第一节 航线评估 航次不论长短均可分为两个主要阶段：准备阶段和执行阶段。准备阶段包括：评估和规划；执行阶段包括：组织和监控。 当进行航次准备工作之前，驾驭这一风险的人需要对可能出现的危险很好地认识。在航行计划的评估阶段需要检查这些风险。如果可选择的话，应评估这些风险，并达成一种折衷的解决方法。由于在评估阶段需要收集所有相关资料，要为航行计划奠定坚实基础，因此，评估被看作是航行计划最重要的一步，尽可能地不去考虑商业航行计划的迫切要求。用一定的时间来评估会在以后的工作中得到收益。 一、信息来源 船长对航次的总体决策依赖于对可用资料的评价，为此，应基于以下信息源进行评价： 图书总目录、航用海图、世界大洋航路、航路图或引航图、航路指南和引航书籍、灯标表、潮汐表、潮流图集、航海通告（航行区域、大西洋和太平洋）、船舶定线资料、无线电信号资料（包括VTS和引航服务）、气候资料、载重线图、里程表、电子导航系统信息、无线电和区域性警告、船东和其它未出版的资料、船舶吃水、个人经验和航海员手册。 1．图书总目录 是指由英国水道测量局每年出版的NP131和由美国国防部每年出版的CATP2V01U。 2．海图 多数商船都使用由英国水道测量局出版的英国海图，但也有一些区域需要航海者使用当地出版的海图。英国海军本部的方针是：绘制全部英国本土和多数英联邦及一些中东水域的能满足安全航海要求的足够比例尺的海图，其它水域则出版应满足航海者横跨大洋和沿岸航行可抵达港口的海图。在英版海图没有详尽地覆盖的多数沿岸航行时，航海者应更好地利用相关国家水道部门出版的海图。 美国和加拿大规定：所有进入该水域的船舶必须配备和使用相应的海图。言外之意就是船舶的配备可能没有达到这一规定，航海人员应确保海图得到改正。 大约有50个国家已经建立了水道测量部门并出版了本国水域的海图。其指定的代理商地址可从《海图代销店的代理目录》中获得。国际标准海图图式和缩写允许外国海图使用，但要注意所采用的海图深度基准面。 3．世界大洋航路 英国水道测量局出版，书号为NP136，包括大洋航线设计、海洋学和海流等资料。 4．航路设计图和引航图 航路设计图是英国水道测量局出版，书号为，与美国国防部出版的引航图类似。 这两种系列图均给出每月的远洋航线、海流、风、冰区界限和各种气象资料。 5．航路指南和引航书籍 英国水道测量局出版的航路指南共74卷，覆盖全世界范围。美国国防部也出版相引航书籍，系列号为SDPUB121-200。一些书籍可用来航行指导、给出与英版的世界大洋航路相同的重要资料，其它书籍给出与英国航路指南相似的资料。 6．灯标和雾号表 英国水道测量局出版，共11卷，书号为NP74-84，覆盖世界范围。由美国海岸警备队出版的7卷灯标表（COMDTM 6502 1-7）给出美国沿岸包括五大湖水域的灯标细节，国防部出版的LLPUB110-6覆盖了世界其它水域。 7．潮汐表 由英国水道测量局每年出版，共4卷，包括世界范围。利用英版的（SHM-159A）一套计算机程序即可容易获得潮时和潮高。美国国家海洋服务公司也出版世界范围的潮汐表。 8．潮流图集 由英国水道测量局出版，包括欧洲西北部，有20个分卷。由美国国家海洋服务公司出版的潮流表，覆盖了北美大西洋沿岸、北美的太平洋沿岸和亚洲。由美国国家海洋服务公司出版的潮流图给出了美国四大港口的情况。 9．航海通告 周版航海通告由英国和美国水道测量部门出版，以使船舶保持海图和其它出版物最新。 10．船舶定线 IMO出版，给出了所有航线、分道通航制、深水航路和IMO采纳的避航区等资料。航路资料也在海图和航路指南中给出。 11．无线电信号资料 英版无线电信号表包括6卷。 Vol 1（1，2）：沿岸无线电台。 Vol 2：无线电助航标志、卫星导航系统、法定时、无线电时号和电子定位系统。 Vol 3（1，2）：海上安全信息服务。 Vol 4：气象观测站。 Vol 5：全球海上遇险与安全系统。 Vol 6（1-5）：引航服务、船舶交通服务和港口业务。 美国国防部出版的RAPUB 117给出了类似的资料。 12．气候资料 气候资料可从上述提及的引航书籍、引航图和世界大洋航路中等资料中获得。英版航海员气象书籍给出了进一步的资料介绍。 13．载重线图 载重线规则是强制的，载重线区域在世界大洋航路或英版D6083海图中给出。 14．里程表 在英版NP350、美国国防部出版的NVPUB151和NOSSPBPORTDIST中都给出了远洋和沿岸的里程表。 15．电子导航系统手册 各类船舶需要该系统的必备资料应随设备一并供应。 16．无线电和区域性警告 有关表明助航仪器等变化的最新资料可从无线电（包括Navtext）和区域性警告中获得，总是被用来航线评估和计划。区域性警告通常由港口当局发布。世界范围内的航行服务资料和发射台站可参阅英版无线电信号表第一卷。 17．船舶吃水 应清楚航行不同阶段的船舶吃水和吃水差，目的是计算浅水区船舶龙骨下富余水深，同时，也应清楚船舶水线上的船舶最大高度――净空高度。 18．船东和其它资料 如可行，船东的补充资料应予考虑，如他船的报告、代理和港口指南资料、规定和进港指南等。 19．个人经验 驶往预定港口和区域的船员个人经历是至关重要的。 20．航海员手册 由英国水道测量局出版，包括了对航海员有利的重要资料。 船长在充分考虑了以上相关资料并征求了驾驶员的意见后，就可以对航线做出总体的评价。 二、航线评价 1．大洋航行评价 大洋航行首先考虑的是港口间的距离、油水和储备情况等。 大圆航线是最短航程航线，但其它因素应予考虑。 气象条件需要考虑，实践证明利用某种气象导航服务是有效的。尽管推荐航线距离较长，但充分地证明了航时较短、船舶遭受损失更小。 有效地利用洋流，可为船舶提供全程更好的航速，从而补偿长航线航行的不足。 天气系统也需要考虑，例如，夏天航行于中国海的船舶易于遭遇热带风暴，需要足够的海域用以归避；高纬度的航线要求考虑冰区条件。 尽管船舶采用推荐航线有其优越性，但要求遵守载重线规则。在某些特殊情况下（通常是政治原因），船舶需要避开特定水域。 2．沿岸航行评价 在评价航线阶段，沿岸航行主要考虑的是保持与海岸线和危险物的一定距离的航线。当船舶航经kenteIMO采纳的分道通航制和定线制的水域时，必须遵守相应的航线。在某些沿岸水域对于特殊船舶的最小距岸距离由有关政府规定。 一些航运公司也规定了距岸的最小距离。 在群岛海峡，必须确定哪些海峡和水道可以使用，是否有引航要求。在某一条件下绕离群岛海峡可能是较好的选择。 在对计划航次进行了评估并清楚了是短途沿岸航线还是远洋长航线后，船长要亲自决定计划并责成一名驾驶员设计航线。对于大多数船舶而言，这项工作由二副来完成；某些船舶，则指定一名驾驶员来完成；有些船舶则必须由船长自己设计航线。不管由谁来设计，都必须要求船长对航线负责。 计划包括所有的偶发事件和应急事件的策略。 航行计划通常是指由引航站到引航站，但IMO决议（VIII）附则A（V）有关STCW78公约II/1指出：尽管引航员在船且有责任和义务，但不能解除当班驾驶员对船舶安全的责任和义务。 显然，即使在某一航段由引航员引航，也需要将航行从泊位计划到泊位。 第二节 航行计划的制定 计划应从下列两段考虑： a)大洋和开阔水域； b)沿岸和河口水域。 当然，有时这两种情形会有融合和重叠的。 一、海图 1．海图 应将计划航线的所有海图收集在一起，并按正确的顺序放好。这些海图应包括那些航线不是绝对需要但需穿越的水域毗邻区域的海图，如沿岸航线部分用的大比例尺港图。虽实际上不是必须使用这样的海图，但这些海图包括了航线中所用到的资料。确保所有的海图和出版物都已根据最近接收到的航海通告和从各种渠道接收到的权威性警告进行了改正。在航行计划完成后的航行过程中，也应进行类似的改正，计划应进行不断的修改完善。 2．禁区 应检查沿岸和河口附近的海图，所有船舶不能进入的区域应用加亮显示或斜线标示，注意不要擦掉诸如航行标志或显著物标的资料，这些区域应视为禁区。在潮差不是特别大的水域，禁区应包括海图水深小于船舶吃水的水域。 在潮差有较大影响的拥挤水域，禁区应根据航行时间而变化。首先应将海图水深小于吃水与一个安全余量的区域和危险物视为禁区，即使是在明确了航经时间时，这样的禁区也应随之改变。 3．安全界限 在海图上标绘航线前，需考虑距禁航区的安全距离。当在海图上标绘船位时，该船位代表的总是定位时的船舶驾驶台的某一部分。对于大船，尽管某时间标绘的船位在禁航区之外，但也可能表明该船舶的某一部分已在禁航区之内，船舶面临着危险的后果。一个安全界限是指距禁航区周围有一个距离，在最不利的可能情况之下，操纵的船舶都不会进入。在决定这个“安全界限”的大小时，应考虑下列因素： （1）船舶的尺度； （2）所使用的导航系统精度； （3）潮流； （4）船舶的操纵特性。 安全界限应能够容易获得并得以监控，为此，应使用如显著物标的避险线或平行方位线等导航系统之一。 安全界限应显示船舶可能偏航距离的大小，但仍处于安全水域。按一般的规律，安全界限要确保船舶处在大于船舶吃水的20％的水深水域。应强调的是：这只是一般规律，航行环境可以使20％的富余量相应地增加，如： （1）测深数据久远或不可靠； （2）船舶处于纵摇或横摇状态； （3）船舶可能处于尾下坐的情形。 4．安全水域 它是指船舶可安全地偏航的水域，该安全水域界限就是由上述提及的安全界限的边界。 5．大洋及开阔水域的航线 首先根据评估航线阶段所作出的决策，在小比例尺海图上绘画大洋和开阔水域的航线。大圆航线或混合航线必须根据SATNAV计算或从大圆海图上获得；恒向线航线可直接绘画在墨卡托海图上，但所有航线都必须符合评估时确定的原则。 6．沿岸和河口水域的航线 沿岸和河口水域的航线也应受评估时所确定的原则约束。首先应绘画在包括大部分海岸线的小比例尺海图上，最好包括从出发港至目的港。这取决于港口附近和海图的情况，多数情况下，须使用多张海图。初始航线是航行计划的基础，可以获得距离和航行时间。一旦离港时间确定，就可确定航线上的各个转向点的ETA。 实际航迹向应显示在航线附近，这一航向不必是保持在该航线上的操舵航向，它仅显示两点间的航迹向。操舵航向应取决于航行时的各种因素。 绘画完航线后，应将这些航线转移到在大比例尺海图上。从一张海图上转移到另一张海图上时应格外小心。 为确保准确无误，应从海图上一易识别的物标如两张海图中的同一个灯标处绘画距离和方位位置线，并利用两张海图上的转移点的经纬度进一步确认其准确性。 7．转换海图 应当明确地在海图上某一位置处标出应转至下一张海图的海图号。 8．航线的重要性 按一般的规律，决不应过于接近危险物而去减少航行距离和航行时间。不过，需要接近危险物时，应遵守一般的最低要求，即船舶应保持在安全水域处距危险物有足够的距离，以尽量减少一旦机器故障或操纵失误而搁浅的可能性。 9．与危险物的距离 与危险物的距离应有多远，目前并没有一个明确的规定。但确定与危险物的距离，一般要考虑： （1）船舶吃水与可用水深的关系； （2）当时的天气条件，强烈的吹拢风或可能突降的雾或雨将要求增加与危险物的距离； （3）潮流或海流的方向和速度； （4）交通流量； （5）海图上的资料测量时间和可信赖程度； （6）可使用的安全水域。 下列原则将有助于确定与危险物的距离。 当海岸陡峭且水深增加很快时，航经危险物时的最小距离为－2 miles。 当海岸有一定的坡度且水深逐渐增加时，航线应保证有足够的龙骨下富余水深。 作为一种指导： 吃水3－6米的船舶，应在10米等深线外通过；吃水6－10米的船舶，应在20米等深线外通过；大于10米吃水的船舶需确保适当的龙骨下水深，并给予以一定的注意。 尽管保留了龙骨下的安全水深，将最近的航行危险物置于右舷的船舶应留出操纵空间以便向右改向来避让它船。 10．规则 也应遵守公司和国内规则中有关离岸距离的规定。 二、偏航 理想的情况是船舶沿计划航线航行，但在某一情况下，如为避开他船而必须转向时就需要偏离航线，即使这样，这种偏航应受到限制以保证船舶不进入危险区域或靠近安全界限处。 三、龙骨下富余水深 1．龙骨下富余水深 在某种情况下，船舶应航行在减少了的龙骨富余下水深区域，重要的是应计划好减少的龙骨下富余水深并清晰地标示。在龙骨下富余水深小于船舶最大吃水的10％或在初始评估阶段认可的比例下，驾驶员不仅需要清楚龙骨下富余水深，也应知道必要时要降低速度以减少船体下沉量。 2．高潮可航区间 在潮汐区域，潮汐达到某一指定的潮高时可以获得足够的龙骨下富余水深，除此之外，视为不可进入区域，这一安全阶段称为高潮可航区间，必须清楚地标示以便驾驶员知晓船舶是否处于安全水域。 3．潮流或海流 在开阔水域，由于潮流或海流的影响使得船舶偏离了航线，因此经常需要修正。 当船舶并未靠近危险物的情况下，这种修正在沿岸水域也是可行的。当计划航线接近沿岸时，最好事先对潮流或海流进行修正。 海流的流向、流速资料通常可从海图上获得，但更详尽的资料在“世界大洋航路”、“航路设计图”和“航路指南”中给出。海流随着地理位置和季节的变化而变化，并受气象条件变化的影响。 潮汐资料可从海图、潮汐表和潮汐图集中获得，更详尽的资料在航路指南中给出。潮流随着高潮的时间和月相（大小潮）的变化而变化，并受当地的气象条件的影响。 当已知通过某一区域的时间时，就可以计算出潮高和潮流，为达到计划航线而采取的航向的允许量应清楚。由于潮流随地点和时间而变化，因此应进行允许量的调整，驾驶员须仔细监控船位适时地调整航向以保证航行在计划航线上。 四、改变航向和转舵 1．