Chapter 5 Knowledge Base for Chief Officer
### 第 5 章：大副知识库（Chapter 5: Knowledge Base for Chief Officer）
在海上，大副正为晋升船长做准备，需要培养高超的操船技能并承担更大的责任。作为船上的核心人物，大副被期望监督与船舶货物和结构相关的主要安全事务。在航行安全方面，当船长疲劳或因其他原因无法履行职责时，大副即为船长的备援力量。航运公司和全体船员都极度依赖大副。不幸的是，超过 50% 的海事事故因各种原因发生在大副值班期间：
* **4-8 班（早班与晚班）：** 对於目视了望来说特别具有挑战性，因为晨昏的阳光以接近水平的角度反射，直射了望人员的眼睛，使其难以发现潜在危险。
* **日出前的时段：** 通常是一天中最容易犯困的时间，会降低值班人员的警觉性。
* **港口周围区域：** 经常出现繁忙的交通，船舶急於靠泊以便上午 08:00 的日班工人开始工作。此外，完成下午装卸作业的沿海船舶也加剧了拥堵。
* **船长对大副的能力信任：** 船长信任大副安全航行和避险的能力。然而，作为船上最忙碌的人，大副可能会低估自己在值班期间的生理和心理疲劳，从而影响表现。
* **过度自信：** 对自身航行值班技能过度自信，可能导致大副忽视潜在风险或未能采取必要的预防措施。
* **分心於其他工作：** 值班的水手（AB）可能正忙於清洗驾驶台等工作，而非专注於了望职责，导致对周围区域的目视监视出现盲区。
对於大副而言，期望是能够有效处理复杂情况，例如在狭窄水道中避免多船碰撞。传统上，大副（C/O）负责培训实习生和初级船员（JO），使其保持对危险徵兆的警觉，并确保他们执行正确的程序来应对这些情况。驾驶台资源管理（BHRM）的这一部分提供了雷达了望技能，因为这些概念——尽管在 20 世纪 50 年代雷达绘图的早期阶段就被注意到——依赖於基於本船目标船「真向量」（True Speed Vector）的可行原则。这些原则受到自动雷达绘图仪（ARPA）精确度和雷达能力的影响。虽然自动识别系统（AIS）信号可以为目标船舶提供真向量数据，但作为计算根本基础的 GPS 位置，由於地缘政治问题引发的伪造（故意偏置输入）而进一步受到威胁。这些也是我们在 BHRM 这部分中要解决和试图排除的挑战。
---
#### 5-01 进入交通繁忙区域（Going into heavy traffic area）
**图 5 - 01：红色本船以航向（COG）100⁰、对地航速（SOG）12.7 节接近长江口灯船**
在图 5-01 中，电子海图（ECDIS）显示本船位置（红线标示）正在接近长江口灯船（L/V）。前方是一个以长江口灯船为中心的十字路口。航行值班人员（OOW）应根据良好的航海技术准备哪些常规的情境意识措施？
##### 雷达 / ARPA / AIS 设定（参照第 3 章）
使用两台或更多不同设定的雷达。
* **X 频段雷达设定（X - band Radar setting）：**
* 若要仅探测大型船舶，值班人员（OOW）应降低雷达的「增益」（Gain）设定，以消除萤幕上的所有小目标和海面杂波。
* 当 X 频段雷达上不再显示小目标的回波时，萤幕上将仅保留大型船舶的回波。
* 值班人员（OOW）可以启动 ARPA 的「自动捕获」（Auto Acquisition）功能来自动捕获大型船舶目标。（请注意，与 S 频段雷达相比，X 频段 3 cm 雷达显示的回波较小；因此，只有大型船舶才能产生足够的回波强度以显示出来。）
* **S 频段雷达设定（S - band Radar setting）：**
* 10 cm 的 S 频段雷达适用於探测近距离的小目标，因为它的回波比 3 cm 雷达上的大，且受雨雪杂波影响较小。
* 要消除 10 cm 雷达上的雨雪或海面杂波，值班人员（OOW）可以降低增益设定。
* 值班人员（OOW）应将探测距离缩小至 3 海里，或将雷达偏心（off-center）以提供前方 5 海里的视野。较小的量程设定会放大萤幕上的回波尺寸。
* 在调整雷达以探测本船周围的小目标时，将目标的速度向量和尾迹（trail）设定为**相对运动**（relative motion）。小目标的相对运动线对观察者来说更加直观可见。
* 在相对运动模式下，本船可以透过将电子方位线（EBL）放置在目标回波上，并根据尾迹的方向检查方位变化，从而发现来自小目标的碰撞风险。
* 这两种方法——使用相对运动速度向量/尾迹以及 EBL 设定——可以快速确认碰撞风险，在了望过程中节省宝贵的时间。
除了这两台雷达的基本设定外，大副还应采用其他了望方法，例如目视观察或位於前桅的第三台雷达，以确保对所有目标进行彻底评估。如果目标船舶较多，应利用真运动速度向量（后续讨论）并配合适当的培训来厘清整体情况。
---
#### 国际海上避碰规则（COLREG）第 20 条与甲板附加灯光
根据 COLREG 第 20 条，在日落至日出的时间内：
* **灯光限制：** 不得显示其他灯光，但不会与 COLREG 指定的灯光混淆的灯光除外。这些灯光不得削弱能见度或显著特徵，且不得干扰保持适当的了望。
* **允许的附加灯光：** 在遵循这些航行灯要求的的前提下，只要符合上述标准，即允许使用甲板上的附加灯光。
* **船长裁量权：** 船长应决定可使用哪些甲板灯或生活区灯光来增强船舶的目视外观。
* **通道灯（Alleyway Lights）：** 正如第一章附录中所提议的，可以使用甲板集装箱或类似结构下方的通道灯，以提高其他船舶对本船的可见度。
* **可见度对比：** 值得注意的是，一辆 50 座的大巴在 12 米的长度内，单侧通常至少有 4 个侧灯。相比之下，长度为 300 至 400 米的船舶每侧只有一个侧灯，在任何给定时间最多只能看到 4 个灯光。
* **探测挑战：** 对於一艘 300 米长的船舶单侧而言，只有 3 个灯光可供识别。这使得探测变得困难，特别是在充斥著大量渔船（平均长度 30 米）和岸边背景灯光的繁忙水域中。
* **反射与了望职责：** 这些旨在充当辅助侧灯的甲板附加灯光，不应产生强烈的反射或妨碍其他船舶的了望工作。
* **航行前检查：** 必须做出使用这些辅助灯光的决定，并在船舶启航前由大副或船长进行检查确认。
* **灯光启动：** 船舶一旦出海，了望人员只需启动这些灯光即可，这些灯光可以透过红胶带标记轻松识别为甲板附加灯光。
像「桑吉号」（Sanchi）和「水晶油轮」（CF Crystal）这样的案例突显了忽视这项预防措施的后果。甲板附加灯光可以发挥关键作用，帮助其他船舶将大型船舶与大量渔船区分开来，特别是在远东水域。强烈建议在碰撞风险高的水域航行的船舶采取此做法。
---
#### 图 5 - 02 雷达设定细节
##### 雷达设定与专业能力
雷达设定反映了你进行有效雷达了望的能力。坚持在搜寻模式下使用雷达至关重要。检查雷达显示萤幕左侧时，可以看到几个关键设定：
* **调谐（Tuning）：**
* **定义：** 调谐涉及调整接收机频率，使其与船上发射机振荡器的频率一致。自动调谐（Automatic tuning）是可接受的配置。这种调整是必要的，因为 X 频段或 S 频段产生的频率并非固定不变。实际使用的频率范围在 8.0 到 12.0 GHz 之间，对应的波长范围为 3.75 到 2.5 cm。自动调谐电路会针对每个发射脉冲调整接收机频率，实际上是在「追逐」刚刚发射的频率。手动为每个脉冲重复此过程几乎是不可能的。
* **增益（Gain）：**
* **配置：** 增益设定为手动，这也是可接受的配置。在搜寻模式下，透过增益设定调整接收机回波强度至关重要，且往往是准确将小目标与杂波区分开来的唯一有效手段。
