Chapter Three Navigation Technology

1. Chapter Three Navigation Technology 5~6 hours

2. Review what we have learned last period Aids to Navigation System Beacon Lights Lighthouses Buoys A lighted buoy A wreck buoy Lateral system and cardinal system 航标 灯标 灯塔 浮筒 灯浮 沉船浮筒 侧标系统和界标系统

3. Passage Two Navigation Process Vocabulary voyage planning 航次计划 track [trAk] n. 航路，航迹 operational commitment 营运任务 construct [kEn5strQkt] vt. 设计，规划，构想 fundamentally [fQndE5mentElI] adv. 根本上地，基本上地 unauthorized [5Qn5C:WEraizd] adj.未经授权的，未经批准的 deviation [7di:vi5eiFEn] n.偏离航向，自差，偏差，背离 There is something fundamentally wrong with your idea. Finding and solving the deviation and problem in the test.

4. great circle 大圆 great circle chart 大圆海图 sailings [5seiliNz] n. 航海术，航行，起航 eliminate [i5limineit] vt. 除去，排除，消除 inherent [in5hiErEnt] adj.内在的，固有的 waypoint[`weipCInt] n. 航路点 leg[le^]n.一段航程 computer-generated 计算机生成的 applicable [5AplikEbl] adj.适用的 pilot chart 航路资料图，引水图 inventory [5invEntri] n. 详细目录，清单 inertial navigator 惯性导航仪 A mark or place at which a vessel is to report to establish its position. These principles are applicable to all minority nationality areas.

5. The Night Order book is the vehicle by which the captain informs the officer of the deck of the captain’s orders for operating the ship. Night Order book 夜航命令簿 vehicle [5vi:ikl] n.工具，手段，交通工具，车辆 pertaining to 与……有关 submarine[5sQbmEri:n, sQbmE5ri:n] n.水下状况，潜水艇 adj.水下的 evolution [7i:vE5lu:FEn, 7evE-] n. 发展，进展 circumstance [5sE:kEmstEns] n. 环境，条件 render [5rendE] vt.使得，提供，使成为 vi.给与补偿 n. 交纳 continuously [kEn5tInjJEslI] adv. 连续不断地 Standing Orders 常规命令簿 fathometer [fE5TCmitE] n. 回声测深仪 CPA closest point of approach 最接近点，最近会遇点 The captain sets the ship’s navigation policy in these orders, for example, required fix intervals, intervals for fathometer operations, minimum CPA’s, and other general navigation and collision avoidance requirements

6. Text Voyage planning determines the safest and most efficient track for the ship to follow to ensure that the vessel completes its operational commitments. Constructing a planned track for a voyage is fundamentally important for ship’s safety. Several ships’ groundings have occurred because of unauthorized deviations from an approved track.

7. Construct the track using a navigation computer, a great circle (gnomonic) chart, or the sailings. This passage will only discuss the navigation computer and the great circle chart. Use a navigation computer if one is available because the computer eliminates the plotting errors inherent in transferring the track from gnomonic to a Mercator projection. 如果有可能，就要使用航用计算机。计算机可以消除航迹从心射投影向墨卡托投影转换中所固有的标绘错误。

8. 计算机计算出两个端点之间标记大圆航迹的航路点。计算机计算出两个端点之间标记大圆航迹的航路点。 When using a navigation computer, the navigator simply inputs the two endpoints of his planned voyage. The computer computes waypoints marking the great circle track between the two endpoints. The computer determines each track leg’s distance and, given a speed of advance, calculates the times the vessel can expect to pass each waypoint. Construct the track on the Mercator chart by plotting the computer-generated waypoints and the tracks between them.

9. Prior to getting the ship underway, inspect all navigation equipment, charts, and publications. The navigator should develop a checklist of navigation equipment specific to his vessel and check that all required equipments are onboard. The navigator should have all applicable Sailing Directions, pilot charts, and navigation charts covering his planned route. He should also have all charts and Sailing Directions covering ports at which his vessel may call.