改变航向 当在开阔海域和沿岸水域使用大区域范围的小比例尺海图时，改向通常和计划航线标示的转向点一致。在拥挤水域使用大比例尺海图航行时，开始转向的施舵点应在航路转向点之前。 2．转舵 引航员应基于本人的经验来决定其转舵位置。计划的转舵位置应根据船舶的操纵数据决定，并在海图上予以标绘。应利用相应的视觉和雷达物标决定转舵位置。最佳的大幅度转向方法包括平行线标绘或下一个航向的平行方位方法，但小角度转向时，采用近距离正横方位转向为好。 即使引航员在操纵船舶，转舵位置也应标注在海图上，以使驾驶员了解其迫切性和重要性。 五、平行标绘法 ispo1．平行标绘 平行标绘是用在能见度不良或能见度良好情况下的一种有效的监控船舶偏移的方法。在初始阶段将计划好的平行标绘线标绘在海图上是种良好的实践。正如任何雷达技术一样，当恶劣的天气使视觉航海方法不奏效时，建议在能见度良好时及早而广泛地使用平行标绘线，以便更全面地评价。 通过观测一个雷达显著助航物标的回波运动轨迹，反射标绘仪上事先画出航迹线，或通过使用ARPA平行线，是连续监控船舶的简单而有效的方法。这种方法在雷达采用北向上、相对运动方式时最有效。 根据一个雷达固定物标如灯塔或陡岬会很明确地标绘出本船的轨迹，即在荧光屏中心，画一条与船舶轨迹平行而方向相反的线，任何由潮流引起的航迹偏移都能通过平行线外的物标偏移情况发现。 平行标绘也可用来监控转舵位置等。在这种情况下，到施舵点时转向物标的距离和方位标绘在平行方位线上，以便随时掌握接近施舵点的距离。 2．ARPA标绘 许多现代的ARPA都能够把储存在检索系统中手工绘制的图形提取出来。在某些情况下，这些图形可通过电子导航系统来建立，但这些系统应是用作辅助的，并不是取代其它系统。 3．航行参考点 参考点应标示在海图上，是计划要改变航向的位置。常常是表示航向的改变，但也可能是下列情况： （1）海上航行的结束或开始； （2）变速； （3）引航员登船点； （4）锚泊位置等。 航行参考点也可成为确定船舶航行时间的有用参考点或是否应保持的程序，尤其是在电子导航系统中。当使用存储了参考点资料的电子助航仪器时，设计的参考点应注意在航行计划的全过程中保证其统一性。 六、中断和应急策略 无论航线计划得多么好和执行得多么严格，但由于环境的变化，原来计划的航线就不得不放弃。 1．中断 当接近拥挤水域时，船舶不得不继续航行。当船舶进入狭窄水道没有了回旋空间或由于落潮和不足的龙骨下水深而无法返回时的位置称为折返临界点。 无论何种原因，计划必须考虑到无法折回或造成船舶受到束缚的事实。这一点需要标绘在海图上，以表明中断航行以使船舶不受束缚。中断点位置随当时的环境如可用水域、船速、旋回圈等变化而变化，必须清晰地标绘出作为安全水域的连续计划航线。 停止航行及决定中断的理由不仅随环境变化而变化，而且应包括： （1）偏离接近线； （2）主机失灵或故障； （3）机器失灵或故障； （4）无可用拖轮或泊位； （5）沿岸或港口危险情况； （6）任何表明航行不安全的情形。 2．应急策略 船舶航经中断点和折返临界点后，驾驶台团队仍需清楚事件并没有像计划的那样而嘎然停止，船舶必须采取应急行动。在计划阶段就应做出应急计划并清晰地标示在海图上，以使驾驶员从事其它的工作而不必花时间去谋划安全行动。 应急策略应包括： （1）可选择的航线； （2）安全锚地； （3）等待区域； tba（4）应急泊位。 应重视应急行动将使船舶进入吃水受限致使船速必须降低的区域，或由于潮汐的限制，船舶仅可进入高潮可航区间水域。这些限制必须清晰地标绘出来。 绘画了禁区、安全界限和计划航线后，就应集中精力确保船舶沿计划航线航行，当成任何事儿不会发生或不应更改似的。 七、定位 目前，各种定位方法均可使用，但必须假设任何一种方法均适合于各种环境。 1．主要和次要的定位方法 为使定位程序简洁、清楚易于理解，航行计划将包括能够用来定位的资料，一种应认为是主要的定位手段，另一种认为是备用的或次要的定位手段。例如，船舶在远离陆地的水域航行时，GPS是主要的定位系统，Loran C是次要的或辅助的定位系统。船舶接近沿岸航行时，GPS仍是主要的定位方法，Loran C变得不那么重要了，雷达定位用于校核GPS定位的准确性。 尽管Loran C一直在使用，最终将成为多余的，更加依赖于称之为仅次于GPS方法的雷达定位手段。在封闭水域，GPS船位变得不精确了，这时，定位应依靠雷达和视觉方法。依赖于一种不变的系统是不可能的，这要取决于设备的可靠性及各种情况下的环境因素。重要的是有关人员知晓某种系统是处于可操作状态，并尽可能跟踪监测。 2．雷达显著物标和视觉助航物标 为减少在沿岸水域航行时的工作压力，驾驶员应确定和计划好主要、次要的定位方法。为进一步减少工作压力，值班驾驶员在设计阶段就应研究海图，确定在各个阶段将使用的雷达显著物标和视觉助航物标。 3．初见灯标 驾驶员不应在初见陆地时，再去确定哪个是初显灯标，而应事先就标示在海图上，以便驾驶员能集中精力寻找关心的灯标，而不是在海图上寻找哪个灯标应该显示。 这一方法同样适用于航经一海岸线或拥挤水域。海图上显示的灯标看上去相似，因此需要研究其各自的特征，这一工作需要在航线计划阶段完成，而不是在航经这些灯标的时候，因为相关驾驶员较忙无暇到海图桌旁。 4．雷达物标 在航线计划阶段花点时间同样能很快确定利用哪个物标作为雷达物标，显然，陡峭的小岛比适淹礁更可靠。 海图上显著的雷达信标和其它显著物标可用于定位。显著的视觉助航物标可用作评价对象，但应区分浮动的和固定的、强光的和弱光的灯标。 5．浮标 无论何时浮标或浮动助航标志用于定位，都必须先检查其位置，并确认在海图上确有其位。若必须使用浮标用于定位，其浮标的位置必须在航线设计阶段通过相对于已知固定物标的距离和方位来确定。 6．定位频率 不管使用了何种定位方法，都还需要确定定位的时间间隔。很显然，这要依赖于当时的环境，如船舶距危险物近，则需比开阔水域的定位时间间隔短。 作为一个建议，船舶的定位应处于不致于使其进入两个船位点间的危险物的时间段。如不能以这样的时间间隔在海图上定位（要求以不少于3分钟的时间间隔定位），则应考虑改变主要的定位手段，如平行方位标绘方法。 7．定位规则 建立了定位频率后，最好要确保实际上以这一频率进行定位，而不是在驾驶员认为合适的时候。如为避让船舶或接近转向点时的航向改变，在这种例外情况，船舶必须尽可能地在转向前、回复原航向及完成时即刻定位。 8．附加资料 尽管对船舶安全不是重要的，但还需将许多附加资料显示在计划中，目的是强调驾驶员的职责，以使驾驶员做出相应的准备并顺利地完成整个航行。这种资料包括： （1）报告点 向相关政府报告，会促进船舶的航行安全。这种报告也可以是强制的。 （2）锚泊监测 标示出需要备锚的位置，免得使有关人员始终等候在船首。 （3）引航员登船处 及时准备引航梯并提醒有关人员按要求做好相应工作。 （4）雇用拖轮 提醒驾驶员及时指派船员系妥拖轮。 （5）交通区域 交通拥挤或偶尔出现交通拥挤，如可能遇到渡轮、渔船。 八、情景意识 安全航行不仅要求驾驶员以一定的时间间隔在海图上定位，还需要不断地了解船舶相对于计划航线的位置和偏离航线是增加还是减少的趋势。尽管有规律的定位会提供这一信息，也有其它的不很明显的获取信息的方法，除了观测自然特征外，许多相关方法可以先计划好并标注在海图上。 1．叠标 海图上可使观测者看到的成一线的两物标－叠标，尽管叠标是单一的位置线，可用于给驾驶员提供一个快速确定船位的方法，其优点是不必使用仪器就可以视觉看到。最大精度是：观测者与前标的距离应不大于三倍的两叠标间距，即使叠标间距比此观测者与前标的距离大。 叠标有时印制在近岸水域的海图上，最好在航线计划阶段就找出天然而清晰易识别的叠标，并标绘在海图上。 叠标也可用作预先采取的行动如转舵，或用作提醒某一事件即将发生的物标。 2．罗经差 叠标可用作通过比较图注和观测方位来确定电罗经和磁罗经误差。 3．叠标导航线 叠标导航线经常标示在海图上。在这种情况，海图上的叠标线是确保船舶安全通过危险物的一条计划航线。通过观测导标成一线，航海人员就可确认船舶在计划航线上。 4．避险物标 避险物标可用于保证船舶处在一个安全区域或没有接近危险物。 5．船首物标 船舶常常要求没有可用叠标的情况下在狭窄水域沿航线航行，则需选择一个合适的船首物标，这一物标是指在海图上很易识别的物标，位于计划航线的延伸线上。只要船首物标的方位经过误差修正且可通过中心线的罗经复示器观测，保持方位值恒定，则船舶就在航线上。需记住的是船舶不必直对着物标，仅保证航行在计划航线上即可，多数情况船舶需要抵消风和潮流的影响。 6．方位避险线 如果无避险物标可利用，海图上的可识别单个物标可同样地使用。 观测方位避险线和避险物标不能认为是确定了船位，它仅能协助驾驶员保证船舶不进入危险区域而已。同样地，初显（隐）距离方法不能认为是精确定位方法，仅能助于驾驶员清楚是否在接近危险中。 | 1 Passage Appraisal Voyages of whatever length, can be broken down into two major stages-preparation, which included in preparation is appraisal and planning and execution of the voyage includes organization and monitoring. Before any voyage can be embarked upon or, indeed, any project undertaken, tho controlling the venture need to have a good idea of the risks involved. The appraisal stage of passage planning examines the risks. If alternatives are available, the risks are evaluated and a compromi solution is reached whereby the level of risk is balanced against commercial expediency. The appraisal could be considered to be the most important part of passage planning as it is at this stage that all pertinent information is gathered and the firm foundation for the plan is built. The urge to commence planning as soon as possible should be resisted. Time allocated to appraisal will pay dividends later. 1.1 Information Sources The Master’s decision on the overall conduct of the passage will be bad upon an appraisal of the available information. Such appraisal will be made by considering the information from sources including: Chart Catalogue, Navigational charts, Ocean Passages for the World, Routeing charts or pilot charts, Sailing Directions and Pilot Books, Light Lists, Tide Tables, Tidal stream atlas, Notices to Mariners (Navareas, Hydrolants, Hydropacs), Routeing information, Radio signal information (including VTS and pilot rvice), Climatic information, Load-line chart, Distance tables, Electronic navigational systems information, Radio and local warnings, Owner’s and other unpublished sources, Draught of vesl, Personal experience and the Mariner’s Handbook. 