* **需要保持警惕：** 由於增益设定为手动，航行值班人员（OOW）必须在整个值班期间保持高度警惕，以防止丢失目标回波。定期调整对於避免错误使用增益设定至关重要。
* **定期调整：** 值班人员（OOW）应经常调整增益设定，以优化在本船雷达探测到的杂波中对目标回波的识别。这种做法可确保微弱或微小的目标不会被忽视。
* **对杂波和回波的影响：** 增益设定直接影响雷达萤幕上显示的海面或雨雪杂波量。较高的增益值会增加海面/雨雪杂波的强度或数量，从而削弱目标回波的强度。如果在搜寻模式下未优化调整增益和杂波设定，目标回波可能不会出现在萤幕上，从而导致潜在的疏忽。
* **能力的体现：** 在雷达上丢失目标轨迹通常表明航行值班能力不足。然而，在某些情况下，目标回波强度与海面或雨雪杂波几乎无法区分。仅靠适当的增益调整可能还不够；在这种情况下，如前所述，尝试使用两台不同的雷达来探测小目标可能会有所帮助。
##### 反射角的影响
目标回波的强度受雷达波反射角的显著影响。当雷达安装在船艏时，它可以从小目标获得更垂直的反射角。与雨雪或海面杂波相比，这种垂直入射会产生更强的雷达波反射，从而有助於在周围杂波中区分小目标回波。
##### 波长的影响
波长为 10 cm 的 S 频段雷达通常会产生更强的回波信号，与波长为 3 cm 的 X 频段雷达相比，它更适合探测小目标。S 频段雷达较长的波长使其能够更有效地与小物体相互作用，在雷达萤幕上产生更明显的回波。
总之，理解并正确调整雷达设定对於有效航行和避碰至关重要。保持这些操作的专业能力对於确保海上作业安全至关重要。
培训航行值班人员（OOW）手动调整雷达以进行搜寻主要是船长的责任。大副也应具备履行此指导角色的能力。每当大副或船长进入驾驶台时，都应核实初级值班人员的雷达设定是否正确。
* **海面 / 雨雪杂波设定（Sea/Rain Clutter Setting）：**
* **手动调整：** 手动海面/雨雪杂波设定是可以接受的，但需要精心管理。
* **定期调整：** 应定期调整海面和雨雪杂波设定，以确保不会设定得过高，因为过高的设定会遮蔽小目标的回波。
* **验证过程：** 每当雷达萤幕显示没有杂波时，值班人员（OOW）应稍微降低海面/雨雪杂波设定，以允许少量杂波重新出现。这种调整有助於确认设定的准确性。
正如桑吉号（Sanchi）的雷达图像（图 5-02）所示，手动海波设定为 40%，这太高了。这导致大型船舶「水晶油轮」（CF Crystal）的回波消失，而三副甚至在紧急情况下也未能调整海波抑制设定。
在海上，大副正为晋升船长做准备，需要培养高超的操船技能并承担更大的责任。作为船上的核心人物，大副被期望监督与船舶货物和结构相关的主要安全事务。在航行安全方面，当船长疲劳或因其他原因无法履行职责时，大副即为船长的备援力量。航运公司和全体船员都极度依赖大副。不幸的是，超过 50% 的海事事故因各种原因发生在大副值班期间：
* **4-8 班（早班与晚班）：** 对於目视了望来说特别具有挑战性，因为晨昏的阳光以接近水平的角度反射，直射了望人员的眼睛，使其难以发现潜在危险。
* **日出前的时段：** 通常是一天中最容易犯困的时间，会降低值班人员的警觉性。
* **港口周围区域：** 经常出现繁忙的交通，船舶急於靠泊以便上午 08:00 的日班工人开始工作。此外，完成下午装卸作业的沿海船舶也加剧了拥堵。
* **船长对大副的能力信任：** 船长信任大副安全航行和避险的能力。然而，作为船上最忙碌的人，大副可能会低估自己在值班期间的生理和心理疲劳，从而影响表现。
* **过度自信：** 对自身航行值班技能过度自信，可能导致大副忽视潜在风险或未能采取必要的预防措施。
* **分心於其他工作：** 值班的水手（AB）可能正忙於清洗驾驶台等工作，而非专注於了望职责，导致对周围区域的目视监视出现盲区。
对於大副而言，期望是能够有效处理复杂情况，例如在狭窄水道中避免多船碰撞。传统上，大副（C/O）负责培训实习生和初级船员（JO），使其保持对危险徵兆的警觉，并确保他们执行正确的程序来应对这些情况。驾驶台资源管理（BHRM）的这一部分提供了雷达了望技能，因为这些概念——尽管在 20 世纪 50 年代雷达绘图的早期阶段就被注意到——依赖於基於本船目标船「真向量」（True Speed Vector）的可行原则。这些原则受到自动雷达绘图仪（ARPA）精确度和雷达能力的影响。虽然自动识别系统（AIS）信号可以为目标船舶提供真向量数据，但作为计算根本基础的 GPS 位置，由於地缘政治问题引发的伪造（故意偏置输入）而进一步受到威胁。这些也是我们在 BHRM 这部分中要解决和试图排除的挑战。
---
#### 5-01 进入交通繁忙区域（Going into heavy traffic area）
**图 5 - 01：红色本船以航向（COG）100⁰、对地航速（SOG）12.7 节接近长江口灯船**
在图 5-01 中，电子海图（ECDIS）显示本船位置（红线标示）正在接近长江口灯船（L/V）。前方是一个以长江口灯船为中心的十字路口。航行值班人员（OOW）应根据良好的航海技术准备哪些常规的情境意识措施？
##### 雷达 / ARPA / AIS 设定（参照第 3 章）
使用两台或更多不同设定的雷达。
* **X 频段雷达设定（X - band Radar setting）：**
* 若要仅探测大型船舶，值班人员（OOW）应降低雷达的「增益」（Gain）设定，以消除萤幕上的所有小目标和海面杂波。
* 当 X 频段雷达上不再显示小目标的回波时，萤幕上将仅保留大型船舶的回波。
* 值班人员（OOW）可以启动 ARPA 的「自动捕获」（Auto Acquisition）功能来自动捕获大型船舶目标。（请注意，与 S 频段雷达相比，X 频段 3 cm 雷达显示的回波较小；因此，只有大型船舶才能产生足够的回波强度以显示出来。）
* **S 频段雷达设定（S - band Radar setting）：**
* 10 cm 的 S 频段雷达适用於探测近距离的小目标，因为它的回波比 3 cm 雷达上的大，且受雨雪杂波影响较小。
* 要消除 10 cm 雷达上的雨雪或海面杂波，值班人员（OOW）可以降低增益设定。
* 值班人员（OOW）应将探测距离缩小至 3 海里，或将雷达偏心（off-center）以提供前方 5 海里的视野。较小的量程设定会放大萤幕上的回波尺寸。
* 在调整雷达以探测本船周围的小目标时，将目标的速度向量和尾迹（trail）设定为**相对运动**（relative motion）。小目标的相对运动线对观察者来说更加直观可见。
* 在相对运动模式下，本船可以透过将电子方位线（EBL）放置在目标回波上，并根据尾迹的方向检查方位变化，从而发现来自小目标的碰撞风险。
* 这两种方法——使用相对运动速度向量/尾迹以及 EBL 设定——可以快速确认碰撞风险，在了望过程中节省宝贵的时间。
除了这两台雷达的基本设定外，大副还应采用其他了望方法，例如目视观察或位於前桅的第三台雷达，以确保对所有目标进行彻底评估。如果目标船舶较多，应利用真运动速度向量（后续讨论）并配合适当的培训来厘清整体情况。
---
#### 国际海上避碰规则（COLREG）第 20 条与甲板附加灯光
根据 COLREG 第 20 条，在日落至日出的时间内：
* **灯光限制：** 不得显示其他灯光，但不会与 COLREG 指定的灯光混淆的灯光除外。这些灯光不得削弱能见度或显著特徵，且不得干扰保持适当的了望。
* **允许的附加灯光：** 在遵循这些航行灯要求的的前提下，只要符合上述标准，即允许使用甲板上的附加灯光。
* **船长裁量权：** 船长应决定可使用哪些甲板灯或生活区灯光来增强船舶的目视外观。
* **通道灯（Alleyway Lights）：** 正如第一章附录中所提议的，可以使用甲板集装箱或类似结构下方的通道灯，以提高其他船舶对本船的可见度。
