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USE RADAR TO ENSURE SAFE NAVIGATION

Fix Vessel’s Position By Radar;

RANGE AND BEARING TO A SINGLE OBJECT:

Preferably, radar fixes obtained through measuring the range and bearing to a single object should be limited to small, isolated fixed objects which can be identified with reasonable certainty. In many situations, this method may be the only reliable method which can be employed. If possible, the fix should be based upon a radar range and visual gyro bearing because radar bearings are less accurate than visual gyro bearings. A primary advantage of the method is the rapidity with which a fix can be obtained. A disadvantage is that the fix is based upon only two intersecting position lines, a bearing line and a range arc, obtained from observations of the same object. Identification mistakes can lead to disaster.Two or More Bearings

Generally, fixes obtained from radar bearings are less accurate than those obtained from intersecting range arcs. The accuracy of fixing by this method is greater when the center bearings of small, isolated, radar-conspicuous objects can be observed. Because of the rapidity of the method, the method affords a means for initially determining an approximate position for subsequent use in more reliable identification of objects for fixing by means of two or more ranges.

TANGENT BEARINGS:

Fixing by tangent bearings is one of the least accurate methods. The use of tangent bearings with a range measurement can provide a fix of reasonably good accuracy. Two or More Ranges

The most accurate radar fixes result from measuring and plotting ranges to two or more objects. Measure objects directly ahead or astern first; measure objects closest to the beam last. This procedure is the opposite to that recommended for taking visual bearings, where objects closest to the beam are measured first; however, both recommendations rest on the same principle. When measuring objects to determine a line of position, measure first those which have the greatest rate of change in the quantity being measured; measure last those which have the least rate of change in that quantity. This minimizes measurement time delay errors. Since the range of those objects directly ahead or astern of the ship changes more rapidly than those objects located abeam, measure objects ahead or astern first.

Record the ranges to the navigation aids used and lay the resulting range arcs down on the chart. Theoretically, these lines of position should intersect at a point coincident with the ship’s position at the time of the fix. However, the inherent inaccuracy of the radar coupled with the relatively large scale of most piloting charts usually precludes such a point fix. In this case, the navigator must carefully interpret the resulting fix.

Aids To Radar Navigation and Safety;

Various aids to radar navigation have been developed to aid the navigator in identifying radar targets and for increasing the strength of the echoes received from objects which otherwise are poor radar targets.

RADAR REFLECTORS:

Buoys and small boats, particularly those boats constructed of wood, are poor radar targets. Weak fluctuating echoes received from these targets are easily lost in the sea clutter on the radarscope. To aid in the detection of these targets, radar reflectors, of the corner reflector type, may be used. The corner reflectors may be mounted on the tops of buoys or the body of the buoy may be shaped as a corner reflector. A radar wave on striking any of the metal surfaces or plates will be reflected back in the direction of its source, i. e., the radar antenna. Maximum energy will be reflected back to the antenna if the axis of the radar beam makes equal angles with all the metal surfaces. Frequently corner reflectors are assembled in clusters to insure receiving strong echoes at the antenna.

Radar Beacons

While radar reflectors are used to obtain stronger echoes from radar targets, other means are required for more positive identification of radar targets. Radar beacons are transmitters operating in the marine radar frequency band which produce distinctive indications on the radarscopes of ships within range of these beacons. There are two general classes of these beacons: racon which provides both bearing and range information to the target and ramark which provides bearing information only. However, if the ramark installation is detected as an echo on the radarscope, the range will be available also.

Racon:

Racon is a radar transponder which emits a characteristic signal when triggered by a ship’s radar. The signal may be emitted on the same frequency as that of the triggering radar, in which case it is automatically superimposed on the ship’s radar display. The signal may be emitted on a separate frequency, in which case to receive the signal the ship’s radar receiver must be capable of being tuned to the beacon frequency or a special receiver must be used. In either case, the PPI will be blank except for the beacon signal. just beyond the position of the radar beacon or as a Morse code signal displayed radially from just beyond the beacon. Racons are being used as ranges or leading lines. The range is formed by two racons set up behind each other with a separation in the order of 2 to 4 nautical miles. On the PPI scope the “paint” received from the front and rear racons form the range. Some bridges are now equipped with racons which are suspended under the bridge to provide guidance for safe passage. The maximum range for racon reception is limited by line of sight.

