Chapter 5 Knowledge Base for Chief Officer
### 第 5 章：大副知識庫（Chapter 5: Knowledge Base for Chief Officer）
在海上，大副正為晉升船長做準備，需要培養高超的操船技能並承擔更大的責任。作為船上的核心人物，大副被期望監督與船舶貨物和結構相關的主要安全事務。在航行安全方面，當船長疲勞或因其他原因無法履行職責時，大副即為船長的備援力量。航運公司和全體船員都極度依賴大副。不幸的是，超過 50% 的海事事故因各種原因發生在大副值班期間：
* **4-8 班（早班與晚班）：** 對於目視瞭望來說特別具有挑戰性，因為晨昏的陽光以接近水平的角度反射，直射瞭望人員的眼睛，使其難以發現潛在危險。
* **日出前的時段：** 通常是一天中最容易犯困的時間，會降低值班人員的警覺性。
* **港口周圍區域：** 經常出現繁忙的交通，船舶急於靠泊以便上午 08:00 的日班工人開始工作。此外，完成下午裝卸作業的沿海船舶也加劇了擁堵。
* **船長對大副的能力信任：** 船長信任大副安全航行和避險的能力。然而，作為船上最忙碌的人，大副可能會低估自己在值班期間的生理和心理疲勞，從而影響表現。
* **過度自信：** 對自身航行值班技能過度自信，可能導致大副忽視潛在風險或未能採取必要的預防措施。
* **分心於其他工作：** 值班的水手（AB）可能正忙於清洗駕駛台等工作，而非專注於瞭望職責，導致對周圍區域的目視監視出現盲區。
對於大副而言，期望是能夠有效處理複雜情況，例如在狹窄水道中避免多船碰撞。傳統上，大副（C/O）負責培訓實習生和初級船員（JO），使其保持對危險徵兆的警覺，並確保他們執行正確的程序來應對這些情況。駕駛台資源管理（BHRM）的這一部分提供了雷達瞭望技能，因為這些概念——儘管在 20 世紀 50 年代雷達繪圖的早期階段就被注意到——依賴於基於本船目標船「真向量」（True Speed Vector）的可行原則。這些原則受到自動雷達繪圖儀（ARPA）精確度和雷達能力的影響。雖然自動識別系統（AIS）信號可以為目標船舶提供真向量數據，但作為計算根本基礎的 GPS 位置，由於地緣政治問題引發的偽造（故意偏置輸入）而進一步受到威脅。這些也是我們在 BHRM 這部分中要解決和試圖排除的挑戰。
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#### 5-01 進入交通繁忙區域（Going into heavy traffic area）
**圖 5 - 01：紅色本船以航向（COG）100⁰、對地航速（SOG）12.7 節接近長江口燈船**
在圖 5-01 中，電子海圖（ECDIS）顯示本船位置（紅線標示）正在接近長江口燈船（L/V）。前方是一個以長江口燈船為中心的十字路口。航行值班人員（OOW）應根據良好的航海技術準備哪些常規的情境意識措施？
##### 雷達 / ARPA / AIS 設定（參照第 3 章）
使用兩台或更多不同設定的雷達。
* **X 頻段雷達設定（X - band Radar setting）：**
* 若要僅探測大型船舶，值班人員（OOW）應降低雷達的「增益」（Gain）設定，以消除螢幕上的所有小目標和海面雜波。
* 當 X 頻段雷達上不再顯示小目標的回波時，螢幕上將僅保留大型船舶的回波。
* 值班人員（OOW）可以啟動 ARPA 的「自動捕獲」（Auto Acquisition）功能來自動捕獲大型船舶目標。（請注意，與 S 頻段雷達相比，X 頻段 3 cm 雷達顯示的回波較小；因此，只有大型船舶才能產生足夠的回波強度以顯示出來。）
* **S 頻段雷達設定（S - band Radar setting）：**
* 10 cm 的 S 頻段雷達適用於探測近距離的小目標，因為它的回波比 3 cm 雷達上的大，且受雨雪雜波影響較小。
* 要消除 10 cm 雷達上的雨雪或海面雜波，值班人員（OOW）可以降低增益設定。
* 值班人員（OOW）應將探測距離縮小至 3 海里，或將雷達偏心（off-center）以提供前方 5 海里的視野。較小的量程設定會放大螢幕上的回波尺寸。
