Introduction
1 This appendix supports the Guidelines for the standardization of
user interface design for navigation equipment by explaining the application
of human factors and cognitive science during the design of navigation systems. This
appendix also provides relevant information on human factors and human error and how
they relate to system design. It also discusses human factors research relating to
icons and display design, the presentation and processing of information and their
effect on decision-making, the effects automation can have on human performance, and
how a ship's systems, information displays and the human element form a distributed
cognition team.
Human factors research
2 Display technology has markedly changed and improved, providing an
operator with an array of multimedia formats for the presentation of information.
The effective design of new types of work systems has required the application of
knowledge regarding human information processing capabilities. This knowledge
requirement has created a greater emphasis on the issues relating to human
cognition, leading to an increased application of cognitive sciences, cognitive
psychology and other discipline knowledge to the design of work environments.
3 Adding to the original complexity of this domain is the fact that most
complex systems have multiple actors with multiple information requirements (e.g. a
master, pilot, OOW, helmsman and look-out on the bridge of a ship entering a busy
port).
4 Well-designed displays should provide support to the front-end of
decision processes (e.g. to an operator attending to and evaluating whether a cue or
piece of information is significant and salient, the operator then formulating a
diagnosis and assessing the situation).footnote Therefore, the proximity of objects on a display
screen becomes important to effective front-end decision-making. Display principles
such as proximity and emergent features help ensure that sources of information that
need to be integrated for the purposes of diagnosing a problem are displayed
simultaneously (not sequentially) to ensure rapid processing with minimal
effort.footnote
5 Well-designed systems have the propensity to support effective back-end
decision-making as well. Decision processes from the back-end of the decision cycle
concern the culmination in a final decision given information processing and the
response to the situation presented. Examples of back-end processes can include
retrieving an appropriate course of action from memory, locating a prescribed
response in the appropriate manual or procedures, adapting a known response to the
specific demands of the current situation, mentally simulating a possible response,
planning a sequence of actions or evaluating alternatives.footnote.
6 From a human-centred perspective, one of standardization's principal benefits, if
designed and implemented properly, is in the reduction of the user's physical and
mental workload. Reduction in mental workload has been identified as beneficial in
areas such as decision choice (e.g. high-risk decision-making under conditions of
uncertainty in unfamiliar situations), and information acquisition and analysis
(e.g. the cost of scanning a cluttered display for information or mentally adding
two numbers).
Icon usability
7 A great deal of research has been conducted to identify the factors that are
important in determining the usability of icons. An examinationfootnote of icon recognition tasks identified the following
effects:
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.1 The extent to which an icon depicts a real-life object as opposed to a
more abstract representation denotes its concreteness. Although a very
important usability trait for when an icon is unfamiliar, concreteness
effects diminish over time as an operator gains experience. Therefore,
an icon should be designed to be as concrete as possible to provide
heightened usability for novice operators. Usability testing is very
important for determining the transferability of these types of icons.
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.2 An icon's level of detail or intricacy is defined as its visual
complexity. A seafarer will be able to infer meaning from an icon more
quickly if it depicts a real-life object in detail. This is due to the
seafarer's understanding of the object via their pre-existing knowledge.
Increased detail in icons also increases visual search times, even
following considerable training. Icons should represent, as far as
practical, the real-life object while taking into account that less
detailed icons decrease visual search times. Icons should be designed to
look like the objects, processes, or operations they represent, by use
of literal, functional or operational representations.
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.3 How close the relationship is between the icon and its meaning is
termed its semantic distance. Semantic distance has been shown to be an
important determinant of novel icon usability.
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.4 A user's level of experience with the object depicted and the icon
itself denotes its familiarity. Familiarity is as important an effect on
icon usability as semantic distance but has been found to be longer
lasting, due mainly to an individual's experience level with an object
coming via access to long-term memory.
Information location
8 Good display design follows the principles that provide for global or holistic
information processing. This type of processing reduces the attentional demand on
the individual because it is preattentive (e.g. organized into objects or groups of
objects) and automatic. This lowering of attentional demand (and therefore the
lowering of fatigue-inducing attentional effort) will occur under two conditions.
First, Gestalt principles, such as proximity and symmetry, and other attention
principles, such as redundancy (e.g. knowing where one item is will lead the
operator to look for a similar or related item in the same location) should be used
to produce groupings of display icons and readout information (e.g. course, heading,
speed, etc.). Second, the organization formed by the spatial proximity of differing
elements on a navigation display must be compatible with the physical entities they
represent, and the seafarer's mental representation of those entities.footnote
9 For example, the essential information available to the navigator from an ECDIS
display should be easily accessed, easily cognitively processed and expected. Then,
it can be combined with what is observed out of the bridge window, the environmental
conditions and other available information, to build a mental model of where the
ship is and where it is heading – in other words, the navigator's situation
awareness. By applying proven display design principles to the proximity, redundancy
and grouping of icons and information readouts on the ECDIS or radar equipment
display, their mental model, and thus their situation awareness, will be enhanced.
