【搬运】【鱼叉5】【海军情报杂志2013】AIS在海军战术兵棋中的应用

《AIS在鱼叉兵棋中的应用》

(译自《海军情报杂志2013-4月版》,部分系笔者私货)

一、何谓AIS?

(一)AIS概述

1.AIS是什么?

AIS(船舶自动识别系统,Automatic Identification System,AIS)是由世界船运组织建议,国际航运组织( International Maritime Organization ,IMO)添加到《国际搜救与人命安全公约 》(SOLAS)的,在2002年6月1日以后建造的所有大于300总吨的从事国际航线与大于500总吨的从事非国际航线的所有船只统一强制安装。

AIS是一种依托于无线电的助航仪器,其会利用无线电全时发送本船的GPS位置、航向、航速,并播发自身信息(如长、宽、吃水、目的地、呼号等),自身状态(正常在航、操纵受限、失控、,锚泊、搁浅)等自身信息;AIS接收设备还会根据自身GPS位置和接收到的AIS信息自动绘算最近会遇距离(CPA)与会遇时间(TCPA),协助船舶驾驶员进行避碰决策;此外AIS信息还可以显示在电子海图(ECDIS)和导航雷达上,可以直观的看出相对态势和雷达目标,如果AIS设备正常工作,每个雷达接触基本上都有AIS信息,可以在不进行目力瞭望的情况下直观的判断目标。

AIS系统最大的优点是受地形的遮挡较小,可以方便的显示山后的目标和远距离的目标。此外,在能见度较差的情况下,可以远距离的指示目标。

对于军用舰船,AIS系统并不是强制安装的。但为了航行安全与辅助判情,目前所有的军用舰船上都安装了AIS接收机,部分舰船上安装了AIS发射机(部分美国船,比如核动力航母,进出港时会打开AIS)。在没有敌视觉查证的情况下,使用AIS伪装成为商船是一个很不错的主意——假装成商船,骗过来干他一炮!这应当视为一种海战诈术,而并非是违反国际法的行为,只要你在开火之前关闭AIS,并及时表明身份。此外,使用AIS信息也可以判断是否为敌人——没有AIS的就是敌人!

2.有没有除了船以外的AIS?

在海上有除了船以外的单位同样有AIS

为了确保渔网的安全,提醒过往船舶不会碰上渔网,部分渔网上也安装了网位仪,这类网位仪也安装有AIS,也能发布AIS信息,不过渔网的AIS很容易区分。

部分浮标、平台、航标上也装备了AIS,以便没有导航雷达的船只或者辅助装备导航雷达的船舶识别。

有些海区沉船、碍航物、锚地等有虚拟AIS(V-AIS),原理是基站播发报文,接受后在AIS接收机上产生AIS目标。这类AIS通常部署在港口附近,代替正常的浮标便于进出港接送引水,最典型的例子是上海港7#浮标,为一个虚拟AIS浮标,虾峙门7#浮标同理。

(二)AIS工作特点

1.AIS设备的分类

AIS分为A/B两类,其有一定的发送时间间隔。

2.发送间隔

AIS设备发送的时间间隔如下表:

信息类型 船舶状态 报告间隔
静态信息,如MMSI码,IMO码、船舶呼号、船名(20字符以内)、船舶类型、定位精度、船舶吃水 全部船舶,无论其在何种状态 6分钟,当数据被更换时、根据请求及数据变化时、接受到发送要求时为每6s
动态信息,如船位(经纬度精确到从1/10000分),船首向(一般来自陀螺罗经,方位精确到0.1°),航迹向(来自GPS),定位精度 锚泊船 3分钟
航速0-14节的船舶 12秒
航速0-14节的变向船舶 4秒
航速14-23节的船舶 6秒
航速14-23节的变向船舶 2秒
航速>23节的变向 3秒
航速>23节的变向船舶 2秒
航次信息,如目的港,抵达时间(ETA) 全部船舶,无论其在何种状态 根据请求每6分钟(当数据被更换时)

必须考虑到,AIS的信息发送有一定的滞后性,由于天线老化等原因,接收信息也不可靠,所以AIS信息只能作为参考,最关键的还是瞭望的双眼。

3.工作频率

AIS工作在甚高频(VHF)波段,具体的频率是156.025-162.025MHz,采用的发射方式是(调幅/调频),(电磁波极化方式为)。其传播距离主要受三个因素的影响:一是AIS天线安装高度,越大的船,其AIS天线往往安装越高,其电磁波理论上传播的越远;二是发射功率,AIS天线发射功率最大为12.5W,理论传播距离在20nm左右;三是大气情况的影响,大气波导也会同样影响AIS信息的传播,当156MHz波段出现波导的情况下,AIS信息可以传播的更远,这与AIS接收机安装的位置有关,如果AIS接收机安装在波导层内,那么就能接受到远方的AIS信息。