* 在調整雷達以探測本船周圍的小目標時，將目標的速度向量和尾跡（trail）設定為**相對運動**（relative motion）。小目標的相對運動線對觀察者來說更加直觀可見。
* 在相對運動模式下，本船可以透過將電子方位線（EBL）放置在目標回波上，並根據尾跡的方向檢查方位變化，從而發現來自小目標的碰撞風險。
* 這兩種方法——使用相對運動速度向量/尾跡以及 EBL 設定——可以快速確認碰撞風險，在瞭望過程中節省寶貴的時間。
除了這兩台雷達的基本設定外，大副還應採用其他瞭望方法，例如目視觀察或位於前桅的第三台雷達，以確保對所有目標進行徹底評估。如果目標船舶較多，應利用真運動速度向量（後續討論）並配合適當的培訓來釐清整體情況。
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#### 國際海上避碰規則（COLREG）第 20 條與甲板附加燈光
根據 COLREG 第 20 條，在日落至日出的時間內：
* **燈光限制：** 不得顯示其他燈光，但不會與 COLREG 指定的燈光混淆的燈光除外。這些燈光不得削弱能見度或顯著特徵，且不得干擾保持適當的瞭望。
* **允許的附加燈光：** 在遵循這些航行燈要求的的前提下，只要符合上述標準，即允許使用甲板上的附加燈光。
* **船長裁量權：** 船長應決定可使用哪些甲板燈或生活區燈光來增強船舶的目視外觀。
* **通道燈（Alleyway Lights）：** 正如第一章附錄中所提議的，可以使用甲板集裝箱或類似結構下方的通道燈，以提高其他船舶對本船的可見度。
* **可見度對比：** 值得注意的是，一輛 50 座的大巴在 12 米的長度內，單側通常至少有 4 個側燈。相比之下，長度為 300 至 400 米的船舶每側只有一個側燈，在任何給定時間最多只能看到 4 個燈光。
* **探測挑戰：** 對於一艘 300 米長的船舶單側而言，只有 3 個燈光可供識別。這使得探測變得困難，特別是在充斥著大量漁船（平均長度 30 米）和岸邊背景燈光的繁忙水域中。
* **反射與瞭望職責：** 這些旨在充當輔助側燈的甲板附加燈光，不應產生強烈的反射或妨礙其他船舶的瞭望工作。
* **航行前檢查：** 必須做出使用這些輔助燈光的決定，並在船舶啟航前由大副或船長進行檢查確認。
* **燈光啟動：** 船舶一旦出海，瞭望人員只需啟動這些燈光即可，這些燈光可以透過紅膠帶標記輕鬆識別為甲板附加燈光。
像「桑吉號」（Sanchi）和「水晶油輪」（CF Crystal）這樣的案例突顯了忽視這項預防措施的後果。甲板附加燈光可以發揮關鍵作用，幫助其他船舶將大型船舶與大量漁船區分開來，特別是在遠東水域。強烈建議在碰撞風險高的水域航行的船舶採取此做法。
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#### 圖 5 - 02 雷達設定細節
##### 雷達設定與專業能力
雷達設定反映了你進行有效雷達瞭望的能力。堅持在搜尋模式下使用雷達至關重要。檢查雷達顯示螢幕左側時，可以看到幾個關鍵設定：
* **調諧（Tuning）：**
* **定義：** 調諧涉及調整接收機頻率，使其與船上發射機振盪器的頻率一致。自動調諧（Automatic tuning）是可接受的配置。這種調整是必要的，因為 X 頻段或 S 頻段產生的頻率並非固定不變。實際使用的頻率範圍在 8.0 到 12.0 GHz 之間，對應的波長範圍為 3.75 到 2.5 cm。自動調諧電路會針對每個發射脈衝調整接收機頻率，實際上是在「追逐」剛剛發射的頻率。手動為每個脈衝重複此過程幾乎是不可能的。
* **增益（Gain）：**
* **配置：** 增益設定為手動，這也是可接受的配置。在搜尋模式下，透過增益設定調整接收機回波強度至關重要，且往往是準確將小目標與雜波區分開來的唯一有效手段。
* **需要保持警惕：** 由於增益設定為手動，航行值班人員（OOW）必須在整個值班期間保持高度警惕，以防止丟失目標回波。定期調整對於避免錯誤使用增益設定至關重要。
* **定期調整：** 值班人員（OOW）應經常調整增益設定，以優化在本船雷達探測到的雜波中對目標回波的識別。這種做法可確保微弱或微小的目標不會被忽視。
