CÂU hỏi PHỎNG vấn sỹ QUAN(ORAL EXAMINATIONS FOR THE MASTERS)

- When a vessel intends to navigate on the starboard side of the other vessel, consist of oneprolonged blast followed by one short blast on the whistle and when the vessel intends tonavi

JISS ORAL EXAMINATIONS FOR THE MASTERS

ELECTRONIC NAVIGATION AND PRINCIPLE OF NAVIGATION

1 What is RADAR range resolution?

- Range resolution is the ability of radar to resolve between two targets on the samebearing, but at slightly different ranges The degree of range resolution depends on the width

of the transmitted pulse, the types and sizes of the targets, and the efficiency of the receiverand the indicator

2 What is bearing range resolution?

- Bearing, or azimuth, resolution is the ability of a radar system to separate objects atthe same range, but at slightly different bearings The degree of bearing resolution depends

on radar beam width and the range of the targets The physical size and shape of the antennadetermines beamwidth Two targets at the same range must be separated by at least one beamwidth to be distinguished as two bi distinguished as two objects

3 Give examples of radar false echo.

- The third class of non-precipitation echoes is false echoes These can occur whenvariations in air density cause the radar signal to refract (or bend) into the earth Thereflected signal is then refracted back to the dish where it shows up as a very strong echo.This situation is rare, but it has been observed

a Ghost echoes

b Multiple echoes

c False echoes caused by side lobe

d Distant false echoes caused by duct phenomenon (Vat bat thuong-Skiff)

4 Explain radar side lobe effects?

- An antenna’s side lobe emissions are low power, and will not register distant targets.However, if there is a strong reflecting target near your boat, it sometimes may appear as acircular-arc false echo on the screen

- Side-lobe effects are readily recognized in that they produce a series of echoes(Figure B) on each side of the main lobe echo at the same range as the latter Semicircles, oreven complete circles, may be produced Because of the low energy of the side lobes, theseeffects will normally occur only at the shorter ranges The effects may be minimized oreliminated, through use of the gain and anti-clutter controls Slotted wave guide antennashave largely eliminated the side lobe problem

5 How will you observe gyro error?

a By Polaris

b By sun amplitude sight

c By sun azimuth sight

6 What is the accuracy of sextant position and GPS?

Sextant – Professional sextants use a click-stop degree measure and a worm adjustment

that reads to a minute, 1/60 of a degree Most sextants also include a Vernier on the worm dialthat reads to 0.2 minute Since 1 minute of error is about a nautical mile, the best, possibleaccuracy of celestial navigation is about 0.1 nautical miles (200 m) At sea, results within severalnautical miles, well within visual range, are acceptable A highly-skilled and experiencednavigator can determine position to an accuracy of about 0.25-nautical-mile (460m)

GPS- the accuracy quoted by the US DoD for GPS in Standard Positioning Services

(SPS) mode, available to anyone with an appropriate receiver, is 33 meters for 95% of thetime This accuracy is approximately equivalent to 0.02 minutes

7 illustrate running fix?

Running fix is a position determined by the intersection of two or more lines of positionestablished at different times, but adjusted to the same time by considering the run of the shipbetween the observations The run should not exceed 5 hours in order to have, at least, areliable distance based on ship’s speed

Practically all running fixes at sea are established by two observations of the sun,taken sufficiently far apart for the azimuth to have change enough to give a good anglebetween the two lines; however, lines obtained from observations of any bodies can be used

Example: At 0900 the navigator observed the sun and obtained an intercept of 3 milestowards Zn 1000, using for the AP the 0900 DR At 1200 an observation for latitude gaveLat 400 – 18.0’N Course 2400, speed 12 Plot the 1200 R fix

Note: Latitude is merely a special case of position The line extends in an east – west directionand hence can be used as the latitude at the time of the sight

8 Differentiate between gnomonic chart and Mercator chart and its uses in navigation.

Gnomonic chart – Gnomonic charts are most often used for planning the great –

circle track between points

- There are three types of gnomonic charts depending on the location of the point oftangency In equatorial gnomonic chats, the point where the plane is tangent is located atsome point on the equator A polar gnomonic chart is tangent at one of the poles Obliquegnomonic charts have their point of tangency at some latitude and longitude between theequator and the poles

- The land features of gnomonic charts become more distorted as the distance from thepoint of tangency increases The most often used gnomonic charts are oblique charts with apoint of tangency located in the center of an ocean basin Gnomonic tracking charts WOXZC

5270 WOXZC 5274, have their points of tangency in the North Pacific and North AtlanticOcean basins, respectively

- The chief advantage of gnomonic charts is that a straight line between two pointsrepresents the great circle between the points If you desired to proceed by great circle, allyou need to do is connect the points of departure and arrival with a straight line Thelatitudes and longitudes of points at intervals along this line may bi measured on thegnomonic chart and then transferred to a Mercator chart When these points are connectedwith straight lines (rhumb lines), the navigator has the “legs” of the great circle track Oncetransferred to the Mercator chart, the course on each leg may be determined, and the sum ofthe distances along each leg gives the total great circle distance

- The main disadvantages of the gnomonic projection are that courses, direction anddistance cannot be readily measured For these reasons, gnomonic projections are not usedfor day-to-day navigation and plotting, and should be used as an aid to voyage planning

Mercator chart – Mercator charts are almost universally used for navigation as they

have two special features Firstly, bearings (directions) plotted on the chart are true bearingsand can be used directly after allowing for compass errors (these will be covered in a laterarticle) Secondly, distances are true distances and can be measured directly so long ascertain rules are followed

9 No of GPS satellites (2 dimensional) actively use for position fixing.

- In order to achieve a two dimensional (2 - D) fix on the earth’s surface at least three pseudo ranges must be obtained the three microprocessor can then resolve the three range

equations to remove the effects of the receiver clock offset error

10 What is the height of GPS satellite?

- The satellites orbit the earth with a speed of 3.9km per second and have a circulationtime of 12h sidereal time, corresponding to 11h58 min earth time This means that the same

satellite reaches a certain position about 4 minutes earlier each day The mean distance fromthe middle of the earth is 26560 km With a mean earth radius of 6360 km, the height of theorbits is then about 20200 km Orbits in this height are referred to as MEO – medium earthsatellites orbit the earth at 42300 km, which is about twice the distance of GPS satellites.