* **可见度对比：** 值得注意的是，一辆 50 座的大巴在 12 米的长度内，单侧通常至少有 4 个侧灯。相比之下，长度为 300 至 400 米的船舶每侧只有一个侧灯，在任何给定时间最多只能看到 4 个灯光。
* **探测挑战：** 对於一艘 300 米长的船舶单侧而言，只有 3 个灯光可供识别。这使得探测变得困难，特别是在充斥著大量渔船（平均长度 30 米）和岸边背景灯光的繁忙水域中。
* **反射与了望职责：** 这些旨在充当辅助侧灯的甲板附加灯光，不应产生强烈的反射或妨碍其他船舶的了望工作。
* **航行前检查：** 必须做出使用这些辅助灯光的决定，并在船舶启航前由大副或船长进行检查确认。
* **灯光启动：** 船舶一旦出海，了望人员只需启动这些灯光即可，这些灯光可以透过红胶带标记轻松识别为甲板附加灯光。
像「桑吉号」（Sanchi）和「水晶油轮」（CF Crystal）这样的案例突显了忽视这项预防措施的后果。甲板附加灯光可以发挥关键作用，帮助其他船舶将大型船舶与大量渔船区分开来，特别是在远东水域。强烈建议在碰撞风险高的水域航行的船舶采取此做法。
---
#### 图 5 - 02 雷达设定细节
##### 雷达设定与专业能力
雷达设定反映了你进行有效雷达了望的能力。坚持在搜寻模式下使用雷达至关重要。检查雷达显示萤幕左侧时，可以看到几个关键设定：
* **调谐（Tuning）：**
* **定义：** 调谐涉及调整接收机频率，使其与船上发射机振荡器的频率一致。自动调谐（Automatic tuning）是可接受的配置。这种调整是必要的，因为 X 频段或 S 频段产生的频率并非固定不变。实际使用的频率范围在 8.0 到 12.0 GHz 之间，对应的波长范围为 3.75 到 2.5 cm。自动调谐电路会针对每个发射脉冲调整接收机频率，实际上是在「追逐」刚刚发射的频率。手动为每个脉冲重复此过程几乎是不可能的。
* **增益（Gain）：**
* **配置：** 增益设定为手动，这也是可接受的配置。在搜寻模式下，透过增益设定调整接收机回波强度至关重要，且往往是准确将小目标与杂波区分开来的唯一有效手段。
* **需要保持警惕：** 由於增益设定为手动，航行值班人员（OOW）必须在整个值班期间保持高度警惕，以防止丢失目标回波。定期调整对於避免错误使用增益设定至关重要。
* **定期调整：** 值班人员（OOW）应经常调整增益设定，以优化在本船雷达探测到的杂波中对目标回波的识别。这种做法可确保微弱或微小的目标不会被忽视。
* **对杂波和回波的影响：** 增益设定直接影响雷达萤幕上显示的海面或雨雪杂波量。较高的增益值会增加海面/雨雪杂波的强度或数量，从而削弱目标回波的强度。如果在搜寻模式下未优化调整增益和杂波设定，目标回波可能不会出现在萤幕上，从而导致潜在的疏忽。
* **能力的体现：** 在雷达上丢失目标轨迹通常表明航行值班能力不足。然而，在某些情况下，目标回波强度与海面或雨雪杂波几乎无法区分。仅靠适当的增益调整可能还不够；在这种情况下，如前所述，尝试使用两台不同的雷达来探测小目标可能会有所帮助。
##### 反射角的影响
目标回波的强度受雷达波反射角的显著影响。当雷达安装在船艏时，它可以从小目标获得更垂直的反射角。与雨雪或海面杂波相比，这种垂直入射会产生更强的雷达波反射，从而有助於在周围杂波中区分小目标回波。
##### 波长的影响
波长为 10 cm 的 S 频段雷达通常会产生更强的回波信号，与波长为 3 cm 的 X 频段雷达相比，它更适合探测小目标。S 频段雷达较长的波长使其能够更有效地与小物体相互作用，在雷达萤幕上产生更明显的回波。
总之，理解并正确调整雷达设定对於有效航行和避碰至关重要。保持这些操作的专业能力对於确保海上作业安全至关重要。
培训航行值班人员（OOW）手动调整雷达以进行搜寻主要是船长的责任。大副也应具备履行此指导角色的能力。每当大副或船长进入驾驶台时，都应核实初级值班人员的雷达设定是否正确。
* **海面 / 雨雪杂波设定（Sea/Rain Clutter Setting）：**
* **手动调整：** 手动海面/雨雪杂波设定是可以接受的，但需要精心管理。
* **定期调整：** 应定期调整海面和雨雪杂波设定，以确保不会设定得过高，因为过高的设定会遮蔽小目标的回波。
* **验证过程：** 每当雷达萤幕显示没有杂波时，值班人员（OOW）应稍微降低海面/雨雪杂波设定，以允许少量杂波重新出现。这种调整有助於确认设定的准确性。
正如桑吉号（Sanchi）的雷达图像（图 5-02）所示，手动海波设定为 40%，这太高了。这导致大型船舶「水晶油轮」（CF Crystal）的回波消失，而三副甚至在紧急情况下也未能调整海波抑制设定。
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Chapter 5: Knowledge Base for Chief Officer
A Chief Officer at sea is preparing for the role of Master, developing advanced maneuvering skills
and assuming greater responsibilities. As a key figure on board, the Chief Officer is expected to
oversee major safety aspects related to the ship's cargo and structure. In terms of navigational
safety, the Chief Officer serves as the Master’s backup whenever the Master is fatigued or otherwise
un able to perform their duties. The shipping company and the entire crew rely heavily on the Chief
Officer. Unfortunately, more than 50% of marine incidents occur during the Chief Officer's watch for
various reasons:
The 4-8 watch (both morning and evening) is particularly challenging for visual lookout, as
the twilight sun reflects at a near-horizontal angle, shining directly into the lookout's eyes and
making it difficult to spot potential hazards.
The hours just before sunrise are typically the sleepiest period of the day, which can reduce
alertness among those on watch.
Heavy traffic often occurs around harbor areas, with vessels eager to dock so that the 0800
day-shift workers can begin their tasks. Additionally, coastal vessels that have completed
afternoon cargo operations contribute to the congestion.
