Question and Answers

    Question
    marinetales September 20, 2021
    Following are the reasons why the long by chron method is preferred over Intercept method during morning sight - 1. Long by chron method takes lesser time 2. Calculations are easier 3. For obtaining the noon position, the plotting is not required as the dlong can be calculated directly from the formula d'long = c corrn x d' lat
    marinetales September 6, 2021
    T & P Notices also called as Temporary and Preliminary Notices, are provided in Weekly Notices to Mariners in Section II. These are shown with suffix (T) or (P) after each Notice Number. Temporary Notice may be issued to inform the mariner of any navigation affecting changes which are temporary in nature. Such eg may include - naval exercise, drilling activities, dredging etc. Preliminary Notices are issued to promulgate navigationally significant data to mariner when - 1. Action or work will shortly be taking place. 2. Information has been received but is too complex to be promulgated by chart updating notice 3. Further confirmation of details is needed. A chart updating Notice will be promulgated or New Edition issued when the details have been confirmed 4. For an ongoing and changeable situation such as a bridge under construction
    marinetales September 6, 2021
    Wheel-over point is a point where the rudder is put over while considering the distance to the new course and the ship's turning characteristics. For a safe turn, it is necessary for a vessel to determine her wheel-over position or point.
    marinetales September 6, 2021
    Great Circle Sailing : shortest distance measured along the earth's surface between two places is called the Great Circle Distance. The departure and arrival positions are marked on a Gnomonic Chart and joined by a straight line. Waypoints are transferred from Gnomonic to Mercator chart and it appears as a Curved line on Mercator chart. Mercator Sailing : Used to find the Rhumb Line course and distance between two positions. It uses the following formula - tan Course = dLong / DMP This holds good when the distance is more than 600 NM. For distances lesser than 600 NM, we use Parallel sailing. The formula is given by - Cos mLat = dep / dLong Rhumb Line: Rhumb Line is a line drawn on a Mercator Chart which cuts all meridian at same angles. Composite Sailing: Sometimes, it is not possible to execute a full great circle for a voyage. This could be due to presence of navigational dangers in between OR if the Master decides not to go beyond a certain latitude owing to weather conditions. In this case, a combination of rhumb line and great circle sailing. Together this type of sailing is called as Composite Sailing.
    marinetales September 6, 2021
    The amplitude of any celestial body is taken, when the centre of the celestial body is at the rational horizon. In the case of moon, when it's centre is at the rational horizon, the moon is not visible on the horizon.
    marinetales September 6, 2021
    The best time to take amplitude is when the body is theoretically rising or setting. This means when the sun's lower limb is half the Semi Diameter above the visible horizon. At this time, the centre of the body is at the rational horizon, but the body is seen above the visible horizon because of refraction.
    marinetales September 1, 2021
    Dead Reckoning position: After a fix is obtained, the next position of the vessel which is found by applying course steered, leeway and engine speed ONLY is called Dead Reckoning position. This is denoted by the symbol 'X'. Estimated Position: If the DR position (obtained above) is adjusted for prevailing set and expected drift then the position is said to be Estimated Position. This is denoted by the triangle symbol. Observed position or FIX: The actual position of the ship is called as the Observed Position or Fix. This is denoted by a Circle. The OP or Fix is the most accurate position of the ship.
    marinetales September 1, 2021
    Following factors affect the squat of the vessel - 1. Speed of the vessel 2. Block Coefficient 3. Blockage factor 4. UKC of the vessel 5. Trim of the vessel 6. Location of the vessel (open seas or canal / channel)
    marinetales August 26, 2021
    Sometimes it is not possible to obtain sextant altitude of the celestial body when it is on the meridian due to clouds, hazy horizon, rain or other reasons. The celestial body is then observed when it is near the meridian. The value of Ex-meridian limits are obtained from the nories tables OR as an estimate, if the Latitude and Declination are the same name then subtract the value and if different names than add the value, the value obtained will be the value of limits in minutes before and after meridian passage for taking sight. This is called Ex meridian limits. Within this window period one should obtained the sight of the celestial body when it is near the meridian.
    marinetales July 27, 2021
    The depths given on a Nautical Chart (whether in meters, foot or fathoms etc) are measured from the Chart datum. Common chart datums are the Lowest Astronomical Tide or Mean Low Low water tide. For Non-tidal areas Mean Sea level (MSL) values are used. The echo sounder gives the depth BELOW KEEL. Let us assume that Echo Sounder is giving you a fairly accurate reading. In order to compare both (Echo sounder and Chart readings) following shall be used - Depth on Chart = Depth obtained from Echo Sounder + draft of the vessel - Value of Tide at the given place Above is just an assumption and the values could be affected by the rolling/pitching, sea conditions and other meteorological phenomenon such as High-low pressure systems.
    marinetales July 26, 2021
    Synchronized pitching is when the period of the vessel pitching, equals the period of encounter of the waves from either ahead or astern. It must be considered extremely dangerous especially if in an area of abnormal waves. It can be overcome by reducing the ship’s speed and changing the period of encounter.