10. He should have all the equipments and publications required to support celestial navigation. Finally, he must have all technical documentation required to support the operation of his electronic navigation suite. Complete this chart, publication, and equipment inventory well before the underway date and obtain all missing items before sailing.

11. Determine gyro compass error at least daily as part of the at-sea routine. Check the gyro compass reading against the inertial navigator if the vessel has an inertial navigator. Report any error greater than 1° to the navigator and commanding officer. Check the gyro repeaters and the magnetic compass against the gyro compass hourly and after each course change. When comparing the magnetic and gyro compasses, navigator should determine changes in variation and deviation. Report any repeater error greater than 1° to the commanding officer.

12. The Night Order book, despite its name, can contain orders for the entire 24-hour period after which the Captain signs it. Such orders include assigned operating areas, maximum speeds allowed, and, regarding submarines, the maximum depth at which the ship can operate.Each department head should include in the Night Order book the evolutions he wants to accomplish during the night that would normally require the captain’s permission. 这些命令包括设定好的航行区域，最大许可船速，对于潜水艇而言，包括潜水艇的最大操纵水深。 每个部门的领导都要在夜航命令簿中写明他想在夜间航行中取得的进展，这些指令通常要得到船长的许可。

13. The captain can add further orders and directions as required. When the captain signs the Night Order book, it becomes an official order to the Officer of the Deck. The Officer of the Deck must not follow the Night Orders blindly. Circumstances under which the captain signed the Orders may have changed, rendering some evolutions ordered impractical to complete. The Officer of the Deck, when exercising his judgment on completing ordered evolutions, must always inform the captain of any deviation from the Night Orders as soon as such a deviation occurs. 甲板部的驾驶员在根据自己的判断完成命令簿中给出的指令时，如果出现相背于夜航命令簿的背离，应立即报告船长。

14. The Commanding Officer’s Night Orders are in effect only for the 24 hours after they are written; his Standing Orders are continuously in force. The captain sets the ship’s navigation policy in these orders. He sets required fix intervals, intervals for fathometer operations, minimum CPA’s, and other general navigation and collision avoidance requirements. The Officer of the Deck must follow the Commanding Officer’s Standing Orders at all times. Report any deviation from these orders immediately to the Commanding Officer.

15. Passage Three Rhumb lines and Great Circles a line crossing all meridians or longitude at the same angle, i.e. a straight line path derived from a defined initial bearing. Vocabulary loxodrome [5lCksEdrEum] n. 恒向线 derive from 源自，来源于 intersect [7intE5sekt] vt.与 …… 相交，相交 oblique [E5bli:k] adj.倾斜的 curvature [5kE:vEtFE] n.弯曲，曲度，曲率 inconvenience [7inkEn5vi:njEns] n. 不便，困难 appealing [E5pi:liN] n. 引起兴趣的，动人的 slope [slEup] n.倾斜，斜度，斜坡 loxodromic curve 恒向线，等角航线 The line AB intersects the line CD at E.

16. The stereographic projection must be supplemented by other constructions. spiral [5spaiErEl] vi.成螺旋状旋转 n.螺旋状物 stereographic projection 极射平面投影 equiangular spiral 等角螺旋 circumference n.圆周 analogue [5AnElC^] n. 类似物，模拟 oblate spheroid 扁球体 ellipsoid [i5lipsCid] n.椭圆体 squash [skwCF] vi.压扁，压制 geodesic [7dVi:Eu5desik] n.最短程线（连接平面或球面上两点之间的最短的线） approximation [E7prCksi5meiFEn] n. 近似值 aviation [7eivi5eiFEn] n. 航空

