Article citation information:
Banachowicz, A., Wolski,
A. Information as an element of the navigation decision making process. Scientific Journal of Silesian University of
Technology. Series Transport. 2016, 92, 5-15. ISSN:
0209-3324. DOI: 10.20858/sjsutst.2016.92.1.
Andrzej BANACHOWICZ[1],
Adam WOLSKI[2]
INFORMATION AS AN ELEMENT OF
THE NAVIGATION DECISION-MAKING PROCESS
Summary. The
operation of vehicles (watercraft, aircraft, land-based, spacecraft, unmanned)
requires the use of navigation systems for their control. These systems can be
characterized by varying degrees of complexity and technological advancement.
However, each system has sources of information about the state (position) of
the navigating object, state of the environment in which the object is moving
and the task to be accomplished. These components are integrated by the
decision-maker (human or automated), who/which makes and implements decisions
adjusted to current conditions.
Keywords: safety of navigation.
1. INTRODUCTION
Navigation is an area of human
activity at sea. It is considered an art, an element of ship management or a
series of operational activities undertaken by engineers, as well as one of the scientific
disciplines. It is generally agreed, however, that it is a utilitarian science,
which has existed since the dawn of maritime civilizations.
Today, navigation is regarded as a
complex process of controlling (conducting) a vessel along
a determined trajectory, following a voyage plan and executing tasks. It is
a dynamic phenomenon because of the variability of external conditions and
possible changes of tasks being performed; thus, it also contains in itself a
decision-making process.
The navigation process is composed
of subprocesses. Generally, they can be categorized as
follows [1, 2]:
· acquisition of necessary and
additional information ensuring the safety of navigation or supporting the
execution of the voyage: it includes measurement and data sources (nautical
publications, electronic databases)
· preparation of a voyage plan:
processing of navigational information and guidelines on the voyage
· monitoring the trajectory, which
includes a number of tasks: determining the status of the implementation of the
planned trajectory (position coordinates, velocity vector of the ship,
deviations from the planned trajectory etc.), vessel position in relation to
navigational dangers
· proceeding along the trajectory,
which is steering the ship, making decisions on changes to the voyage plan
By its nature, navigation as the
decision-making process is largely based on information, the quality of which
has a significant impact on the safety and efficiency of human activities at
sea.
Navigational accidents lower voyage
economic indicators, reduce the safety of navigation or may even prevent the
execution of a ship’s tasks. Basic causes of navigational accidents related to
the quality or quantity of navigational information are as follows:
· lack of information
· outdated or incorrect information
· insufficient accuracy of the
information
To properly execute the navigation
process on the ship, one must carefully consider each of the subprocesses, take into account the different categories of
navigational accidents (through their elimination or considerable reduction)
and incorporate it into the relevant criteria of the ship. This issue is very
complex and so far has not found a full and satisfactory solution. Problems
related to the quality of navigational information and human factors are
commonly encountered in most ships and shipping areas.
2. DECISION-MAKING
We make choices in many different
situations, which is why we make decisions. These situations are called
decision-making situations and the person (or system) making decisions is the
decision-maker. In general, the decision-making situation is a description of
the conditions, limitations and purpose of making a decision. However, we
can rarely make just any decision. The actual situation often imposes
limitations on the choice, as we have to take into account the so-called
limiting conditions. The decision that meets the limiting conditions is called
the admissible decision. Not every admissible decision generates the same
effects. From the point of view of the objectives pursued by a decision-maker,
decisions can be better or worse. Therefore, we need to choose the best
decision for a given criterion: the optimal decision. This criterion is
called the choice (assessment) criterion.
The decision-making process can be
divided into the following stages [8]:
·
formulation
of the decision problem
·
construction
of a mathematical model or its simulated analogue version (stage of
formalization of the problem)
·
acquisition
and processing of output information necessary to determine the model
parameters (model identification)
·
calculation
procedures or simulations using a selected algorithm
·
qualitative
analysis of solutions
·
model
verification (relevance check, validation)
·
implementation
of the solution
There are various methods of
decision-making. These include [5]:
1. Receptive methods -
These are given to every human by nature or acquired in the learning
process, for example, instinctive actions, trial and error, habit and routine,
standard, experience, personal knowledge, character and experience exchange.
2. Associative methods
- Their essence is the intuition of a person or group of people. The methods
included in this group are characterized by unfettered thinking, imagination,
curiosity and human creativity, such as brainstorming, fictions or thought
experiments.