1.1.1 Chart Catalogue Published annually by the Hydrographer to the Navy (British) as NP 131 and by the Defence Mapping Agency (US) as CATP2V01U. 1.1.2 Charts Many merchant ships carry British charts published by the Hydrographer of the Navy. However, there are areas of the world where the mariner may well be advid to consider using locally published charts as well. British Admiralty policy is to chart all British home and most Commonwealth and some Middle Eastern waters on a scale sufficient far safe navigation. Elwhere the policy is to publish such charts as will enable the mariner to cross the oceans and proceed along the coasts to reach the approaches to ports. Along many coasts not covered in detail by British charts the mariner may find it better to u the charts of the hydrographic office of the relevant country. Both US and Canadian regulations require that vesls in their waters must carry and u the appropriate charts. This means that the vesl’s chart outfit may not meet the regulations. Navigators need to ensure that they have the correct charts. Approximately 50 countries are listed as having established hydrographic offices publishing charts of their national waters. Address of the agents appointed by such offices may be obtained from The Catalogue of Agents for the Sale of Charts. International standard chart symbols and abbreviations allow foreign charts to be ud with little difficulty but care must be taken to establish the chart datums ud. 1 Ocean Passage for the World Published by the Hydrographer of the Navy (British) as NP136; contains information on planning ocean passages, oceanography and currents. 1.1.4 Routeing Charts & Pilot Charts Routeing charts are published by the Hydrographer of the Navy (British) as Charts Nos.5124-8. The are similar to the Pilot Charts published by the Defence Mapping Agency (USA). Both ries give monthly information on ocean routeing, currents, winds and ice limits and various meteorological information. 1.1.5 Sailing Directions and Pilot Books British pilot books are published in 74 volumes by the Hydrographer of the Navy and give worldwide coverage. Sailing directions are published by the Defence Mapping Agency (USA) in the ries SDPUB 121-200. Some of the books are referred to as Planning Guides, giving information esntially the same as the British Ocean Passages for the World, others as Enroute, giving similar information to the British pilot books. 1.1.6 Lists of Lights and Fog Signals Published by the Hydrographer of the Navy (British) in 11 volumes (NP74-84) giving world wide coverage. Seven volumes of Light Lists are published by the US Coast Guard, (COMDTM 165021-7) giving details of all US coastal lights, including the Great Lakes. DMA publications LLPUB 110-6 cover the rest of the world. 1.1.7 Tide Tables Published by the Hydrographer of the Navy (British), annually, in four volumes, covering the world. Tidal times and heights may be readily obtained by using a computer program published by the British Admiralty (SHM- 159A). Worldwide tide tables are also published by the US National Ocean Service (NOSPBTT…repair是什么意思). 1.1.8 Tidal Stream Atlas Published by the Hydrographer of the Navy (British), the atlas cover certain areas of North West Europe and there are 20 parate volumes. 武汉私教培训Tidal current tables are published by the US National Ocean Service, covering the Atlantic coast of North America and the Pacific coast of North America and Asia. Tidal current charts are published by the US National Ocean Service for four major US ports. 1.1.9 Notices to Mariners Notices to Mariners are published in weekly editions by both the British and US hydrographic authorities, enabling ships to keep their charts and other publications up to date. 1.1.10 Ship’s Routeing Published by IMO, this publication gives information on all routeing, traffic paration schemes, deep water routes and areas to be avoided which have been adopted by IMO. Routeing information is also shown on charts and is included in the sailing directions. 1.1.11 Radio Signal Information The (British) Admiralty List of Radio Signals consists of six volumes of text covering the following: Vol 1 (1 & 2) coast radio stations. Vol 2 radio aids to navigation, satellite navigation systems, legal time, radio time signals and electronic position-fixing systems. Vol 3 (1 & 2) maritime safety information rvices. Vol 4 meteorological obrvation stations. Vol 5 global maritime distress and safety system (GMDSS). Vol 6 (1-5) pilot rvices, vesl traffic rvices and port operations. Similar information is available in US DMA publication RAPUB 117. 1.1.12 Climatic Information Climatic information is available from a variety of sources including the pilot books, pilot charts and Ocean Passages for the World already mentioned. The British Admiralty book Meteorology for Mariners gives further general information. 1.1.13 Load Line Chart Load Line Rules are mandatory and the load line zones are shown in Ocean Passages for the World or BA Chart D6083. 1.1.14 Distance Tables Both Ocean and Coastal Distance Tables are available from a variety of sources including British Admiralty (NP350) and US DMA publications NVPUB 151 and NOSSPBPORTSDIST. 1.1.15 Electronic Navigation Systems Handbooks Information required will depend upon the systems in u on the particular ship and should have been supplied with the equipment. 1.1.16 Radio and Local Warnings The latest information available on changes to navigation aids, etc., will be obtained from radio (including Navtext) and local warnings and must always be made available to tho responsible for appraisal and planning. Local information is often available from the harbour authority. For information on the worldwide navigational rvices and the transmitting stations e Admiralty List Of Radio Signals Vol 2. 