11 Why taking route in Aleutian channel from and to Japan?

- The route across the North Pacific to Alaska from Japan is one that is very possibleand can give you the opportunity to stop at some of the remote and beautiful AleutianIslands The typhoons become more frequent in Japan in June/July, so you heed to time yourcrossing so you are out of the way of the typhoons in southern Japan, but not too early in thenorthern Pacific to encounter bad gales and cold The currents circulate against you on thisroute and the weather dependent on the passage of low pressure systems These trackpredominately either up the coast of Japan or across from Siberia, and on through theAleutian chain to Alaska The choice is whether to miss the western end of Aleutian Islandsand try to skirt around the south side of the low pressures and so keep following winds, orhead for Attu and risk headwinds en route In our experience it would be a shame to missthese remote islands on your way past and, if carefully watching the weather faxes, this can

be a feasible option

What is the effect of squat on the vessel?

- Squat is the combination of sinkage and trim, the largest change and location of thatchange along the ship’s hull depending on the location of maximum change in trim

- Squat is a natural phenomena as a ship moves through a restricted channel The shipdisplaces an amount of water equal to her own weight this water must move outward fromand around the hull in all directions The water so displaced moves primarily along andunder the hull and returns astern of the ship to “fill” the space left by the ship as she moves

on Naturally, the faster the ship is moving, the greater the velocity of this flow under andalong her hull, and the greater the velocity of this flow under and along her hull, and thegreater the corresponding pressure drop as a result of that increased velocity

- As the ship enters shallow water the flow of water becomes increasingly restricteddue to reduced clearance under the hull If the channel is shallow and narrow, the flow ofwater becomes restricted both under and on one or both sides of the hull depending on theship’s location in the channel

1 Explain turning circle diagram (Showing which one is the advance, transfer, tactical

diameter, final diameter)

Advance – the distance gained in the original direction until a ship steadies on its final

course

Transfer – the distance gained at right angles to the direction of the original course until the

ship steadies on its final course

Turning Circle – the path followed by a ship’s pivot point when executing a 360o turn

Tactical Diameter – the transfer involved in the execution of a single turn of 180o

Final Diameter – the diameter of the turning circle that ship would scribe when turning 360oindefinitely (Typically less than tactical diameter due to initial “kick” of the ship)

2 Explain super refraction.

The distance to the radar horizon is extended Super refraction occurs in case weatherwith no turbulence and there is an upper layer of warm dry air over surface layer of coldmoist air This increases the downward bending of the rays and thus increases the range at

which contents may be detected It often in the tropics when warm land breeze blows overcooler ocean currents.

3 What is the accuracy of GPS system (2D & 3D)? (At least 4 satellite to determine the

Lat, Long, Height, time)

- GPS horizontal position fixes are typically accurate to about 15 meters (50 ft) GPSuses a constellation of between 24 and 32 medium Earth orbit satellites that transmit preciseradio wave signals, which allow GPS receivers to determine their current location, the time,and their velocity

A GPS fix obtained by measuring the ranges from a series of a selected satellites to thereceiver Ranges are determined by measuring the propagation time of the satellite datatransmission The ranges measured are not true ranges, but are termed “Pseudo Ranges”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 threepseudo ranges must be ranges must be obtained; three microprocessor can then resolve thethree range equations to remove the effects of the receiver clock offset error Similarly, fourpseudo ranges would be required to obtain a three dimensional (3-D) fix

4 Under IMO, what is the maximum target can be track on the ARPA.

- 20 targets where automatic acquisition is provided, whether automatically or manual

acquired; and

- 10 targets, if only manual acquisition is provided.

5 Give examples of ARPA alarms.

a) Watch zone (new target)

b) Tracking overload

c) Collision warning

d) Lost target

f) System failure

METEOROLOGY AND OCEANOGRAPHY

1 What is the direction of Kurushio current?

- It flows northeast from the Philippines along the eastern coast of Japan Near northernJapan, the Kuroshio merges with a cold, southeastern current The two currents become theNorth Pacific Current, which runs east through the Pacific Ocean and brings mild

temperatures to the west coast of North America The Kuroshio Current carries tropicalwaters and heat energy into the temperate latitudes along the east coast of Asia.

2 Speed of kurushio current

- On the equator, the South Equatorial Current is driven directly by the trade winds whichblow from east to west

- In the Indian Ocean, the westward - flowing South Equatorial Current is well-developedonly south of the equator Directly on the equator, the winds reverse twice a year due to themonsoons, and so the surface current can be either eastward or westward

4 What is the direction of North equatorial current?

- Flows east - to - west between about 100 north and 200 north It is the southern side of aclockwise subtropical gyre Despite its name, the North Equatorial Current is not connected

to the equator In both oceans, it is separated from the equatorial by the EquatorialCountercurrent (also known as the North Equatorial Countercurrent), which flows eastward.The westward surface flow at the equator in both oceans is part of the South EquatorialCurrent

5 Illustrate global weather pattern.

- Weather patterns are important in forecasting Sometimes, one is able to predicts what thenext day's weather will be based on the concepts of persistence Today's weather may repeat

or persist until the following day This is especially true in regions where the commonweather patterns are usually consistent or unchanging atmospheric conditions This is easilyseen in warm regions where summers are consistently warm for several months

- The resulting wind patterns in the northern hemisphere would be with northerlywinds moving out from the poles down to about 60 degrees, a southerly wind from 60 to 30degrees and a northerly from there to the equator The reverse would be true in the southernhemisphere.

6 Illustrate dangerous and navigable semi-circle.

North spheroid

dangerous and navigable

southern hemisphere.

Northern hemisphere

Right of dangerous semicircle - steamers: Bring the wind on the starboard bow make as

much way as possible, and if obliged to heave to, do so head to sea Sailing vessels: Keepclose-hauled on the starboard tack, make as much way as possible, and if obliged to heave-

to, do so on the starboard tack

Left of navigable semicircle - Steam and sailing vessels: Bring the wind on the starboardquarter, note the course and hold it If obliged to heave to, steamers may do so stern to sea;sailing vessels on the port tack

Southern Hemisphere

Left of dangerous semicircle - Steamers: Bring the wind on the port bow, make as much way

as possible, and if obliged to heave to do so head to sea Sailing vessels; Keep close - hauled

on the port tack, make as much way as possible, and if obliged to heave to do so on the porttack

Right or navigable semicircle - Steam and sailing vessels: Bring the wind on the port quarter,note the course and hold it If obliged to heave to, steamers may do so stern to sea; sailingvessels on the starboard tack

8 Illustrate wind circulation in Northern hemisphere.

- Winds would blow directly from high pressure to low pressure in much the same way aswater flows from high ground to low ground, and if our Earth was not rotating this would bethe case.