* **對雜波和回波的影響：** 增益設定直接影響雷達螢幕上顯示的海面或雨雪雜波量。較高的增益值會增加海面/雨雪雜波的強度或數量，從而削弱目標回波的強度。如果在搜尋模式下未優化調整增益和雜波設定，目標回波可能不會出現在螢幕上，從而導致潛在的疏忽。
* **能力的體現：** 在雷達上丟失目標軌跡通常表明航行值班能力不足。然而，在某些情況下，目標回波強度與海面或雨雪雜波幾乎無法區分。僅靠適當的增益調整可能還不夠；在這種情況下，如前所述，嘗試使用兩台不同的雷達來探測小目標可能會有所幫助。
##### 反射角的影響
目標回波的強度受雷達波反射角的顯著影響。當雷達安裝在船艏時，它可以從小目標獲得更垂直的反射角。與雨雪或海面雜波相比，這種垂直入射會產生更強的雷達波反射，從而有助於在周圍雜波中區分小目標回波。
##### 波長的影響
波長為 10 cm 的 S 頻段雷達通常會產生更強的回波信號，與波長為 3 cm 的 X 頻段雷達相比，它更適合探測小目標。S 頻段雷達較長的波長使其能夠更有效地與小物體相互作用，在雷達螢幕上產生更明顯的回波。
總之，理解並正確調整雷達設定對於有效航行和避碰至關重要。保持這些操作的專業能力對於確保海上作業安全至關重要。
培訓航行值班人員（OOW）手動調整雷達以進行搜尋主要是船長的責任。大副也應具備履行此指導角色的能力。每當大副或船長進入駕駛台時，都應核實初級值班人員的雷達設定是否正確。
* **海面 / 雨雪雜波設定（Sea/Rain Clutter Setting）：**
* **手動調整：** 手動海面/雨雪雜波設定是可以接受的，但需要精心管理。
* **定期調整：** 應定期調整海面和雨雪雜波設定，以確保不會設定得過高，因為過高的設定會遮蔽小目標的回波。
* **驗證過程：** 每當雷達螢幕顯示沒有雜波時，值班人員（OOW）應稍微降低海面/雨雪雜波設定，以允許少量雜波重新出現。這種調整有助於確認設定的準確性。
正如桑吉號（Sanchi）的雷達圖像（圖 5-02）所示，手動海波設定為 40%，這太高了。這導致大型船舶「水晶油輪」（CF Crystal）的回波消失，而三副甚至在緊急情況下也未能調整海波抑制設定。
在海上，大副正為晉升船長做準備，需要培養高超的操船技能並承擔更大的責任。作為船上的核心人物，大副被期望監督與船舶貨物和結構相關的主要安全事務。在航行安全方面，當船長疲勞或因其他原因無法履行職責時，大副即為船長的備援力量。航運公司和全體船員都極度依賴大副。不幸的是，超過 50% 的海事事故因各種原因發生在大副值班期間：
* **4-8 班（早班與晚班）：** 對於目視瞭望來說特別具有挑戰性，因為晨昏的陽光以接近水平的角度反射，直射瞭望人員的眼睛，使其難以發現潛在危險。
* **日出前的時段：** 通常是一天中最容易犯困的時間，會降低值班人員的警覺性。
* **港口周圍區域：** 經常出現繁忙的交通，船舶急於靠泊以便上午 08:00 的日班工人開始工作。此外，完成下午裝卸作業的沿海船舶也加劇了擁堵。
* **船長對大副的能力信任：** 船長信任大副安全航行和避險的能力。然而，作為船上最忙碌的人，大副可能會低估自己在值班期間的生理和心理疲勞，從而影響表現。
* **過度自信：** 對自身航行值班技能過度自信，可能導致大副忽視潛在風險或未能採取必要的預防措施。
* **分心於其他工作：** 值班的水手（AB）可能正忙於清洗駕駛台等工作，而非專注於瞭望職責，導致對周圍區域的目視監視出現盲區。
對於大副而言，期望是能夠有效處理複雜情況，例如在狹窄水道中避免多船碰撞。傳統上，大副（C/O）負責培訓實習生和初級船員（JO），使其保持對危險徵兆的警覺，並確保他們執行正確的程序來應對這些情況。駕駛台資源管理（BHRM）的這一部分提供了雷達瞭望技能，因為這些概念——儘管在 20 世紀 50 年代雷達繪圖的早期階段就被注意到——依賴於基於本船目標船「真向量」（True Speed Vector）的可行原則。這些原則受到自動雷達繪圖儀（ARPA）精確度和雷達能力的影響。雖然自動識別系統（AIS）信號可以為目標船舶提供真向量數據，但作為計算根本基礎的 GPS 位置，由於地緣政治問題引發的偽造（故意偏置輸入）而進一步受到威脅。這些也是我們在 BHRM 這部分中要解決和試圖排除的挑戰。
