电子海图显示及信息系统

电子海图，一直强调它是一种用来加强安全的手段。在过去几年提供给海事组织的多项调查显示，这是预期的结果。但是，在实践中，电子海图是否会让一些船舶驾驶员过于自信，甚至导致安全系数降低？

事实上，电子海图系统的安全运行使得我们必须要开发一个新的用户理念，比起使用纸质海图，电子海图有许多截然不同的地方。一个好的理念应该灌输给用户，作为电子海图培训的重要组成部分，而且不能过于强调通过死记硬背去学习任何一个特定的电子海图操作，牢牢掌握基本原理才是最重要的。它不仅帮助灌输正确的理念，还帮助用户去熟悉不同船舶上不同的电子海图的运用。

电子海图的劣势

在电子海图这个理念当中，使用者应该充分了解使用电子海图基础系统的优缺点。让我们从它的劣势开始说起。最重要的是电子海图是完全以电子为基础的系统。电子化能导致系统的彻底瘫痪，又或者是形成操作的失误。为了识别它的失误，国际海事组织总是要求船舶要配备一套作为电子海图的备用系统。虽然这可能只是一个纸质海图系统，但对于大多数的船舶来说这并不是一个明智的选择，这是由于运作和财政方面的原因造成的。在一般情况下，最合适的后备方案就是再准备第二个电子海图系统。用来避免众所周知的复杂状况，必须使备用电子海图和主要的电子海图保持一致。

有恰当使用电子海图理念的用户，应该确保备用的电子海图系统总是能有效地参与正在进行的航海过程，例如，能够显示出与主系统不同比例的视图。为由此提高对周围环境状况的认知，定期地检测一下备用的电子海图，以确保当主要系统瘫痪的时候，这个系统可以备不时之需地成为主要系统。它也帮助识别出在任何一个系统中发生的故障。尤其特别的是，它同时还帮助确保那个备用系统正在正确加载运行目前的航线以及及时更新电子海图。

标准电子海图以及电子海图显示与信息系统设备的数据标准都是相当详细的，这些数据标准是它们成为迄今为止最为复杂的船上系统。时不时会有一些未被预期的突发状况发生。船舶驾驶员应该一直清楚地了解到这些问题是存在的，并且同时知道解决这些问题的方法。这些解决方案可能包括一些临时的措施。当然，公司详细的安全管理体系都会全力支持船舶在这方面的需求。

一般而言，水道测量局可以根据编制的数据，很快解决那些由于电子海图所引起的不正确的数据编码。虽然这有时候也需要花费几周的时间。由于各种各样的原因，通常这些设备的异常问题需要满意地解决，要花费制造商更长的时间，所以一般来说，升级电子海图软件是相当有必要的。使用者需要了解所使用设备的状况，包括这个软件所有没有被解决的问题。不幸的是，许多航运公司没有对航海设备的软件进行升级，尽管遵从了国际海事组织的指导，比如在 2012年的 12月颁布的 MSC.1/ Cire.1389航海相关文件所指出的内容。

然而，使用者很容易就会对于电子海图的异常感到过度的焦虑。在实践中，发生异常的相关数据真的很小，这些数据总是被见多识广的使用者牢牢地印入脑海之中。如果有好的程序并且用户也坚信这样的程序确实存在，他们正确使用电子海图，安全是不存在问题的，然而，如果电子海图被无知地使用，那么他们将造成事故的发生。

显示屏尺寸以及用户界面

电子海图最大的劣势在于显示屏的尺寸大小，和纸质的图表相比，电子海图上的字是极小的，由于显示屏的关系，标准允许电子海图的尺寸大小只有270毫米X270毫米。除非你很合理地使用，电子海图可能会造成一个让使用者产生“视野狭窄”的趋向，因此它必须具有自然顺畅的放大和缩小，以及屈卷表格的功能，而且还具备保持一个好的影像功能，就是当船通过这个地方，这个地方的布局能被很好地反映出来。如同之前所提到的一样，备用的电子海图能被有潜力地应用正于此处。

