深度文章系列 02 • AIS • 暗船偵測 • SAR 衛星
Article Series 02 • AIS • Dark Vessel Detection • SAR Satellite
AIS（Automatic Identification System，自動識別系統）是一種裝設在船隻上的無線電應答器，透過 VHF 超短波自動廣播船舶資訊。根據國際海事組織（IMO）的 SOLAS 公約規定，300 總噸以上的遠洋船舶及所有客輪，都必須裝設並啟動 AIS 系統。
AIS 每隔幾秒鐘廣播一次，讓附近的其他船隻、港口管理當局、海巡單位，乃至全球衛星網路，都能追蹤這艘船的即時位置。
AIS (Automatic Identification System) is a radio transponder installed on vessels that automatically broadcasts ship information via VHF radio. Under the IMO's SOLAS convention, all ocean-going vessels over 300 gross tons and all passenger ships are required to have AIS installed and activated.
AIS broadcasts every few seconds, allowing nearby vessels, port authorities, coast guards, and global satellite networks to track the ship's real-time position.
| 資料欄位 | 說明 | 範例 |
|---|---|---|
| MMSI | 船舶識別號碼（9位數，如國家身分證） | 416123456 |
| 船名 | 船隻登記名稱 | XING SHUN 39 |
| 呼號 | 無線電通訊識別碼 | VRCS7 |
| IMO 號碼 | 國際海事組織永久識別碼（理論上終身不變） | 9876543 |
| 船舶類型 | 貨船、油輪、漁船、客輪等 | Cargo |
| 船旗國 | MMSI 前三碼即 MID 代碼 | Tanzania (677) |
| 緯度 / 經度 | GPS 定位，精度約 10 公尺 | 25.12°N 121.8°E |
| SOG | 對地速度（節） | 4.2 kn |
| COG | 對地航向（度） | 185° |
| 目的港 | 由船員手動輸入，可能不準確 | KAOHSIUNG |
這些資訊本身就是寶貴的情報。船舶類型、旗幟國、速度、航向，都可以用來判斷一艘船是否有異常行為。本站收集的正是這些資料。
| Data Field | Description | Example |
|---|---|---|
| MMSI | Maritime Mobile Service Identity (9 digits, like a national ID) | 416123456 |
| Vessel Name | Registered ship name | XING SHUN 39 |
| Call Sign | Radio communication identifier | VRCS7 |
| IMO Number | Permanent IMO identifier (theoretically unchangeable) | 9876543 |
| Vessel Type | Cargo, tanker, fishing, passenger, etc. | Cargo |
| Flag State | Encoded in first 3 digits of MMSI (MID code) | Tanzania (677) |
| Lat / Lon | GPS position, ~10m accuracy | 25.12°N 121.8°E |
| SOG | Speed over ground (knots) | 4.2 kn |
| COG | Course over ground (degrees) | 185° |
| Destination | Manually entered by crew — may be inaccurate | KAOHSIUNG |
This information is itself valuable intelligence. Vessel type, flag state, speed, and heading can all be used to identify anomalous behavior. This site collects exactly this data.
AIS 系統的最大問題在於，它是完全自願廣播的——沒有人能強迫一艘船保持訊號開啟。任何船員都可以在幾秒鐘內按下幾個按鈕，讓這艘船從所有 AIS 追蹤平台上消失。
這種行為在業界稱為「走暗」（going dark）。走暗並不一定違法——某些合法情況下，船長有理由關閉 AIS，例如在海盜出沒區域保護安全。但在台灣周邊海域，一艘船在靠近海底電纜時突然關閉 AIS，那就是一個非常值得警戒的信號。
除了關閉，AIS 還可以被偽造——船隻可以廣播假的位置座標、虛報速度，甚至播送其他船隻的身分。這種「AIS 欺騙」（AIS Spoofing）是我們評分系統中特別關注的項目。
The biggest problem with AIS is that it's entirely voluntary broadcasting — nobody can force a ship to keep its signal on. Any crew member can make a vessel disappear from all AIS tracking platforms in a few button presses.
This is called "going dark" in the industry. Going dark isn't necessarily illegal — there are legitimate reasons for a captain to disable AIS, such as for safety in piracy-prone areas. But in Taiwan's surrounding waters, a vessel suddenly disabling AIS while approaching a submarine cable route is a very serious warning signal.
Beyond switching off, AIS can also be spoofed — vessels can broadcast false position coordinates, fake speeds, or even another vessel's identity. This "AIS Spoofing" is an item our scoring system specifically monitors.
AIS 走暗並不代表船隻消失了——只是消失在一般的追蹤系統中。合成孔徑雷達（SAR, Synthetic Aperture Radar）衛星可以透過雷達掃描發現任何在水面上的金屬物體，完全不受天氣、雲層或日夜影響。
本站使用的 SAR 資料來自 Global Fishing Watch（全球漁業觀察），他們透過 SAR 衛星在台灣周邊海域進行掃描，將偵測到的船隻位置與 AIS 資料進行交叉比對：
這些「暗船」就成為本站優先監測的對象。一艘在海底電纜路線附近被 SAR 偵測到、卻沒有 AIS 訊號的船隻，立刻引發高度警覺。
Going dark on AIS doesn't mean a vessel has disappeared — only that it's vanished from conventional tracking systems. Synthetic Aperture Radar (SAR) satellites can detect any metallic object on the water surface via radar scanning, completely unaffected by weather, cloud cover, or time of day.
The SAR data used by this site comes from Global Fishing Watch, which scans Taiwan's surrounding waters via SAR satellites and cross-references detected vessel positions against AIS data:
These "dark vessels" become priority monitoring targets. A vessel detected by SAR near a submarine cable route with no AIS signal immediately triggers high-level alertness.
有些船隻更進一步——不只關閉 AIS，還頻繁更換船名、呼號甚至虛報 IMO 號碼，製造身分混淆。這種行為本身就是一個重大警訊。
Some vessels go further — not just disabling AIS, but frequently changing their name, call sign, or even falsely reporting their IMO number to create identity confusion. This behavior itself is a major red flag.
現在我們可以看清楚這條邏輯鏈：
這套邏輯就是本站監測系統的核心。想了解完整的評分方法，請參閱第 06 篇：本網站所使用之方法。
Now we can see the clear logical chain:
This logic is the core of our monitoring system. For the full scoring methodology, see Article 06: Our Methodology.
AIS 訊號要被「看見」，必須先被接收。理解接收的兩種方式，才能明白「走暗」與「覆蓋盲區」的差別。
這對監測的意義很關鍵：當一艘船在地面站範圍外、兩次衛星通過之間的空檔消失，可能是真的關閉 AIS（走暗），也可能只是覆蓋盲區。要分辨兩者，就得引入獨立的 SAR 衛星偵測——這也是本站把 AIS「going dark」判定與 SAR 暗船交叉比對的原因。
An AIS signal has to be received before it can be "seen." Understanding the two ways it is received is what separates real "going dark" from a mere coverage gap.
This matters for monitoring: when a ship vanishes beyond terrestrial range, between satellite passes, it may have genuinely switched off AIS (gone dark) — or it may just be in a coverage hole. Telling the two apart requires independent SAR satellite detection, which is exactly why this site cross-references AIS "going dark" with SAR dark-vessel hits.
The concepts on this page can be verified against these public, authoritative sources:
This page is for research and education; detection signals are leads to investigate, not legal or factual findings. See the methodology.