1.1.17 Draught of Ship The anticipated draught and trim of the ship at different stages of the passage will need to be known in order to calculate the under-keel clearance when in shallow water. The extreme height of the ship above the waterline, known as the air draught, may also be required. 1.1.18 Owner’s and Other Sources Supplementary information from the vesl’s owners should be consulted, when available, as should reports from other vesls, information from agents and port authority handbooks, regulations and guides to port entry. 1.1.19 Personal Experience The personal experiences of crew members who have been to the anticipated ports and areas may prove of value. 1.1.20 The Mariner’s Handbook Published by the Hydrographer of the Navy (British), this book contains information of general interest to the mariner. Having collected together all the relevant information the Master, in consultation with his officers, will be able to make an overall appraisal of the passage. 1.2 Passage Appraisal 1.2.1 ocean passage appraisal The passage may be a transocean route in which ca the first consideration will need to be the distance between ports, the availability of bunkers and stores, etc. A great circle is the shortest distance but other considerations will need to be taken into account. Meteorological conditions will need to be considered and it may well prove advantageous to u one of the weather routeing rvices. Although the recommended route may be longer in distance it may well prove shorter in time and the ship suffer less damage. Ocean currents may be ud to advantage, favourable ones giving the ship a better overall speed thus offtting the disadvantage of taking a longer route. Weather systems also need to , a ship in the China Sea in summer needs plenty of a room if it is liable to be involved in a tropical revolving storm and a passage in high latitudes may require ice conditions to be considered. Irrespective of the advantages of using a preferred track, the Load Line Rules must always be obeyed. In certain circumstances, often political, a ship may need to keep clear of specified areas. 1.2.2 coastal passage appraisal The main consideration at the appraisal stage will be to determine the distance tracks should be laid off coastlines and dangers. When the ship is passing through areas where IMO-adopted traffic paration and routeing schemes are in operation, such routeing will have to be followed. In some coastal areas minimum distances off for specified vesls is determined by the relevant State. Some shipping companies may also specify minimum distance off. In archipelagos, it will be necessary to determine which straits and passages are to be ud and whether or not pilotage is required. Under certain circumstances it may be preferable to divert around an archipelago. Having made his appraisal of the intended voyage, whether it is a short coastal passage or a major transocean passage, the master will determine his strategy and then delegate one of his officers to plan the voyage. On most ships this will be the Second Mate, on some a designated navigating officer, on others the Master may have to do his own planning. Irrespective of who actually does the planning, it has to be to the requirements of the Master, who carries the final responsibility for the plan. The plan needs to include all eventualities and contingencies. Passage plans are often made from pilot station to pilot station but IMO Resolution A.285(VIII), Annex A (v), subquently incorporated in the STCW Convention 1978, Regulation II/1 states: Despite the duties and obligations of a pilot, his prence on board does not relieve the officer in charge of the watch from his duties and obligations for the safety of the ship. This makes it quite clear that it is necessary to plan from berth to berth even though it is anticipated that there will be a pilot conducting the vesl at certain stages of the voyage. 2 Making the Passage Plan Planning may be considered in two stages: a) ocean and open water; b) coastal and estuarial; though, at times, the two stages will merge and overlap. 2.1 Charts 2.1.1 Charts Collect together all the charts for the intended voyage, putting them into the correct order. Charts not absolutely necessary for the voyage but which are adjacent to the area to be traverd should be included, as should very large , port plans on the coastal part of the voyage. Although it may not be necessary actually to u such charts, they may include information which could prove of u during the voyage. Ensure that all charts and publications have been corrected to the latest Notice to Mariners available and that any authentic Navwarnings, etc., received from any source are also included. Similar corrections may also have to be made during the voyage after the plan has been completed and the plan may have to be subquently modified. 2.1.2 No-go Areas Coastal and estuarial charts should be examined and all areas where the ship can not go carefully shown by highlighting or cross-hatching, taking care not to , a navigation mark or a conspicuous object. Such areas are to be considered as no-go areas. In waters where the tidal range may not be very large, no-go areas will include all charted depths of less than the ship’s draught. In confined waters, where the tidal height may have a large influence, such no-go areas will vary according to the time of passage. Initially all areas and dangers showing charted depths of less than the draught plus a safety margin should be considered no-go, though such no-go areas may subquently be amended when the actual time of passage is known. 