电子海图理念必须随着显示细节的变化而变化。尽管在不同的纸质海图上没有什么很大的变化，在电子海图上却有着微妙的变化。对那些不了解状况的用户来说，在关键的时刻，他们可能会使用那些规模不恰当的图表。在船的前方，图表应该经常被展示出来，并且运用最大的尺寸，这样做的目的在于在状况良好的情况下识别潜在的危险。在设置正确的情况下，电子海图会对某一条航线上的危险给予自动的警告并在图表上显示出来。如果这些警告使用户感到诧异，那么他们自己的监视是存在问题的。

除了以上关于屏幕尺寸的评价，电子海图显示器正在越变越大。但是，最重要的是显示器的分辨率。一般而言，60英寸的显示器像素和 20英寸的是一样的，因此在如此大的显示器上看一个完整的纸质海图会导致显示模糊，无法阅读。不幸的是在电子海图能挑战纸质海图之前，我们必须等待可负担得起的高像素的显示器诞生，这可能要等待很长时间。

电子海图的最后一个主要缺点是用户界面（例如控制装置、菜单结构以及显示器的具体布局）没有一个统一的标准。这和雷达以及其他的航海设备相似，但是这个系统的复杂性要高得多，第一次使用某种特定设备的用户在瞭望之前必须很好地熟悉船上的系统。

这需要额外的培训。该培训应以电脑和平板电脑为基础。电子海图理念体系应为此做好准备，只有成功地完成国际海事组织电子海图课程的培训，才有能力使用电子海图系统。因为只有非常熟悉装在船上的实际系统，才能实现该目标。

电子海图的优势

与使用纸质海图比较后，电子海图的优点大于缺点，很多并没有在文章范围内指出。再次，如果用户们想充分地使用电子海图的优势并且避免滥用的风险的话，他们需要有正确的思维模式。

最为重要的优势（也是最容易被滥用的地方）是内置的船位显示设备，该设备持续显示船舶在图表上的位置。相反的，运用全球导航卫星系统（例如GPS 全球定位系统）在纸质海图上绘制方位是非常乏味，容易出错的。然而，电子海图理念体系会从绘制方位上节省更多的时间，并把这些时间用于评估被显示方位的完整性。用电子海图进行完整性评估比用纸质海图容易得多，这不仅仅由于电子海图能持续显示方位，并且还由于电子海图的安装接近主控位置。

因此，在沿海水域，通常非常容易从GNSS(全球导航卫星系统)那里得到的位置与从窗户外看到的景象联系起来，以及与从其他主要的航海工具（特别是雷达）那里得到的信息相连接。事实上，每当船舶驾驶员看电子海图时，他们应该将其与其他资源作比较，并通过寻找来识别任何可能的位置错误。当与外界的视野作比较时，使用航向向上或迎风航行的模式尤其有用，要记住在保持总体意识时，要用不一样的思维模式，这与使用北面向上的纸质海图略有不同。

另外，通过视觉以及雷达所获得的轨迹线（LOPs）应该被输入进电子海图中，并保持合适的间隔。在设计完备的驾驶舱里，单个的轨迹线，包括雷达范围，能够被快速地绘制好，然后转入到电子海图中来，由此来确认他们的船离他们指定的位置非常接近。通过这种方法检查全球导航卫星系统的精确性，特别是在障碍物总量少的状况下。当然，应该选择连续的方位，但要使他们尽可能地不在一条直线上。

此外，在电子海图思维体系中，单个轨迹线（LOPs）能自动被相关设备合并起来并形成一个方位预测装置。电子海图考虑到每个轨迹线（LOPs）所用的时间，并运用DR或是EP将其连接起来。这个功能真正的优点在于它储存轨迹线（LOPs）输入数据以及由此而产生的方位，这为将来的运作提供了必要的参考。这取代了“船位误差三角形”(cocked hat)的纸质方位检测，这项工作由港口国检查官们承担，他们检测全球卫星导航系统定位是否能被证实。

很高兴看到由英国航海学会设计的ePelorus现在被用于船舶上。简单地按一下按钮就能通过陀螺仪视觉定位线，把数据发送到电子海图，完整的评估时间也会明确的被显示出来。这从很大程度上缓解了视觉压力并进一步减少了障碍物。应该注意的是电子海图软件更新非常必要，因为这样就能与ePelorus相连接了。