The Master has confidence in the Chief Officer's ability to navigate safely and avoid danger.
However, as the busiest person on board, the Chief Officer may underestimate their own
physical and mental fatigue during the watch, which can impact performance.
Overconfidence in their watchkeeping skills can lead the Chief Officer to overlook potential
risks or fail to take neces sary precautions.
Instead of focusing on lookout duties, the able-Bodied Seaman ( ab) on duty may be
occupied with tasks like cleaning the bridge, creating gaps in visual surveillance of the
surrounding area
For a Chief Officer, the expectation is to handle complex situations effectively, such as avoiding
multi-ship collisions in confined waterways. Traditionally, the Chief Officer (C/O) is responsible for
training cadets and Junior Officers (JOs) to keep them aware of danger signs and ensure they execute
proper procedures to cope with such situations. This part of Bridge Human Resource Management (
BHRM) provides radar lookout skills, as these concepts—although noted in the early stages of radar
plotting in the 1950s—rely on applic able principles based on the True Speed Vector of the ownship
and target vessels. These principles are influenced by the precision of Automatic Radar Plotting Aid (
ARPA) and radar cap abilities. While Automatic Identification System ( AIS) signals can provide True
Speed Vector data for target vessels, their GPS positions—which form the fundamental basis for
calculations—are further jeopardized by spoofing (deliberate biased input) due to geopolitical issues.
These are also the challenges we address and aim to resolve in this part of BHRM.
5- 01 Going into heavy traffic area
Fig 5 - 01 Red Ownship approaching Chang Jiang Mouth L/V with COG 100⁰ SOG 12.7 Knots
In Figure 5-01, the ECDIS display shows the ownship's position (indicated by the red line)
approaching the Chang Jiang Mouth Light Vessel (L/V). Ahead, a crossroads is centered on the Chang
Jiang Mouth light vessel. What should the Officer of the Watch ( OOW) prepare as routine situational
awareness measures in line with good seamanship?
Radar/ ARPA/ AIS Settings (as per Chapter 3)
Use two set radars or more in different setting.
X - band Radar setting:
To detect only large vessels, the OOW should reduce the radar's "gain" setting to eliminate
all small targets and sea clutter from the screen.
When small target echoes are no longer visible on the X-band radar, only echoes from large
vessels will remain on the screen.
The OOW can activate the ARPA "Auto Acquisition" function to automatically acquire targets
from large vessels. (Note that the X-band 3 cm radar displays smaller echoes compared to
the S-band radar; thus, only large vessels generate sufficient echo strength to appear.)
S - band Radar setting:
The 10 cm S-band radar is useful for detecting smaller targets at close range, as its echoes
are larger than those on the 3 cm radar and are less affected by snow or rain clutter.
To eliminate rain or sea clutter on the 10 cm radar, the OOW can lower the gain setting.
The OOW should reduce the detection range to 3 nautical miles or off-center the radar to
provide a 5-nautical-mile view ahead. A smaller range setting enlarges echo sizes on the
screen.
When adjusting the radar to detect small targets around the ownship, set the target speed
vector and trail to relative motion. Relative motion lines of small targets are more intuitively
visible to observers.
In relative motion mode, the ownship can detect collision risks from small targets by placing
the Electronic Bearing Line ( EBL) on the target's echo and checking for bearing variations
based on the trail's direction.
These two methods—using relative motion speed vectors/ trails and EBL settings—allow for
quick confirmation of collision risks, saving valu able time during lookout.
In addition to these basic settings with the two radars, the Chief Officer should also employ other
lookout methods, such as visual observation or a third radar located on the foremast, to ensure all
targets are thoroughly evaluated. If there are many target vessels, one should utilize the true motion
speed vector (discussed later) to clarify the overall situation, along with proper training.
COLREG Rule 20 and Extra lights on the deck
According to COLREG Rule 20, during the hours from sunset to sunrise:
Lighting Restrictions: No additional lights should be displayed, except those that cannot be
confused with the lights specified in the COLREGs. These lights must not diminish visibility
or distinctive character and should not interfere with maintaining a proper lookout.
Permissible Extra Lights: By adhering to these navigation light requirements, extra lights on
the deck are allowed, provided they meet the aforementioned criteria.
Master’s Discretion: The Master of the vessel should determine which deck or
accommodation lights can be used to enhance the ship's visual appearance.
Alleyway Lights: As proposed in the annex of the first chapter, alleyway lights
under deck containers or similar structures can be utilized to improve the visibility
of the vessel to others.
Comparative Visibility: It is quite remark able to note that a 50-seat bus typically
has at least four side lights on one side within a span of 12 meters. In contrast, a
vessel measuring 300 to 400 meters in length has only one sidelight per side, with
a maximum of four lights visible at any given time.
Detection Challenges: For one side of a 300-meter-long vessel, it has only three
lights to be visible. This makes detection difficult, especially in congested waters
filled with numerous fishing vessels (averaging 30 meters in length) and
background lights from the shoreline.
Reflection and Lookout Duties: These extra deck lights, intended to function as
auxiliary sidelights, should not create strong reflections or hinder lookout duties on
other vessels.
Pre- sailing Checks: The decision to utilize these auxiliary lights must be made,
and the arrangement should be verified by the Chief Officer or Master before the
vessel departs.
Activation of Lights: Once the vessel is at sea, the lookout merely needs to activate
these lights, which can be easily identified by red tape markings as deck extra
lights.
Instances like the sanchi and CF Crystal highlight the consequences of neglecting this precaution.
Extra deck lights can play a crucial role in helping other vessels distinguish large ships from the
multitude of fishing boats, especially in the waters of the Far East. It is strongly recommended that
vessels operating in high collision risk areas adopt this practice.
Figure 5 - 02 details of radar setting
Radar Settings and Competence
Radar settings are a reflection of your competence in conducting an effective radar lookout. It is
essential to utilize radar in search mode consistently. When examining the left-hand side of the radar
display, several key settings are visible:
Tuning:
Definition: Tuning involves adjusting the receiver frequency to align with the frequency of the
onboard transmitter oscillator. Automatic tuning is an accept able configuration. This
adjustment is neces sary because the frequencies generated in the X-band or S-band are
not fixed. The actual frequency range used is between 8.0 and 12.0 GHz, corresponding to a
wavelength range of 3.75 to 2.5 cm. Automatic tuning circuits adjust the receiver frequency
to each transmitted pulse, effectively "chasing" the frequencies just transmitted. Replicating
this process manually for each pulse is nearly impossible.
Gain:
Configuration: The gain is set to manual, which is also an accept able configuration. In
search mode, adjusting the receiver echo strength through the gain setting is crucial and
often the only effective means of accurately distinguishing small targets from clutter.
Vigilance Required: Since the gain is set to manual, the Officer of the Watch ( OOW) must
maintain high vigilance throughout their watch to prevent the loss of target echoes. Periodic
adjustments are essential to avoid misuse of the gain setting.
Regular Adjustments: The OOW should frequently adjust the gain setting to optimize the
identification of target echoes within the clutter detected by the ownship's radar. This practice
ensures that faint or small targets are not overlooked.
Impact on Clutter and Echoes: The gain setting directly impacts the amount of sea or rain
clutter displayed on the radar screen. A higher gain value increases the strength or number
of sea/rain clutter, which can diminish the strength of target echoes. If the gain and clutter
settings are not optimally adjusted during search mode, target echoes may not appear on the
screen, leading to potential oversight.