3. Methods of
collecting and ordering - They are distinguished by problem presentation in an
ordered form by the systematization of structures or concepts, e.g., a decision
tree, the search for synonyms, classification, group training and so on.
4. Combined methods -
These contain elements of the previous methods. These combinations make it
possible to achieve other quality features, which is very useful for very
complex decision problems. The methods include psychodrama,
thesis-antithesis-synthesis, projection, the “devil’s advocate” method etc.
5. Deductive methods -
These are characterized by the tendency to logically organize structures and
concepts. The essential ones are strict definition, analysis, abstraction or
formula, while other methods in this category are identification of causes,
dividing problems into partial ones, decision tables, analysis of costs and
restrictions, etc.
6. Mathematical models
- These include the “black box”, deterministic models, probabilistic models,
fuzzy models, simulation, extrapolation, sociometry,
transport algorithms, econometric methods, optimization methods etc.
7. Inductive methods -
These include schematic diagrams, matrices of hypotheses, network methods,
experiments and SWOT analyses.
8. Integrated methods
- These combine some features of the above methods and include value analysis,
integrated information management systems, the Kepner-Tregoe
method, cost-benefit analysis.
Ship management is based on the
autocratic-hierarchical system. As a result, in order to eliminate the human
factor, which is the main cause of navigational accidents, decision-making
methods, subject to automation, are used; these are mainly mathematical and
related modelling and expert methods.
Every decision-making process is
based on information. Its quantity, relevance to the present situation, timeliness
and other attributes significantly affect the decisions and the consequences.
In line with the nature of the
acquired information, we deal with deterministic models, models in terms of
randomness (risk) or under conditions of uncertainty. In deterministic models,
parameters are known and constant (or change in a known manner). In case of
risk models, distributions of random variables are given. In models with
uncertainty, input data distributions are not known. These models also refer to
rules of enemy behaviour in a conflict (e.g., in game theory).
The navigational situation is a
specific kind of a decision situation. The identification of
a navigational situation consists of its formal description, thereby
enabling an analysis. The navigational situation is characterized by its
space-time variability. You can assume that an assessment of a navigational
situation is a dynamic change in the decision situation, i.e., limiting
conditions, which impose a different set of admissible decisions.
3. INFORMATION AND NAVIGATIONAL
SITUATION
A piece of information is a factor
with which the receiver (human, another living organism, organization,
automatic device) can improve their knowledge of the environment and improve
their deliberate actions. It is usually believed that information is directed
specifically to someone. That is not quite true because conclusions drawn on
the basis of data, obtained from the environment in the process of research,
archives (databases) or elsewhere, are also information.
Taking into account the practical
considerations, information must have the following characteristics:
· exist
· be credible, not misleading
· withstand disturbances
· be available (able to be
transmitted)
· allow for reasoning and making
decisions
Maximized use of information is
important in decision-making, not just in terms of its storage. When not used,
information becomes useless.
Information is knowledge obtained by
interpreting data, which in a fixed context have a specific meaning and
refer to entities, such as facts, events, phenomena, processes and ideas.
Data are a representation of
information, suitable for communication, interpretation and processing. Data
take the form of alphanumeric characters, including digits and letters (more
generally, literals, which include alphanumeric and special characters),
symbols, images and other forms of records comprehensible to humans, or
applicable to computer processing or transmission. Computer data frequently
occur in the binary form. Data themselves are meaningless, only by
interpretation (human or computer) do they become information that can be used
to enrich knowledge.
Navigation takes place in a specific
physical space (geographical), hence its geospatial reference. Geospatial
information is obtained by the interpretation of geospatial data [6].
Navigational information is a
special case of geospatial information, which contains essential information
about navigating and other objects, the latter either being helpful to or
interfering with the movement of the navigating object.
Navigational information can be
divided into four subsets associated with the respective objects:
· information related to the ship (its technical
parameters and dimensions, manoeuvring characteristics, i.e., the dynamics of
the ship, autonomy etc.)
· information about the sailing area and its
geometry (geographical location, fairway size, bathymetry, distance to
navigational hazards etc.)
· information on hydro-meteorological and
climatic conditions (wind, currents, waves, icing etc.)
· information on the infrastructure at sea and on
adjacent coastline (including aids to navigation, equipment, communications,
logistics, legal status etc.)
Navigation information helps
identify a navigational situation, which is understood as a reciprocal
space-time location and an interaction of the navigating object, the
environment (its state is a hydro-meteorological and an astronomical situation)
and other objects affecting navigation (navigational dangers, e.g., collision
situation, aids to navigation etc.).