Ramark:

Ramark is a radar beacon which transmits either continuously or at intervals. The latter method of transmission is used so that the PPI can be inspected without any clutter introduced by the ramark signal on the scope. The ramark signal as it appears on the PPI is a radial line from the center. The radial line may be a continuous narrow line, a series of dashes, a series of dots, or a series of dots and dashes.

Use Parallel Indexing in Radar Navigation;

§ To check the direction of the heading marker while using an off-centre display.

§ To obtain the bearing of a target while using an off-centre display.

§ To obtain the bearing between two targets.

§ To obtain distance between two targets.

§ To obtain the CPA range quickly (RM display only).

§ To obtain the course and speed of a target quickly.

Parallel index is the art of maneuvering a ship to a desired position, or along desired track, in such a manner that the entire maneuver is carried out while watching the PPI only. The chart is consulted before hand, and a little pre-computation may be done, but no fixes are plotted on the chart because continuos fixing is done on the PPI with the help of parallel index. Allowances for current and wind are made, as when necessary, during the maneuver, by inspection of the ship’s progress on the PPI. There are a lot of techniques are available for using parallel index but mainly I can tell passing distance techniques and course alteration techniques.

THE SYSTEM FOR AUTOMATIC PLOTTING:

Radars With Semi And Full Automatic Plotting Capabilities;

The availability of low cost microprocessors and the development of advanced computer technology during the 1970s and 1980s have made it possible to apply computer techniques to improve commercial marine radar systems. Radar manufactures used this technology to create the Automatic Radar Plotting Aids (ARPA). ARPAs are computer assisted radar data processing systems which generate predictive vectors and other ship movement information.

The International Maritime Organization (IMO) has set out certain standards amending the International Convention of Safety of Life at Sea requirements regarding the carrying of suitable automated radar plotting aids (ARPA). The primary function of ARPAs can be summarized in the statement found under the IMO Performance Standards. It states a requirement of ARPAs....“ in order to improve the standard of collision avoidance at sea: Reduce the workload of observers by enabling them to automatically obtain information so that they can perform as well with multiple targets as they can by manually plotting a single target” .As we can see from this statement the principal advantages of ARPA are a reduction in the workload of bridge personnel and fuller and quicker information on selected targets.

A typical ARPA gives a presentation of the current situation and uses computer technology to predict future situations. An ARPA assesses the risk of collision, and enables operator to see proposed maneuvers by own ship. While many different models of ARPAs are available on the market, the following functions are usually provided:

1. True or relative motion radar presentation.

2. Automatic acquisition of targets plus manual acquisition.

3. Digital read- out of acquired targets which provides course, speed, range, bearing, closest point of approach (CPA, and time to CPA (TCPA).

4. The ability to display collision assessment information directly on the PPI, using vectors (true or relative) or a graphical Predicted Area of Danger (PAD) display.

5. The ability to perform trial maneuvers, including course changes, speed changes, and combined course/ speed changes.

6. Automatic ground stabilization for navigation purposes.

ARPA processes radar information much more rapidly than conventional radar but is still subject to the same limitations. ARPA data is only as accurate as the data that comes from inputs such as the gyro and speed log.

Over the past 10 years, the most significant changes to the ARPA systems has been in their design. The majority of ARPAs manufactured today integrate the ARPA features with the radar display. The initial development and design of ARPAs were Stand- alone units. That is they were designed to be an addition to the conventional radar unit.

All of the ARPA functions were installed on board as a separate unit but needed to interfaced with existing equipment to get the basic radar data. The primary benefits were cost and time savings. This of course was not the most ideal situation and eventually it was the integral ARPA that gradually replaced the stand- alone unit. The modern integral ARPA combines the conventional radar data with the computer data processing systems into one unit. The main operational advantage is that both the radar and ARPA data are readily comparable.

Operating a ARPA System:

Types of display of ARPA

From the time radar was first introduced to the present day the radar picture has been presented on the screen of a cathode ray tube. Although the cathode ray tube has retained its function over the years, the way in which the picture is presented has changed considerably. From about the mid-1980s

The first raster-scan displays appeared. The radial-scan PPI was replaced by a raster-scan PPI generated on a television type of display. The integral ARPA and conventional radar units with a raster-scan display will gradually replace the radial-scan radar sets.

The development of commercial marine radar entered a new phase in the 1980s when raster-scan displays that were compliant with the IMO Performance Standards were introduced.