- The resulting wind patterns in the northern hemisphere would be with northerly windsmoving out from the poles down to about 60 degrees, a southerly wind from 60 to 30 degreesand a northerly from there to the equator The reverse would be true in the southernhemisphere

- However, our Earth does rotate once every twenty-four hours and this causes the winds to

be deflected to the right in the northern hem sphere and to the left south of the equator

- This is known as the Coriolis Effect and is why the winds blow clockwise around highpressure and anticlockwise around low pressure in the northern hemisphere and not directlyfrom high to low (Actually they are deflected a small amount at the surface by friction andthe angle of deflection depends on the stability of the air and the ground or sea surface overwhich it is traveling) So the resulting general circulation wind pattern ends up, in thenorthern hemisphere, with cold northeasterly winds blowing out from the North Pole.Predominant southwesterly winds across much of our latitudes bring us the rain bearingfronts from the Atlantic but give us regular rain all for growing our crops

9 Why the initial movement of typhoon in NH is "westerly"?

- It’s because of the trade winds at the surface blow from the belts of high pressure towardthe equatorial belts of low pressure, because of the rotation of the earth; the moving air isdeflected toward the west.

- Recall that the deflection due to the Coriolis effect plus the frictional coupling of wind andwater cause net movement of surface water at about 90 degrees to the right of the winddirection in the Northern Hemisphere

10 Why the typhoon moves "easterly" in higher latitude in N Hemisphere?

- On the poleward side of the high pressure belt in each hemisphere, the atmosphericpressure again diminishes The currents of air set in motion along these gradients toward the

poles are diverted by the Earth's rotation toward the east, becoming southwesterly winds in

the Northern Hemisphere known as the prevailing westerlies of the temperate zones

11 Why does the typhoon not come to 5 deg North to 5 deg south?

- Because the effective of Coriolis in the area between 5 deg north to 5 deg south is too small

or nearly by zero

- Wind and atmosphere/ temperature not have much different in there area

JAPAN DOMESTIC LAWS

1 Unumerate the 11 traffic routes under Maritime Safety Law

a) Uraga Suido Traffic Route

b) Naka-no-Se Traffic Route

c) Irago Suido Traffic Route

d) Akasi Kaikyo Traffic Route

e) Bisan seto East Traffic Route

f) Uko East Traffic Route

g) Uko West Traffic Route

h) Bisan Seto North Traffic Route

i) Bisan Seto South Traffic Route

j) Mizusima Traffic Route

k) Krusima Kaikyo Traffic Route

2 What is miscellaneous vessel?

- The term "miscellaneous vessels" means launches, lighters, small boats, and any craftpropelled wholly or primarily by oar These craft are small ones or those which navigatemainly inside a port

3 What are the overtaking signals?

- When a vessel intends to navigate on the starboard side of the other vessel, consist of oneprolonged blast followed by one short blast on the whistle and when the vessel intends tonavigate on the port side of the other vessel, consist of one prolonged blast followed by twoshort blasts on the whistle

4 What is the signal in case of fire in port?

- In the event of a fire having broken out on board a vessel in a specified port the vessel, ifequipped with a whistle or siren, must sound five prolonged blasts repetitively

- The above sound signal may not be made while under way and the method of the alarmmust be displayed in a place easily seen by persons in charge of sounding the alarm, to avoidmistakes in emergencies

5 Give examples of traffic routes which are considered as one way traffic.

- In Naka-no-Se Traffic route, one way traffic is in effect in the northern direction

- Uko East Traffic Route one way traffic in the northern direction

- Uko west Traffic Route one way traffic route in the southern direction

- Bisan Seto North Traffic Route one way traffic in the western direction

- Bisan Seto South Traffic Route one way traffic in the eastern direction

6 What is the direction of traffic flow in Bisan Seto North and Bisan Seto South?

- When a vessel intends to navigate Bisan Seto North Traffic Route along the course of suchroute, the vessel shall navigate westward

- When a vessel intends to navigate Bisan Seto South Traffic Route along the course of suchroute, the vessel shall navigate eastward

7 How will you navigate in Kurushima Kaikyo when the current is against and when current is favorable?

- To navigate Kurushima Kaikyo Naka Suido (hereafter referred to as "Naka Suido") with thetidal current and to navigate Kurushima Kalkyo Nishi Suldo (hereafter referred to as "NishiSuido") against the tidal current Provided that, if there is a direction change of the thesechannels, the vessel may continue to navigate the channel and that a vessel navigating NishiSuido to enter the channel between O-shima and Hashihama or a vessel intending to enterfrom the same channel into Kurushima Kaikyo Traffic Route and to navigate Nishi Suido,may navigate Nishi Suido even when navigatin with the tidal current

8 What is the sound signal in Kurushima?

- Four (4) prolonged blasts

9 What is the day and night signal for huge vessel?

BY NIGHT - an all-round green light flashing at regular intervals at a frequency between

180 and 200 per minute

BY DAY - Two black cylindrical shapes (0.6m x 1.2m or bigger) placed vertically

10 Is overtaking allowed in Port Regulation Law? Why?

- No Chapter III Article 14#4 of Port Regulation Law states that "A vessel shall notovertake any other vessel within a passage"

11 What are the prohibitions when entering port under port regulation law?

A vessel other than miscellaneous vessels which intends to enter, clear of pass through aspecified port shall navigate the passage prescribed by the Ministry of Transport Ordinance(hereafter referred to as "Passage"), provided that this shall not apply to the cased where thevessel intends to avert an accident or where these exist unavoidable circumstances

A vessel shall not, accepts in any of the following cases, cast anchor or release a vesseltowed within a passage:

a) In a case where a vessel intends to avert an accident

b) In a case where a vessel is not under command

b) In a case where a vessel is engaged in rescue of human life or a vessel in imminent dangerc) In a case where a vessel is engaged in construction or any other similar operations underthe permission of the Captain of the Port in accordance with Article 31

12 Whose duty to keep clear? What flag signal by vessel B?

of Transport Ordinance.

13 What is the speed limit in traffic routes?

- Any vessels shall not navigate at a speed exceeding 12 knots in all areas (7 traffic only: uraga suido, nakanose, irago suido, bisan seto east, bisan seto north, bisan seto south, mizhushima

14 What is the flag signal other than small vessel?

- She must display conspicuously the international code flag “1” on the mast.

SHIP'S STABILITY AND SHIP OPERATION

- GZ = Righting lever measured from G

- KB = Height of center buoyancy from keel

- KM = height of Metacenter form keel

KM = KG + GM

KM = KB + BM

GZ = KN – KG × sin Φ where KN can be found from KN curves.