2.1.3 Margins of Safety Before tracks are marked on the chart the clearing distance from the no-go areas needs to be considered. When a fix is plotted on a chart it invariably reprents the position of a certain part of the ship’s bridge at the time of the fix. With large ships, although the plotted fix at a certain time may be outside a no-go area, it is possible that another part of the ship may already be in it-with disastrous results. A safety margin is required around the no-go areas at a distance that, in the worst probable circumstances, the part of the ship being navigated (the bridge) will not pass. Among the factors which need to be taken into account when deciding or the size of this ‘Margin of Safety’ are: (1)The dimensions of the ship; (2)The accuracy of the navigational systems to be ud; (3)Tidal streams; (4)The manoeuvring characteristics of the ship. The margins of safety should be chon so that they can be readily monitored. To achieve this they need to be related to one of the navigation systems in u (e.g., clearing bearings related to a headmark or parallel indexes). Margins of safety will show how far the ship can deviate from track, yet still remain in safe water. As a general rule the margin of safety will ensure that the ship remains in waters of a depth greater than draught +20%. It is stresd that this is only a general rule, circumstances may dictate that the 20% clearance will need to be considerably incread –e.g. (1)Where the survey is old or unreliable; (2)In situations where the ship is pitching or rolling; (3)When there is a possibility that the ship may be experiencing squat. 2.1.4 Safe Water Areas where the ship may safety deviate are considered to be safe water and the limits of this safe water are bounded by margins of safety. 2 Ocean and Open Water Tracks Ocean and open-water tracks should first be drawn on the small-scale charts, according to the decisions made at the appraisal stage regarding the route to be taken. Great circle and composite great circle tracks will have to be calculated or obtained from the Satnav computer or from great circle charts; rhumb lines may be drawn straight on to the Mercator chart, but all tracks will have to conform to the limits determined at the appraisal. 2.1.6 Coastal and estuarial tracks Coastal and estuarial tracks will also be constrained by the decisions made at the appraisal stage and should be first drawn on the small-scale charts covering large portions of the coastline, preferably from the departure port to the arrival port. This will depend upon the proximity of the ports and the charts of the area and, in most cas, more than one chart will have to be ud. The first tracks will form the basis of the plan and from them may be obtained distances and steaming times. When the departure time is known, the ETA (Estimated Time of Arrival) at the various waypoints en route can be established. The True direction of the track should be shown in clo proximity to the track. This will not necessarily be the cour steered to make this track; it only indicates the direction to make good. The cour to steer will depend upon various factors at the time of making the passage. When completed, the tracks should be transferred to and drawn on the large-scale charts of the area to be traverd. Transfer of a track from one chart to another must be done with great care. To ensure that no mistakes are made, it is good practice doubly to check this operation by using a range and bearing of the transfer position from a readily , a light common to both charts-and confirming this position on both charts by the latitude and longitude of the point. 2.1.7 Charts Change It should be quite clearly shown on a chart the position where it is required to transfer to the next chart, giving the next chart’s number. 2.1.8 Track Considerations As a general rule there is nothing to be gained by cloly approaching a danger other than to reduce passage distance and, conquently, steaming time. Even so, when it does become necessary to approach a danger there are general minimum rules that should be followed. The ship always has to remain in safe water and remain sufficiently far off a danger to minimize the possibility of grounding in the event of a machinery breakdown or navigational error. 2.1.9 Distance off It is not possible to lay down hard and fast rules regarding the distance off a danger that a ship should maintain; it will depend on: (1)The draught of the ship relative to the depth of water; (2)The weather conditions prevailing; a strong onshore wind or the likely ont of fog or rain will require an increa in distance off; (3)The direction and rate of the tidal stream or current; (4)The volume of traffic; (5)The age and reliability of the survey from which the information shown on the chart has been derived; (6)The availability of safe water. The following guidelines will help in determining just how far to pass off dangers. Where the coast is steep to and offshore soundings increa quickly, the minimum passing distance should be 1.5-2 miles. Where the coast shelves and offshore soundings increa gradually, the track should ensure that adequate under-keel clearances (UKC) are maintained. mature womenAs a guideline: Vesl’s draught 3-6 metres, pass outside 10-metre contour; Vesl’s draught 6-10 metres, pass outside 20-metre contour; Vesls with a draught of more than 10 metres must ensure that there is sufficient under-keel clearance, exercising due caution. Irrespective of the safe UKC, a ship in a situation where the nearest navigational danger is to starboard must allow manoeuvring space to allow alteration of cour to starboard for traffic avoidance. 