航运的完整性

桥窗、来自电子海图的信息和雷达能共同反映出完整的航运状况——不仅仅只显示出地理位置而已。拥有良好电子海图理念体系的用户会一直检查信息的一致性。对于任何不一致的信息系统将会发出“一切并不顺利，需要额外的关心”的警告。

当独立的信息被相互连接起来后，避免危险变得尤为简单。然而，需要被持续关注的是，雷达应被用作首要的防撞设备，而电子海图被用作首要的图标援助工具。尽管这两个系统中有越来越多的重叠信息，但从根本上来说，我们不能将这些重叠信息简单地等同起来。

如果仅仅只有一个可用的数据来源，例如船舶自动识别系统显示目标船从某地航海回来，这对该船而言很重要，需要被密切关注。是否因为信号干扰或设备装置较差导致了雷达无法接收信号？是否由于能见度太差而导致了看不清航行路线？是不是全球卫星导航系统或是陀螺仪出了问题？是不是船舶自动识别系统信号有误？是信号故障还是海盗可能开始行动了？显然任何决定都必须将这些问题考虑进去，此外需做好安全措施。

用户必须知道如何用电子海图在海上建立完整的地理位置。自动的DR/EP设备对于长时间检查全球卫星导航系统的重大错误起到重要作用。卫星定位系统应被融入到电子海图中，这能对全球卫星导航系统进行额外的检验。如果一个完整的全球卫星导航系统发生故障，电子海图内置设备很有价值，无论是在沿海还是海上，它都能通过视角、雷达景象或卫星定位装置的辅助，长时间保持DR/EP定位。我们是否经常听到一些极其错误的观点“没有电子定位系统，电子海图无法正常工作”？

利用这些替代方法，定期确认全球卫星导航系统的定位完整性，并确保能在紧急情况下使用这些方法至关重要。此外，假设在全球卫星导航系统完全丧失功能的前提下，举行定期演习也十分必要。通过演习能确保在船上有相关的措施来应对这样的状况，并让所有工作人员了解该状况。

信息显示及路径规划

电子海图另一个优点是用户能更多地控制显示信息，这一点远远超过纸质海图。安装好后，电子海图就会显示与本船相关的信息，而不是创造多余信息。尤其是在安全的水域，它可以很清楚地描述状况（反之亦然）。然而，要做到这点，用户必须完全熟悉安全“等高线”和“等深线”的用途，要进入浅于安全“等高线”水域，必须设置显示信息及操作步骤，这样才能顺利地进入港口。如果没有很好地设置电子海图，那么在实际操作中可能会出现问题。

一个技巧熟练的用户一定知道电子海图的内部信息设备，特别是“选择报告”这个操作，它可以用来获得图上任意一点的详细信息。例如 ,他们如果不能理解某个标志，一个简单的操作就会显示出关于这个标志的所有已知信息。具有电子海图理念体系的用户都知道如何快速的找到所需信息而不被其他相关信息所干扰。一般来说，使用电子海图的视觉体验和使用纸质海图的体验完全不同，电子海图构成了一个重要的新型思维模式。

电子海图理念体系还包括要对路径规划进程十分了解。运用电子海图，可以很容易地设计出一个全新的路径图，或以之前的路径图为基础进行设计。尤为重要的是在使用之前必须要进行人工检查，并用最新的电子海图数据进行修改，传统的规划信息（无论是纸质或电子形式）能很好地支持这些工作。针对该状况，必须向船员们发布最新的临时或初步通告。

在进行核查的时候，最大尺寸的图表必须被用于线路的所有部分。一旦人工检查被执行了，运行自动安全检查很有好处。它会独立检查线路，但也要小心的调节，以防止总是跳出安全警告。有良好电子海图理念体系的用户应知道自动检查设备不是绝对可靠的，人工检测也是如此。两者同时使用可以降低错误发生的概率。更重要的是，手工检查给设计者一个有价值的意识。这个意识是关于一个完整路线的设计。

迄今为止，电子海图理念体系的最大挑战是去克服一种错误的安全意识。问题在于电子海图似乎十分准确，这很容易让人错误地认为它永远是100%正确的。即使在最好的情况下，其准确性还是受到潜在电子海图数据质量的限制，这一点能被100年甚至更久以前的调查所证实。（但是，当然，正确的理念体系总是能检查目前CATZOC的情况）。在最坏的情况下 ,一系列的错误可能导致信息不准确。如果电子海图想真正地变得更安全，所有的用户都必须有一个正确的理念体系，该理念体系决定了所预见状况的完整性，所有的航海决策都应该建立在这个理念的基础上。

