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Chapter 6 Situational Awareness for Chief Officer
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### 第六章 船长/一副之情境意识 (Situational Awareness for Chief Officer)
#### 第一部分：多佛尔海峡 TSS 多目标碰撞预防准备 (Dover Strait TSS multiple target collision preparedness)
**1999 年货柜船与邮轮碰撞事件的迷思 (The Myth of the Container Ship Collision with a Cruiser, 1999)**
##### 碰撞发生与最初的求救呼叫
1999 年 8 月 24 日当地时间约 00:55，多佛尔海峡发生了一起涉及一艘货柜船与一艘邮轮的碰撞事故。就在碰撞发生前不久（00:54:37），多佛尔海岸警卫队在 VHF 频道 16 录到一段紧急且未表明身分的通话发声：「Starboard, starboard, starboard (右满舵、右满舵、右满舵)」。这声极度慌张的呼叫极可能来自其中一艘船上的工作人员，企图做最后的挣扎以避免灾难发生。
##### 历史与技术背景
此事故发生於约 26 年前（以 2025 年为基准），正值航海技术变革的关键时期。当时，许多新兴技术尚未普及：
* 差分全球定位系统（DGPS）仍处於早期应用阶段，尚未在各类船舶上广泛装设。
* 航行资料记录器（VDR，即黑盒子）尚未问世，无法记录关键数据以供事后分析。
* 自动雷达测绘板（ARPA）系统大约在 1997 年才开始逐渐普及。
当时的航海业正处於过渡期：从传统的目视了望方法（旧一代航海员所坚持的原则），转型为使用更先进的 ARPA 系统。尽管技术在演进，ARPA 的性能标准仍紧密结合相对运动速度向量的原则，强调追踪目标时对於本船相对精准度与可靠性的要求。
##### 相关的 IMO ARPA 性能标准
国际海事组织（IMO）於 1995 年 11 月 23 日通过的第 A.823(19) 号决议案是一项重要的参考依据。该决议详细规定了「自动雷达测绘板（ARPA）性能标准」，以确保这些系统能提供及时且精确的数据来支援安全航行。具体如下：
| 数据情境 | 相对航向 (度) | 相对速度 (节) | 最近碰撞点距离 CPA (海里) | 到达最近碰撞点时间 TCPA (分) | 真航向 (度) | 真速度 (节) |
| --- | --- | --- | --- | --- | --- | --- |
| **1** | 3.0 | 0.8 | 0.5 | 1.0 | 7.4 | 1.2 |
| **2** | 2.3 | 0.3-- | 2.8 | 0.8 | — | — |
| **3** | 4.4 | 0.9 | 0.7 | 1.0 | 3.3 | 1.0 |
| **4** | 4.6 | 0.8 | 0.7 | 1.0 | 2.6 | 1.2 |
* **第 3.8.3 条**：ARPA 应在稳定追踪目标的三分钟内，呈现该目标的运动数据，并符合以下精准度要求（95% 概率值）：
* **相对航向**：±3° 或更佳。
* **相对速度**：±0.5 节或更佳。
* **最近碰撞点距离 (CPA)**：±0.3 海里或更佳。
* **到达最近碰撞点时间 (TCPA)**：±0.5 分钟或更佳。
*(注：原始决议中的具体精准度指标可能包含更多细节；完整参考资料请查阅 IMO 官方文件。)*
##### ARPA 性能标准 (IMO Resolution A.823(19))
IMO 第 A.823(19) 号决议第 3.8.3 条指出：「ARPA 应在稳定追踪目标的三分钟内，呈现该目标的运动数据，并符合规定的精准度要求（95% 概率值）。」
该决议包含一份表格，根据目标与本船速度等因素，概述了四种不同情境下的精准度要求：
在相关情境下，前提是必须对目标进行至少三分钟的稳定追踪，可接受的最近碰撞点距离（CPA）精准度值（95% 概率）高达 0.7 海里。若追踪时间少於三分钟，ARPA 数据可能会不可靠，应谨慎处理。使用这些数据取决於值班航行员（OOW）的裁量，并伴随潜在风险。从历史上看，值班航行员有时会忽视 ARPA 性能标准，未能仔细审查数据中的重大误差——这与过去在近距离内忽略雷达回波的情况十分相似。