The radar picture of a raster-scan synthetic display is produced on a television screen and is made up of a large number of horizontal lines which form a pattern known as a raster. This type of display is much more complex than the radial-scan synthetic display and requires a large amount of memory. There are a number of advantages for the operator of a raster-scan display and concurrently there are some deficiencies too. The most obvious advantage of a raster-scan display is the brightness of the picture. This allows the observer to view the screen in almost all conditions of ambient light. Out of all the benefits offered by a raster-scan radar it is this ability which has assured its success. Another difference between the radial-scan and raster-scan displays is that the latter has a rectangular screen. The screen size is specified by the length of the diagonal and the width and height of the screen with an approximate ratio of 4:3. The raster-scan television tubes have a much longer life than a traditional radar CRT. Although the tubes are cheaper over their counterpart, the complexity of the signal processing makes it more expensive overall.

Raster-scan PPI:

The IMO Performance Standards for radar to provide a plan display with an effective display diameter of 180mm, 250mm, or 340mm depending upon the gross tonnage of the vessel. With the diameter parameters already chosen, the manufacturer has then to decide how to arrange the placement of the digital numerical data and control status indicators. The raster-scan display makes it easier for design engineers in the way auxiliary data can be written.

Monochrome and Color CRT:

A monochrome display is one which displays one color and black. The general monochrome television uses white as the color. This however is not an appropriate color for the conditions under which a commercial marine radar is viewed. Unlike a television screen, marine radar displays tend to be viewed from the shorter distance and the observer has a greater concentration on the details of the screen and therefore is subject to eyestrain. For this reason the color most common to monochrome raster-scan applications was green. The green phosphor provides comfortable viewing by reducing eye strain and stress. The color tube CRT differs from its monochrome counterpart in that it has three electron guns, which are designated as red, green, and blue.

Controls:

HM OFF

Temporarily erases the heading marker.

ECHO TRAILS

Shows trails of target echoes in the form of simulated afterglow.

MODE

Selects presentation modes: Head- up, Head- up/ TB, North- up, Course- up, and True Motion.

GUARD ALARM

Used for setting the guard alarm.

EBL OFFSET

Activates and deactivates off- centering of the sweep origin.

BKGR COLOR

Selects the background color.

INDEX LINES

Alternately shows and erases parallel index lines.

X2 ZOOM

enlarges a user selected portion of picture twice as large as normal.

CU, TM RESET

Resets the heading line to 000 in course- up mode; moves own ship position 50% radius in stern direction in the true motion mode.

INT REJECT

Reduces mutual radar interference

RANGE RINGS

Adjusts the brightness of range rings.

DISPLAY CONTROLS - PLOTTING KEYPAD:

ORIGIN MARK

Show and erases the origin mark (a reference point).

VECTOR TRUE/ REL

Selects true or relative vector.

VECTOR TIME

Sets vector length in time.

RADAR MENU

Opens and closes RADAR menus.

E- PLOT, AUTO PLOT MENU

Opens and closes E- plot and AUTO PLT menus.

NAV MENU

Opens and closes NAV menu.

KEYS 0- 9

Select plot symbols. Also used for entering numeric data.

CANCEL

Terminates plotting of a specified target or all tracked targets.

ENTER

Used to save settings on menu screen.

TARGET DATA

Displays the acquired target data.

TARGET BASED DATA

Own ship’s speed is measured relative to a fixed target.

AUTO PLOT

Activates and deactivates the Auto Plotter.

TRIAL

Initiates a trial maneuver.

LOST TARGET

Silences the lost target audible alarm and erases the lost target symbol.

HISTORY

Shows and erases past positions of tracked targets.

MARK

Enter/ erase mark.

CHART ALIGN

Used to align chart data.

VIDEO PLOT

Turns the video plotter on/ off.

OPERATION OF THE RADAR

Types of Radar Display – Set UP and Maintain Radar Display;

There are two basic displays used to portray target position and motion on the PPI’s of navigational radars. The relative motion display portrays the motion of a target relative to the motion of the observing ship. The true motion display portrays the actual or true motions of the target and the observing ship. Depending upon the type of PPI display used, navigational radars are classified as either relative motion or true motion radars. However, true motion radars can be operated with a relative motion display. In fact, radars classified as true motion radars must be operated in their relative motion mode at the longer-range scale settings. Some radars classified as relative motion radars are fitted with special adapters enabling operation with a true motion display. These radars do not have certain features normally associated with true motion radars, such as high persistence CRT screens.