Righting moment = ∆ × GZ where ∆ = displacement

BM = 2nd moment of water plane area/ volume of displacement = l (metre)/V

Where l = L x B3 (metre 4) for a rectangular barge/ 12

Calculation of GM

GM = KM – KG

A/ Calculation of GM when loading or discharging a small cargo.

GM change due to loading or discharging a small cargo

Loading: GG’=W*d/(W+w)

Discharging: GG’=W*d/(W-w)

When shifting: GG’=w*d/W

W: Vessel displacement before load/ discharge w on/ off vessel

w: weight of small cargo loaded/ discharged

d: Distance from old to new position of center of gravity of cargo w

2 What is Doppler Effect?

The Doppler effect (or Doppler shift), named after Austrian physicist Christian Doppler whoproposed it in 1842, is the change in frequency of a ware for an observer moving relative tothe source of the waves It is commonly heard when a vehicle sounding a siren approaches,passes and recedes from an observer The received frequency is increased (compared to theemitted frequency) during the approach, it is identical at the instant of passing by, and it isdecreased during the recession

For waves that propagate in a medium, such as sound waves, the velocity of the observer and

of the source is relative to the medium in which the waves are transmitted The total DopplerEffect may therefore result from motion of the source, motion of the observer, or motion ofthe medium Each of these effects is analyzed separately Fore waves which do not require a

medium, such as light or gravity in special relativity, only the relative difference in velocitybetween the observer and the source needs to be considered.

3 Illustrate stability curve.

- The stability curve is a graphic presentation of a boats static stability As the boat heels itdevelops righting moment which the force is created by the ballast and hull buoyancy thatworks to resist the heeling The stability curve shows this righting arm (righting momentdivided by displacement) as a function of heel angle When the righting arm turns negative(at 123 degree for this diagram) the boat will no longer resist the heeling force and willcapsize

- When a series of values for GZ (the ship's righting arm) at successive angles of heel areplotted on a graph, the result is a STABILITY CURVE The stability curve, as shown infigure 12 - 24, is called the CURVE OF STATIC STABILITY The word static indicates that

it is not necessary for the ship to be in motion for the curve to apply If the ship ismomentarily stopped at any angle during its roll, the value of GZ given by the curve will stillapply

4 Given with stability curve, identify initial GM, max, GZ, angle of vanishing stability.

5 Longitudinal moments problem solving.

Fuel consumption in Metric Tons

T2-T1=85 - 15 = 70 x 0.000654 = 0.0457

Corrected SG = SG @ T2 - SG @ T15

Sp Gravity @ 850 C = 9886 - 0.0457

= 0.9429

c) Fuel Consumption in Metric Ton

Fuel Consumption = L x 24 x corrected SG / 100

2430 Liters x 24 hours = 58,320L

58,320 L /1000 = 58,32m3

58,32 x 0.9429 = 54.98 MT

7 Describe free surface effect.

When a vessel with partially filled spaces heels over, the contents of the spaces will shirt.The center of gravity moves over to the side, making the vessel less stable To avoid this freesurface effect, try to have as few partially filled tanks and compartments as possible

- You cannot always avoid partly filled spaces By dividing a tank into two equal parts with abaffle, the free surface effect is greatly reduced Using boards to divide fish wells intocompartments will also help

8 Explain bow cushion and bank suction

Bow Suction - a force acting on the bow of a ship in a manner which forces the ship awayfrom the bank in a restricted channel, especially where the banks are steep this a force whichopposes bank suction/suction

Bank suction - force acting on the bow, of a ship in a manner which forces the ship away

from the bank in a restricted channel, especially where the banks are steep

9 Written - rise of GM, given KG and KM, size of ballast tank to empty and displacement, density of water Find final GM after pumping out.

GM = KM - KG

Free surface constant and moment of inertia are the same It is found by this formula:

FSE = 1/12 x L*B3 so GM” = 1 x Sum DLi x (L x B 3 ) i

12 DisplacementWhere:

L = Length of tank D = Density water where

B = Breadth of tank the vessel floats

DL = Density of liquid N = number of tank subdivisions

i = Tank number

Final GM = Old GM - FSE

10 What is rolling period? Soive for rolling period given GM and breadth of the vessel.

Rolling Period The time it takes a vessel to make a complete roll, that is, from port tostarboard and back to port again

Multiply the Beam of the ship to 0.44 in feet and 0.797 in meters if you get the answer divide

it with the Root of GM

Formula: Rolling Period or "T" = 0, 44 x beam "B"/GM

Or GM = [(0.44 x B) /T]2

Note: 0.44 for feet and 0.797 for meter

11 What is TPC, MTC? Why TPC varies at different drafts?

TPC of box-shaped vessel is the same for all drafts because the waterplane area is the same

at any given draft But for the ship-shaped vessel, TPC varies because the waterplane area atany given draft also varies TPC of the ship is given in hydrostatic table or deadweight scale

12 When vessel consumes 40 tons/day at 16 knots, how much is the FO consumption in

19 knots?

It must be calculate as:

40*193/163 = 66.982 ton

(New consumption/Old consumption = N speed3/ O Speed3)

13 Describe how you will execute Williamson turn.

The Williamson Turn is a maneuver used to bring a ship or boat under power back to a point

it previously passed through, often for the purpose of recovering a man overboard It wasnamed for John Williamson, USNR, who used it in 1943 However, according to uncommonCarriers by John McPhee, the maneuver was originally called the "Butakov pipe" and wasused in the Russo - Japanese War of keeping guns at the same distance from an enemy (1)

The Williamson Turn is most appropriate at night or in reduced visibility, or if the point can

be allowed to go (or already has gone) out of sight, but is still relatively near For othersituations, an Anderson turn (Quickest method) or a Scharnow turn might be moreappropriate The choices of which method will in large part depend on the prevailing windand weather conditions

1 Put the rudder over full

2 If in response to a man overboard, put the rudder toward the person (e.g if the person fellover the starboard side, put the rudder over full to starboard)

3 After deviating from the original course by about 60 degrees, shift the rudder full to theopposite side

4 When heading about 20 degrees short of the reciprocal, put the rudder amidships so thatvessel will turn onto the reciprocal course

5 Bring the vessel upwind of the person, stop the vessel in the water with the personalongside, well forward of the propellers

If dealing with a man overboard, always bring the vessel upwind of the person Stop thevessel in the water with the person well forward of the propellers

14 At what speed a bow thruster is effective?

- Less than 5 knots

15 Generally, how much is the tug bollard pull?

- The value for bollard pull (towing force) varies with the type of main engine andpropulsion system The bollard pult of a Z type tug is said to be approximately 1.5 tons aheadand 1.4 tons astern per 100 BHP of the tug

- The bollard pull of a VSP type tug is said to be approximately 1.0 ton ahead and 0.7 tonastern per 100 BHP of the tug

16 What is stiff and tender ship?

Stiff - when a ship has a comparatively large GM, for example 2m to 3m, the rightingmoments at small angles of heel will also be comparatively large It will thus require largermoments to incline the ship When inclined ship she will tend to return more quick to the

initial position The result is that the ship will have a comparatively short time period, andwill, roll quickly - and perhaps violently - from side to side.

