Chapter 3 Navigation Technology

1. Chapter 3 Navigation Technology 9~10 hours

2. Review what we have learned last period. Important Definitions Routing System Traffic Separation Scheme Separation Zone or Line Traffic Lane Roundabout Inshore Traffic Zone

3. Two-way Route Recommended Route Recommended Track Deep-Water Route Precautionary Area Area To Be Avoided Established Direction of Traffic Flow Recommended Direction of Traffic Flow

4. Part Four Tides and Tidal Currents Introduction Passage One Types of Tide Passage Two Tidal Datum

5. You mustn't rotate the wheel with your hand. Introduction periodic [piEri5Cdik] adj.定期的，定时的 attractive force 引力 rotate [rEu5teit] vi.转动，旋转 hinder [5hindE] vt.阻碍，妨碍 tidal current 潮流 intelligent [in5telidVEnt] adj. 理智的，明智的 prediction [pri5dikFEn] n.预报，预测 expeditious [ekspI5dIFEs] adj. 迅速的，敏捷的 accompany [E5kQmpEni] vt. 伴随 clarity [5klAriti] n.清楚，透明 flood [flQd] vi. 涨潮 ebb [eb] vi. 落潮 access [5Akses] n.通路，抵达 Prevent the progress of sth. eg. Reform should be deepened to break through the obstacles that hinder the development of productivity. When the sea water flow toward the land. When the sea water flow toward the sea.

6. 一、什么是潮汐？ 潮汐是海面周期性升降运动，周期大约为半天或一天。

7. HHW LHW HLW LLW 潮汐术语 1.高潮(满潮) HW 在一次潮周期中，海面升到最高。 2.平潮Slack 高潮发生后，海面有一段时间呈现停止升降的现象。 3.低潮(干潮) LW 在一次潮周期中，海面降到最低。 4.停潮Stand 低潮发生后，海面有一段时间呈现停止升降的现象。

8. 涨 潮 落 潮 潮差 潮汐术语 5.涨潮(Flood Tide) 潮汐过程中海面上升的过程。 6.落潮(Ebb Tide ) 潮汐过程中海面下降的过程。 7.潮差(Tidal Range) 相邻高、低潮潮高之差。

9. 潮汐术语 8.潮高基准面(TD) 计算潮高的起算面。 9.海图深度基准面(CD) 计算海图深度的起算面。 10.平均海面(MSL) 根据长期潮汐观测记录算得的某一时期的海面平均高度。

10. 二、潮汐的成因 1.引潮力 1)月球的引力 2)惯性离心力 2.月潮椭圆体

11. 三、潮汐的特征 HHW LHW HLW LLW 1.潮汐周日不等 在同一个太阴日中所发生的两次高潮或两次低潮的潮高以及相邻的高、低潮的时间间隔不相等，这种现象称为潮汐周日不等，周期一个太阴日,约24小时50分。

12. 潮汐术语 11.回归潮(Tropic Tide) 月球赤纬最大时的潮汐。 12.分点潮(Equinoctial Tide) 月球赤纬最小时的潮汐。 回归朝潮汐周日不等现象最显著，分点潮潮汐周日不等现象最小。

13. 三、潮汐的特征 2.潮汐半月不等 由于月球、太阳和地球在空间周期性地改变着它们的相对位置而发生了潮汐半月不等现象 。 朔、望大潮（Spring Tide），两弦小潮（Neap Tide），周期半个塑望月(约14.5日)。

14. 潮汐术语 13.潮龄(Tidal Age) 由朔望至实际大潮发生的时间间隔。 14.大潮升(Spring Rise) 从潮高基准面到平均大潮高潮面的高度。 15.小潮升(Neap Rise) 从潮高基准面到平均小潮高潮面的高度。

15. 三、潮汐的特征 3.潮汐视差不等 由于月球是沿椭圆轨道绕地球转动的，地球在椭圆轨道的一个焦点上。当月球位于近地点时其引潮力要比位于远地点时的大约40％，这种由于地球和月球距离变化而产生的潮汐不等，称为潮汐视差不等，其周期为1个恒星月，约27.32日。