Relative motion radar:

Through continuous display of target pips at their measured ranges and bearings from a fixed position of own ship on the PPI, relative motion radar displays the motion of a target relative to the motion of the observing (own) ship. With own ship and the target in motion, the successive pips of the target do not indicate the actual or true movement of the target. A graphical solution is required in order to determine the rate and direction of the actual movement of the target. If own ship is in motion, the pips of fixed objects, such as landmasses, move on the PPI at a rate equal to and in a direction opposite to the motion of own ship. If own ship is stopped or motionless, target pips move on the PPI in accordance with their true motion.

True motion radar:

True motion radar displays own ship and moving objects in their true motion. Unlike relative motion radar, own ship’s position is not fixed on the PPI. Own ship and other moving objects move on the PPI in accordance with their true courses and speeds. Also unlike relative motion radar, fixed objects such as landmasses are stationary, or nearly so, on the PPI. Thus, one observes own ship and other ships moving with respect to landmasses. True motion is displayed on modern indicators through the use of a microprocessor computing target true motion rather than depending on an extremely long persistence phosphor to leave “trails”.

The use of the radar controls are counted below:

Joystick: The joystick is used to move the cursor around the display. The joystick is also used to move the pointeron the menus.

Data controls: There are two rotary data controls, either of which increase a value by rotaing clockwise, and decrease a value by rotating counter-clockwise.

VRM/Data: The VRM/Data control is used to change the VRM positions or for general data input when prompted.

EBL/Data: The EBL/Data control is used to change the EBL bearings or for general data input when prompted.

Gain: The gain control is used to vary the levelof the radar signals displayed on the screen.

Anti-clutter sea: With A/C MANUAL selected, the Anti-clutter sea control is used to reduce the clutter appearing on the display due to the radar signals from the sea surface.

Anti-clutter rain: With A/C MANUAL selected, the Anti-clutter rain control is used to reduce the clutter appearing on the display due to the radar signals from the rain surface.

Tune: The tune control is used to manually tune the receiver.

Panel brilliance: The panel brill control is used to set the brilliance of the control panel illumination.

Display brilliance: This control is used to set the brilliance of the display.

Pulse-St by: When in stand by, a short press of the key will switch the radar to transmit, whenin transmit, short press of the key will cycle through the available pulse lengths available on the selected range scale.

Stab-Unstab: When unstabilised, the display is head-up. Pressing the key when unstabilised will change the display to north up, another pressing will change to course-up, and another pressing will change again to north-up. A long press when stabilised will change the display oto head-up.

TM-RM: When in relative motion, a short press of the key changes the display to Fixed Origin True Trails (FOTT). Pressing the key while in FOTT changes the display to true motion. Further short press of the key will change the display between TM and FOTT. A long press selects relative motion. If relative motion is selected, either stabilized or unstabilized maybe selected. If true motion or FOTT is selected only NU and CU may be selected.

Trails-Perm: Short press of the key will set the trails to off, short, and long. A long press of the key will change the trails to permanent.

Auto-Enhance: Short press of the key selects either manual anti-clutter at automatic anti-clutter. Long presses of the key selects enhance on-off exept when range scale is below 0,75 miles.

Center-Shift: A short press centers the radar screen. To shift from the center this key should be pressed continuously, at the same time joystick sholuld be moved to the desired point, and the key should be relaesed.

Hm off: During the press of this key hedeing marker disapears.

EBL/Off: A short press of this key displays EBL1, second short press adds EBL. By presing shift&carring from the menu, EBL can be offset with the joystick.

G zone-Clear: Two guard zones are available. A short press of key selects which of these guard zones is adjustable. A long press of the key clears the zone.

Vector-Time: A short press of the key changes between true and relative vectors.

Cancel: To cancel aplot , use the joystick to position the cursor over the target end of the vector and press the key.

Mark-Clear: A short press of the key places a mark at the cursor position, as set by joystick marks can be cleared by long press of the key with the cursor.

Plot-Select: A short press of the key produces a plot at the position of the cursor, as set by joystick. After 30 seconds a second plot can be made, and target course, speed, CPA and TCPA is displayed. Plots are automatically dropped after 12 minutes.