##### 重新审视 1999 年碰撞事故调查
客轮「挪威之梦号 (Norwegian Dream)」与货柜船「长彩轮 (Ever Decent)」於 1999 年 8 月 24 日 00:55 在多佛尔海峡接近段发生碰撞。该调查报告发布於 26 年多以前，如今已略显过时，其结论值得结合后续的技术进步进行重新审视。
自那时以来，海上了望流程发生了重大变化，从依赖自动雷达测绘板（ARPA）系统转变为自动识别系统（AIS）。现在 ARPA 和 AIS 的输入参数精准得多，特别是在 AIS 中整合了全球定位系统（GPS）数据后——手动输入航向和航速已不再是标准或可接受的做法。一项关键改进是使用对地航速（SOG），它考量了水流和风等外部因素。25 年多以前，不建议将 SOG 用於 ARPA 输入，因为当时它依赖对船舶过去位置的估算，往往不精确。相比之下，现代的差分 GPS（DGPS）机能提供高精度的 SOG，位置误差通常仅为 5 到 10 公尺——即使对於靠泊等精细操作也绰绰有余。
如今，在使用可携式引水终端（PPU）进行靠泊或避碰时，讨论很少再强调对水航速（SOW），因为来自卫星系统的 SOG 已成为可靠的标准。
##### 重新审视调查报告建议
以下各节将简要回顾 2000 年针对 1999 年「挪威之梦号」与「长彩轮」碰撞事故调查报告中的核心建议。针对每项建议，将先提供原始摘要，随后给出更新后的建议，该更新考量了过去 25 年以上的技术与程序进展，包括 GPS 整合的改进及驾驶台资源管理（BRM）实务。
###### 给所有船东 (To All Shipowners)
* **关於雷达使用的原始建议：**
当使用一台以上的雷达/自动雷达测绘板（ARPA）时，应仅在一台雷达上进行防碰撞绘算。
* **更新建议：** 利用两台雷达的优势互补：一台 10 公分（S 频段）雷达用於在相对运动余辉（trails）模式下追踪小型目标；一台 3 公分（X 频段）雷达设置於 ARPA 自动捕捉模式，用於快速参考大型船舶。仅依赖单一了望方法是不够的；值班航行员（OOW）应始终保持对小型目标的目视了望，若条件允许，应使用第三台雷达或系统来监控较大的船舶。
* **关於速度向量的原始建议：**
若要使用 ARPA 向量判定碰撞风险，应仅使用相对向量；真向量则应用於评估态势（Aspect）。
* **更新建议：** 对於小型目标，使用相对运动模式下 10 公分雷达上的相对向量。对於 3 公分雷达上的较大目标，采用真运动模式下的真向量来评估态势与整体交通动态。
* **关於速度输入的原始建议：**
应提醒所有驾驶台值班人员，雷达/ARPA 上防碰撞绘算的速度输入必须始终是对水航速（SOW），而非对地航速（SOG）。
* **更新建议：** 为 ARPA 采用来自差分全球定位系统（DGPS）的自动速度输入，因为它能提供精确的对地航速（SOG）数据，这在现代系统中比手动或以水为基准的输入更受青睐。
###### 给邮轮公司 (To Cruise Lines)
* **关於雷达了望的原始建议：**
碰撞发生时邮轮的值班航行员（OOW）应接受进一步的雷达使用培训。邮轮公司应确保尽快完成此项培训，并确保其船队内的其他驾驶台值班人员完全熟悉他们需要操作的驾驶台设备。
* **更新建议：** 所有值班航行员（OOW）均应研读相关海事资源（例如本书或同等指南），并接受雷达与电子航海的针对性培训。传统的培训课程可能无法充分涵盖先进的雷达了望知识。
* **关於驾驶台人力配置（Bridge Manning）的原始建议：**
邮轮船长应根据公司程序手册制定更明确的「船长常规命令（Standing Orders）」，以明确值班航行员（OOW）何时应呼叫驾驶台支援。邮轮公司应确保为其所有船舶制定令人满意的船长命令。
* **更新建议：** 应评估船员的胜任能力水平，而非仅仅评估 OOW 的人数，并针对不同风险区域（如高交通流量区）的特定需求进行调整。提供详细的能力要求和指南，而非仅依赖通用的常规命令。
---
### 第六章 船长/一副之情境意识 (Situational Awareness for Chief Officer)
#### 第一部分：多佛尔海峡 TSS 多目标碰撞预防准备 (Dover Strait TSS multiple target collision preparedness)
**1999 年货柜船与邮轮碰撞事件的迷思 (The Myth of the Container Ship Collision with a Cruiser, 1999)**
##### 碰撞发生与最初的求救呼叫
1999 年 8 月 24 日当地时间约 00:55，多佛尔海峡发生了一起涉及一艘货柜船与一艘邮轮的碰撞事故。就在碰撞发生前不久（00:54:37），多佛尔海岸警卫队在 VHF 频道 16 录到一段紧急且未表明身分的通话发声：「Starboard, starboard, starboard (右满舵、右满舵、右满舵)」。这声极度慌张的呼叫极可能来自其中一艘船上的工作人员，企图做最后的挣扎以避免灾难发生。