Tender - when the GM is comparatively small, for example 0.16m to 0.20m the rightingmoments at small angles of heel will also be small The ship will thus be much easier toincline and will not tend to return so quickly to initial position The time period will becomparatively long and a ship, for example 30 to 35 seconds, in this condition is said to betender

17 What are the drills to be conducted every 3 months and drills to be conducted monthly by cargo ships?

Every 3 months

a) Operation of Emergency generator by all officers

b) Launching and maneuvering lifeboat

c) Immersion suit

d) EEBD

e) IMDG/Leak spill

COLREGS

1 Rules in sailing vessels.

a When two sailing vessels are approaching one another, so as to involve risk of collision,one of them shall keep out of the way of the other as follows:

(i) When each has the wind on a different side, the vessel which has the wind on the port sideshall keep out of the way of the other

(ii) When both have the wind on the same side, the vessel which is to windward shall keepout of the way of the vessel which is to leeward

(iii) If the vessel with the wind on the port side sees a vessel to windward and cannotdetermine with certainty whether the other vessel has the wind on the port or on the starboardside, she shall keep out of the way of the other

b For the purposes of this Rule the windward side shall be deemed to be the side opposite tothat on which the mainsail is carried or, in the case of a square-rigged vessel, the sideopposite to that on which the largets fore-and aft sail is carried

2 Enumerate the 6 types of vessels giving 1 prolong blast and 2 short blast in restricted visibility.

- A vessel not under command

- a vessel restricted in her ability to manouevre

- a vessel constrained by her draught,

- a sailing vessel

- a vessel engaged in fishing

- a vessel engaged in towing or pushing another vessel

3 What sound signal to use when altering course in restricted visibility?

Altering course to starboard one short blast

Altering course to port two short blasts

Astern propulsion … three short blasts

4 What are the signals for overtaking vessel in restricted visibility?

(i) a vessel intending to overtake another shall in compliance with Rule 9 (e) (i) indicate her intention by the following signals on her whistle:

* two prolonged blasts followed by one short blast to mean "I intend to overtake you on your starboard side"

* two prolonged blasts followed by two short blasts to mean "I intend to overtake you on your port side"

5 What are the overtaking signals?

(i) a vessel intending to overtake another shall in compliance with Rule 9(e)(i) Indicate her intention by the following signals on her whisite

* tow prolonged blasts follwed by one short blast to mean "I in tend to overtake you on your starboard side"

(ii) the vessel about the be overtaken when acting in accordance with Rule

9 (e) (i) shall indicate her agreement by the following signal on the

- She shall sound one prolonged blast at intervals of not more than 2 minutes

7 What are the safety measures to be taken during restricted visibility?

- Proper look out

- Safe speed

- Hand steering

- Fog signal

- A vessel which detects by radar alone the presence of another vessel shall determine if aclose - quarter’s situation is developing and/or risk of collision exists If so, she shall takeavoiding action in ample time, provided that when such action consists of an alteration ofcourse, so far as possible the following shall be avoided.

(i) An alteration of course to port for a vessel forward of the beam, other than for a vesselbeing overtaken

(ii) An alteration of course towards a vessel abeam or abaft the beam

Except where it has been determined that a risk of collision does not exist every vessel whichhears apparently forward of the beam the fog signal of another vessel or which cannot avoid

a close - quarters situation with another vessel forward of the beam, shall reduce her speed tothe minimum at which she can be keps on her course She shall if necessary take all her wayoff and in any event navigate with extreme caution until danger of collision is over

8 What are the precautions when navigating in narrow channel?

- A vessel proceeding along the course of a narrow channel or fairway shall keep as near tothe outer limit of the channel or fairway which lies on her starboard side as is safe andpracticable

- A vessel of less than 20 meters in length or a sailing vessel shall not impede the passage of

a vessel which can safely navigate only within a narrow channel or fairway

-A vessel engaged in fishing shall not impede the passage of any other vessel navigatingwithin a narrow channel or fairway

- A vessel shall not cross a narrow channel or fairway if such crossing impedes the passage

or a vessel which can safely navigate only within such channel or fairway The latter vesselmay use the sound signal prescribed in Rule 34 (d) if in doubt as to the intention of thecrossing vessel

9 What is the day signal for deep draft vessel?

- Black cylinder

10 What is the lights signal for deep draft vessel?

- Three all - round red lights in a vertical line

11 What is the warning signal to give way vessel?

- Is she see a red light in her starboard quarter she shall after her course to stbd to give wayfor the other vessel

12 What is the sound signal in narrow channel?

- A vessel nearing a bend or area of a channel or fairway where other vessel may be obscured

by an intervening obstruction shall sound one prolonged blast Such signal shall be answeredwith a prolonged blast by any approaching vessel that may be within hearing around the bend

or behind the intervening obstruction

13 How will you determine risk of collision in overtaking situation and crossing situation? If you are in doubt between overtaking and crossing situation, what will you do?

- RULE 7: RISK OF COLLISION

(a) Every vessel shall use all available means appropriate to the prevailing circumstances andconditions to determine if risk of collision exists

If there is any doubt such risk shall be deemed to exist

Proper use shall be made of radar equipment if fitted and operational including long - rangescanning to obtain early warning of risk of collision and radar plotting or equivalentsystematic observation of scanty information, especially scanty radar information

(c) In determining if risk of collision exists the following considerations shall be amongthose taken into account

(i) Such risk shall be deemed to exist if the compass bearing of an approaching vessel doesnot appreciably change

(ii) Such risk may sometimes exist even when an appreciable bearing change is evident,particularly when approaching a very large vessel or a how or when approaching a vessel atclose range

When a vessel is in any doubt as to whether she is overtaking another, she shall assume thatthis is the case and act accordingly

MASTER

1 DGPS - how many meters accuracy?

Differential Global Positioning Service achieved Full Operational Capability (FOC) on 15March 1999 The maritime DGPS service provides 10 meter (2 dRMS) navigation accuracy,integrity alarms for GPS and DGPS out-of-tolerance conditions within 10 seconds ofdetection, availability of 99.7% per month.