4. ATTRIBUTES OF
NAVIGATIONAL INFORMATION
Navigational information has
specific characteristics and is characterized by space-time variability. We can
identify some of its properties, which enable us to categorize it by quality
and quantity. The most widely known are accuracy criteria of navigational
information. However, the accuracy measures themselves do not fully reflect the
practical or theoretical usability of this information. Navigational
information as space-time information has some attributes (properties), the
most important of which are given below [3, 4]:
·
accuracy
·
repeatability
·
precision
·
resolution
·
variability
·
timeliness
·
reliability
·
availability
·
completeness
·
validity
·
cost,
·
value
Each of these attributes is
described below. The practical role of each attribute is different, but they
can be used in multi-criteria analysis of different sources of navigational
information.
All measurements, regardless of the
conditions and measuring instruments, are characterized by errors, caused by
several reasons, which can be divided into the following basic groups:
· imperfection of equipment and
measuring instruments
· imperfection of measurement and
data-processing methods
· variation of measurement conditions
· imperfection of the observer’s
senses
The imperfection of equipment and
measuring instruments is caused by the difference between the theoretical model
(physical or mathematical) of the fabricated device. Variable conditions of
performing measurements, as well as both external (environment) and internal
changes in physical parameters of measuring devices, are major causes of
errors. Continuous changes of the environmental, hydro-meteorological and
astronomical conditions significantly affect direct observations and
navigational measurements (which take optical bearings, measurement of the
height of celestial bodies, horizontal and vertical angles).
Generally defined, accuracy is a
distance from the true or real value. This feature applies primarily to
attributes of navigational data. Accuracy is determined by random, system and
absolute errors. The accuracy of a navigational parameter is characterized in
relation to its real value or the average (expected) value.
Repeatability of navigational
parameter measurements is understood as the statistical conformance of
measurements of the same navigational parameter when measurements are
performed:
· using various methods
· with different navigational devices
(systems)
· by different observers, in case of
non-automated measurements
· under different conditions
·
at
relatively long time intervals compared to the duration of a single measurement
Repeatability characterizes the
possible extent to which we can determine the correct (or real) value of a
quantity, regardless of the applied measuring instrument, device or system.
It is thus the broadest concept defining the possibility of making
measurements of a given quantity and corresponding accuracy. However, we are
interested not only in measurement results, but also to what extent they are
correct and what their range can be.
The precision of measurements is
another concept often confused with accuracy. This is particularly the case
when we are not aware of the presence of significant system errors, which
hinder assessment.
The repeatability of measurements is
therefore the internal measurement conformity of the navigation device
(system). It is sometimes called repeatable accuracy. The repeatability of
navigational measurements is estimated using average error (or variance) in the
case of scalar parameters or error ellipses, circular errors, and covariance
matrix determined empirically for the device (the system) under specified
measuring conditions. The measurements’ precision characterizes
repeatability.
In general, precision means accuracy
in relation to the average value of a given quantity. Sometimes, however, the
term precision is viewed as the
number of digits that are significant in a numerical record or to read-out
accuracy on the measuring scale.
In spatial information systems,
including navigational systems, the concept of repeatability also includes
mutual conformity of data:
· recorded at the input
· presented at the output
This necessitates elimination of
generating errors (disturbances, data distortion) by the data-processing
system.
By the term resolution (differentiation), we mean the ability to detect or
differentiate subsequent levels of the value of data in question. Resolution is
also the smallest distinguishable piece of an image, i.e., the pixel, e.g., of
a map, or the coordinates calculation unit, e.g., 0.0001’ in the DGPS. As we see, this notion can often be confused with the precision
of measurements and instrumental errors.
As a
measure of variability, we assume the average time frame, after which the value
of this attribute changes in reality. The variability of some navigational
parameters is relatively easy to determine, such as position coordinates or
components of the velocity vector in the case of continuous measurements
(or frequently performed). In other cases, we may not be aware of the
variability of navigational information, as evidenced by cases of navigational
accidents caused by a dredging anchor, i.e., the deviation from a safe position
(apart from situations caused by humans, although, in this case, too, we deal
with the variability of navigational information). Unlike the data in commonly
used geographic information systems, navigational information is highly
variable; and, in the case of air and space navigation, the variability is
substantially greater.
The
concept of information variability is closely linked to its timeliness or
validity. The validity time is the interval between the moment of
inputting an attribute value change to the system and the time of the next
change in attribute value. The data received during that period are valid. The
data out of this time span are invalid. The period of variation is the difference
of instants of subsequent changes to attribute values; this refers to discrete
(step) measurements or to a situation where the parameter itself is a discrete
quantity.