AIS在航海实践上的特点

AIS在航海实践上主要用于复杂条件下避碰,AIS信息导入导航雷达、电子海图中,可以直观的显示来往船只类型,从而为避碰提供建议。

为了便于航运管理,部分公司收集提供AIS信息,并在航运网站上查询的业务,这些业务便于船运公司进行商船管理,这样的话可以节约一大笔卫星通信费用(没有这种业务,商船与公司之间就必须保持专用的卫星联络,这将产生一大笔费用;为什么不用短波电台呢,一方面是由于电磁频谱管控,另一方面是短波电台也不可靠),最典型的例子是船讯网。当然,如果有民用互联网,军用船舶也可以使用这一点进行对超视距目标的识别——前提是没有电子卫星侦察民用互联网通信的情况下。

在实践中,AIS信息可以传达到50-60nm外,这一点受大气波导的影响。由于AIS系统设备的频率较低,波长较长,其更容易利用大气波导

三、AIS在鱼叉兵棋中的运用

(一)观察距离

根据气象条件,AIS接收机传播距离可分为正常条件、表面波导距离两种。

1.正常气象条件下

(1)水面目标观察

正常气象条件下,AIS发射机发射功率(正常A类发射机)、接收机接受渔船,渔网等AIS发射机的距离如下表

发送者

接收者 接收者天线位置
大型 中型 小型 微型 海平面 备注
正常

AIS发射机

(商船) 大型 26 25 23 20 16 正常发送距离20nm
中型 24 23 21 18 14
小型 22 21 19 16 12
微型 19 18 16 13 9
海平面 14 12 10 8 3
渔船用

AIS发射机 小型 22 21 19 16 12 正常发送距离8nm
微型 19 18 16 13 9
海平面 14 12 10 8 3
渔网用

AIS发射机 海平面 5 2.5 2 1 0.5 正常发送距离5nm
备注:根据接收者天线高度与发射者高度查表,与备注中的数据相比较,取两者中的最小值。

(2)无人机观察

如果想定中出现使用无人机搭载AIS设备进行侦察等情况,根据无人机飞行高度不同列表如下(建议使用公式)

发送者

接收者 接收者天线位置
中空 低空 超低空 备注
正常

AIS发射机

(商船) 大型 2.1*(H)^1/2+14 65 26 正常发送距离20nm
中型 2.1*(H)^1/2+12 60 25
小型 2.1*(H)^1/2+10 60 23
微型 2.1*(H)^1/2+7 55 20
海平面 2.1*(H)^1/2+2 50 16
渔船用

AIS发射机 小型 2.1*(H)^1/2+10 60 23 正常发送距离8nm
微型 2.1*(H)^1/2+7 55 20
海平面 2.1*(H)^1/2+2 50 16
渔网用

AIS发射机 海平面 5 5 5 正常发送距离5nm
备注:根据接收者天线高度与发射者高度查表,与备注中的数据相比较,取两者中的最小值。

2.波导气象条件下

由于电磁波波长长,更容易利用波导层,AIS设备能更好的利用波导,无人机超低空飞行时也能利用波导。

发送者

接收者 接收者天线位置
超低空 大型 中型 小型 微型 海平面 备注
正常

AIS发射机

(商船) 大型 75 70 65 60 50 35 出现异常波导条件下,发射功率不计
中型 65 65 60 55 45 30
小型 60 60 50 50 40 25
微型 50 50 40 40 30 20
海平面 35 35 25 20 20 5
渔船用