Indicator of Competence: Losing target traces on the radar is generally indicative of
incompetence in navigational watchkeeping. However, there are instances where target echo
strength is nearly indistinguish able from that of sea or rain clutter. Proper gain adjustment
alone may not suffice; in such cases, attempting to detect small targets using two different
radar sets, as previously mentioned, can be beneficial.
Influence of Reflection Angle
The strength of target echoes is significantly affected by the reflection angle of the radar waves.
When the radar is positioned on the bow of a vessel, it can achieve a more perpendicular reflection
angle from small targets. This perpendicular incidence results in stronger reflected radar waves
compared to those from rain or sea clutter, facilitating the differentiation of small target echoes amidst
surrounding clutter.
Influence of Wavelength
The S-band radar, with a wavelength of 10 cm, generally produces stronger echo signals, making
it more suit able for detecting small targets compared to X-band radar, which has a wavelength of 3
cm. The longer wavelength of the S-band radar allows it to interact more effectively with small objects,
generating more notice able echoes on the radar screen.
In summary, understanding and correctly adjusting radar settings is crucial for effective navigation
and collision avoidance. Maintaining competence in these practices is vital for ensuring safe maritime
operations.
Training the Officer of the Watch ( OOW) in manually adjusting the radar for search purposes is
primarily the responsibility of the Master. The Chief Officer should also be equipped to fulfill this
mentoring role. Whenever the Chief Officer or Master visits the bridge, they should verify that the radar
settings are correct for junior OOWs..
Sea/Rain Clutter Setting:
Manual Adjustment: A manual sea/rain clutter setting is accept able, but it requires careful
management.
Periodic Adjustments: The sea and rain clutter settings should be adjusted regularly to
ensure they are not set too high, as excessive settings can mask the echoes of small targets.
Verification Process: Each time the radar screen indicates no clutter, the OOW should
slightly reduce the sea/rain clutter setting to permit a small amount of clutter to reappear.
This adjustment helps confirm the accuracy of the setting.
As illustrated in the radar image of the sanchi (Figure 5-02), the manual sea clutter setting was set
at 40%, which was too high. This resulted in the echo of the large vessel CF Crystal di sappearing, and
the Third Officer failed to adjust the sea clutter setting even during the emergency.
Adjusting Range Based on Target Density:
If there are numerous targets, reduce the display range to a smaller area. For instance, in Figure
5-03, the left side shows a range setting of 6 nautical miles (nm) with too many targets. In this case, the
radar range should be reduced to 3 nm (as shown on the right side). If 3 nm still displays an excessive
number of targets, further reduce it to a 1.5 nm detection range.
Analysis of Figure 5-03
On the left-hand side of Figure 5-03, the range setting of 6 nm displays an excessive number of
targets, making it challenging to determine which pose a danger. Typically, 6 nm is a common range for
junior Officers of the Watch ( OOWs) in open sea conditions.
However, if the Master observes a Third Officer (3/O) using a 3 nm range for radar lookout, they
should question the reasoning behind this choice. Several important considerations arise:
If there aren't many small targets, could the ownship be too close to the shore? Both
scenarios—an abundance of small targets or proximity to the shore—heighten the risk of
collision or grounding.
What about large targets that could potentially sink the ownship? Early warning is crucial for
these threats, which is only feasible with a long-range radar view.
Are the crew members competent enough to conduct an effective lookout and execute
collision-avoidance procedures within this limited 3 nm range for timely warnings?
While the 3/O might use the 3 nm range to positively identify small targets, this approach can
lead to overlooking large, fast-approaching vessels that quickly move beyond the 3 nm limit.
In a scenario with numerous small vessels, utilizing an additional radar set to detect ocean
going vessels would be advantageous.
This distinction is why senior and junior lookout procedures differ. The Chief Officer (C/O) will
alternate the detection range between 3 and 6 nm, while a 3/O may fixate on a single vessel,
as seen in the case of the 3/O on the sanchi, who focused solely on one target at a time.
Performance requirements for the Automatic Radar Plotting Aid ( ARPA) are often exceeded when
there are over 20 targets. It is unneces sary to track or collect data on every single target, as our short
term memory cannot manage such a large volume of information. Instead, categorize the workload into
two primary groups: large vessels on X-band radar and small fishing boats on S-band radar.
Job assignments for identifying small and large targets on the radar screen should be clearly
delineated. It is crucial not to rely blindly on past experiences in all situations. As noted in the previous
chapter, even a Master may struggle to fully master the skills required for effective radar lookout. This
seemingly minor oversight, stemming from improper radar lookout practices, can ultimately lead to a
collision incident.
Figure 5 - 04 Correct Trail setting in radar lookout
Radar Trails and Colision Avoidance
Where is the trail of the small vessel we are looking for?
In the left-hand image of Figure 5-04, the radar trails for targets were not correctly set, preventing
the Master from immediately assessing the collision risk. In contrast, Figure 2-19 displays radar echoes
with trails, facilitating better situational awareness.
Relative-Motion Trails: These trails can be quite long when there is high relative speed,
which may obscure the echoes of other targets.
True-Motion Trails: These are more advantageous when immediate information about target
movement is required.
When approaching a dense group of fishing boats, most of which are stationary, it is essential to
understand the behavior of these vessels. Fishermen, in order to avoid collisions with other boats in the
same school, typically have two options: they can either remain stationary or move in the same
direction and at the same speed as the other vessels.
In the first situation, a quick glance at the true-motion trail can significantly reduce the
perceived threat from stationary fishing vessels.
In the second situation, true-motion trails can easily help identify vessels with different
course and speed from other fishing vessels, which may indicate large ocean-going vessels.
In the 3-nm radar picture on the right, the radar trail was set to a 3-minute true motion, which is
shorter than the 6-minute true-motion setting for speed vectors.
The Master set the target trail to 3 minutes to indicate the past movement of the target,
allowing for an assessment of whether the target had changed course in the past three
minutes.
The Master utilized the acquired target true motion speed vectors (set to 6 minutes) to
determine the target's course and speed. However, for targets that had not been acquired, it
was challenging to accurately estimate their true course and speed using only the 3-minute
trail.
We recommend setting the trail length to match the time interval of the speed vectors, which in
this case should be 6 minutes. In this particular collision scenario, this seemingly minor difference in
settings was a contributing factor to the incident. The Master may have either overestimated the speed
of the two targets at the starboard bow or lacked reli able information about their speed without
displayed speed vectors, as these two targets had not been acquired.
Initially, the Master could have safely passed these two small vessels, proceeding ahead of
the towing vessel with a tow and astern of the fast-moving vessel, based on an
understanding of collision position observation.
However, because the Master did not set the target trail to match the time interval of the
speed vectors, he was un able to accurately compare the ownship's speed vector with the
target's trail (which was also set to 6 minutes) to predict their future positions relative to the
ownship when making course alteration decisions.
The notion of using the appropriate trail length setting to estimate the positions of the two
small vessels and the ownship after 6 minutes did not occur to him.
If the Master had doubts about being able to pass ahead of the tugboat with the tow using
either the radar trail or the speed vectors, he should have opted to maneuver around it
(alter course to pass behind the target), as outlined in Chapter 2.
Unfortunately, this incorrect decision led to an encounter with even more dangerous targets
on the starboard side, leaving an indelible mark on his career.
For an immediate estimation to target movement, it is advi sable to set the trail length to match the
duration of the speed vectors.
This alignment eliminates the need to double-check the trail time setting during an
emergency. With the same time setting for both speed vectors and trails, the speed
vectors of small targets can be mentally projected to match the length and direction of their
trails.
These trail settings are particularly useful when a target vessel changes course in the last
few minutes.
The ownship can determine whether the target vessel's past course has changed by
observing the shape of its trail within the designated time interval.