最后，公司也需要有一个电子海图理念体系，这尤其要体现在他们的安全管理系统上。从纸质海图转向电子海图预示着在很多领域将发生具体的改变。这些领域包括风险评估、应急准备、操作程序、演习与操练、培训和强化。如果不这样做，一个良好的用户理念体系就达不到预期的要求并很好地被实现。

The ECDIS Mindset

Dr Andy Norris, FNI

The move to ECDIS has been firmly underlined as a means to further increase safety. A number of investigations presented to IMO in the last few years have shown that this is the expected result. But, in practice, will ECDIS further contribute to the overconfidence of some OOWs, resulting in an even greater narrowing of safety margins?

In fact, the safe operation of ECDIS necessitates the development of a new user mindset, which in many ways is quite different to that needed when using paper charts. The makings of a good mindset have to be instilled in users as a major component of basic ECDIS training and must not be obscured by an overemphasis on rote learning the specific operation of any one particular ECDIS. A firm grip of the fundamentals is essential; it not only helps instil the correct mindset but allows much easier familiarization when transferring between ships with different ECDIS on board.

ECDIS weaknesses

The ECDIS mindset fully appreciates the strengths and weaknesses of using an ECDIS-based system. Let’s start with its weaknesses. The most important of these is that ECDIS is an entirely electronically based system. It can therefore fail outright and can also develop faulty operation. In recognition of its vulnerability to failure, IMO has always required vessels to carry a backup to the main ECDIS unit. Although this could be a paper chart system, it is not a sensible choice for most ships for numerous operational and financial reasons. In general, the most suitable backup is a second ECDIS. To avoid familiarization complexities this ideally needs to be identical to the main ECDIS. A user with a proper ECDIS mindset ensures that the backup ECDIS is always efficiently involved in the ongoing navigational process, for example, by showing a different scale view to that displayed on the primary equipment. As well as the improved situational awareness that results, regular reference to the backup ensures that the system is immediately ready to become the primary, should the main system fail. It also helps to identify any developing faults in either system. In particular, it helps to ensure that the backup is properly loaded with the current route and upto-date ENCs.

The data standards for ENCs and ECDIS equipment are highly detailed, making it by far the most complex system on the bridge of a ship. From time to time, unexpected issues are uncovered. OOWs must always be aware that such problems can exist, together with the methods that are used to indicate these problems, which may include temporary procedures to be followed. Of course, the detail of the company’s Safety Management System must fully support this need.

In general, issues that arise from incorrect data coding of ENCs are quickly resolved by the hydrographic office that has compiled the data – although this can sometimes take some weeks. For a number of reasons, it generally takes rather longer for manufacturers to satisfactorily resolve equipment anomalies, which generally necessitate ECDIS software updates. The user needs to be aware of the software status of the equipment in use, including any unresolved issues. Unfortunately, many shipping companies do not yet appear to have latched onto the issues connected with software updates for navigational equipment, despite firm guidance from IMO, such as that given within MSC.1/ Circ.1389, issued in December 2010.

However, it is easy to be unduly anxious about ECDIS anomalies. In practice, their number has been relatively small and they can all easily be kept in mind by a well-informed user, provided good procedures are in place and the user mindset is completely switched on to the fact that such issues can exist. Their significance to safety on a correctly used ECDIS is likely to remain of a relatively minor nature but, nevertheless, they could lead to accidents if ECDIS is ignorantly used.

Display size and user interface

A significant weakness of ECDIS is the size of the chart display. Compared to a paper chart this can be minuscule the standards allow the display area to be as small as 270 x 270 mm. Unless used sensibly, ECDIS can create a tendency for the user to develop ‘tunnel vision’. It must therefore become natural to not only be regularly zooming in and out and scrolling the chart but also to retain a good mental image of the general layout of the area in which the ship is traversing. As previously noted, the backup ECDIS is potentially useful here.