2.1.10 Regulations Both company and national regulations regarding offshore distances must also be obrved. candyman2.2 Deviation from Track Ideally the ship will follow the planned track but under certain circumstances it may be necessary to deviate from , having to alter for another ship. Even so, such deviation from track should be limited so that the ship does not enter areas where it may be at risk or cloly approaching the margins of safety. 2.3 Under-keel Clearance 2.3.1 Under-keel Clearance In certain circumstances a ship may be required to navigate in areas with a reduced under-keel clearance. It is important that the reduced UKC has been planned for and clearly shown. In cas where the UKC is less than 10% of the deepest draught, or other such percentage as was agreed at the appraisal stage, then it is not only necessary that the OOW is aware of such UKC but also that he is aware that speed needs to be reduced in order to reduce squat with its conquent reduction in draught. 2.3.2 Tidal Window In tidal areas, adequate UKC may only be attainable during the period that the tide has achieved a given height. Outside that period the area must be considered no-go. Such safe periods, called the tidal window, must be clearly shown so that the OOW is in no doubt as to whether or not it is safe for the ship to proceed. 2.3.3 Stream/Current Allowance In open a situations track correction is often made after the ship has been t off track by the tidal stream and/or current. Such correction may be adequate in offshore situations, where the ship is not clo to danger, but as the planned track approaches the coast it is better to make tidal and current correction prior to its taking effect. Current information, t and rate is often available on the chart though more detailed information is given in Ocean Passages for the World, routeing charts and pilot books. Currents vary according to their location and the ason and may be influenced by changes in meteorological conditions. Tidal information is available from charts, tide tables and tidal atlas, further local information being available in pilot books. Tidal streams vary according to the time of high water and the pha of the moon (neaps and springs) and can be influenced by local meteorological conditions. When the actual time of transit of a given area is known, the tidal heights and streams can be calculated and due allowances made for the streams in order to find the cour to steer to achieve a planned track. As well as adjusting the allowances as the tidal stream varies according to location and time, the OOW must still carefully monitor the ship’s position and adjust the cour steered to maintain the planned track. 2.4 Cour Alterations & Wheel-over 2.4.1 Cour Alterations In the open a and offshore coastal waters when navigating on small-scale large-area charts, cour alterations will usually coincide with the planned track interctions. This will not be the ca in confined waters when navigating on large-scale charts and where the margins of safety may require the ship to commence altering cour at the wheel-over position some distance before the track interction in order to achieve the new planned track. pos2.4.2 Wheel-over Often such wheel-over positions will be determined by the pilot using his own judgment, bad upon experience. Planned wheel-over positions should be determined from the ship’s manoeuvring data and marked on the chart. Suitable visual and radar cues should then be chon to determine when the ship is at the wheel-over position. The best cues for large alterations of cour consist of parallel indexes or bearings parallel to the new track, whereas for small alterations a near beam bearing is often better. Even when the pilot has the con, the wheel-over position should be shown on the chart so that the OOW will be aware of its imminence and importance. 2.5 Parallel Index 2.5.1 parallel index The parallel index (PI) is a uful method of monitoring cross-track tendency in both poor and good visibility. It is a good practice to mark the planned PI on the chart inconspicuously at the planning stage. Like any radar technique, it is advisable to practice using PIs extensively in good visibility before placing total reliance on them when thick weather makes visual navigation methods impossible. This simple and effective method of continuously monitoring a ship’s progress is carried out by obrving the movement of the echo of a radar-conspicuous navigation mark with respect to track lines previously prepared on the reflection plotter or by using ARPA index lines. It is most effective when the radar is in the north-up, relative motion mode. A fixed radar target, such as a lighthou or a headland, will apparently track past the own ship, depicted as being at the center of the screen, as a line parallel and opposite to the ship’s ground track. Any cross track tendency, such as may be caud by a tidal stream, will become apparent by the target moving off the parallel line. The parallel index may also be ud to monitor , wheel-over position. In this ca the range and bearing of the target at the wheel-over point is marked on the PI. This also allows for a distance countdown to be made. 2.5.2 ARPA mapping Many modern ARPAs have the facility to generate synthetic maps which can be stored in a retrieval system. In some instances, such maps may be stabilized through an electronic navigational system, but such facilities should be ud in addition to and not to the exclusion of other systems. 