Since course changes of targets are not graphically indicated on the Automatic Radar
Plotting Aid ( ARPA), only the trail can effectively reveal such changes through its shape,
eliminating the need to remember the original course data.
Figure 5-03 illustrates how detection range reflects traffic density. To emphasize the importance of
radar trail settings in helping manage the workload of radar lookout, we further demonstrate the
concepts in Figure 5-04: Correct Trail Settings in Radar. The left picture shows the original setting of
the ownship, where the trail (3 minutes) is half the time length of the true-motion speed vector (6
minutes). In the right drawing, we added a 6-minute trail to help clarify the points made. The red
speed vector at the starboard bow vessel is a reflection of its blue trail behind, used to estimate the
meeting situation with the ownship.
When there are numerous small targets at sea and visual lookout has difficulty determining their
distance from the ownship, radar trails become essential. Regardless of how proficient one is at radar
setting; visual lookout always takes precedence. Radar lookout has inherent limitations due to the
equipment, even for those highly skilled in radar searching and acquisition procedures. Each time we
change vessels after a contract, our experience with radar may be challenged by new brands or
layouts. Even if you are a Chief Officer, you should ask yourself, “Can I accurately determine the
distance of a target with my unaided eyes?” If you lack confidence in your visual skills, you must take
steps to improve them now.
Radar Speed Vector Setting and Colision Risk
In this radar, a 6-minute speed vector setting in true-motion mode facilitates easier cross
referencing with the Electronic Chart Display and Information System ( ECDIS).
Collision Risk Assessment: A 6-minute speed vector setting allows for the assessment of
collision risk within a 6-minute time frame. This extended period provides a broader
perspective on the movement and potential paths of nearby vessels, en abling a more
comprehensive evaluation of risk.
Adjusting Based on Target Density: The length of the speed vector is analogous to the range
setting. When there is a high density of targets on the radar screen, it is neces sary to reduce
the time interval of the speed vector setting. Shortening it to, for example, 1.5 or 3 minutes
helps decrease the number of targets under consideration simultaneously, making it easier to
focus on the most relevant threats.
Target Scarcity Consideration: Conversely, when the number of targets is low, setting a
longer time period for the speed vector—such as 9 or 12 minutes—can be beneficial. This
longer-term view helps identify potential collision risks with vessels that might be
approaching from a distance or on trajectories that could intersect with the ownship's path in
the future.
Minimum Requirement: A 3-minute speed vector setting is regarded as the minimum
requirement for effective radar lookout. This duration provides the ownship with adequate
time to maneuver and avoid a collision. Anything less would limit the time avail able for safe
evasive actions.
The time period for speed vector settings varies depending on the situation and the skill levels of
the personnel involved. A 9- or 12-minute setting is considered appropriate for Junior Officers (JOs), as
it accommodates their slower risk recognition, provides more time for situational evaluation, and allows
additional time for the vessel to respond to their decisions. A 6-minute setting is suit able for Chief
Officers (C/Os), not neces sarily due to their greater competence, but because the coastal waters they
navigate only have this timeframe to assess and clarify collision risks. Ultimately, Masters must be able
to manage 3-minute speed vector scenarios to maintain a clearer understanding of congestion and
harbor conditions. The varying skill levels and evolving knowledge bases in these settings play a
significant role in our competence. Our upcoming chapters will further illustrate these points.
A Chief Officer at sea is preparing for the role of Master, developing advanced maneuvering skills
and assuming greater responsibilities. As a key figure on board, the Chief Officer is expected to
oversee major safety aspects related to the ship's cargo and structure. In terms of navigational
safety, the Chief Officer serves as the Master’s backup whenever the Master is fatigued or otherwise
un able to perform their duties. The shipping company and the entire crew rely heavily on the Chief
Officer. Unfortunately, more than 50% of marine incidents occur during the Chief Officer's watch for
various reasons:
The 4-8 watch (both morning and evening) is particularly challenging for visual lookout, as
the twilight sun reflects at a near-horizontal angle, shining directly into the lookout's eyes and
making it difficult to spot potential hazards.
The hours just before sunrise are typically the sleepiest period of the day, which can reduce
alertness among those on watch.
Heavy traffic often occurs around harbor areas, with vessels eager to dock so that the 0800
day-shift workers can begin their tasks. Additionally, coastal vessels that have completed
afternoon cargo operations contribute to the congestion.
The Master has confidence in the Chief Officer's ability to navigate safely and avoid danger.
However, as the busiest person on board, the Chief Officer may underestimate their own
physical and mental fatigue during the watch, which can impact performance.
Overconfidence in their watchkeeping skills can lead the Chief Officer to overlook potential
risks or fail to take neces sary precautions.
Instead of focusing on lookout duties, the able-Bodied Seaman ( ab) on duty may be
occupied with tasks like cleaning the bridge, creating gaps in visual surveillance of the
surrounding area
For a Chief Officer, the expectation is to handle complex situations effectively, such as avoiding
multi-ship collisions in confined waterways. Traditionally, the Chief Officer (C/O) is responsible for
training cadets and Junior Officers (JOs) to keep them aware of danger signs and ensure they execute
proper procedures to cope with such situations. This part of Bridge Human Resource Management (
BHRM) provides radar lookout skills, as these concepts—although noted in the early stages of radar
plotting in the 1950s—rely on applic able principles based on the True Speed Vector of the ownship
and target vessels. These principles are influenced by the precision of Automatic Radar Plotting Aid (
ARPA) and radar cap abilities. While Automatic Identification System ( AIS) signals can provide True
Speed Vector data for target vessels, their GPS positions—which form the fundamental basis for
calculations—are further jeopardized by spoofing (deliberate biased input) due to geopolitical issues.
These are also the challenges we address and aim to resolve in this part of BHRM.
5- 01 Going into heavy traffic area
Fig 5 - 01 Red Ownship approaching Chang Jiang Mouth L/V with COG 100⁰ SOG 12.7 Knots
In Figure 5-01, the ECDIS display shows the ownship's position (indicated by the red line)
approaching the Chang Jiang Mouth Light Vessel (L/V). Ahead, a crossroads is centered on the Chang
Jiang Mouth light vessel. What should the Officer of the Watch ( OOW) prepare as routine situational
awareness measures in line with good seamanship?
Radar/ ARPA/ AIS Settings (as per Chapter 3)
Use two set radars or more in different setting.
X - band Radar setting:
To detect only large vessels, the OOW should reduce the radar's "gain" setting to eliminate
all small targets and sea clutter from the screen.
When small target echoes are no longer visible on the X-band radar, only echoes from large
vessels will remain on the screen.
The OOW can activate the ARPA "Auto Acquisition" function to automatically acquire targets
from large vessels. (Note that the X-band 3 cm radar displays smaller echoes compared to
the S-band radar; thus, only large vessels generate sufficient echo strength to appear.)
S - band Radar setting:
The 10 cm S-band radar is useful for detecting smaller targets at close range, as its echoes
are larger than those on the 3 cm radar and are less affected by snow or rain clutter.
To eliminate rain or sea clutter on the 10 cm radar, the OOW can lower the gain setting.
The OOW should reduce the detection range to 3 nautical miles or off-center the radar to
provide a 5-nautical-mile view ahead. A smaller range setting enlarges echo sizes on the
screen.
When adjusting the radar to detect small targets around the ownship, set the target speed
vector and trail to relative motion. Relative motion lines of small targets are more intuitively
visible to observers.
In relative motion mode, the ownship can detect collision risks from small targets by placing
the Electronic Bearing Line ( EBL) on the target's echo and checking for bearing variations
based on the trail's direction.