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#### 5-01 進入交通繁忙區域（Going into heavy traffic area）
**圖 5 - 01：紅色本船以航向（COG）100⁰、對地航速（SOG）12.7 節接近長江口燈船**
在圖 5-01 中，電子海圖（ECDIS）顯示本船位置（紅線標示）正在接近長江口燈船（L/V）。前方是一個以長江口燈船為中心的十字路口。航行值班人員（OOW）應根據良好的航海技術準備哪些常規的情境意識措施？
##### 雷達 / ARPA / AIS 設定（參照第 3 章）
使用兩台或更多不同設定的雷達。
* **X 頻段雷達設定（X - band Radar setting）：**
* 若要僅探測大型船舶，值班人員（OOW）應降低雷達的「增益」（Gain）設定，以消除螢幕上的所有小目標和海面雜波。
* 當 X 頻段雷達上不再顯示小目標的回波時，螢幕上將僅保留大型船舶的回波。
* 值班人員（OOW）可以啟動 ARPA 的「自動捕獲」（Auto Acquisition）功能來自動捕獲大型船舶目標。（請注意，與 S 頻段雷達相比，X 頻段 3 cm 雷達顯示的回波較小；因此，只有大型船舶才能產生足夠的回波強度以顯示出來。）
* **S 頻段雷達設定（S - band Radar setting）：**
* 10 cm 的 S 頻段雷達適用於探測近距離的小目標，因為它的回波比 3 cm 雷達上的大，且受雨雪雜波影響較小。
* 要消除 10 cm 雷達上的雨雪或海面雜波，值班人員（OOW）可以降低增益設定。
* 值班人員（OOW）應將探測距離縮小至 3 海里，或將雷達偏心（off-center）以提供前方 5 海里的視野。較小的量程設定會放大螢幕上的回波尺寸。
* 在調整雷達以探測本船周圍的小目標時，將目標的速度向量和尾跡（trail）設定為**相對運動**（relative motion）。小目標的相對運動線對觀察者來說更加直觀可見。
* 在相對運動模式下，本船可以透過將電子方位線（EBL）放置在目標回波上，並根據尾跡的方向檢查方位變化，從而發現來自小目標的碰撞風險。
* 這兩種方法——使用相對運動速度向量/尾跡以及 EBL 設定——可以快速確認碰撞風險，在瞭望過程中節省寶貴的時間。
除了這兩台雷達的基本設定外，大副還應採用其他瞭望方法，例如目視觀察或位於前桅的第三台雷達，以確保對所有目標進行徹底評估。如果目標船舶較多，應利用真運動速度向量（後續討論）並配合適當的培訓來釐清整體情況。
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#### 國際海上避碰規則（COLREG）第 20 條與甲板附加燈光
根據 COLREG 第 20 條，在日落至日出的時間內：
* **燈光限制：** 不得顯示其他燈光，但不會與 COLREG 指定的燈光混淆的燈光除外。這些燈光不得削弱能見度或顯著特徵，且不得干擾保持適當的瞭望。
* **允許的附加燈光：** 在遵循這些航行燈要求的的前提下，只要符合上述標準，即允許使用甲板上的附加燈光。
* **船長裁量權：** 船長應決定可使用哪些甲板燈或生活區燈光來增強船舶的目視外觀。
* **通道燈（Alleyway Lights）：** 正如第一章附錄中所提議的，可以使用甲板集裝箱或類似結構下方的通道燈，以提高其他船舶對本船的可見度。
* **可見度對比：** 值得注意的是，一輛 50 座的大巴在 12 米的長度內，單側通常至少有 4 個側燈。相比之下，長度為 300 至 400 米的船舶每側只有一個側燈，在任何給定時間最多只能看到 4 個燈光。
* **探測挑戰：** 對於一艘 300 米長的船舶單側而言，只有 3 個燈光可供識別。這使得探測變得困難，特別是在充斥著大量漁船（平均長度 30 米）和岸邊背景燈光的繁忙水域中。
* **反射與瞭望職責：** 這些旨在充當輔助側燈的甲板附加燈光，不應產生強烈的反射或妨礙其他船舶的瞭望工作。
* **航行前檢查：** 必須做出使用這些輔助燈光的決定，並在船舶啟航前由大副或船長進行檢查確認。
* **燈光啟動：** 船舶一旦出海，瞭望人員只需啟動這些燈光即可，這些燈光可以透過紅膠帶標記輕鬆識別為甲板附加燈光。