AIS发射机 小型 — — — — — — 由于发射功率低,不考虑其影响
渔网用

AIS发射机 海平面 — — — — — —
备注:只使用该表

(二)使用机理

AIS信息只在启用中立海运或者白方情况下使用;白方船只强制显示AIS。一方可以使用伪装AIS,但事先必须向裁判组通报;裁判组会为使用伪装AIS方保密。。

AIS信息在一方装备有AIS接收机的单位进入AIS范围内的情况下会概率显示给探测方,每个战术回合探测概率为95%,中继回合会自动发现。

在大气波导条件下,AIS范围使用大气波导中的AIS范围。
附:原文
The revolution in military affairs of the last decade has been widely reported in professional journals of all services in many nations. One of the technologies fueling that revolution did not even begin within the military, although it has now been enthusiastically embraced by the vast majority of maritime powers.
The Automatic Identification System (AIS) was born out of the need for operators in the world’s Vessel Transport System (think of it as the FAA for merchant ships) to better handle the volume of commercial traffic on the world’s waterways.
AIS provides a wealth of information (see below for a complete description) to operators facilitating ship routing, collision avoidance, customs inspection scheduling and a host of other efficiencies. This is not intelligence information. It is information vital for the safe navigation on the world’s busy waterways.
The technology was so promising that in December 2000 the International Maritime Organization (IMO) amended the International Convention for the Safety of Life at Sea (SOLAS) to include the requirement that AIS “be fitted aboard all ships of 300 gross tonnage and upwards engaged on international voyages, cargo ships of 500 gross tonnage and upwards not engaged on international voyages and passenger ships irrespective of size built on or after 1 July 2002.”
The SOLAS convention does not apply to warships or naval vessels, such as our USNS ships, that are owned and operated by the government and not engaged in commercial trade. As a result, although the SOLAS mandate was to be phased in for commercial vessels with full compliance by 2007, most of the world’s navies lagged far behind. In 2004/2005 the US Navy made tremendous strides in fielding AIS systems to the fleet.
So that’s the requirement, but what does AIS do? The following is an excerpt from the USCG website regarding AIS: “Picture a shipboard radar display, with overlaid electronic chart data, that includes a mark for every significant ship within radio range, each as desired with a velocity vector (indicating speed and heading). Each ship “mark” could reflect the actual size of the ship, with position to GPS or differential GPS accuracy. By clicking on a ship mark, you could learn the ship name, course and speed, classification, call sign, registration number, MMSI, and other information. Maneuvering information, closest point of approach, time to closest point of approach and other navigation information, more accurate and more timely than information available from an automatic radar plotting aid, could also be available.Display information previously available only to modern Vessel Traffic Serviceoperations centers could now be available to every AIS-equipped ship.”
This is an amazing treasure trove of information automatically available on every contact on your radar scope. AIS relies on a VHF transponder and is generally limited to the limits of LOS communications. The higher the antenna, the more information can be received, for surface ships generally that means about 20 nm. Aircraft with AIS receivers offer considerably better reception ranges.
A Class A AIS unit broadcasts the following information every 2 to 10 seconds while underway, and every 3 minutes while at anchor at a power level of 12.5 watts. The information broadcast includes:
• MMSI number - unique referenceable identification
• Navigation status (as defined by the COLREGS - not only are “at anchor” and “under way using engine” currently defined, but “not under command” is also currently defined)
• Rate of turn - right or left, 0 to 720 degrees per minute (input from rate-of-turn indicator)
• Speed over ground - 1/10 knot resolution from 0 to 102 knots
• Position accuracy - differential GPS or other and an indication if (Receiver Autonomous Integrity Monitoring) RAIM processing is being used
• Longitude - to 1/10000 minute and Latitude - to 1/10000 minute
• Course over ground - relative to true north to 1/10th degree
• True Heading - 0 to 359 degrees derived from gyro input
• Time stamp - The universal time to nearest second that this information was generated
In addition, the Class A AIS unit broadcasts the following information every
6 minutes:
• MMSI number - same unique identification used above, links the data above to described vessel
• IMO number - unique referenceable identification (related to ship’s construction)
• Radio call sign - international call sign assigned to vessel, often used on voice radio
• Name - Name of ship, 20 characters are provided
• Type of ship/cargo - there is a table of possibilities that are available
• Dimensions of ship to nearest meter
• Location on ship where reference point for position reports is located
• Type of position fixing device - various options from differential GPS to undefined
• Draught of ship - 1/10 meter to 25.5 meters [note “air-draught” is not provided]
• Destination - 20 characters are provided
• Estimated time of arrival at destination - month, day, hour, and minute
in UTC
So what does this mean for the Harpoon gamer? For any scenario taking place after 2006 or 2007 at the latest, any merchant ships over 300 tons, would be automatically identified by any naval units. I can’t say with any certainty when all the world’s navies adopted AIS, but based on the information available “for free” and the relatively inexpensive receivers it is unlikely, in my opinion, that they waited much beyond 2007 to acquire systems. Warships and other government owned/operated vessels are not required to have AIS installed and thus are not required to broadcast AIS information even if they do have the transponder installed, they can operate in a receive-only mode protecting their position and identity. As a guideline I would offer the following:

  1. 2003-2004: 25% chance that a warship in is fitted with an AIS receiver.
  2. 2005: 50% chance that a warship is fitted with an AIS receiver.
  3. 2006: 75% chance that a warship is fitted with an AIS receiver.
  4. 2007 and beyond: All warships are fitted with AIS.
    AIS can be spoofed by entering false information regarding vessel type, port of call etc., or it can simply be turned off, all of which gives a referee some flexibility in dealing with the fog of war.
    If you are interested in further reading,the USCG has an excellent website detailing AIS at www.navcen.uscg.gov.