These two methods—using relative motion speed vectors/ trails and EBL settings—allow for
quick confirmation of collision risks, saving valu able time during lookout.
In addition to these basic settings with the two radars, the Chief Officer should also employ other
lookout methods, such as visual observation or a third radar located on the foremast, to ensure all
targets are thoroughly evaluated. If there are many target vessels, one should utilize the true motion
speed vector (discussed later) to clarify the overall situation, along with proper training.
COLREG Rule 20 and Extra lights on the deck
According to COLREG Rule 20, during the hours from sunset to sunrise:
Lighting Restrictions: No additional lights should be displayed, except those that cannot be
confused with the lights specified in the COLREGs. These lights must not diminish visibility
or distinctive character and should not interfere with maintaining a proper lookout.
Permissible Extra Lights: By adhering to these navigation light requirements, extra lights on
the deck are allowed, provided they meet the aforementioned criteria.
Master’s Discretion: The Master of the vessel should determine which deck or
accommodation lights can be used to enhance the ship's visual appearance.
Alleyway Lights: As proposed in the annex of the first chapter, alleyway lights
under deck containers or similar structures can be utilized to improve the visibility
of the vessel to others.
Comparative Visibility: It is quite remark able to note that a 50-seat bus typically
has at least four side lights on one side within a span of 12 meters. In contrast, a
vessel measuring 300 to 400 meters in length has only one sidelight per side, with
a maximum of four lights visible at any given time.
Detection Challenges: For one side of a 300-meter-long vessel, it has only three
lights to be visible. This makes detection difficult, especially in congested waters
filled with numerous fishing vessels (averaging 30 meters in length) and
background lights from the shoreline.
Reflection and Lookout Duties: These extra deck lights, intended to function as
auxiliary sidelights, should not create strong reflections or hinder lookout duties on
other vessels.
Pre- sailing Checks: The decision to utilize these auxiliary lights must be made,
and the arrangement should be verified by the Chief Officer or Master before the
vessel departs.
Activation of Lights: Once the vessel is at sea, the lookout merely needs to activate
these lights, which can be easily identified by red tape markings as deck extra
lights.
Instances like the sanchi and CF Crystal highlight the consequences of neglecting this precaution.
Extra deck lights can play a crucial role in helping other vessels distinguish large ships from the
multitude of fishing boats, especially in the waters of the Far East. It is strongly recommended that
vessels operating in high collision risk areas adopt this practice.
Figure 5 - 02 details of radar setting
Radar Settings and Competence
Radar settings are a reflection of your competence in conducting an effective radar lookout. It is
essential to utilize radar in search mode consistently. When examining the left-hand side of the radar
display, several key settings are visible:
Tuning:
Definition: Tuning involves adjusting the receiver frequency to align with the frequency of the
onboard transmitter oscillator. Automatic tuning is an accept able configuration. This
adjustment is neces sary because the frequencies generated in the X-band or S-band are
not fixed. The actual frequency range used is between 8.0 and 12.0 GHz, corresponding to a
wavelength range of 3.75 to 2.5 cm. Automatic tuning circuits adjust the receiver frequency
to each transmitted pulse, effectively "chasing" the frequencies just transmitted. Replicating
this process manually for each pulse is nearly impossible.
Gain:
Configuration: The gain is set to manual, which is also an accept able configuration. In
search mode, adjusting the receiver echo strength through the gain setting is crucial and
often the only effective means of accurately distinguishing small targets from clutter.
Vigilance Required: Since the gain is set to manual, the Officer of the Watch ( OOW) must
maintain high vigilance throughout their watch to prevent the loss of target echoes. Periodic
adjustments are essential to avoid misuse of the gain setting.
Regular Adjustments: The OOW should frequently adjust the gain setting to optimize the
identification of target echoes within the clutter detected by the ownship's radar. This practice
ensures that faint or small targets are not overlooked.
Impact on Clutter and Echoes: The gain setting directly impacts the amount of sea or rain
clutter displayed on the radar screen. A higher gain value increases the strength or number
of sea/rain clutter, which can diminish the strength of target echoes. If the gain and clutter
settings are not optimally adjusted during search mode, target echoes may not appear on the
screen, leading to potential oversight.
Indicator of Competence: Losing target traces on the radar is generally indicative of
incompetence in navigational watchkeeping. However, there are instances where target echo
strength is nearly indistinguish able from that of sea or rain clutter. Proper gain adjustment
alone may not suffice; in such cases, attempting to detect small targets using two different
radar sets, as previously mentioned, can be beneficial.
Influence of Reflection Angle
The strength of target echoes is significantly affected by the reflection angle of the radar waves.
When the radar is positioned on the bow of a vessel, it can achieve a more perpendicular reflection
angle from small targets. This perpendicular incidence results in stronger reflected radar waves
compared to those from rain or sea clutter, facilitating the differentiation of small target echoes amidst
surrounding clutter.
Influence of Wavelength
The S-band radar, with a wavelength of 10 cm, generally produces stronger echo signals, making
it more suit able for detecting small targets compared to X-band radar, which has a wavelength of 3
cm. The longer wavelength of the S-band radar allows it to interact more effectively with small objects,
generating more notice able echoes on the radar screen.
In summary, understanding and correctly adjusting radar settings is crucial for effective navigation
and collision avoidance. Maintaining competence in these practices is vital for ensuring safe maritime
operations.
Training the Officer of the Watch ( OOW) in manually adjusting the radar for search purposes is
primarily the responsibility of the Master. The Chief Officer should also be equipped to fulfill this
mentoring role. Whenever the Chief Officer or Master visits the bridge, they should verify that the radar
settings are correct for junior OOWs..
Sea/Rain Clutter Setting:
Manual Adjustment: A manual sea/rain clutter setting is accept able, but it requires careful
management.
Periodic Adjustments: The sea and rain clutter settings should be adjusted regularly to
ensure they are not set too high, as excessive settings can mask the echoes of small targets.
Verification Process: Each time the radar screen indicates no clutter, the OOW should
slightly reduce the sea/rain clutter setting to permit a small amount of clutter to reappear.
This adjustment helps confirm the accuracy of the setting.
As illustrated in the radar image of the sanchi (Figure 5-02), the manual sea clutter setting was set
at 40%, which was too high. This resulted in the echo of the large vessel CF Crystal di sappearing, and
the Third Officer failed to adjust the sea clutter setting even during the emergency.
Adjusting Range Based on Target Density:
If there are numerous targets, reduce the display range to a smaller area. For instance, in Figure
5-03, the left side shows a range setting of 6 nautical miles (nm) with too many targets. In this case, the
radar range should be reduced to 3 nm (as shown on the right side). If 3 nm still displays an excessive
number of targets, further reduce it to a 1.5 nm detection range.
Analysis of Figure 5-03
On the left-hand side of Figure 5-03, the range setting of 6 nm displays an excessive number of
targets, making it challenging to determine which pose a danger. Typically, 6 nm is a common range for
junior Officers of the Watch ( OOWs) in open sea conditions.
However, if the Master observes a Third Officer (3/O) using a 3 nm range for radar lookout, they
should question the reasoning behind this choice. Several important considerations arise:
If there aren't many small targets, could the ownship be too close to the shore? Both
scenarios—an abundance of small targets or proximity to the shore—heighten the risk of
collision or grounding.
What about large targets that could potentially sink the ownship? Early warning is crucial for
these threats, which is only feasible with a long-range radar view.
Are the crew members competent enough to conduct an effective lookout and execute
collision-avoidance procedures within this limited 3 nm range for timely warnings?