##### 历史与技术背景
此事故发生於约 26 年前（以 2025 年为基准），正值航海技术变革的关键时期。当时，许多新兴技术尚未普及：
* 差分全球定位系统（DGPS）仍处於早期应用阶段，尚未在各类船舶上广泛装设。
* 航行资料记录器（VDR，即黑盒子）尚未问世，无法记录关键数据以供事后分析。
* 自动雷达测绘板（ARPA）系统大约在 1997 年才开始逐渐普及。
当时的航海业正处於过渡期：从传统的目视了望方法（旧一代航海员所坚持的原则），转型为使用更先进的 ARPA 系统。尽管技术在演进，ARPA 的性能标准仍紧密结合相对运动速度向量的原则，强调追踪目标时对於本船相对精准度与可靠性的要求。
##### 相关的 IMO ARPA 性能标准
国际海事组织（IMO）於 1995 年 11 月 23 日通过的第 A.823(19) 号决议案是一项重要的参考依据。该决议详细规定了「自动雷达测绘板（ARPA）性能标准」，以确保这些系统能提供及时且精确的数据来支援安全航行。具体如下：
| 数据情境 | 相对航向 (度) | 相对速度 (节) | 最近碰撞点距离 CPA (海里) | 到达最近碰撞点时间 TCPA (分) | 真航向 (度) | 真速度 (节) |
| --- | --- | --- | --- | --- | --- | --- |
| **1** | 3.0 | 0.8 | 0.5 | 1.0 | 7.4 | 1.2 |
| **2** | 2.3 | 0.3-- | 2.8 | 0.8 | — | — |
| **3** | 4.4 | 0.9 | 0.7 | 1.0 | 3.3 | 1.0 |
| **4** | 4.6 | 0.8 | 0.7 | 1.0 | 2.6 | 1.2 |
* **第 3.8.3 条**：ARPA 应在稳定追踪目标的三分钟内，呈现该目标的运动数据，并符合以下精准度要求（95% 概率值）：
* **相对航向**：±3° 或更佳。
* **相对速度**：±0.5 节或更佳。
* **最近碰撞点距离 (CPA)**：±0.3 海里或更佳。
* **到达最近碰撞点时间 (TCPA)**：±0.5 分钟或更佳。
*(注：原始决议中的具体精准度指标可能包含更多细节；完整参考资料请查阅 IMO 官方文件。)*
##### ARPA 性能标准 (IMO Resolution A.823(19))
IMO 第 A.823(19) 号决议第 3.8.3 条指出：「ARPA 应在稳定追踪目标的三分钟内，呈现该目标的运动数据，并符合规定的精准度要求（95% 概率值）。」
该决议包含一份表格，根据目标与本船速度等因素，概述了四种不同情境下的精准度要求：
在相关情境下，前提是必须对目标进行至少三分钟的稳定追踪，可接受的最近碰撞点距离（CPA）精准度值（95% 概率）高达 0.7 海里。若追踪时间少於三分钟，ARPA 数据可能会不可靠，应谨慎处理。使用这些数据取决於值班航行员（OOW）的裁量，并伴随潜在风险。从历史上看，值班航行员有时会忽视 ARPA 性能标准，未能仔细审查数据中的重大误差——这与过去在近距离内忽略雷达回波的情况十分相似。
##### 重新审视 1999 年碰撞事故调查
客轮「挪威之梦号 (Norwegian Dream)」与货柜船「长彩轮 (Ever Decent)」於 1999 年 8 月 24 日 00:55 在多佛尔海峡接近段发生碰撞。该调查报告发布於 26 年多以前，如今已略显过时，其结论值得结合后续的技术进步进行重新审视。
自那时以来，海上了望流程发生了重大变化，从依赖自动雷达测绘板（ARPA）系统转变为自动识别系统（AIS）。现在 ARPA 和 AIS 的输入参数精准得多，特别是在 AIS 中整合了全球定位系统（GPS）数据后——手动输入航向和航速已不再是标准或可接受的做法。一项关键改进是使用对地航速（SOG），它考量了水流和风等外部因素。25 年多以前，不建议将 SOG 用於 ARPA 输入，因为当时它依赖对船舶过去位置的估算，往往不精确。相比之下，现代的差分 GPS（DGPS）机能提供高精度的 SOG，位置误差通常仅为 5 到 10 公尺——即使对於靠泊等精细操作也绰绰有余。
如今，在使用可携式引水终端（PPU）进行靠泊或避碰时，讨论很少再强调对水航速（SOW），因为来自卫星系统的 SOG 已成为可靠的标准。
##### 重新审视调查报告建议
以下各节将简要回顾 2000 年针对 1999 年「挪威之梦号」与「长彩轮」碰撞事故调查报告中的核心建议。针对每项建议，将先提供原始摘要，随后给出更新后的建议，该更新考量了过去 25 年以上的技术与程序进展，包括 GPS 整合的改进及驾驶台资源管理（BRM）实务。