2 GPS - how many meters accuracy?

The specified accuracy of positions of the Global Positioning System under the influence ofS/A (Selective Availability) is that the horizontal coordinates will be within 100 meters oftruth 95 percent of the time

3 UKC

Under Keel Clearance (referred to as UKC) refers to the distance between the keel of avessel and the sea floor

4 Chart correcting

5 Drills, training and instructions explain the differences.

Drills - to teach and train by repeated exercise Onboard, drills are conducted on a schedule

basis for the seafarer’s to be trained well in any case of emergency that may occur onboard.For them the seafarers to act accordingly and to know how to handle the pressure whilehandling an emergency

Trainings - The action of one who trains, educate and develop ones self Drills are part of

the trainings given to the seafarers onboard Through this seafarers are being educated,instructed and practiced most especially in the case of emergency

Instructions - These are directions and orders given or taught to a person or a seafarer for

him to be informed and be knowledgeable

6 Pulse rate of radar.

The pulse repetition rate (PRR) is the number of pulses transmitted per second, return fromany target located within the maximum workable range of the system Otherwise, thereception of the echoes from the more distant targets would be blocked by succeedingtransmitted pulses The maximum measurable range of a radar set depends upon the peakpower in relation to the pulse repetition rate The PRR must the high enough so thatsufficient pulses hit the target and enough are returned to detect the target

7 Bearing & range resolution.

Range Resolution is a measure of the capability of radar set to detect the separation betweenthose targets on the same bearing but having small differences in range If the leading edge

of a pulse strikes a target a a slightly greater range while the trailing part of the pulse is stillstriking a closer target, it is obvious that the reflected echoes of the two targets will appear assingle elongated image on the radar scope

Bearing Resolution - Bearing, or azimuth, resolution is the ability of a radar system toseparate objects at the same range, but at slightly different bearings The degree of bearingresolution depends on radar beam width and the range of targets at the same range must beseparated by at least one beam width to the distinguished as two objects, some externalfactors that affect radar performance are operator skill, size, composition, angle, and altitude

of the target, possible electronic attack (EA) activity; readiness of equipment (completedplanned maintenance system requirements); and weather conditions

8 Draw & explain statical stability curve.

STATICAL STABILITY CURVE (RIGHTING ARM CURVE)

When a ship is inclined through all angles of heel, and the righting arm for each angle ismeasured, the statical stability curve is produced This curve is “snapshot” of the ship’sstability at that particular loading condition

Curves for various displacements up to and past load displacement The ordinates are angles

of inclination Intersection of ordinates with curves produces - the abscissas (righting arms)

Much information can be obtained from this curve, including:

In a case where a vessel is engaged in construction or any other similar operations under thepermission of the Captain of the Port

STABILITY

1) Definition/explain: GM, KG, KM, G2, FREE SURFACE EFFECT, STIFF AND TENDER VESSEL, STABLE/NEUTRAL/UNSTABLE EQUILIBRING SHIFT OF G, FWA, CHANGE OF DRAFET FROM SW TO SW & VICE VERSA.

Ship Stability diagram, showing Center of Gravity (G), Center of Buoyancy (B) andMetacenter (M) with ship upright and heeled over to one side, Note that for small angles G

is fixed, While B and M move as the ship heels

- Metacentric height (GM) is the distance between the center of gravity of a ship and itsmetacenter The GM is used to calculate the stability of a ship and this must be done before itproceeds to sea The GM must equal or exceed the minimum required GM for that ship forthe duration of the forthcoming voyage This is to ensure that the ship has adequate stability

- KM - the distance that the transverse metacenter, M, measured in feet, is above the keel, K,

is designated KM, KM is the sum of KB and BM Any change in the value of KB and BMchanges the value of KM

- Stable equilibrium – a ship is said to be equilibrium if, when inclined, she tends to return tothe initial position, For this to occur the center of gravity must be below the metacenter, that

is, the ship must have positive initial metacentric height

- Unstable equilibrium - when a ship is inclined to a small angle tends to heel over stillfurther, she is said to be in unstable equilibrium For this to occur the ship must have anegative GM

- Neutral equilibrium - when G coincides with M, the ship is said to be in neutralequilibrium, and if inclined to a small angle she will tend to remain at the angle of heel untilanother external force is applied

- Fresh Water Allowance - amount that load lines assigned for sea water may be submergedwhen loading in fresh water, amount by which the ship would, submerge when going fromsalt water to fresh water

Free Surface Effect - In tanks or spaces that are partially, filled with a fluid or semi-fluid,stay level This results in a displacement of the center of gravity of the tank or space relative

to the overall center of gravity The effect is similar to that of carrying a large flat tray ofwater When an edge is tipped, the water rushes to that side which exacerbates the tip evenfurther The significance of this effect is proportional to the square of the width of the tank orcompartment so two baffles separating the area into thirds will reduce the displacement of

the centre of gravity of the fluid by a factor of 9 This is always of significance in ship fueltanks or ballast tanks, tanker cargo tanks, and in flooded or partially flooded compartments

of damaged ships Another worrying feature of free surface effect is that a positive feedbackloop can be established, in which the period of the roll is equal or almost equal to the period

of the motion of the centre of gravity in the fluid, resulting in each roll increasing inmagnitude until the loop is broken or the ship capsizes

Stiff-when a ship has a comparatively large GM, for example 2m to 3m, the rightingmoments at small angles of heel will also be comparatively large It will thus require largestmoments to incline the ship When inclined ship she will tend to return more quickly to theinitial position The result is that the ship will have a comparatively short time period, andwill roll quickly - and perhaps violently - from side to side

Tender - when the GM is comparatively small, for example 0.16m to 0.20m the rightingmoments at small angles of heel will also be small The ship will, thus be much easier toincline and will not tend to return so quickly to the initial position The time period will becomparatively long and a ship, for example 30 to 35 seconds, in this condition is said to betender

Change of draft from SW to FW - When a vessel passes from water of one density to water

of another density, there is a change of mean draft Also there is likely to be a change of trim,

as well as a drill in principles of stability and trim

Which way a vessel will trim when passing from fresh to salt water, or vice versa, dependsupon the relative longitudinal position of the center of floating (LCF) and the center ofbuoyancy Assuming that the usual merchant vessel has its center of buoyancy forward of thecenter of flotation, the following rules can be laid down:

a) When a vessel passes from salt to fresh water, there will be a decrease in mean draft, andthe trim to the vessel will change slightly so that the draft will increase and the draft forwardwill decrease

b) When a vessel passer from salt to fresh water, there will be an increase in mean draft, andthe trim of the vessel will change slightly so that the draft aft will decrease, and the draftforward will increase

2) Problem solving: rolling period (in meter), parallel sinkage, change of trim, change

of draft/FWA.

