1. Features of fog navigation
The so-called foggy navigation is a customary name for sailing in poor visibility.
The main characteristics of fog navigation are: poor visibility and limited line of sight; Due to poor visibility, it is difficult to find the situation around the ship in time, which makes it difficult for the ship to locate, navigate and avoid; When the safe speed is adopted in fog, the influence of airflow on the ship increases, which reduces the accuracy of speed and voyage calculation, and has a great influence on navigation safety near narrow waterways and shoals.
2. Preparation before the ship enters the fog.
(1) Take a safe speed and issue a fog signal as required; (2) Determine the position of the ship as accurately as possible, and make clear the surrounding state of the ship; (3) Turn on VHF and radar, and assign lookouts; (4) Report to the captain in time and notify the engine room to prepare the vehicle; (5) Change the automatic rudder into manual rudder; (6) Keep quiet and open the bridge doors and windows for listening observation; (7) Exceed the weather forecast, meteorological fax, navigation warning and fog warning in time.
3. Matters needing attention in fog navigation
(1) Strengthen observation in fog. Lookout is an important link to ensure the safety of fog navigation. Lookout includes visual observation, auditory observation and radar observation. In order to distinguish between small objects, lights and weak sounds, the captain should arrange head personnel, and when sailing in narrow waterways and harbors, in order to observe the movement of overtaking ships or avoid ships touching surrounding objects, the tail personnel can be arranged at the stern. Forecasters and lookouts should keep in touch with the bridge with walkie-talkies and report the observed situation to the captain and bridge at any time.
① Visual observation: When the familiar land is marked, it should be carefully identified. If you find a suspicious target, you should stop or reverse the car. Before you see the land shore, you can find the sound of waves lapping on the shore in the fog. When finding an island at close range, if in doubt, stop immediately and continue sailing after the ship's position is confirmed.
② Auditory observation: When the visibility is limited, stop the noise of the ship's deck and superstructure, keep quiet, and stop when necessary, so as to reduce the noise of machines and wind waves, so as to listen to the fog signals of the surrounding ships. The ship's fog calls should not be too close together. If there is a cliff on the shore, you can judge the direction by the echo of the horn. When you hear the fog signal, you should immediately judge the direction and distance of the nearby ships, analyze the surrounding sea conditions and determine your own avoidance measures in time. The bridge shall communicate with nearby ships through high frequency, communicate each other's positions and avoidance measures to ensure mutual safety.
(3) Radar observation: Start the two radars equipped on board and adjust the observation range to short-range and medium-range. Ocean navigation can be adjusted to 12 to 24 nautical miles, coastal navigation to 6 to 12 nautical miles, and narrow waterway navigation to 2 to 6 nautical miles. When sailing in fog, there should be a special person responsible for radar observation and plotting.
(2) When sailing in foggy areas, the distance between the ship's route and the shore should be adjusted in time to ensure that there is enough room for manoeuvre between the ship and the shore, and the distance between the route and the coast should be adjusted to 3 ~ 4 nautical miles. The following conditions can be used as a reference for us to preliminarily judge the distance between this ship and the nearby coast and surrounding ships or other dangerous objects:
① The wind direction and wind speed are stable, and the waves suddenly weaken, indicating that the ship is close to the windward coast or shallow water area; (2) The sailing conditions remain unchanged, and the wind suddenly decreases, indicating that the ship may approach the high and steep shore; ③ The seawater becomes turbid, indicating that the ship is close to the coast or estuary; (4) Oil, garbage or fishing gear are found on the sea surface, indicating that there are ships nearby; (5) There are floating objects such as seaweed on the sea surface, indicating that it is close to the shore; 6. If a large number of seabirds or marine animals are found in groups, it means that they are close to icebergs or land.
(3) When the visibility is seriously poor, the captain must immediately go to the bridge to direct the ship's operation, and insist on being on duty to continuously listen to VHF 16/70. Autopilot is strictly prohibited.
(4) Sounding, positioning and navigation: Sounding, positioning and navigation with echo sounder are common methods in fog navigation, and the navigation time between two adjacent water depth points is calculated according to the speed as the basis for determining the sounding time. In this way, continuous sounding is carried out, time, logging readings and water depth data are recorded, and the measured water depth is corrected to the depth datum corresponding to the chart. Chart water depth = sounding value of sounder+draft-tide level. Then draw the planned route and the estimated ship position on the transparent line according to the same scale as the chart, mark the corrected water depth near the corresponding estimated ship position, move the transparent paper near the planned route on the chart, and move the transparent paper in parallel to keep the planned route on it parallel to the planned route on the chart until the water depth point on the transparent line is basically the same as the corresponding water depth point on the chart. At this time, the position of the last water depth point is the approximate position of the ship at the time of the last sounding.
(5) Navigation in fog: Point-by-point navigation refers to the navigation method in which one object is facing the next. This method can be used if there are suitable beacons, buoys or fog stations in the navigation area and there are few dangerous objects around. According to the speed and the distance between two objects, the time of the next object is estimated, and the lookout is strengthened during the voyage. If you don't find the object in time, you must anchor and wait for the voyage, and you must not sail blindly. The advantages of this method are that it can continuously control and reduce the calculation error; However, it is more dangerous to approach the target in poor visibility.
(6) Remember three S's, two warning circles and a separation line. First of all, the three S's include: ① Safe speed: refers to the speed that is convenient for taking appropriate and effective avoidance measures; And stop the ship at a distance suitable for the environment and situation at that time. (2) Starboard: For the target in front of the right cross, if the rudder must be used to avoid it, it must be starboard, and it must be avoided to the right at a large angle. (3) Stop the ship: it is an effective and simple measure to avoid moving the ship, which can effectively resolve the tension. Secondly, the two warning circles refer to: the 5-nautical-mile deceleration warning circle and the 2-nautical-mile stop warning circle. Thirdly, the traffic separation line is stipulated by the traffic separation system, which can avoid unnecessary navigation crossing and reduce the chance of collision. Drivers should abide by the rules and regulations of traffic separation system.
In a word, the safety of fog navigation not only requires the crew to have good rowing skills and strict and responsible working attitude, but also requires the crew to be familiar with and implement the navigation regulations related to fog navigation.
References:
Chen Jiahui, Zhang Jiping. Marine meteorology and oceanography. Dalian Maritime University Press, 2007.
[2] Guo Yu. Navigation. Dalian Maritime University Press, 1993[3] Pan Qixiang. Navigation (Volume II). Dalian maritime university press.
[4] Ding Yong. Navigation. [5] Zhang Wenjun Dalian Maritime University Press, 2000. Navigation. Dalian Maritime University Press, 200 1
[6] The captain's business. Editor-in-Chief of China Maritime Service Center, 2008[7] Feng Ye. Basic countermeasures to prevent fog navigation accidents [J]. Navigation Technology, 20 12( 1)