###### 给所有船东 (To All Shipowners)
* **关於雷达使用的原始建议：**
当使用一台以上的雷达/自动雷达测绘板（ARPA）时，应仅在一台雷达上进行防碰撞绘算。
* **更新建议：** 利用两台雷达的优势互补：一台 10 公分（S 频段）雷达用於在相对运动余辉（trails）模式下追踪小型目标；一台 3 公分（X 频段）雷达设置於 ARPA 自动捕捉模式，用於快速参考大型船舶。仅依赖单一了望方法是不够的；值班航行员（OOW）应始终保持对小型目标的目视了望，若条件允许，应使用第三台雷达或系统来监控较大的船舶。
* **关於速度向量的原始建议：**
若要使用 ARPA 向量判定碰撞风险，应仅使用相对向量；真向量则应用於评估态势（Aspect）。
* **更新建议：** 对於小型目标，使用相对运动模式下 10 公分雷达上的相对向量。对於 3 公分雷达上的较大目标，采用真运动模式下的真向量来评估态势与整体交通动态。
* **关於速度输入的原始建议：**
应提醒所有驾驶台值班人员，雷达/ARPA 上防碰撞绘算的速度输入必须始终是对水航速（SOW），而非对地航速（SOG）。
* **更新建议：** 为 ARPA 采用来自差分全球定位系统（DGPS）的自动速度输入，因为它能提供精确的对地航速（SOG）数据，这在现代系统中比手动或以水为基准的输入更受青睐。
###### 给邮轮公司 (To Cruise Lines)
* **关於雷达了望的原始建议：**
碰撞发生时邮轮的值班航行员（OOW）应接受进一步的雷达使用培训。邮轮公司应确保尽快完成此项培训，并确保其船队内的其他驾驶台值班人员完全熟悉他们需要操作的驾驶台设备。
* **更新建议：** 所有值班航行员（OOW）均应研读相关海事资源（例如本书或同等指南），并接受雷达与电子航海的针对性培训。传统的培训课程可能无法充分涵盖先进的雷达了望知识。
* **关於驾驶台人力配置（Bridge Manning）的原始建议：**
邮轮船长应根据公司程序手册制定更明确的「船长常规命令（Standing Orders）」，以明确值班航行员（OOW）何时应呼叫驾驶台支援。邮轮公司应确保为其所有船舶制定令人满意的船长命令。
* **更新建议：** 应评估船员的胜任能力水平，而非仅仅评估 OOW 的人数，并针对不同风险区域（如高交通流量区）的特定需求进行调整。提供详细的能力要求和指南，而非仅依赖通用的常规命令。
售价 NT$ 1
Chapter 6- Situational Awareness for Chief Officer
Part one: Dover Strait TSS multiple target collision preparedness
The Myth of the Container Ship Collision with a Cruiser, 1999
####### The Collision and Initial Distress Call
On August 24, 1999, at approximately 00:55 local time, a collision occurred in the Dover Strait,
involving a container ship and a cruiser. Just moments before, at 00:54:37, the Dover Coastguard
recorded an urgent, unidentified transmission on VHF Channel 16: "Starboard, starboard, starboard."
This frantic call likely came from personnel on one of the vessels, a desperate attempt to avert disaster.
Historical and Technological Context
This incident unfolded roughly 26 years ago (as of 2025), during a pivotal period in maritime
navigation. At that time, emerging technologies were not yet prevalent:
The Differential Global Positioning System (DGPS) was still in its early adoption phase and