16. 四、潮汐的分类 1.正规半日潮 在1个太阴日内发生2次高潮和低潮。2次高潮和两次低潮的高度都相差不大，而涨、落潮时也很接近。例：青岛 2.全日潮 它基本上还具有半日潮的特性，但在1个太阴日内相邻的高潮或低潮的潮位相差很大，涨潮时和落潮时也不等。例：北部湾 3.不正规日潮 在半个月中，日潮的天数不超过7天，其余天数为不正规半日潮。例：南海的暹罗湾。 4.不正规半日潮 在半个月中有连续1/2以上天数是日潮，而在其余日子则为半日潮。例：浙江镇海港和亚丁湾。 混合潮

17. 五、潮流的概念 海水周期性涨落同时产生的周期性水平流动，称为潮流(Tidal Current)

18. 流向 潮流的流向是指海水流去的方向，常用圆周法和罗经点法表示。

19. 流速 潮流的流速是指海水在单位时间内流经的水平距离，通常以节(或米/秒)为单位。 潮流在大洋中，一般很小，但在近岸的浅海，则非常显著，尤其在海峡、湾口、狭水道中常有强大的潮流，其原因在于每半个周期内，必须有大量的海水流经这些通道。例如，在温哥华岛和大陆之间的西摩尔海峡北端潮流最强时达10kn。我国著名的钱塘江潮，大潮时的潮流流速可达8-10kn。

20. 六、潮流的分类 1.回转流 回转流一般表现在一个潮流周期内流向随时间顺时针(或逆时针)方向变化360，流速也随时间变化。 回转流主要发生在开阔海域，旋转方向视潮流的前进方向和海区的地形特点等因素确定。

21. 六、潮流的分类 2.往复流 往复流是由于地形的影响而产生的涨、落潮流向相反或接近相反的潮流，大多发生在海峡、江河、港湾和沿岸一带。海水从外海向内海流动为涨潮流(Flood Tide Stream)；海水从内海向外海流动为落潮流(Ebb Tide Stream)。涨潮流与落潮流转换的时间为转流时间，转流时间流速为零。 涨潮流 落潮流

22. 涨潮流 ● 涨潮流 涨潮流 落潮流 ● ● 涨潮流 ● ● ● 落潮流 ● 往复流与高、低潮的关系 转流时间如果和高、低潮时一致，则高潮后就开始落潮流，低潮后就开始涨潮流。 转流时间如果是处在高、低潮时之间某个时刻，则高潮后的一段时间内仍是涨潮流，低潮后的一段时间内仍为落潮流。

23. Introduction Text What causes the tide? Tides are the periodic motion of the waters of the sea due to changes in the attractive forces of the moon and sun upon the rotating earth. Tides can either help or hinder a mariner. A high tide may provide enough depth to clear a bar, while a low tide may prevent entering or leaving a harbor. How can a tide affect a mariner?

24. Mariners can make good use of tides. Tidal current may help progress or hinder it, may set the ship toward dangers or away from them. By understanding tides, and by making intelligent use of predictions published in tide and tidal current tables and of descriptions in sailing directions, the navigator can plan an expeditious and safe passage. quick or swift

25. The rise and fall of tide is accompanied by horizontal movement of the water called tidal current. It is necessary to distinguish clearly between tide and tidal current, for the relation between them is complex and variable.

26. What is the difference between tides and tidal current? For the sake of clarity mariners have adopted the following definitions: Tide is the vertical rise and fall of the water, and tidal current is the horizontal flow. The tide rises and falls, the tidal current floods and ebbs. The navigator is concerned with the amount and timeof the tide, as it affects access to shallow ports. The navigator is concerned with the time, speed, and direction of the tidal current, as it will affect his ship’s position, speed, and course. From which aspect does tide and tidal currents affects navigators?

27. Passage One Types of Tide Tremor is a tiny, rapid oscillation superimposed on drifts. 震颤则是在漂移时发生的微小、快速振动。 Vocabulary oscillation [7Csi5leiFEn] n. 振荡，振动，摆动，波动 basin [5beisn] n. 凹地，海盆 diurnal [dai5E:nl] adj.每日的，白天的 semidiurnal [5semidai5E:nl] adj.半日的 semidiurnal tide 半日潮

28. diurnal tide 全日潮 Gulf of Mexico 墨西哥湾 Java Sea 爪哇海 Gulf of Tonkin 东京湾 mixed tide 混合潮 inequality [7ini(:)5kwCliti] n.潮差，不平等，不均衡 prevalent [5prevElEnt] adj. 流行的，普遍的 Los Angeles 洛杉矶 Seattle 西雅图 Honolulu 火奴鲁鲁 the state of being not equal The problem of racial inequality exists in the world until now.