10 When the seafarer needs to take information from two or more information sources
but they are required to be mapped onto a single task, the information needs to be
mentally integrated.
11 The designer has several ways to manipulate display proximity to help this
cognitive activity take place. Display proximity can be improved by placing readouts
closer to each other on the screen and thus reducing cognitive effort in the act of
integration. This same effect can be achieved through using similar-coloured
objects, cognitively linking two objects by drawing a line between them or abutting
two objects.
12 Research has shown that the closer the proximity of two objects in a display, the
better the seafarer's performance in integrating the information provided by the two
objects. However, there will also be a higher likelihood that performance will be
disrupted on a focused attention task. If a seafarer needs to focus on a readout in
a display and another readout or object is too close, it can act as a distractor and
slow their information processing. This has been identified as a property of display
clutter and this type of minimal separation or partial masking of one item over
another has been seen to be a design issue.footnote
Distributed cognition
13 The function of display icons and information is to enhance team situation
awareness. A navigator will use the physical world, the ship's systems and members
of the bridge team as sources of information and as extensions of their own
knowledge and reasoning systems. They can operate as a type of distributed
intelligence where much of their intelligent behaviour results through the
interaction of cognitive processes with bridge systems and the environment outside
the bridge window. Researchers have found that cognition may not necessarily be
confined to an individual's grey matter.footnote
14 The information and knowledge required to complete tasks is available in the
systems, resources, environment and other individuals they have at their disposal –
whether these artefacts are collocated, transmitted via voice/text or viewed on a
high definition display. When a seafarer's intellect is tightly coupled to their
windows on the world (e.g. their displays, their automation, the symbols and icons
that access the information they require and the bridge window), decision-making and
action can take place within the context established by the physical environment,
where the structures put in place can often take some of the memory and
computational burden off the human.
Projection to the real world
15 Sound navigational principles have been built on using a chart oriented to North
up. Information processing research and literature related to chart orientation has
shown that a seafarer may find navigational performance improvements by using a
chart which is oriented to the direction of travel (e.g. Heading or Course up). When
a frame of reference is not aligned (i.e. what is seen out the window is not a
direct representation of what they see on the chart – such as, they are heading
south using a North-up chart), the seafarer will need to mentally transform their
frame of reference. Research indicates that this requires cognitive processing and
an increase in mental workload, which may increase the likelihood of errors. Thus, a
frame of reference transformation from true to relative reference of a situation can
have an impact on human performance.
16 If the chart is an electronic display and can automatically rotate in the
direction of travel (e.g. "track up" or "heading up"), mental rotation effort is
minimized because text and symbols will rotate too, however, three other human
performance costs may be encountered:
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.1 It becomes more difficult for a user to build a mental model (or an
"understanding") of the environment. Research has shown people are less
able to reconstruct the environment after having operated with a
rotating chart.
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.2 There are substantial individual differences in mental rotation
ability. Some people will have no difficulty navigating with a north-up
chart, with minimal human performance costs in maintaining an awareness
of the greater spatial environment.
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.3 When communication is required between operators (e.g. between ships,
and ship to shore, such as VTS) who may not share the same momentary
frames, world referenced (exocentric or north-south-east-west) language
is more universal and less ambiguous than relative referenced (port,
starboard, ahead and astern) information. It is for these reasons that
electronic charts with a fixed north-up orientation mode are included as
a standard.footnote
17 The ability to orient to head or course up provides a benefit to navigation in
some situations (i.e. operating at high speeds or in littoral waters), but primacy
of a North-up chart orientation is in keeping with the fundamental principles of
navigation. Future research in this area is required to ascertain whether training
in the use of head up/course up charts in conjunction with North-up charts can
provide improved navigational performance.
Human factors methods for engineering and design
18 Navigational operators, who are the main users of navigational equipment, should
find that their displays provide a natural and intuitive interface between the
equipment, the tasks they need to perform and themselves. There are many
comprehensive methods for measuring and evaluating the cognitive, ergonomic and
organizational elements of system design and manufacture. Research into such areas
as human capabilities and limitations, human-machine interaction, teamwork,
interface design and organizational design spanning back over many decades has
provided the evidence for the validity of these methods and they continue to be used
widely. Evaluating new interface designs using the methods outlined in human factors
referencesfootnote and ergonomic standards,footnote in conjunction with the guidance of a human
factors/ergonomic expert/practitioner, is recommended.