17. Text In navigation, a rhumb line (or loxodrome) is a line crossing all meridians or longitude at the same angle, i.e. a straight line path derived from a defined initial bearing. That is, upon taking an initial bearing, one proceeds along the line defined by it, and continues this line without changing one’s true (not magnetic) direction. Its use in navigation is directly linked to the style, or projection of certain navigational maps. A rhumb line will always be a straight line on a Mercator projection map. 也就是说一旦采用了初始方位，船舶将沿着既定的路线航行，一直沿着这条航线航行不需要改变真方向（不是罗方向）。

18. 平面上，这是短距离条件下两点之间最短的距离，这时地球的曲度不会造成什么影响，因此可以用来标绘船舶的航向。平面上，这是短距离条件下两点之间最短的距离，这时地球的曲度不会造成什么影响，因此可以用来标绘船舶的航向。 On a plane surface this would be the shortest distance between two points over short distances, where the curvature of the earth is not a major factor, and thus can be used for plotting a ship’s course. Over longer distances great circle routes provides the shortest routes. However the inconvenience of having to continuously change bearings while travelling a great circle route makes rhumb line navigation appealing in certain instances. On a Mercator projection map, a loxodrome is a straight line; beyond the right edge of the map it continues on the left with the same slope. 然而采用大圆航路时要不断地改变方位造成了很大的不便，这就使在很多情况下利用恒向线进行航行更理想。

19. 经度方向的子午线以及纬度方向的平行线都构成了恒向线的特殊情况，它们与恒向线的交角分别是0°和90°。经度方向的子午线以及纬度方向的平行线都构成了恒向线的特殊情况，它们与恒向线的交角分别是0°和90°。 Meridians of longitude and parallels of latitude provide special cases of the rhumb line, where their angles of intersection are respectively 0° and 90°. Rhumb lines which cut meridians at oblique angles are loxodromic curves which spiral towards the poles. On a stereographic projection map, a loxodrome is an equiangular spiral whose center is the North (or South) Pole. 在极射平面投影上，恒向线是等角螺旋，中心就是北极（或南极）。

20. A great circle of a sphere is a circle that runs along the surface of that sphere so as to cut it into two equal halves. The great circle therefore has both the same circumference and the same center as the sphere. It is the largest circle that can be drawn on a given sphere.

21. 球面几何 Great circles serve as the analogue of “straight lines” in spherical geometry. The great circle is the path with the smallest cruvature, and hence, an arc of a great circle is the shortest path between two points on the surface. The distance between any two points on a sphere is therefore known as the great-circle distance. The great-circle route is the shortest path between two points across the surface of a sphere. 大圆是曲度最小的路线，因此大圆弧线是球面上两点之间最短的距离。

22. Strictly speaking the Earth is not a perfect shpere (it’s an oblate spheroid or ellipsoid - i.e slightly squashed at the poles), which means that the shortest distance between two points (a geodesic) is not quite a great circle. Nevertheless, the sphere model can be considered a first approximation.

23. When long distance aviation or nautical routes are drawn on a flat map (for instance, the Mercator projection), they often look curved. This is because they lie on great circles. A route that would look like a straight line on the map would actually be longer. An exception is the gnomonic projection, in which all straight lines represent great circles. On the Earth, the meridians are all great circles, and the equator is a great circle. Other lines of latitude are not great circles, because they are smaller than the equator; their centers are not at the center of the Earth -- they are small circles instead.

24. 如果沿着大圆航行，人工操舵是非常困难的，因为船首向要不停地改变（除非在地球上最南部，最北部或沿着赤道航行）。如果沿着大圆航行，人工操舵是非常困难的，因为船首向要不停地改变（除非在地球上最南部，最北部或沿着赤道航行）。 Great circle routes are used by ships and aircraft where currents and winds are not a significant factor. If one were to travel along a great circle, it would be difficult to steer manually as the heading would constantly be changing (except in the case of due north, south, or along the equator). Thus, Great Circle routes are often broken into a series of shorter rhumb lines which allow the use of constant headings between waypoints along the Great Circle.

25. Summary of this period. Home work: • Review what we have learned today. • Recite the new words and expressions. • Finish some of the exercises. • 4. Preview next part of the text.