any other external influences.The navigator uses dead reckoning in many ways, such as to determine sunrise and sunset,
to predict landfall, sighting lights and arrival times,
to evaluate the accuracy of electronic positioning information,
to predict which celestial bodies will be available for future observation.
The most important use of dead reckoning is to project the position of the ship into the immediate future and avoid hazards to navigation.A prudent navigator carefully tends the DR plot, updating it when required, and uses it to evaluate external forces acting on the ship. The navigator also consults the DR plot to avoid potential navigation hazards. A fix taken at each DR position will reveal the effects of current, wind, and steering error, and allow the navigator to stay on track by correcting for them.The use of DR when an Electronic Charts Display and Information System (ECDIS) is the primary plotting method will vary with the type of system. An ECDIS allows the display of the ship’s heading projected out to some future position as a function of time, the display of waypoint information, and progress toward each waypoint in turn.Until ECDIS is proven to provide the level of safety and accuracy required, the use of a traditional DR plot on paper charts is a prudent backup, especially in restricted waters.Before the development of the lunar distance method or the marine chronometer, dead reckoning was the primary method of determining longitude available to mariners such as Christopher Columbus and John Cabot on their trans-Atlantic voyages.
to predict landfall, sighting lights and arrival times,
to evaluate the accuracy of electronic positioning information,
to predict which celestial bodies will be available for future observation.
The most important use of dead reckoning is to project the position of the ship into the immediate future and avoid hazards to navigation.A prudent navigator carefully tends the DR plot, updating it when required, and uses it to evaluate external forces acting on the ship. The navigator also consults the DR plot to avoid potential navigation hazards. A fix taken at each DR position will reveal the effects of current, wind, and steering error, and allow the navigator to stay on track by correcting for them.The use of DR when an Electronic Charts Display and Information System (ECDIS) is the primary plotting method will vary with the type of system. An ECDIS allows the display of the ship’s heading projected out to some future position as a function of time, the display of waypoint information, and progress toward each waypoint in turn.Until ECDIS is proven to provide the level of safety and accuracy required, the use of a traditional DR plot on paper charts is a prudent backup, especially in restricted waters.Before the development of the lunar distance method or the marine chronometer, dead reckoning was the primary method of determining longitude available to mariners such as Christopher Columbus and John Cabot on their trans-Atlantic voyages.
Wednesday, February 27, 2008
Modern Technique of Navigation
Most modern navigation relies primarily on positions determined electronically by receivers collecting information from satellites. Most other modern techniques rely on crossing lines of position or LOP.A line of position can refer to two different things: a line on a chart and a line between the observer and an object in real life. A bearing is a measure of the direction to an object. If the navigator measures the direction in real life, he can then draw the angle on a nautical chart and presume he lies on that line on the chart.In addition to bearings, navigators also often measure distances to objects.. On the chart, a distance produces a circle or arc of position. Circles, arcs, and hyperbolae of positions are often referred to as lines of position.
If the navigator draws two lines of position, and they intersect he must be at that position.A fix is the intersection of two or more LOPs.If only one line of position is available, this may be evaluated against the dead reckoning position to establish an estimated position.Lines (or circles) of position can be derived from a variety of sources:
celestial observation (actually, a short segment of the circle of equal altitude, but generally represented as a line),
terrestrial range (natural or man made) when two charted points are observed to be in line with each other,.compass bearing to a charted object,
radar range to a charted object,
on certain coastlines, a depth sounding from echo sounder or hand lead line.
There are some older methods seldom used today such as "dipping a light" to calculate the geographic range from observer to lighthouse
Methods of navigation have changed through history. Each new method has enhanced the mariner’s ability to complete his voyage safely and expeditiously.One of the most important judgments the navigator must make involves choosing the best method to use.. Some commonly recognized types of navigation are depicted in the table.
If the navigator draws two lines of position, and they intersect he must be at that position.A fix is the intersection of two or more LOPs.If only one line of position is available, this may be evaluated against the dead reckoning position to establish an estimated position.Lines (or circles) of position can be derived from a variety of sources:
celestial observation (actually, a short segment of the circle of equal altitude, but generally represented as a line),
terrestrial range (natural or man made) when two charted points are observed to be in line with each other,.compass bearing to a charted object,
radar range to a charted object,
on certain coastlines, a depth sounding from echo sounder or hand lead line.
There are some older methods seldom used today such as "dipping a light" to calculate the geographic range from observer to lighthouse
Methods of navigation have changed through history. Each new method has enhanced the mariner’s ability to complete his voyage safely and expeditiously.One of the most important judgments the navigator must make involves choosing the best method to use.. Some commonly recognized types of navigation are depicted in the table.
Basic Concepts of Navigation
Latitude
The latitude of a place on the earth's surface is the angular distance north or south of the [equator]. Latitude is usually expressed in [degree (angle)degrees]] (marked with °) ranging from 0° at the Equator to 90° at the North and South poles. The latitude of the North Pole is 90° N, and the latitude of the South Pole is 90° S. Longitude
Similar to latitude, the longitude of a place on the earth's surface is the angular distance east or west of the prime meridian or Greenwich meridian.. Longitude is usually expressed in degrees (marked with °) ranging from 0° at the Greenwich meridian to 180° east and west. Sydney, Australia, for example, has a longitude of about 151° east. New York City has a longitude of about 74° west.
The latitude of a place on the earth's surface is the angular distance north or south of the [equator]. Latitude is usually expressed in [degree (angle)degrees]] (marked with °) ranging from 0° at the Equator to 90° at the North and South poles. The latitude of the North Pole is 90° N, and the latitude of the South Pole is 90° S. Longitude
Similar to latitude, the longitude of a place on the earth's surface is the angular distance east or west of the prime meridian or Greenwich meridian.. Longitude is usually expressed in degrees (marked with °) ranging from 0° at the Greenwich meridian to 180° east and west. Sydney, Australia, for example, has a longitude of about 151° east. New York City has a longitude of about 74° west.
What is Navigation??
Navigation is the process of planning, recording, and controlling the movement of a craft or vehicle from one place to another. The word navigate is derived from the Latin roots navis meaning "ship" and agere meaning "to move" or "to direct. Different navigational techniques have evolved over the ages in different cultures, but all involve locating one's position compared to known locations or patterns. It is also used in computer science as a term related to the Internet
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