not widely implemented on vessels.
Voyage Data Recorders (VDRs), which capture critical ship data for post-incident analysis,
were not yet available.
Automatic Radar Plotting Aid (ARPA) systems had only begun to gain traction around 1997.
The maritime industry was in the midst of transitioning from traditional visual lookout methods—
principles upheld by older generations of seafarers—to more advanced ARPA-based systems. Despite
this evolution, the performance standards for ARPAwere closely aligned with the principles of relative
motion speed vector, emphasizing the need for reliability and accuracy in tracking targets relative to the
vessel.
Relevant IMO Standards for ARPA
A significant reference point is the International Maritime Organization (IMO) Resolution A.823(19),
adopted on November 23, 1995. This resolution detailed the "Performance Standards for Automatic
Radar Plotting Aids (ARPAs)," ensuring that these systems could deliver timely and precise data to
support safe navigation. Specifically:
Data
Scenario
Relative
course
(degrees)
Relative
speed
(knots)
CPA
(nautical
miles)
TCPA
(min)
True course
(degrees)
True
speed
(knots)
1 3.0 0.8 0.5 1.0 7.4 1.2
2 2.3 0.3-- 2.8 0.8
3 4.4 0.9 0.7 1.0 3.3 1.0
4 4.6 0.8 0.7 1.0 2.6 1.2
Section 3.8.3: An ARPAshould present, within three minutes of steady-state tracking, the motion of
a target with the following accuracy values (95% probability values):
Relative course: ±3° or better.
Relative speed: ±0.5 knots or better.
Closest Point of Approach (CPA): ±0.3 nautical miles or better.
Time to Closest Point of Approach (TCPA): ±0.5 minutes or better.
(Note: The exact accuracy metrics in the original resolution may include additional details; for a
complete reference, consult the official IMO documentation.)
ARPAPerformance Standards (IMO Resolution A.823(19))
Section 3.8.3 of IMO Resolution A.823(19) states: "An ARPAshould present within three minutes of
steady-state tracking the motion of a target with the following accuracy values (95% probability
values)."