Rolling period T, Base on GM = (k x B/T)2

Where: T = is a full natural rolling period in seconds

B = is the beam of the vessel

k = 0.797 if GM unit is metre

k = 0.44 if GM unit is feet

Parallel Sinkage = W/TPI

Change of trim is found by noting the trim or that of the vessel before loading or dischargingand the trim of the vessel after loading or discharging The initial and final trims are thencompared and change of trim found according to the following rules:

If the trims are both by the head or both by the stern, subtract the lesser from the greater Ifthe trims are different, that is one by the head and the other by the stern, add the two toproduce change of trim

Change of trim = w x d where: w = weight

MCT 1cm d = distanceChange of draft aft in cm = (l/L) x change of trim in cm

Where: l = the distance of center of flotation from aft in meters

L = the ship's length in meters

Changer of draft Fore in cm = change of trim - change of draft aft

Fresh Water Allowance (mm) = Displacement (in tonnes)

4 x TPC

SHIP HANDLING

1) Anchoring procedures

2) Required number of shackles - good or rough weather

How to determine length of chain:

For good weather = 3D + 90 D = depth of water

For bad weather = 4D + 145

Conversion: 1 shackle = 27.5 meters

3) Effect of right/left handed when going ahead/astern

Right Handed Propeller

- When going ahead, the bow cants to port, the swing decreasing as way is gathered andpossibly changing in the opposite sense

- When going astern, the bow cants strongly to starboard and will continue to do so untilcorrecting helm is used

Left Handed propeller

- When going ahead, the bow cants to starboard

- When going astern, the bow cants to port

4) How to maneuver in restricted water, say in small port

- Ship-handling is about arriving and departing a berth or buoy, maneuvering in confinedchannels and harbours and in proximity to other ships, whiles at all times navigating safely.Two other types of operations come to mind, berthing alongside another ship andreplenishment at sea A key ability for a ship handler is an innate understanding of how thewind, tide and swell, the passage of other vessels, as well as the shape of the seabed, willaffect a vessel's movement, which, together with an understanding of a specific vesselsperformance, should allow that vessel a safe passage

5) Turning circle

The path followed by the pivoting point of a ship making a turn of 360 degrees or more Forthe ordinary ship, the bow will be inside, and the stern outside, this circle

6) MOB procedure

If you witness someone going overboard:

1 Keep your eyes on them, DON'T lose sight of them

2 Yell: "MAN OVERBOARD" and you are closest to the Dan Buoy or Man OverboardRaft:

1 Release the Dan Buoy or raft

2 Yell: "DAN BUOY (or) RAFT RELEASED"

3 Make sure the watch officer has heard you:

4 Go to your muster station

If you hear "MAN OVERBOARD" and you are in, or closest to the

Deckhouse:

1 Go to the GPS unit and push the "Man Overboard" button

2 Yell : "GPS BUTTON PUSHED"

3 Go to your muster station

If you are on the helm and you hear "MAN OVERBOARD":

1 Be ready for the Watch Officer's instructions and carry them out

2 Stay on the helm, but make sure the Toa knows you are there

Otherwise if you hear "MAN OVERBOARD"

1 If you do not already have it on, put on the protective gear you have close to hand asquickly as possible

2 Quickly put on your lifejacket.

3 Go to your muster station, ready to work

7) Squat

- It is the combination of sinkage and trim, the largest change and location of that changealong the ship's hull depending on the location of maximum change in trim It is a naturalphenomenon as a ship moves through a restricted channel The ship displaces an amount ofwater equal to her own weight This water must move outward from and around the hull inall directions The water so displaced moves primarily along and under the hull and returnsastern of the ship to "fill" the space left by the ship as she moves on Naturally the faster theship is moving, the greater the velocity of this flow under and along her hull and the greaterthe corresponding pressure drop as a result of that increased velocity

8) UKC/minimum required UKC

- Under Keel Clearance - the distance between the deepest point of the vessel's hull and thesea bed

- The OOW shall check prior to arriving at positions where minimum UKC is determiningthe UKC, the Master shall take into account all factors that have influence on the actualUKC, and these factors include, but are not limited to the following

1 The effect of Squat

2 Environmental conditions, e.g the prevailing weather, height of swell, tidal

height and range, atmospheric pressure, and changes in the density of sea and

in land waters

3 The nature and stability of the bottom (e.g sand wave phenomena)

4 The vessel's size and handling characteristics, and increase in draught due

to heel

5 The reliability of ship's draught observations and calculations, including

Estimates of hogging or sagging

6 The accuracy of hydrographic data and tidal predictions

7 Reduced depths over pipelines

Minimum UKC for various areas of navigation:

1 Open Sea - minimum 6 meters

2 Narrow Channels - 16% of the deepest draught

3 In Port Navigation - 10% of the deepest draught (see Note A below)

4 Alongside Berth - Minimum 0,50 meter

In Port Navigation, if the vessel is required to reduce UKC below 10%, the Master must takefull account of the factors listed above, which govern determination of a safe UKC.

RADAR/ARPA

1) Define/explain: super/sub refraction, ducting - which phenomena is

good/bad for vessel

Super Refraction

The distance to the radar horizon Super refection occurs in calm weather with no turbulenceand there is an upper layer of warm dry air over a surface layer of cold moist air Thisincreases the downward bending of the radar rays and thus increases the range at whichcontents may be detected It occurs often in the tropics when warm land breeze blows overcooler ocean currents

Sub - Refraction

The distance to the radar horizon is reduced Sub-refraction occurs when a layer of cold,moist air overrides a layer of warm dry air The effect of sub-refraction is to end the radarrays upward and thus decrease the maximum ranges at which confacts may be detected Sub-refraction also affects minimum ranges and may result in failure to detect low-lying contacts

b) Elevated Ducting - due to a reflecting layer of warm air, well elevated above earth's level,for ex at 250 meters In other words, a temperature inversion exists cases like these, morethan one discontinuity in temperature might occur and radar energy is conducted along aduct, well above the earth's surface as shown (See figure 1.4.2d).

2) Different causes of radar false echoes.