30. A body of water has a natural period of oscillation, dependent upon its dimensions. None of the oceans is a single oscillating body; rather each one is made up of several separate oscillating basins. As such basins are acted upon by the tide-producing forces, some respond more readily to daily or diurnal forces, others to semidiurnal forces, and others almost equally to both. 这些海盆在受到产生潮汐力量的作用时，有些对全日的力量迅速做出反应，有些对半日的力量反应较快，另外一些对两种力量产生相同的反应。

31. What are the three different types of tides? Hence, tides are classified as one of three types, semidiurnal, diurnal, or mixed, according to the characteristics of the tidal pattern. In the semidiurnal tide, there are two high and two low waters each tidal day, with relatively small differences in the respective highs and lows. Tides on the Atlantic coast of the United States are of the semidiurnal type. What is the characteristic of semidiurnal tide?

32. What is the characteristic of diurnal tide? In the diurnal tide, only a single high and single low water occur each tidal day. Tides of the diurnal type occur along the northern shore of the Gulf of Mexico, in the Java Sea, the Gulf of Tonkin, and in a few other localities.

33. HHW LHW HLW LLW 混合潮中，全日震荡和半日振荡都是重要因素，这种潮汐的特点是相邻的两个高潮或两个低潮潮位相差很大，或两者皆有。 In the mixed tide, the diurnal and semidiurnal oscillations are both important factors and the tide is characterized by a large inequality in the high water heights, low water heights, or in both. There are usually two high and two low waters each day, but occasionally the tide may become diurnal. Such tides are prevalent along the Pacific coast of the United States and in many other parts of the world. What is the characteristic of mixed tides?

34. At Los Angeles, it is typical that the inequalities in the high and low waters are about the same. At Seattle the greater inequalities are typically in the low waters, while at Honolulu it is the high waters that have the greater inequalities.

35. Summary of this period. Homework: 1. Review what we have learned today. 2. Keep the new words and expressions in mind. 3. Finish of the exercises.

36. Tidal Datum Vocabulary tidal datum 潮高基准面 low water datum 低潮基准面 sounding datum 测深基准面 hydrographic survey 海道测量，水道测量 mean [mi:n, min] n. 平均数 mean low water 平均低潮面 mean low water springs 平均大潮低潮面 spring tide 大潮 mean lower low water 平均低低潮面 mean lower low water springs 平均大潮低低潮面 lowest normal low water 某地一般出现的最低水位

37. Your account of what happened approximate to the real facts. approximate [E5prCksimeit] vt. 接近，约等于 lowest low water 最低潮 disregarding [7disri5^B:d] adj. 不管，忽视，不考虑 conform [kEn5fC:m] vt. 与 …… 一致 retain [ri5tein] vt.保留，保持 indefinite [in5definit] adj. 不确定的 primarily [5praimErili] adv.首先，主要地 Baltic Sea 波罗的海 half-tide level 半潮位 inconsistency [9InkEn`sIstEnsI] n.不一致，不协调 terminology [7tE:mi5nClEdVi] n. 术语 In order to be accepted for production, the design must conform to these rigid guidelines. Plants and animals exist primarily to be used by humans.

38. The fund was specified to maintain the ancient buildings. specify [5spesifai] vt.规定，列举，详细说明 high water datum 高潮基准面 terrestrial [ti5restriEl] adj. 地球的，地面的 feature [5fi:tFE] n. 地形，地物，特征 territory [5teritEri] n. 版图，领海，领土 possession [pE5zeFEn] n. 占领地 mean high water 平均高潮 mean high water springs 平均大潮高潮 mean higher high water 平均高高潮 considerable [kEn5sidErEbl] adj.重要的，值得考虑的，明显的 Terrestrial latitude is measured in degrees north or south from the equator. For most people, it takes considerable effort to learn a long poem by heart.