Range: Two range controls changes the range of the radar.

Index-Clear: One short press produces a parallel index line. This index can be chached using the data controls. A long press of the key will clear the index.

Speed: Pressing this key we can chose manual speed or the speed information took from GGPS.

Rings: Shows the rings.

Alarm ack: This key allow us to acknowledge any given alarm.

Menu: Pressing this key menu will be displayed on the screen.

Enter: Provide us to chose some choices in the menu, and to tour through the menues.

THE BASIC THEORY OF MARINE RADAR

We have two radars on board one is S band JRC radar and the other is RAYTHEON radar.We do not use JRC radar. Ray theon is a X band , semi-arpa radar. The technical characteristics of the radar are counted below:

Frequency: 9410 ± 30 MHZ

Magnetron peak power: 25 KW

Pulse length/PRF: 0,05 µs/ 1200 Hz

0,25 µs/ 1200 Hz

1,00 µs/ 600Hz

Horizontal beam width: 1,3º

Vertical beam width: 24º

Display type: Colour, 15 inch

Scan form: Raster Scan

This radar meets all performans standards required by IMO

Factors Affecting the Radar Display;

There are four factors that are affecting the radar display these are namely, maximum range, minimum range, range accuracy and bearing accuracy. All these factors are effected that factors which I mentioned on the below.

Frequency;

The higher the frequency of a radar (radio) wave, the greater is the attenuation (loss in power), regardless of weather. Lower radar frequencies (longer wavelengths) have, therefore, been generally superior for longer detection ranges.

Peak Power:

The peak power of a radar is its useful power. Range capabilities of the radar increase with peak power. Doubling the peak power increases the range capabilities by about 25 percent.

Pulse Length:

The longer the pulse length, the greater is the range capability of the radar because of the greater amount of energy transmitted.

Pulse Repetition Rate:

The pulse repetition rate (PRR) determines the maximum measurable range of the radar. Ample time must be allowed between pulses for an echo to return from any target located within the maximum workable range of the system. Otherwise, echoes returning from the more distant targets are blocked by succeeding transmitted pulses. This necessary time interval determines the highest PRR that can be used. The PRR must be high enough, however, that sufficient pulses hit the target and enough echoes are returned to the radar. The maximum measurable range can be determined approximately by dividing 81,000 by the PRR.

Beam Width:

The more concentrated the beam, the greater is the detection range of the radar.

Target Characteristics:

Targets that are large can be seen on the scope at greater ranges, providedline- of- sight exists between the radar antenna and the target. Conductingmaterials (a ship’s steel hull, for example) return relatively strong echoeswhile nonconducting materials (a wood hull of a fishing boat, for example) return much weaker echoes.

Receiver Sensitivity:

The more sensitive receivers provide greater detection ranges but are more subject to jamming.

Antenna Rotation Rate:

The more slowly the antenna rotates, the greater is the detection range of the radar. For a radar set having a PRR of 1,000 pulses per second, a horizontal beam width of 2.0°, and an antenna rotation rate of 6 RPM (1 revolution in 10 seconds or 36 scanning degrees per second), there is 1 pulse transmitted each 0.036° of rotation. There are 56 pulses transmitted during the time required for the antenna to rotate through its beam width. With an antenna rotation rate of 15 RPM (1 revolution in 4 seconds or 90 scanning degrees per second), there is only 1 pulse transmitted each 0.090° of rotation. There are only 22 pulses transmitted during the time required for the antenna to rotate through its beam width. From the foregoing it is apparent that at the higher antenna rotation rates, the maximum ranges at which targets, particularly small targets, may be detected are reduced.

GPS (Global Position System)

There are 24 satelites which 3 three of them are spare satelites, in 6 orbital planes in GPS system. Four satelites are equally spaced in each plane.They are at the distance of 11.000 miles from the earth. The angle between each satellite orbit is 60 degrees. In this way, for each position in the earth there are at least 4 satellites that can see that position.The satellites transmit accurately time codes along with a message that includes satellites position, precise time correction signals to the receiver. GPS receiver compares the his code and code received from the satellite and measures how much time took the electromagnetic code to arrive to him. It allows the receiver to calculate the distance between satellite and receiver. As I said above a receiver can see 4 satellites at the same time. It allows the receiver to have four range datas from the satelites. Because, the posiitions of the satellites are known the position of the receiver can be found by intersecting all four ranges.