The determination of
information reliability is related to major terminological problems. These
result, for example, from what is commonly understood by the term reliability. Navigators are familiar
with the term integrity associated
with the GPS. The reliability, or should we say, integrity of the system is
differently understood by IT specialists. Thinking of a human as a source
of information, we assume that he is trustworthy if he does not fail our trust;
we can just believe him. However, it takes time before we start to trust a man.
We deal with a similar type of reliability in the case of nautical
publications, which are authorized by hydrographic offices. Such publications
require updating by introducing valid information corrections provided by the publishers.
However, in relation to navigational equipment and systems, especially to
rapidly changing nautical information, the trust ought to be of a different
nature and differently justified. Reliability is intuitively associated with
the concept of the uncertainty of information.
The uncertainty of information is
marked by the following terms: probable,
possible, necessary, plausible and credible. Everything that can be
inferred from a collection of factual knowledge is credible. The problem is how
to practically verify the trustworthiness of received information. We deal best
with probabilistic types of information. It is harder when it comes to the
assessment of information, when burdened with system errors or different
sources pass around different information, which is often contradictory.
Considering
information reliability, we often understand reliable to mean correct, within acceptable limits, rather than in
the colloquial sense, i.e., information that we have no reason to reject. It is
simply possible information. On the other hand, the technical system is
reliable when it is operational, performing the tasks that the system was
designed to do. Reliability is also conformity, within the limits of
measurement errors, of the information from measurements in the system and the
real state at the time of data retrieval. Non-conformity may result from
invalidity or different kinds of mistakes, including getting wrong data.
Acquired navigational information can be tested, often by statistical tests,
for instance, by comparing with average values or verifying the conformity with
other sources of information. We simply use the fact that reliable information
is not completely random and we have some knowledge enabling us to verify it to
some extent.
We must also realize that the
reliability of navigational information is not only affected by equipment and
technical systems from which this information is obtained, but also by its
processors: people, algorithms and computer programs.
The concept of reliability is very
broadly understood with regard to information systems. Dependability is an attribute we rely on in order to trust the
services offered by a computer system. Dependability is a high-level attribute.
It can be decomposed to lower-level attributes, as follows:
·
reliability
·
availability
·
safety
·
security
Reliability determines the ability
of a system to deliver continuously expected services, in certain operating
conditions. Reliability is well defined with regard to technical systems.
Safety means that, in the event of a failure,
the system will not cause danger (accident, disaster etc.). This becomes
important, as the process of navigation is subject to widely implemented
automation. Automatic collision avoidance systems, intelligent autopilots
controlling the trajectory, and similar types of systems and devices must not
introduce new risks. This known issue concerns one-man watchkeeping
or unmanned vehicles. These problems are scientific, technical, economic and,
above all at present, legal in nature.
System security involves access to
information being processed, stored or transmitted by the system. This applies
in three respects:
· confidentiality - determining the
degree of protection against unauthorized access to information (GPS)
· integrity - determining the degree
of protection against unauthorized modification (in a different sense
to the GPS)
· availability - determining the
degree of assurance that the information will be immediately accessible to
authorized staff
Factors that may reduce the
reliability of the system fall into two categories:
· system failures, which make the
system operation deviate from the specification of desired behaviour, including
software defects
· defects (errors) of the
specification
Therefore, a reliable system must
assure:
· detection of failures (errors)
· early warning
· location of failures
· correctness of interpretation
The reliability of a computer system
so understood lacks reference to the reliability of the very information
processed in this system. It is commonly known that the reliability of output
data also depends on:
· the reliability of input data
· the correctness of the software
(processing)
The concept of reliability is most
prevalent in relation to the GPS, although it applies to all types of systems
and navigational information. Previously, it was sometimes considered in the Loran-C
system in air navigation applications. Currently, in the more widely developed
theory and technology, the integrity of the GPS, formally speaking, is narrowed
to mean the “ability to alert that the position given by the receiver is
incorrect, because the system is not working properly” [7]. Other definitions
are of a similar nature. For example, according to the definition of the
US Federal Radionavigation Plan: “Integrity includes
the ability of the system to provide timely warnings to users when the
system should not be used for navigation”. In some cases, it is assumed
outright that “the integrity of the system is the ability to provide a
pilot with a warning within 10 s of error exceeding 0.3 nautical mile”.