像「桑吉號」（Sanchi）和「水晶油輪」（CF Crystal）這樣的案例突顯了忽視這項預防措施的後果。甲板附加燈光可以發揮關鍵作用，幫助其他船舶將大型船舶與大量漁船區分開來，特別是在遠東水域。強烈建議在碰撞風險高的水域航行的船舶採取此做法。
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#### 圖 5 - 02 雷達設定細節
##### 雷達設定與專業能力
雷達設定反映了你進行有效雷達瞭望的能力。堅持在搜尋模式下使用雷達至關重要。檢查雷達顯示螢幕左側時，可以看到幾個關鍵設定：
* **調諧（Tuning）：**
* **定義：** 調諧涉及調整接收機頻率，使其與船上發射機振盪器的頻率一致。自動調諧（Automatic tuning）是可接受的配置。這種調整是必要的，因為 X 頻段或 S 頻段產生的頻率並非固定不變。實際使用的頻率範圍在 8.0 到 12.0 GHz 之間，對應的波長範圍為 3.75 到 2.5 cm。自動調諧電路會針對每個發射脈衝調整接收機頻率，實際上是在「追逐」剛剛發射的頻率。手動為每個脈衝重複此過程幾乎是不可能的。
* **增益（Gain）：**
* **配置：** 增益設定為手動，這也是可接受的配置。在搜尋模式下，透過增益設定調整接收機回波強度至關重要，且往往是準確將小目標與雜波區分開來的唯一有效手段。
* **需要保持警惕：** 由於增益設定為手動，航行值班人員（OOW）必須在整個值班期間保持高度警惕，以防止丟失目標回波。定期調整對於避免錯誤使用增益設定至關重要。
* **定期調整：** 值班人員（OOW）應經常調整增益設定，以優化在本船雷達探測到的雜波中對目標回波的識別。這種做法可確保微弱或微小的目標不會被忽視。
* **對雜波和回波的影響：** 增益設定直接影響雷達螢幕上顯示的海面或雨雪雜波量。較高的增益值會增加海面/雨雪雜波的強度或數量，從而削弱目標回波的強度。如果在搜尋模式下未優化調整增益和雜波設定，目標回波可能不會出現在螢幕上，從而導致潛在的疏忽。
* **能力的體現：** 在雷達上丟失目標軌跡通常表明航行值班能力不足。然而，在某些情況下，目標回波強度與海面或雨雪雜波幾乎無法區分。僅靠適當的增益調整可能還不夠；在這種情況下，如前所述，嘗試使用兩台不同的雷達來探測小目標可能會有所幫助。
##### 反射角的影響
目標回波的強度受雷達波反射角的顯著影響。當雷達安裝在船艏時，它可以從小目標獲得更垂直的反射角。與雨雪或海面雜波相比，這種垂直入射會產生更強的雷達波反射，從而有助於在周圍雜波中區分小目標回波。
##### 波長的影響
波長為 10 cm 的 S 頻段雷達通常會產生更強的回波信號，與波長為 3 cm 的 X 頻段雷達相比，它更適合探測小目標。S 頻段雷達較長的波長使其能夠更有效地與小物體相互作用，在雷達螢幕上產生更明顯的回波。
總之，理解並正確調整雷達設定對於有效航行和避碰至關重要。保持這些操作的專業能力對於確保海上作業安全至關重要。
培訓航行值班人員（OOW）手動調整雷達以進行搜尋主要是船長的責任。大副也應具備履行此指導角色的能力。每當大副或船長進入駕駛台時，都應核實初級值班人員的雷達設定是否正確。
* **海面 / 雨雪雜波設定（Sea/Rain Clutter Setting）：**
* **手動調整：** 手動海面/雨雪雜波設定是可以接受的，但需要精心管理。
* **定期調整：** 應定期調整海面和雨雪雜波設定，以確保不會設定得過高，因為過高的設定會遮蔽小目標的回波。
* **驗證過程：** 每當雷達螢幕顯示沒有雜波時，值班人員（OOW）應稍微降低海面/雨雪雜波設定，以允許少量雜波重新出現。這種調整有助於確認設定的準確性。
正如桑吉號（Sanchi）的雷達圖像（圖 5-02）所示，手動海波設定為 40%，這太高了。這導致大型船舶「水晶油輪」（CF Crystal）的回波消失，而三副甚至在緊急情況下也未能調整海波抑制設定。
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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.