The resolution includes a table outlining accuracy requirements across four scenarios, based on
factors such as target and own-ship speeds:
The acceptable Closest Point of Approach (CPA) accuracy value (95% probability) is up to 0.7
nautical miles in relevant scenarios, assuming at least three minutes of steady-state target tracking. If
the tracking time is less than three minutes, ARPAdata may be unreliable and should be treated with
caution. The use of this data falls under the Officer of the Watch's (OOW) discretion and involves
inherent risks. Historically, OOWs have sometimes overlooked ARPAperformance standards, failing to
scrutinize significant errors in data—similar to how radar echoes were often disregarded at close
range.
Re-Examining the 1999 Collision Investigation
The collision between the passenger vessel Norwegian Dream and the container ship Ever Decent
occurred in the approaches to the Dover Strait at 00:55 on August 24, 1999. The investigation report,
issued over 26 years ago, is now somewhat outdated, and its conclusions merit re-examination in light
of subsequent technological advancements.
Since that time, maritime lookout processes have evolved significantly, shifting from reliance on
Automatic Radar Plotting Aid (ARPA) systems to the Automatic Identification System (AIS). The input
parameters for ARPAand AISare now far more accurate, particularly with the integration of Global
Positioning System (GPS) data in AIS—manual entry of course and speed is no longer standard or
acceptable practice. A key improvement is the use of Speed Over Ground (SOG), which accounts for
external factors such as currents and wind. Over 25 years ago, SOG was not recommended for
ARPAinputs, as it relied on estimates from past ship positions, often imprecise. In contrast, modern
Differential GPS (DGPS) provides SOG with high accuracy, typically featuring position errors of only 5
to 10 meters—adequate even for precise operations like berthing.
Today, discussions seldom emphasize Speed Over Water (SOW) when utilizing tools like Portable
Pilot Units (PPUs) for docking or collision avoidance, as SOG from satellite-based systems has
become the reliable standard.
Review of Report Recommendations
The following sections will briefly review the key recommendations from the 2000 investigation
report into the 1999 collision between the Norwegian Dream and Ever Decent. For each
recommendation, the original summary will be provided, followed by an updated recommendation that
considers technological and procedural advancements over the past 25+ years, including
improvements in GPS integration and bridge resource management practices.
To All Shipowners
Original Recommendation on radar usage:
When using more than one radar/Automatic Radar Plotting Aid (ARPA), an anti-collision plot
should be maintained on only one.
Updated Recommendation: Utilize two radars to leverage their complementary strengths: a 10-cm
(S-band) radar for tracking small targets in relative motion trails mode, and a 3-cm (X-band) radar in
ARPAauto-acquisition mode for quick reference of larger vessels. Relying solely on one lookout
method is insufficient; the Officer of the Watch (OOW) should always include visual lookout for small
targets and, if available, a third radar or system for monitoring larger vessels.
Original Recommendation on speed vector:
To determine the risk of collision using ARPAvectors, only relative vectors should be used. True
vectors should be utilized to assess aspect.
Updated Recommendation: For small targets, use the relative vector on a 10-cm radar in relative
motion mode. For larger targets on a 3-cm radar, employ the true vector in true motion mode to
evaluate aspectand overall traffic dynamics.
Original Recommendation on speed input:
All bridge watchkeepers should be reminded that the speed input for an anti-collision plot on
radar/ARPAshould always be speed through the water, not speed over the ground.
Updated Recommendation: Utilize auto-speed input from Differential Global Positioning System
(DGPS) for ARPA, as it provides accurate Speed Over Ground (SOG) data, which is now preferred
over manual or water-referenced inputs in modern systems.
To Cruise Lines
Original Recommendation on radar lookout:
The OOWof the cruiser at the time of the collision should undertake further training in radar usage.
Cruise lines should ensure that this is completed as soon as possible and that other bridge
watchkeepers within their fleet are fully familiar with the bridge equipment they will need to operate.
Updated Recommendation: All OOWs should engage with relevant maritime resources (such as
this book or equivalent guides) and undergo targeted training in radar and electronic navigation.
Traditional training programs may not adequately cover advanced radar lookout knowledge.