However, it should be noted that
these definitions of navigation system integrity
are directed primarily to navigator practitioners and show what practical
effects they can expect as a result of appropriate processes and system
security. Currently, the concept of GPS integrity is already close to the views
presented by IT specialists and comprises the entire navigation measurement and
information system, not just measurements.
The availability of data
characterizes the percentage of time that the services of the system are
usable, provided they are within the specified coverage area. It is a
characteristic related to the ease and speed of obtaining data from the system.
It may depend on the system, the user or data type. Availability of the
navigation system or, more broadly, navigational information, is also spatial
in nature. Therefore, the availability of navigational data depends on the
region, time and navigation equipment of the ship and the area, as well as the
communications systems of the specific vessel. These are reminiscent, in the
era of satellite systems, operation zones and ranges, of radio navigation
systems. The issue also refers to such navigational information as the
determination of the availability of pseudorange
corrections from the DGPS.
Completeness is an attribute that
can be expressed as the ratio of the number of data stored in the system to the
number of data that the system should contain. You can divide completeness by
area and content. This attribute is generally difficult to determine. The exceptions
are cases when we can precisely define a set of necessary navigational
parameters and the range of their values. They are mostly cases determined by
specific regulations (SOLAS Convention, presently
determined requirements of AIS, port regulations, pilotage requirements etc.).
Relevance expresses the degree to
which information demands of the user are satisfied. A precise definition
of this characteristic encounters similar difficulties to those of data
completeness. Relevance is only well defined in routine situations, while, in
other cases, it is difficult to determine, a fact well known to those navies
that have had a long experience of planning the navigational and hydrographic
security of operations.
Cost is the feature often
overlooked, probably because the ship, from the point of view of the crew,
usually has specific, fixed navigation equipment already. Similarly, regardless
of the ship’s navigator, aids to navigation within a specific region currently
exist. The only costs of obtaining navigational information at the
decision-making level are those of purchasing navigational aids, their
updating, pilotage fees etc. Most of the institutions involved in navigation
services to ships are the ones that are really aware of the actual costs of
nautical information. In general, the cost of navigational data consists of the
costs for the following component:
· data acquisition
· data processing
· providing the user with data in a
particular form
It is not important who currently
incurs these costs. Free navigational warnings received on board have also been
paid for: namely, the cost of the shipboard receiver and the cost of the entire
system of information acquisition and distribution.
The value of data, or, more
precisely, the information obtained from the data, can be determined by:
· the benefit of using the obtained
information instead of, or in addition to, the information already
possessed
· the loss that the user would suffer
if the information was not used
In maritime navigation, especially
in what we call the safety of navigation, the value of data is most often
associated with possible loss. The exception to this is the optimization of the
voyage based on weather routing.
5. CONCLUSION
The article presents the main concepts
related to the navigational situation and information, as well as the relations
of the latter with the process of navigation. Problems associated with
navigation subprocesses, navigational information and
its processing have already been dealt with by many authors. From the viewpoint
of the entire process of navigation, no comprehensive approach has been taken
to date. In practice, studies of navigational and hydrographic security of navy
operations are the only exception, in which navigation is viewed as
a whole, not as isolated processes and entities, such as the ship, the
harbour master’s office, VTS and so on. The same
applies to the problem of the demand for navigational information from
different users and different kinds of navigation, namely, sea, air, land and
space.
Analysis of the navigational
situation and particular attributes of navigation information imply that the
following actions are necessary:
· develop correct and acceptable
definitions of the accuracy of navigational parameters (more broadly, nautical
information)
· determine the real accuracy of
navigational information, not just measurement accuracy
· determine the variability and
validity of navigational information (navigational parameters, meteorological
and hydrographic data)
· develop a methodology for verifying
the reliability of navigational information
· develop consistent and reliable
methods of navigational data fusion, in particular, measurement (point) methods
with imaging and text (verbal) methods
Quantitative estimates of the other
attributes of navigational information would allow for optimizing the selection
of nautical information depending on the adopted criteria, i.e., availability,
cost, value etc., and the trading regions and tasks performed by vessels. The degree
of satisfying the information demand of the navigator (or information
relevance) depends on the tasks performed by the vessel, the
hydro-meteorological conditions prevailing in the area, the area parameters and
the regulations in force (including vessel traffic organization and control).
Another issue for consideration is the provision of a wide access to the
current situation and navigational information to a large group of
non-professional leisure boat users.
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Received 15.02.2016;
accepted in revised form 21.06.2016
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