    marinetales July 25, 2021
    Engaging with tugs must always be considered as a high risk area of work and as such the following points would go some way to making the task as safe as possible: (a) Clarify beforehand the method of engagement as to whether the tugs line is to be used or the ship’s line and which ‘lead’ is intended. (b) All persons involved in the operation should be adequately kitted out in protective clothing and briefed as to the nature of the activities involved. (c) Adequate communications, tested beforehand, should be available between towing stations to the bridge and the towing vessel if appropriate. (d) If the tugs line is to be used, this should be inspected to be free of defects and be seen to be of adequate strength. (e) Throughout the operation all personnel should be advised to keep clear of bights in wires/ropes. (f) The eye of the towline should not be placed on the ‘bitts’ but the wire should be set in a figure ‘8’, turns, around the bollards. The top turns should be lightly lashed to prevent accidentally jumping off. (g) Non-essential personnel should be kept well clear of towlines and the towing area.
    marinetales July 25, 2021
    The advantages of the Mediterranean Moor are: • That more vessels can berth with restricted quay space. • Cargo ships can work both port and starboard sides into barges. • Tanker vessels can load/discharge through stern manifolds. • Roll on–Roll off (Ro-Ro) vessels can operate stern ramps. The disadvantages are: • The vessel is exposed from the shore. • Cargo ships are denied the use of shore side cranes. • Loading and discharge must take place into barges. • A boat is required to go ashore.
    marinetales July 24, 2021
    The fouled anchor is the description given to when the anchor itself is fouled by some object like a cast off fishing wire, or even by its own cable turned around the fluke. A fouled hawse occurs when the vessel has moored with two anchors and ship’s anchor cables have become entwined, usually caused by a change in the wind direction, causing the vessel to swing in opposition to the lay of cables.
    marinetales July 24, 2021
    Short stay is a term used to express a short amount of visible cable at a steep angle from the hawse pipe to the water surface. Whereas long stay is a term which describes where the cable is in a more horizontal direction towards being parallel to the surface of the water. The cable is said to ‘grow’ from a shorter stay to a long stay aspect.
    marinetales July 24, 2021
    By watching the cable after applying the brake once the required scope has been played out. If the cable rises up, to long stay and then bows, to form a ‘catenary’, then rises again. This cable movement is an indication that the vessel is riding to her anchor not dragging her anchor. If the cable stays taught all the time it may be assumed that the anchor is dragging under the tension.
    marinetales July 24, 2021
    Good Holding Ground : Mud and clay Bad Holding Ground : Ooze, marsh, soft sand, rock, pebble.
    marinetales July 23, 2021
    OA represents the apparent motion of the target. WA represents the true course and speed of the target. OW represents own ship’s motion (course and speed).
    marinetales July 21, 2021
    Place the engines on ‘stand-by’ and the situation may make it necessary to take all way off my own ship. Further actions would include: (a) Advising the Master of the situation of the vessel aground. (b) Carrying out a ‘chart assessment’ to include my own ship’s position and the position of the vessel aground. (c) Switch on the echo sounder and note the Under keel Clearance. (d) Position lookouts and turn from auto pilot to manual steering. (e) Communicate with the vessel aground, with station identification, obtaining the draught of the aground vessel and the time of grounding. (f) Carry out an assessment of the extent of the shoal that the vessel has run aground on.
    marinetales July 21, 2021
    The OOW remains the Master’s representative in the absence of the Master, despite the presence of a pilot (exception Panama Canal). During any pilotage period he would be expected to maintain an effective lookout at all times. In addition, he would continually monitor the ship’s position by primary and secondary means and ensure that the under keel clearance is adequate throughout. His duties will also include the management of the bridge personnel and he would ensure that the pilot’s instructions are executed in a correct manner by the members of the ‘bridge team’. He would further ensure that the pilot is made familiar with the bridge instrumentation and advised of compass errors and any defects which may affect the safe navigation of the vessel.
    marinetales July 21, 2021
    While taking over/keeping an Anchor watch, the OOW shall comply with the procedures laid down by the company's SMS through means of a checklist. Such checklist may contain following - 1. maintain an effective lookout, by all available means, including visual, audible and radar. 2. check the position at regular intervals to ensure that the ship is not ‘dragging her anchor’ 3. Position monitoring by primary and secondary position fixing methods, i.e. checking Visual Anchor Bearings, Radar Range and Bearings, Global Positioning System (GPS) etc. 4. Monitor the state of visibility, the state of the weather, especially wind and tide changes 5. Traffic movement in and out of the anchorage 6. Listening watch on VHF 7. Log books to be maintained 8. Access to the ship to be monitored and ISPS to be complied with
    marinetales July 21, 2021
    The OOW should call the Master in any of the following circumstances: (a) In the event of visibility dropping below 4 miles (company policy may be more or less than this figure). (b) If traffic was causing concern effecting the safe passage of the vessel. (c) In the event of failure of any of the ship’s navigational equipment. (d) If failing to sight a landfall when expecting to. (e) If sighting a landfall when it is unexpected. (f) If soundings are shelving when unexpected. (g) In the event that difficulty is experienced in maintaining the course. (h) If a scheduled position is unattainable or suspect. (i) In the event that the man management of watch keepers becomes untenable. (j) In the event of heavy weather or on receipt of a bad weather forecast. (k) On sighting ice, or receiving an ice warning of ice being reported on or near the vessels track. (l) If sighting oil on the surface. (m) On any issue of security or shipboard alert. (n) In any other emergency, such as fire or flooding, imminent contact or contact with a submerged object.
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