Original Recommendation on Bridge Manning:
The Master of the cruiser should establish more explicit Standing Orders in accordance with the
Company Procedure Manual to clarify when the Officer of the Watch (OOW) should call for assistance
on the bridge. Cruise lines should ensure that satisfactory master’s orders are in place for all of their
ships.
Updated Recommendation: Assess crew competence levels rather than just the number of OOWs,
and tailor responses to the specific demands of varying risk areas (e.g., high-traffic zones). Provide
detailed competence requirements and guidelines instead of relying solely on generic standing orders.
Part one: Dover Strait TSS multiple target collision preparedness
The Myth of the Container Ship Collision with a Cruiser, 1999
####### The Collision and Initial Distress Call
On August 24, 1999, at approximately 00:55 local time, a collision occurred in the Dover Strait,
involving a container ship and a cruiser. Just moments before, at 00:54:37, the Dover Coastguard
recorded an urgent, unidentified transmission on VHF Channel 16: "Starboard, starboard, starboard."
This frantic call likely came from personnel on one of the vessels, a desperate attempt to avert disaster.
Historical and Technological Context
This incident unfolded roughly 26 years ago (as of 2025), during a pivotal period in maritime
navigation. At that time, emerging technologies were not yet prevalent:
The Differential Global Positioning System (DGPS) was still in its early adoption phase and
not widely implemented on vessels.
Voyage Data Recorders (VDRs), which capture critical ship data for post-incident analysis,
were not yet available.
Automatic Radar Plotting Aid (ARPA) systems had only begun to gain traction around 1997.
The maritime industry was in the midst of transitioning from traditional visual lookout methods—
principles upheld by older generations of seafarers—to more advanced ARPA-based systems. Despite
this evolution, the performance standards for ARPAwere closely aligned with the principles of relative
motion speed vector, emphasizing the need for reliability and accuracy in tracking targets relative to the
vessel.
Relevant IMO Standards for ARPA
A significant reference point is the International Maritime Organization (IMO) Resolution A.823(19),
adopted on November 23, 1995. This resolution detailed the "Performance Standards for Automatic
Radar Plotting Aids (ARPAs)," ensuring that these systems could deliver timely and precise data to
support safe navigation. Specifically:
Data
Scenario
Relative
course
(degrees)
Relative
speed
(knots)
CPA
(nautical
miles)
TCPA
(min)
True course
(degrees)
True
speed
(knots)
1 3.0 0.8 0.5 1.0 7.4 1.2
2 2.3 0.3-- 2.8 0.8
3 4.4 0.9 0.7 1.0 3.3 1.0
4 4.6 0.8 0.7 1.0 2.6 1.2
Section 3.8.3: An ARPAshould present, within three minutes of steady-state tracking, the motion of
a target with the following accuracy values (95% probability values):
Relative course: ±3° or better.
Relative speed: ±0.5 knots or better.
Closest Point of Approach (CPA): ±0.3 nautical miles or better.
Time to Closest Point of Approach (TCPA): ±0.5 minutes or better.
(Note: The exact accuracy metrics in the original resolution may include additional details; for a
complete reference, consult the official IMO documentation.)
ARPAPerformance Standards (IMO Resolution A.823(19))
Section 3.8.3 of IMO Resolution A.823(19) states: "An ARPAshould present within three minutes of
steady-state tracking the motion of a target with the following accuracy values (95% probability
values)."
The resolution includes a table outlining accuracy requirements across four scenarios, based on
factors such as target and own-ship speeds:
The acceptable Closest Point of Approach (CPA) accuracy value (95% probability) is up to 0.7
nautical miles in relevant scenarios, assuming at least three minutes of steady-state target tracking. If
the tracking time is less than three minutes, ARPAdata may be unreliable and should be treated with
caution. The use of this data falls under the Officer of the Watch's (OOW) discretion and involves
inherent risks. Historically, OOWs have sometimes overlooked ARPAperformance standards, failing to
scrutinize significant errors in data—similar to how radar echoes were often disregarded at close
range.