The ECDIS mindset also has to work with the changes in displayed detail that occur when zooming. Although this is essentially the same issue as working with different scale paper charts, the effects can be more subtle. To the unaware user, this can lead to inappropriately scaled images being used in critical situations. The chart must be regularly scrolled ahead of the vessel, using the largest scale data, to identify potential hazards in good time. When properly set up, ECDIS should give automatic warnings of charted hazards on the immediate route. If these warnings come as a surprise to the user then it is their own monitoring that is at fault.

Despite the comments on screen size above, ECDIS displays are getting larger all the time. However, of more importance is the display resolution. In general, a 60 inch display has the same number of pixels as, say, a 20 inch version and so trying to view a full scale paper chart image on such a large display would just result in an unreadable blur. Unfortunately we must wait for affordable high resolution displays to become available before ECDIS rivals the area of a paper chart. This could be a long wait. The last main weakness of ECDIS is that the user interface, such as the controls, menu structure and the detailed layout of the display, are not rigorously standardized. This is similar to the case for radar and other navigational equipment but is magnified by the complexity of the system. A user new to the particular equipment must therefore become properly familiarized with the system on board before undertaking a watch.

This requires an additional element of training. It makes great sense for this training to be computer or tablet-based. The ECDIS mindset should be ready for this, understanding that while the satisfactory completion of a course complying with the IMO ECDIS Model Course requirements is a statement of competence to use ECDIS, this is only the case provided there has been appropriate familiarization with the actual fitted system to be used onboard ship.

ECDIS strengths

The weaknesses of ECDIS are dwarfed by its strengths compared to the use of paper charts, many of which lie outside the scope of this article. Again, users need the right mindset if they are to use these strengths to their fullest extent, and avoid the perils of misuse.

Perhaps the most important strength – and the one most prone to misuse – is the built-in continuous display of the ship’s position on the chart. Conversely, on a paper chart plotting position from a Global Navigation Satellite System such as GPS is tedious and prone to error. However, the ECDIS mindset knows that much of the time saved in plotting the position should be readdressed to assessing the integrity of the displayed position. Integrity assessment is much easier with ECDIS than when using paper charts, not only because the position is continuously displayed but also because ECDIS is generally installed close to the main conning position.

Therefore, in coastal waters, it is generally very easy to correlate the GNSS derived position with the view from the bridge windows, as well as with information from other prime navigational aids, particularly radar. In fact, every time the OOW looks at ECDIS, they should make a mental correlation with these other sources, seeking to identify any possible positional errors. The use of course-up or head-up mode can be particularly beneficial when making the correlation with the outside view, bearing in mind that a subtly different mindset is required in maintaining overall awareness compared to using a North-up paper chart.

In addition, visual and radar derived Lines of Position (LOPs) in coastal waters should be input into ECDIS at appropriate intervals. On a well designed bridge, single LOPs, including radar ranges, can be rapidly made and transferred to the ECDIS in order to confirm that they pass very close to own ship’s indicated position and therefore provide an excellent check on GNSS accuracy, especially with the low overall latency that can be achieved. Of course, consecutive bearings should be chosen such that they are as far out of alignment as possible.

Furthermore, the ECDIS mindset knows that subsequent single LOPs can be automatically combined by the equipment to form a positional estimate. ECDIS takes into account the time at which each LOP was applied and uses DR/EP techniques to perform the merger. The real beauty of this functionality is that it stores the input LOP data together with the derived position for future reference. This replaces the ‘cocked hat’ positional checks on paper charts so beloved of port state inspectors when assessing whether the position given by the GNSS position is being appropriately verified.

It is good to see that the ePelorus proposed by The Nautical Institute is now available for fitting to ships. A simple press of a button sends the data of gyro-referenced visual LOPs to the ECDIS, complete with the time reference of the measurements. This considerably eases the task of applying visual sights and further reduces latency. It should be borne in mind that a software upgrade to the ECDIS may be necessary to connect to an ePelorus.

Navigational integrity

The view from the bridge windows and information from ECDIS and radar jointly establish the best overview of the complete navigational situation – not just position. A user with a good ECDIS mindset is constantly checking all this information for consistency. Any inconsistency provides a warning that all is not well and that extra care or understanding is needed.