GPS system consist of three main parts. These parts are satellites, Land

Earth Stations, and receivers. I mentioned above about the satellites.

The Main Parts of the GPS;

The Federal Radionavigation Plan has designated the Navigation System using Timing and Ranging (NAVSTAR) Global Positioning System (GPS) as the primary navigation system of the U.S. government. GPS is a spaced-based radio positioning system, which pro-vides suitably, equipped users with highly accurate position, velocity, and time data. It consists of three major segments: a space segment, a control segment, and a user segment. The space segment contains 24 satellites. Precise spacing of the satellites in orbit is arranged such that minimums of four satellites are in view to a user at any time on a worldwide basis. Each satellite transmits signals on two radio frequencies, superimposed on which are navigation and system data. Included in this data is predicted satellite ephemeris, atmospheric propagation correction data, satellite clock error information, and satellite health data. This segment consists of 21 operational satellites with three satellites orbiting as active spares. The satellites orbit in six separate orbital planes. The orbital planes have an inclination relative to the equator of 55° and an orbital height of 20,200 km. The satellites complete an orbit approximately once every 12 hours.

The control segment includes a master control station (MCS), a number of monitor stations, and ground antennas located throughout the world. The master control station, located in Colorado Springs, Colorado, consists of equipment and facilities required for satellite monitoring, telemetry, tracking, commanding, control, uploading, and navigation message generation. The monitor stations located in Hawaii, Colorado Springs, Kwajalein, Diego Garcia, and Ascension Island, passively track the satellites, accumulating ranging data from the satellites’ signals and relaying them to the MCS. The MCS processes this information to determine satellite position and signal data accuracy, updates the navigation message of each satellite and relays this information to the ground antennas. The ground antennas then transmit this information to the satellites. The ground antennas, located at Ascension Island, Diego Garcia, and Kwajalein, are also used for transmitting and receiving satellite control information. The user segment is designed for different requirements of various users. These receivers can be used in high, medium, and low dynamic applications. An example of a low dynamic application would be a fixed antenna or slowly drifting marine craft. An example of a medium dynamic application would be a marine or land vehicle traveling at a constant controlled speed. Finally, an example of a high dynamic application would be a high performance aircraft or a spacecraft. The user equipment is designed to receive and process signals from four or more orbiting satellites either simultaneously or sequentially. The processor in the receiver then converts these signals to three-dimensional navigation information based on the World Geodetic System 1984 reference ellipsoid. The user segment can consist of stand-alone receivers or equipment that is integrated into another navigation system. Since GPS is used in a wide variety of applications, from marine navigation to land surveying, these receivers can vary greatly in function and design.

Frequencies used for GPS Coding;

GPS satellites transmit pseudorandom noise (PRN) sequence-modulated radio frequencies, designated L1 (1575.42 MHz) and L2 (1227.60 MHz). The satellite transmits both a Coarse Acquisition Code (C/A code) and a Precision Code (P code). Both the P and C/A codes are transmitted on the L1 carrier; only the P code is transmitted on the L2 carrier. Superimposed on both the C/A and P codes is the Navigation message. This message contains satellite ephemeris data, atmospheric propagation correction data, and satellite clock bias.

The Principles of Obtaining a Fix in GPS;

A GPS position fix is obtained by measuring the ranges from a series of selected satellites to a receiver. Ranges are determined by measuring the propagation time of the satellite data transmissions. However, it is not possible to precisely synchronize the satellite and receiver clocks, the ranges measured are not true ranges, but are termed ‘pseudoranges’ since they contain a receiver clock offset error. In order to achieve a two-dimensional (2-D) fix on the Earth’s surface at least three ‘pseudoranges’ must be obtained; the receiver microprocessor can then resolve the three range equations to remove the effects of receiver clock offset error. Similarly four ‘pseudoranges’ would be required to obtain a 3-D fix.

Types of GPS receivers onboard;

We have two normal type (not dgps) on board.

Ecdis;

We have no ecdis on board so I have no sufficient information about ecdis.

SPEED LOGS

Types of Speed Using in Navigation;

Speed (S) is rate of motion, or distance per unit of time. Aknot (kn.), the unit of speed commonly used in navigation, is a rate of 1 nautical mile per hour. The expression speed of advance (SOA) is used to indicate the speed to be made along the intended track. Speed over the ground (SOG) is the actual

speed of the vessel over the surface of the earth at any given time. To calculate speed made good (SMG) be-tween two positions, positions by the time elapsed between the two positions.