Re-Examining the 1999 Collision Investigation
The collision between the passenger vessel Norwegian Dream and the container ship Ever Decent
occurred in the approaches to the Dover Strait at 00:55 on August 24, 1999. The investigation report,
issued over 26 years ago, is now somewhat outdated, and its conclusions merit re-examination in light
of subsequent technological advancements.
Since that time, maritime lookout processes have evolved significantly, shifting from reliance on
Automatic Radar Plotting Aid (ARPA) systems to the Automatic Identification System (AIS). The input
parameters for ARPAand AISare now far more accurate, particularly with the integration of Global
Positioning System (GPS) data in AIS—manual entry of course and speed is no longer standard or
acceptable practice. A key improvement is the use of Speed Over Ground (SOG), which accounts for
external factors such as currents and wind. Over 25 years ago, SOG was not recommended for
ARPAinputs, as it relied on estimates from past ship positions, often imprecise. In contrast, modern
Differential GPS (DGPS) provides SOG with high accuracy, typically featuring position errors of only 5
to 10 meters—adequate even for precise operations like berthing.
Today, discussions seldom emphasize Speed Over Water (SOW) when utilizing tools like Portable
Pilot Units (PPUs) for docking or collision avoidance, as SOG from satellite-based systems has
become the reliable standard.
Review of Report Recommendations
The following sections will briefly review the key recommendations from the 2000 investigation
report into the 1999 collision between the Norwegian Dream and Ever Decent. For each
recommendation, the original summary will be provided, followed by an updated recommendation that
considers technological and procedural advancements over the past 25+ years, including
improvements in GPS integration and bridge resource management practices.
To All Shipowners
Original Recommendation on radar usage:
When using more than one radar/Automatic Radar Plotting Aid (ARPA), an anti-collision plot
should be maintained on only one.
Updated Recommendation: Utilize two radars to leverage their complementary strengths: a 10-cm
(S-band) radar for tracking small targets in relative motion trails mode, and a 3-cm (X-band) radar in
ARPAauto-acquisition mode for quick reference of larger vessels. Relying solely on one lookout
method is insufficient; the Officer of the Watch (OOW) should always include visual lookout for small
targets and, if available, a third radar or system for monitoring larger vessels.
Original Recommendation on speed vector:
To determine the risk of collision using ARPAvectors, only relative vectors should be used. True
vectors should be utilized to assess aspect.
Updated Recommendation: For small targets, use the relative vector on a 10-cm radar in relative
motion mode. For larger targets on a 3-cm radar, employ the true vector in true motion mode to
evaluate aspectand overall traffic dynamics.
Original Recommendation on speed input:
All bridge watchkeepers should be reminded that the speed input for an anti-collision plot on
radar/ARPAshould always be speed through the water, not speed over the ground.
Updated Recommendation: Utilize auto-speed input from Differential Global Positioning System
(DGPS) for ARPA, as it provides accurate Speed Over Ground (SOG) data, which is now preferred
over manual or water-referenced inputs in modern systems.
To Cruise Lines
Original Recommendation on radar lookout:
The OOWof the cruiser at the time of the collision should undertake further training in radar usage.
Cruise lines should ensure that this is completed as soon as possible and that other bridge
watchkeepers within their fleet are fully familiar with the bridge equipment they will need to operate.
Updated Recommendation: All OOWs should engage with relevant maritime resources (such as
this book or equivalent guides) and undergo targeted training in radar and electronic navigation.
Traditional training programs may not adequately cover advanced radar lookout knowledge.
Original Recommendation on Bridge Manning:
The Master of the cruiser should establish more explicit Standing Orders in accordance with the
Company Procedure Manual to clarify when the Officer of the Watch (OOW) should call for assistance
on the bridge. Cruise lines should ensure that satisfactory master’s orders are in place for all of their
ships.
Updated Recommendation: Assess crew competence levels rather than just the number of OOWs,
and tailor responses to the specific demands of varying risk areas (e.g., high-traffic zones). Provide
detailed competence requirements and guidelines instead of relying solely on generic standing orders.