2.5.3 Waypoints A waypoint is a position, shown on the chart, where a planned change of status will occur. It will often be a change of cour but may also be an event such as: (1)End or beginning of a passage; (2)Change of speed; (3)Pilot embarkation point; (4)Anchor stations etc. Waypoints may also be ud as uful reference points to determine the ship’s passage time and whether or not a schedule is being maintained, particularly when they have been included in the appropriate electronic navigational system. Where an electronic navaid which stores waypoint information is in u, care should be taken to ensure that waypoint designators remain uniform throughout the plan. 2.6 Aborts and Contingencies No matter how well planned and conducted a passage may be, there may come the time when, due to a change in circumstances, the planned passage will have to be abandoned. 2.6.1 Aborts When approaching constrained waters the ship may be in a position beyond which it will not be possible to do other than proceed. Termed the point of no return, it will be the position where the ship enters water so narrow that there is no room to return or where it is not possible to retrace the track due to a falling tide and insufficient UKC. Whatever the reason, the plan must take into account the point of no return and the fact that thereafter the ship is committed. A position needs to be drawn on the chart showing the last point at which the passage can be aborted and the ship not commit herlf. The position of the abort point will vary with the , water availability, speed, turning circle, etc.-but it must be clearly shown, as must a subquent planned track to safe water. The reasons for not proceeding and deciding to abort will vary according to the circumstances but may include: (1)Deviation from approach line. (2)Machinery failure or malfunction. 我需要你英文(3)Instrument failure or malfunction. (4)Non availability of tugs or berth. (5)Dangerous situations ashore or in the harbour. (6)Any situation where it is deemed unsafe to proceed. 2.6.2 Contingencies Having pasd the abort position and point of no return, the bridge team still needs to be aware that events may not go as planned and that the ship may have to take emergency action. Contingency plans will have been made at the planning stage and clearly shown on the chart, so that the OOW does not have to spend time looking for and planning safe action when his duties require him to be elwhere. Contingency planning will include: (1)Alternative routes. (2)Safe anchorages. (3)Waiting areas. (4)Emergency berths. It will be appreciated that emergency action may take the ship into areas where it is constrained by draught, in which ca speed will have to be reduced; or tidally constrained, whereby it can only enter such areas within the tidal window. Such constraints must be clearly shown. Having drawn no-go areas, the margins of safety and the track to be followed, the planning should now be concentrated on ensuring that the ship follows the planned track and that nothing will occur which is unexpected or cannot be corrected. 2.7 Position fixing A variety of position fixing methods is now available but it must not be assumed that any one of the methods will suit all circumstances. 2.7.1 Primary and condary position fixing In order that the position fixing process is smooth, uneventful and clearly understood by all concerned, the passage plan will include information as to which fixing methods are to be ud, which one is to be considered the primary method and which one(s) are to be ud as backup or condary. For example, whilst the ship is out of sight of land it may well be that the GPS is the primary system with Loran C as the conds or back-up system. As the ship approaches the coast, the GPS will still be providing the primary fixing, the Loran C becoming less important and the radar fix confirming the GPS fix. Eventually the Loran C, although running, will become redundant and more reliance placed on the radar fix with the GPS taking the condary role. In enclod waters the GPS position may become inappropriate and position fixing depend upon radar and visual methods. It is not possible to determine an invariable system; it depends upon the equipment available and the circumstances of the individual ca. The important thing is that all concerned are aware that a system is in operation and that it should be followed as far as is practicable. 2.7.2 Radar Conspicuous Objects and Visual Navaids In order to reduce the workload while navigating in coastal waters, the navigator will have determined and planned his primary and condary methods of fixing. To reduce further the OOW’s workload the navigator will have studied his chart at the planning stage and decided which radar conspicuous marks and visual aids are to be ud at each stage of the passage. 2.7.3 Landfall Lights When making a land fall it should not be necessary for the OOW to have to examine the chart minutely to find which lights will be en first. The should have been clearly shown on the chart so that the OOW can concentrate on actually looking for the light concerned, not looking on the chart trying to discover which lights should be visible. chameThe same applies when passing along a coastline or through constrained waters. All lights shown on a chart look similar and need to be studied to determine their individual significance. This needs to be done at the planning stage, not the operational stage when the OOW concerned may be too busy to spend time behind the chart table. 2.7.4 Radar Targets Similarly with radar targets-a little time spent at the planning stage will soon determine which are the targets to look for and u; a steep-to islet is going to be more reliable than a rock awash. Highlight on the chart Racons and other radar conspicuous object which will be ud for position fixing. Highlight visual navaids as appropriate, differentiating between floating and fixed navaids and high-powered and low-powered lights. 