When independent sources of information agree, avoiding hazards becomes much more straightforward. However, care must be taken to ensure that radar is always used as the primary collision avoidance aid and ECDIS as the primary charting aid. Despite the increasing overlap of data than can be displayed on both systems, fundamentally neither is the equivalent of the other. If there is only one source of available data, for example a target’s AIS return from an area navigationally significant to own ship, great care is needed. Has it been missed by radar because of clutter or poor equipment set-up? Has it been missed visually because of poor visibility? Are there GNSS or gyro problems? Is the AIS signal in error? Is the signal a spoof, perhaps pirate initiated? Any decision must obviously take into account all such questions, and may ultimately require a very wide safety margin. The user must also know how ECDIS can be useful in establishing positional integrity in ocean waters. The automatic DR/EP facility is invaluable in keeping a check on GNSS gross errors over long periods. Celestially fixed position can also be plotted onto ECDIS as an additional check on GNSS. In the event of a complete GNSS failure the inbuilt ECDIS facilities are invaluable in maintaining a DR/EP fix over an extended time, whether in coastal or ocean waters, assisted as appropriate, by visual and radar sights or celestially derived position. How often do we hear the highly erroneous statement that ‘ECDIS cannot work without an electronic position fix system’?

Use of these alternative methods in the regular confirmation of GNSS positional integrity maintains the skill base needed to use them under emergency situations. In addition, it is essential that there are regular drills that mimic complete loss of GNSS, ensuring that the onboard procedures for such a situation are workable and fully understood by all.

Information display and route planning

Another huge advantage of ECDIS over paper charts is the control that the user has over what is displayed. When well set up, ECDIS shows all the charted information relevant to own ship and is far from creating any information overload. In particular, safe water areas (and vice-versa) can be very clearly depicted. However, to do this the user must be fully conversant with the role of safety contours and depths, setting the display detail and knowing what procedures to apply when having to enter waters less deep than the available safety contour, perhaps to enable port entry. If ECDIS is not properly set up then real problems can occur.

A skilled user is mindful of the embedded information facilities of ECDIS, particularly the ‘Pick Report’, which can be used to gain detailed information about any point on the chart. For instance, if they do not understand a particular symbol then a simple operation will display all known information at that point. The user with an ECDIS mindset knows how to rapidly find the required information and will not be phased by all the other information displayed that is also relevant to that point. In general, the visual experience of using ECDIS is very different to that of paper charts, forming an important part of the new mindset.

Having an ECDIS mindset also means being very knowledgeable about the route planning process. It is easy to design a route from scratch on ECDIS or to use a previous route as a basis. It is very important, however, that the route is manually checked and refined using up-to-date ENC data before each use, supported by all the traditional planning information, whether in paper or digital form. This especially needs to include the latest Temporary and Preliminary Notices to Mariners.

When undertaking this check, the largest available scale chart must be used for all portions of the route. Once a manual check has been performed it is highly beneficial to run the automatic safety check. This independently rechecks the route but needs to be carefully set up to prevent it coming up with a host of overcautious warnings. A user with a good ECDIS mindset will recognize that the auto check facility is not infallible - but neither is a check by a human. Performing both reduces the probability of an error. Even more importantly, the manual check gives the planner an invaluable awareness of the complete route.

By far the greatest challenge to the ECDIS mindset is in overcoming the tendency to a false sense of security. The problem is that ECDIS often appears to be highly accurate and it is all too easy to assume that this is true 100% of the time. At best, its accuracy is limited by the quality of the underlying ENC data which may have been taken from surveys made 100 years ago or more. (But, of course, the correct mindset always checks the current CATZOC status.) At worst, a combination of errors can make it highly inaccurate. If ECDIS is to really improve safety, all users must have a mindset that can determine the likely integrity of the perceived situation and use this as the basis for establishing the optimum navigational decision.

Finally, the company must also have an ECDIS mindset which should particularly be reflected in their Safety Management System. Migrating from paper charts to ECDIS implies detailed changes in such areas as risk assessment, emergency preparedness, operating procedures, drills and exercises, training and familiarization. Without this action, the requirements for a good user’s ECDIS mindset cannot be fulfilled.

Andy Norris is a Fellow of The Nautical Institute and is currently the Vice-President of the Royal Institute of Navigation. He is the author of the NI published textbook ECDIS and Positioning, which is extensively used by training colleges and shipping companies.