39. Important abbreviations • M=mean • LW=low water • L=lower • S=springs • HW=high water • H=higher

40. Tidal datum 1 Low Water Datum 1.1 MLW: is the average height of all low waters at a given place 1.2 MLWS: is the average level of the low waters that occur at the times of spring tides 1.3 MLLW: is the average height of the lower low waters of each tidal day 1.4 MLLWS: is the average level of the lower of the two low waters on the days of spring tides 1.5 lowest normal low water: is a datum that approximates the average height of monthly lowest low waters

41. 2. High Water Datum 2.1 MHW: is the average height of all high waters over a 19 year period 2.2 MHWS: is the average level of high waters that occur at the time of spring tides. 2.3 MHHW: is the average height of the higher high waters of each tidal day

42. Text Low Water Datum A tidal datum is a level from which tides are measured. There are a number of such levels of reference that are important to the mariner. The most important level of reference to the mariner is the sounding datum shown on charts. Since the tide rises and falls continually while soundings are being taken during a hydrographic survey, the tide is recorded during the survey so that soundings taken at all stages of the tide can be reduced to a common sounding datum. 测深基准面

43. 图注水深显示的是所选择的低潮基准面（有时也是平均海平面）以下的水深，潮汐表中预报潮位是高于或低于这一基准面的高度或深度。 Soundings on charts show depths below a selected low water datum (occasionally mean sea level), and tide predictions in tide tables show heights above and below the same level. The depth of water available at any time is obtained by adding the height of the tide at the time in question to the charted depth.

44. By international agreement, the level used as chart datum should be low enough so that low waters do not fall very far below it. At most places, the level used is one determined from a mean of a number of low waters (usually over a 19 year period); therefore, some low waters can be expected to fall below it. The following are some of the datums in general use.

45. 平均低潮面 Mean low water (MLW) is the average height of all low waters at a given place. About half of the low waters fall below it, and half above. Mean low water springs (MLWS), usually shortened to low water springs, is the average level of the low waters that occur at the times of spring tides. Mean lower low water (MLLW) is the average height of the lower low waters of each tidal day. 平均大潮低潮面 平均低低潮面

46. Mean lower low water springs (MLLWS) is the average level of the lower of the two low waters on the days of spring tides. Lowest normal low water is a datum that approximates the average height of monthly lowest low waters, disregarding any tides disturbed by storms. Lowest low water is an extremely low datum. It conforms generally to the lowest tide observed, or even somewhat lower. Once a tidal datum is established, it is sometimes retained for an indefinite period, even though it might differ slightly from a better determination from later observations. 平均大潮低低潮面 某地一般出现的最低水位

47. In some areas where there is little or no tide, such as the Baltic Sea, mean sea level (MSL) is used as chart datum. This is the average height of the surface of the sea for all stages of the tide over a 19 year period. This may differ slightly from half-tide level, which is the level midway between mean high water and mean low water.

48. 大比例尺海图通常采用的是测深基准面，图上的潮汐注释描述了图中某个地点或某些地方的平均潮高。大比例尺海图通常采用的是测深基准面，图上的潮汐注释描述了图中某个地点或某些地方的平均潮高。 Inconsistencies of terminology are found among charts of different countries and between charts issued at different times. Large-scale charts usually specify the datum of soundings and may contain a tide note giving mean heights of the tide at one or more places on the chart. These heights are intended merely as a rough guide to the change in depth to be expected under the specified conditions. They should not be used for the prediction of heights on any particular day, which should be obtained from tide tables.

49. 海图上所标注的地面物体高度通常参照高潮基准面。海图上所标注的地面物体高度通常参照高潮基准面。 High Water Datums Heights of terrestrial features are usually referred on nautical charts to a high water datum. This gives the mariner a margin of error when passing under bridges, overhead cables, and other obstructions. The one used on charts of the United States, its territories and possessions, and widely used elsewhere, is mean high water (MHW), which is the average height of all high waters over a 19 year period. Any other high water datum in use on charts is likely to be higher than this. 平均高潮

50. 平均大潮高潮 Other high water datums are mean high water springs (MHWS), which is the average level of the high waters that occur at the time of spring tides; mean higher high water (MHHW), which is the average height of the higher high waters of each tidal day. A reference merely to “high water” leaves some doubt as to the specific level referred to, for the height of high water varies from day to day. Where the range is large, the variation during a two-week period may be considerable. 平均高高潮 仅仅说“高潮”在确定所指的确切潮高方面有一定的模糊，因为高潮的潮位每天都在变化。