2.7.5 Buoyage Whenever buoys or other floating navmarks are being ud as position fixing aids, their own position must be first checked and confirmed that they are as shown on the chart. In situations where buoy fixing is critical, such positions can be predetermined at the planning stage by noting their range and bearing from a known fixed object. 2.7.6 Fix Frequency Irrespective of the method of fixing to be ud, it is necessary to establish the required frequency of the fixing. Quite obviously, this is going to depend on the circumstances prevailing; a ship clo to danger will need to be fixed much more frequently than one in the open a. As a guideline it is suggested that fixing should be at a time period such that it is not possible for a ship to be put into danger between fixes. If it is not possible to fix the position on the chart at such a frequency (fixes at intervals of less than three minutes can be very demanding) then alternative primary navigation methods-for example, parallel indexing -should be considered. 2.7.7 fix Regularity Having established the fix frequency, it is good practice to ensure that fixes are in fact made at that frequency, not as and when the OOW thinks fit. The only exception to this will be if the OOW has other priorities with which , cour alterations for traffic or approaching a critical wheel-over position. In this latter ca, the ship's position should have been established immediately before the turn and again, as soon as possible, on completion. 2.7.8 Additional information Although not esntial to the safety of the ship, a lot of additional information can be shown on the plan which, by reminding the OOW of his obligations or reminding him to make certain preparations, will make the execution of the voyage simpler. Such information will include: 1） Reporting Points Reporting to the relevant authority as and where required can only make the vesl's routeing safer. Such reporting may also be compulsory. 2） Anchor Clearance Positions where anchor stations need to be called and the anchors cleared should be shown in order not to be overlooked. 3） Pilot Boarding Area Timely preparation of the pilot ladder and warning to involved personnel to stand by as required. 4） Tug Engagement Reminder to OOW to call the crew necessary to cure tugs. 5) Traffic Areas Areas where heavy traffic or where occasionally , ferries or fishing boats may be met. 2.8 Situational Awareness Safe navigation of the ship does not only require fixing the position of the ship on the chart at regular intervals. The OOW needs to be constantly updating himlf regarding the position of the ship relative to the required track and its tendency to increa or decrea its deviation from track. Although the regular fixing will give this information there are other, less obvious ways of obtaining such information, often requiring little input other than just obrving natural features. Many of the can be planned in advance and marked on the chart. 2.8.1 Transits Transits (known as ranges in the USA)-i.e., the line on the chart upon which an obrver would e two identifiable objects in line-can be ud to give the OOW a quick indication of his position. Although it is only a single position line its advantage is that it requires no u of instruments but can be en by eye. For extreme accuracy the distance between the obrver and the nearer object should be no more than 3 times the distance between the objects obrved, though transits of greater than this distance can be ud to advantage. Transits are sometimes printed on charts of inshore waters, but good u can be made of natural and clearly identifiable transits found at the planning stage and drawn on the chart. Transits can also be ud as a cue for a pre-arranged action to , wheel-over,-or as a reminder than an event is about to occur. 2.8.2 Compass Errors Transits may be ud to determine gyro and magnetic compass errors by comparing charted and obrved bearings. 2.8.3 Leading lines Leading lines are often shown on charts. In this ca the transit printed on the chart is a track line to be followed to ensure that the ship pass clear of danger. By obrving that the leads are in line the navigator is assured that his ship is on the planned track. 2.8.4 Clearing Marks Clearing marks can be ud to ensure that a ship is remaining within a safe area or is not approaching a danger. 2.8.5 Head Mark Often a ship is required to follow a track in narrow waters without the benefit of a leading line. In this ca a suitable head marker should be lected. This should be a readily identifiable conspicuous object shown on the chart, which lies on the projection of the required track at that part of the passage. As long as the bearing of the head marker, corrected for errors and preferably taken with a centre line repeater, remains constant (i.e., the same as the required track), the ship is remaining on track. It should be noted that the ship need not necessarily be heading directly at the object, only that it is on the line of the required track. In most cas the ship's head will need to be offt to allow for tide or leeway. 2.8.6 clearing bearings In the event that no clearing marks are available a single identifiable charted object may be similarly ud. Obrving clearing bearings and clearing marks cannot be considered to be 'fixing' the ship but can assist the OOW in ensuring that his ship is not standing into danger. Similarly, using dipping distances, whilst not being considered to be an accurate fix, can make the OOW more aware that he is approaching danger. | |
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