While the 3/O might use the 3 nm range to positively identify small targets, this approach can
lead to overlooking large, fast-approaching vessels that quickly move beyond the 3 nm limit.
In a scenario with numerous small vessels, utilizing an additional radar set to detect ocean
going vessels would be advantageous.
This distinction is why senior and junior lookout procedures differ. The Chief Officer (C/O) will
alternate the detection range between 3 and 6 nm, while a 3/O may fixate on a single vessel,
as seen in the case of the 3/O on the sanchi, who focused solely on one target at a time.
Performance requirements for the Automatic Radar Plotting Aid ( ARPA) are often exceeded when
there are over 20 targets. It is unneces sary to track or collect data on every single target, as our short
term memory cannot manage such a large volume of information. Instead, categorize the workload into
two primary groups: large vessels on X-band radar and small fishing boats on S-band radar.
Job assignments for identifying small and large targets on the radar screen should be clearly
delineated. It is crucial not to rely blindly on past experiences in all situations. As noted in the previous
chapter, even a Master may struggle to fully master the skills required for effective radar lookout. This
seemingly minor oversight, stemming from improper radar lookout practices, can ultimately lead to a
collision incident.
Figure 5 - 04 Correct Trail setting in radar lookout
Radar Trails and Colision Avoidance
Where is the trail of the small vessel we are looking for?
In the left-hand image of Figure 5-04, the radar trails for targets were not correctly set, preventing
the Master from immediately assessing the collision risk. In contrast, Figure 2-19 displays radar echoes
with trails, facilitating better situational awareness.
Relative-Motion Trails: These trails can be quite long when there is high relative speed,
which may obscure the echoes of other targets.
True-Motion Trails: These are more advantageous when immediate information about target
movement is required.
When approaching a dense group of fishing boats, most of which are stationary, it is essential to
understand the behavior of these vessels. Fishermen, in order to avoid collisions with other boats in the
same school, typically have two options: they can either remain stationary or move in the same
direction and at the same speed as the other vessels.
In the first situation, a quick glance at the true-motion trail can significantly reduce the
perceived threat from stationary fishing vessels.
In the second situation, true-motion trails can easily help identify vessels with different
course and speed from other fishing vessels, which may indicate large ocean-going vessels.
In the 3-nm radar picture on the right, the radar trail was set to a 3-minute true motion, which is
shorter than the 6-minute true-motion setting for speed vectors.
The Master set the target trail to 3 minutes to indicate the past movement of the target,
allowing for an assessment of whether the target had changed course in the past three
minutes.
The Master utilized the acquired target true motion speed vectors (set to 6 minutes) to
determine the target's course and speed. However, for targets that had not been acquired, it
was challenging to accurately estimate their true course and speed using only the 3-minute
trail.
We recommend setting the trail length to match the time interval of the speed vectors, which in
this case should be 6 minutes. In this particular collision scenario, this seemingly minor difference in
settings was a contributing factor to the incident. The Master may have either overestimated the speed
of the two targets at the starboard bow or lacked reli able information about their speed without
displayed speed vectors, as these two targets had not been acquired.
Initially, the Master could have safely passed these two small vessels, proceeding ahead of
the towing vessel with a tow and astern of the fast-moving vessel, based on an
understanding of collision position observation.
However, because the Master did not set the target trail to match the time interval of the
speed vectors, he was un able to accurately compare the ownship's speed vector with the
target's trail (which was also set to 6 minutes) to predict their future positions relative to the
ownship when making course alteration decisions.
The notion of using the appropriate trail length setting to estimate the positions of the two
small vessels and the ownship after 6 minutes did not occur to him.
If the Master had doubts about being able to pass ahead of the tugboat with the tow using
either the radar trail or the speed vectors, he should have opted to maneuver around it
(alter course to pass behind the target), as outlined in Chapter 2.
Unfortunately, this incorrect decision led to an encounter with even more dangerous targets
on the starboard side, leaving an indelible mark on his career.
For an immediate estimation to target movement, it is advi sable to set the trail length to match the
duration of the speed vectors.
This alignment eliminates the need to double-check the trail time setting during an
emergency. With the same time setting for both speed vectors and trails, the speed
vectors of small targets can be mentally projected to match the length and direction of their
trails.
These trail settings are particularly useful when a target vessel changes course in the last
few minutes.
The ownship can determine whether the target vessel's past course has changed by
observing the shape of its trail within the designated time interval.
Since course changes of targets are not graphically indicated on the Automatic Radar
Plotting Aid ( ARPA), only the trail can effectively reveal such changes through its shape,
eliminating the need to remember the original course data.
Figure 5-03 illustrates how detection range reflects traffic density. To emphasize the importance of
radar trail settings in helping manage the workload of radar lookout, we further demonstrate the
concepts in Figure 5-04: Correct Trail Settings in Radar. The left picture shows the original setting of
the ownship, where the trail (3 minutes) is half the time length of the true-motion speed vector (6
minutes). In the right drawing, we added a 6-minute trail to help clarify the points made. The red
speed vector at the starboard bow vessel is a reflection of its blue trail behind, used to estimate the
meeting situation with the ownship.
When there are numerous small targets at sea and visual lookout has difficulty determining their
distance from the ownship, radar trails become essential. Regardless of how proficient one is at radar
setting; visual lookout always takes precedence. Radar lookout has inherent limitations due to the
equipment, even for those highly skilled in radar searching and acquisition procedures. Each time we
change vessels after a contract, our experience with radar may be challenged by new brands or
layouts. Even if you are a Chief Officer, you should ask yourself, “Can I accurately determine the
distance of a target with my unaided eyes?” If you lack confidence in your visual skills, you must take
steps to improve them now.
Radar Speed Vector Setting and Colision Risk
In this radar, a 6-minute speed vector setting in true-motion mode facilitates easier cross
referencing with the Electronic Chart Display and Information System ( ECDIS).
Collision Risk Assessment: A 6-minute speed vector setting allows for the assessment of
collision risk within a 6-minute time frame. This extended period provides a broader
perspective on the movement and potential paths of nearby vessels, en abling a more
comprehensive evaluation of risk.
Adjusting Based on Target Density: The length of the speed vector is analogous to the range
setting. When there is a high density of targets on the radar screen, it is neces sary to reduce
the time interval of the speed vector setting. Shortening it to, for example, 1.5 or 3 minutes
helps decrease the number of targets under consideration simultaneously, making it easier to
focus on the most relevant threats.
Target Scarcity Consideration: Conversely, when the number of targets is low, setting a
longer time period for the speed vector—such as 9 or 12 minutes—can be beneficial. This
longer-term view helps identify potential collision risks with vessels that might be
approaching from a distance or on trajectories that could intersect with the ownship's path in
the future.
Minimum Requirement: A 3-minute speed vector setting is regarded as the minimum
requirement for effective radar lookout. This duration provides the ownship with adequate
time to maneuver and avoid a collision. Anything less would limit the time avail able for safe
evasive actions.
The time period for speed vector settings varies depending on the situation and the skill levels of
the personnel involved. A 9- or 12-minute setting is considered appropriate for Junior Officers (JOs), as
it accommodates their slower risk recognition, provides more time for situational evaluation, and allows
additional time for the vessel to respond to their decisions. A 6-minute setting is suit able for Chief
Officers (C/Os), not neces sarily due to their greater competence, but because the coastal waters they
navigate only have this timeframe to assess and clarify collision risks. Ultimately, Masters must be able
to manage 3-minute speed vector scenarios to maintain a clearer understanding of congestion and
harbor conditions. The varying skill levels and evolving knowledge bases in these settings play a
significant role in our competence. Our upcoming chapters will further illustrate these points.