Characteristics by which indirect echoes may be recognized are summarized as follows:

1 Indirect echoes will often occur in shadow sectors

2 They are received on substantially constant bearings, although the true

3 They appear at the same ranges as the corresponding direct echoes

4 When plotted, their movements are usually abnormal

5 Their shapes may indicate that they are not direct echoes

Side - Lobe effects are readily recognized in that they produce a series of echoes on each side

of the main lobe echo at the same range as the latter Semicircles, or even complete circles,may be produced Because of the low energy of the side-lobes, these effects may beminimized or eliminated, through use of the gain and anti-clutter controls Slotted waveguide antennas have largely eliminated the side-lobe problem

Distortion effects of radar shadow, beam width, and pulse length when near another radar

operating in the same frequency band as that of the observer’s ship, is usually seen on thePPI as a large number of bright dots either scattered at random or in the form of dotted linesextending from the center to the edge of the PPI

Interference effects are greater at the longer radar range scale settings The interference

effects can be distinguished easily from normal echoes because they do not appear in thesame places on successive rotations of the antenna

Hour-glass effect appears as either a constriction or expansion of the display near the center of the PPI The Expansion effect is similar in appearance to the expanded center

display This effect, which can be caused by a nonlinear time base or the sweep not starting

on the indicator at the same instant as the transmission of the pulse, is most apparent when innarrow rives or close to shore

The echo from an overhead power cable can be wrongly identified as the echo from aship on a steady bearing and decreasing range Course changes to avoid the contact areineffective; the contact remains on a steady bearing, decreasing range This phenomenon isparticularly apparent for the power cable spanning the Straits of Messina.

3) Minimum acquisition capacity of ARPA (IMO standard)

The ARPA should be able to automatically track, process, simultaneously

display and continuously update the information on at least;

a) Twenty targets, if automatic acquisition is provided, whether automatically or

manually acquired

b) Ten targets, only if manual acquisition is provided

4) Different causes of ARPA alarms

The following alert/alarms are just some of the available nowadays There areprobably more, as newer and more advanced features are being installed on modern ARPAunits

a) Collision alert – this alarm is activated by two primary reasons either one or both ofthe CPA and TCPA have reached their minimum preset limits, which is preset by theoperator

b) Guard ring/Zone alarm – if a Radar echo return over crosses the preset guardring/zone, both an aural and visual alarm will activate, alerting the operator this case, it doesnot need to have the target acquired in order to activate alarm

c) Lost Target Alarm – when acquiring a target, the echo return must constant in itsmovement and appearance on the PPI scope in order the acquisition is successful If asuspected target is acquired and it does remain its constancy in both appearance andmovement, the target may considered lost and an aural and visual alarm is activated

d) Anchor Watch Alarm – a turning circle with a radius determined and preset theoperator is also displayed around own ship It remains fixed on the scope and when the shipwanders off turning circle, both an aural and visual alarm will activate

e) Maximum/Minimum Range of Target Acquisition – Most ARPA units at continuouslyexpanding its maximum acquisition range A modern ARPA units has a maximumacquisition range of 32 nautical miles and a minimum three cables (0.3 Nm) If suchminimum presets are met, either or both visual and aural alarm will activate

f) Maximum Number of Target Acquired – whenever an ARPA unit exceeds themaximum number of targets it can activate

g) Gyro/GPS Interface Missing – When the gyro or the GPS (if fitted) interface has lostits connection with the ARPA unit.

h) System Fault – this alarm will only be triggered if a technical problem occurs withinthe ARPA system

GPS/DGPS

1) Principles of GPS/DGPS

GPS – the principle behind GPS is the measurement of distance (or “range” between

the satellites and the receiver The satellites tell us exactly where they are in their orbits bybroadcasting data the receiver uses to compute their positions It works something like this:

If we know our exact distance from a satellite in space, we know we are somewhere on thesurface of an imaginary sphere with a radius equal to the distance to the satellite radius If weknow our exact distance from two satellites, we know that we are located somewhere on theline where the two spheres intersect And, if we take a third and a fourth measurement fromtwo more satellites, we can find our location The GPS receiver processes the satellite rangemeasurements and produces its position GPS uses a system of coordinates called WGS 84,which stands for World Geodetic System 1984 It allows surveyors all around the world toproduce maps like the ones you see in school, all with a common reference frame for thelines of latitude and longitude that locate places and things Likewise, GPS uses time fromthe United States Naval Observatory in Washington, D.C., to synchronize all the timingelements of the GPS system, much like Harrison’s chronometer was synchronized to the time

at Greenwich

DGPS

A high accuracy GPS receiver located at a precisely surveyed position consists of areference station When receiving GPS signals, the reference station calculates errors in thesatellite signals And, then the corrections will be broadcast in a standard format by thetransmission station to users in the area The user’s DGPS receiver app1ies the correctionmessage to improve the accuracy of The Radio Beacon / Deferential Global PositioningSystem is an aids to navigation system which, by broadcasting differential correctioninformation, provides high accuracy positioning service to public user

2) Number/ height of satellites

Currently, the global positioning system includes a constellation of 24 systematically arranged satellites orbiting the earth in six orbital planes with four satellites in each plane The constellation is arranged to guarantee radio reception from at

least four satellites from any location anytime, anywhere on Earth GPS receivers normallyreceive signals from eight to nine satellites in location without obstructions like buildings ortrees.

The 21 functioning satellites are evenly spaced in circular orbits inclined 55

degrees to the equatorial plane, approximately 20,000 km above the surface of the earth.

At a height of over three times the radius of the earth, each satellite orbits the earth onceevery twelve hours A particular satellite is visible to a user on earth for approximately fivehours each rotation Depending on the location of the user and the time of day, between fourand ten satellites are visible at any time Five control stations, spaced evenly around theworld, control the satellites These stations are responsible for predicting and correcting theorbits of the satellites, and for transmitting data up to the satellites, including clockcorrections

3) Minimum number of satellites to obtain fix

At least 4 satellites are required to measure the position of object with GPS

device The measured parameters include latitude, longitude, altitude and time.

4) Accuracy of GPS/DGPS (errors in meter)

The accuracy of a position determined with GPS depends on the type ofreceiver Most hand-held GPS units have about 10-20 meter accuracy Other types ofreceivers use a method called Differential GPS (DGPS) to obtain much higher accuracy.DGPS requires an additional receiver fixed at a known location nearby Observations made

by the stationary receiver are used to correct positions recorded by the roving units,producing an accuracy greater than 1 meter

DRILL

1) Different types of drill: weekly, monthly, quarterly

Japan International Ship System Examination

Questionnaires given by MLIT (Ministry of Land, Infrastructure, Transport and Tourism)

1) Explain and Illustrate – MO (U) G 8s (Buoy)

- This Indicates that the light is Morse (U) in which color is Green (G) repeatedevery Eight second (8s)