1. Heading 船首向
By heading is understood the direction in which the vessel is pointing.
It is the angle between the fore-and-aft line of the vessel and the true north, expressed in degrees.
2. Course 航向
By course is understood the intended sailing direction of the vessel. In other words, it is the direction in which the vessel is steered in order to reach her destination. It is expressed in degrees.
3. Track 航迹
A track consists of one, or a number of course lines along which the navigator intends to proceed for a safe passage.
4. Great circle 大圆航向
A great circle course will form the shortest connection between two places on the earth.
5. Rhumb line 恒向线
A Rhumb line, or loxodrome, will form a line whereby all the angles made by the course line and the meridians (子午线) are equal.
6. Course over ground (实际航迹向) and course made good (航迹向)
By course over ground is understood the course that the ship will follow if no allowances are made for the effects caused by wind and sea.
By course made good is understood the course that the ship will follow after allowing for the effects caused by wind and sea.
7. Position 位置、定位
The vessel's position can be determined in a number of ways, for example, by means of pilotage (coastal navigation), cross bearings, a cocked hat, a running fix, dead reckoning, astronomical navigation or satellite.
1) Pilotage (coastal navigation) 沿岸航行
When sailing along the coast, compass bearings of conspicuous (明显的) objects are taken at regular intervals.
A CONSPICUOUS OBJECT (CONSPIC) is an object on land or at sea, which is mentioned and described in the pilot book.
2) Cross bearings 交叉方位
Cross bearings form an intersection of two bearing lines that have been taken of two conspicuous objects.
3) Cocked hat 误差三角形
If a third conspic is available, a third bearing ('check line') can be taken.
As the ship is proceeding, the two bearing lines and the check line will form a triangle, called cocked hat.
The ship's position is in or at the cocked hat.
4) Running fix (移线定位)
A running fix is made when there is only one conspicuous object available.
A position fix is made by taking two bearings of the same conspic at interval. The angle between the two bearing lines must be more than 30 degrees.
5) Dead reckoning (DR) 推算船位
By “Dead Reckoning” (DR)is meant finding one’s position by taking into consideration:
last known position and time;
course and speed;
sea and weather conditions.
6) Estimated position (EP) 估算船位
Estimated Position requires applying the effects of any tidal stream to the DR position.
An EP should be plotted every hour when on an open water passage or at every course change in more confined waters.
7) Astronomical navigation (天文导航)
With astronomical navigation or celestial navigation, observations are taken of celestial bodies (the sun, the moon or the stars).
With a sextant, the angle between celestial body and the horizon is measured.
Now with the aid of the chronometer and the tables in the nautical almanac(航海天文历) the ship’s position can be determined.
8) Satellite navigation (卫星导航)
In the Global Positioning System, a signal is transmitted from the satellite. The vessel’s position is determined by data received from the satellite, and shown on the GPS display on the bridge.
注：本文中部分内容图片来源于南通职业技术学院课件
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