We have no speed log on board, we could just learn the speed that we made from the GPS and this the speed accorcing to the land.

ECHO-SOUNDER

There are 5 controls on the echo sounder. These controls are counted below:

Power(On/Off): This control operates the echo-sounder if the control is switched to on.

Dimmer: This control regulates the light of the system, in case that it is used inthe dark places.

Range: This control regulates the range to be measured. It has three positions. First position is 0-50 meters, second position is 0-500 meters, and last position measures the range of 500-1000 meters. A second control related to the range control adjusts the unit of the measurement. It can be adjusted to measure according meters or fathoms.

Mark: This control burning the paper makes a mark on the paper and separates one depth measurement from the following measurment.

Gain: Gain controls the intensity of the echo so that a more clear measurment can be obtained.

Firstly, power control is made on and echo-sounder starts to work. Light can be adjusted depending of the light condition. Then, accoding to the depth that we are present range control is regulated. Also, the unit that we want to measure the depth is chosen. Then we shoud look at the paper.We can read the depth looking at the table at the side. If the depth can not be seen the sensitivity of the gain control shold be increased.

The inside of the echo-sounder is apt to dirt inside by the carbon powder. Sometimes this dirt should be cleaned.

Gyro Compass

The compass errors, compass correction,

i) North Speed Error & Correction,

The gyro system installed on our ship provides automatic correction of the north speed error. If the correction is active, the system permanently calculates the north speed error from the current speed and position and corrects the gyrocompass heading data accordingly.

ii) Alignment Error & Correction,

In order to obtain correct heading data, the existing alignment error (i.e. the angle between the compass’ and the vessel’s longitudinal axes) must be determined and the required correction applied. Alignment error 0 degree if the sides of the compass housing run exactly parallel to the vessel’s longitudinal axis and the back of the housing points dead ahead. Alignment error correction is carried out electronically by setting the required correction value in the service setup of the gyro system.

The Starting of the Compass;

Switch on the gyrocompass three hours before it is required for service.

- To start, turn the gyro power switch from off position to the on position.

- When the above switch is turned to the on position, the gyro power supply lamp (blue) and the repeater power supply lamp (amber) both light. Then after about ten minutes, the gyro running-up lamp (green) lights.

- The buzzer in the steering stand sounds when the gyro power switch is turned to the on position, silence it by turning the alarm silence switch.

With the above operations, the master compass starts its north seeking action and settles after about three hours.

Repeaters;

We have three repeaters on the bridge one in port , one in starboard, one in the center of the bridge.

We have three controls on auto pilot. These controls are weather,

counter rudder, and rudder controls. These controls are explained below:

Weather (Yawning): This control has 4 positions. These are 0, 1, 2, 3 positions. This control adjusts the sensitivity of the auto pilot according to the weather conditions.

Counter rudder: When changing the course the heading will tend to go beyond the necessary course. To prevent this thing the angle of the rudder is increased in short periods. When this control is off the movement of the rudder is done freely.

Rudder: This control adjusts the rudder angle applied when the deviating

course of the ship is 1 degree.

Pilot watch: During auto-steering, when the course deviation exeeds the

calue set at this control, the alarm generates to warn the officer.

The Use of Gyro Input to Navigation Equipment;

The gyrocompass has been essential source for seamen since it has been invention. It is more reliable than magnetic compass. It is stable between 70°N-70°S latitudes. It is accepted as a north by the seafarers. This reasons which mentioned above and also additionally too many reasons; the gyrocompass is our one of the most important navigation equipment. With correction of gyrocompass its input can be used on the charts.

The Alarms Fitted to a GyroCompass;

The alarm buzzer incorporated on the gyrocompass when the power supplies of the master and repeater compasses are off. After the trouble has been confirmed, turn the alarm silence switch to the opposite side to stop buzzer. When the trouble is solved, the buzzer sounds again, turn alarm silence switch to the opposite side to silence buzzer.

Genel gemi bölümLeri

BOW (geminin baş tarafı)













AFT (geminin kıç tarafı)













GENERAL MORING (genel gemi baglama planı)










SHIP PLAN (genel gemi planı)










AFT (geminin kıç tarafı)