International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 2
Number 1
March 2008
69
On an Advanced Shipboard Information and
Decision-making System for Safe and Efficient
Passage Planning
S.V. Hansen
Svendborg International Maritime Academy (SIMAC), Svendborg, Denmark
E. Pedersen
Norwegian University of Science and Technology (NTNU), Trondheim, Norway
ABSTRACT: Shipboard weather information and decision-support systems have been developed to assist the
officer on watch by supplying dedicated weather forecasts along a planned route. An added value can be
achieved by combining an existing system with functionalities providing information about the ship’s
performance in a seaway and an optimum routing algorithm. This paper describes functionalities for
predicting slamming, green water on deck, synchronous and parametric roll and the implementation in an
existing system to support safe and efficient ocean passage planning. A full scale test on board a container
ship crossing the North Atlantic Ocean has been carried out in order to gain operational experience for
evaluation of the concept. Further testing is required for validation purposes.
1 INTRODUCTION
An electronic nautical chart system is suitable as
platform to offer sophisticated and user-friendly
navigational functionalities with high accuracy
rendition of the geographic and environmental
information. Data from various sources can be fully
integrated and provide the user a total situation
awareness. It can be an expert system capable of pro-
viding solutions to navigational and safety problems.
Various shipboard information and decision-
support systems have been developed to assist the
OOW. An example is WeatherView
TM
(a product of
C-Map by Jeppesen) that is providing the mariner
with dedicated weather forecast.
This paper proposes and evaluates functionalities
suitable for an advanced shipboard information and
decision-making system that support safe and
efficient passage planning. A test system has been
developed on the software platform of Weather
View
TM
and includes implementation of functio-
nalities for prediction of slamming, green water,
synchronised and parametric roll. Relevant graphical
and numerical outputs are presented.
The system has been tested on board an
A.P.Møller-Maersk container ship for evaluation
purposes. It is argued that the proposed
functionalities are capable to provide valuable
information to the OOW in ocean passage planning.
Further testing is required to determine that
sufficiently accurate and reliable outputs can be
obtained.
2 SYSTEM
WeatherView
TM
is a weather information system
that supplies the user with information about the
forecasted weather and satisfies the demand for low
cost downloads. The system has a route planning
functionality where a selected route can be shown on
an electronic chart display. This enables information
about the weather to be compared for several routes.
The most suitable route (regarding the weather) can
then be selected and exported to a Word document
to be used in documentation for the passage
planning. Along the route it is also possible to
monitor response calculations for the ship where
70
heave, pitch and roll are calculated. A polar diagram
highlights area of danger where synchronous roll has
a probability to occur.
Fig. 1. Screenshot of WeatherView
TM
The calculations are based on basic ship data and
its load condition. The results can give an indication
of the ship’s performance in a seaway. Tidal
information is given for selected ports as well as
information of ice concentration. Typhoon warnings
and forecasted development of these are also shown
on the chart. It is possible to identify various danger
areas given by input from the user and these can be
displayed on a timeline if chosen.
3 ADDED FUNCTIONALITIES
3.1 IMO MSC 707 parameters
A ship sailing under heavy weather conditions may
encounter various kinds of dangerous phenomena
which may lead to severe roll motions capable of
causing damage to cargo, equipment and people on
board. The sensitivity of a ship to dangerous
phenomena depends on actual stability parameters,
hull geometry, size and speed of the ship. This
implies that the vulnerability to the dangerous
response and its probability of occurrence in a
particular sea state may differ for each ship.
The guidance issued by IMO’s Maritime Safety
Committee [IMO MSC 707, 1995], aims at giving
seafarers caution on dangerous phenomena that may
be encountered when navigating in following/
quartering seas. It provides the basis for a decision
on ship handling in order to avoid such dangerous
situations as well as advice on safe and unsafe
combinations of ship speed and course relative to
waves in a simplified form of a polar diagram.
Phenomena like synchronous/parametric roll,
broaching/surfriding and high wave group encounter
are included in the guidance.
3.2 Synchronous and parametric roll
Synchronous rolling resonance conditions occur
when the natural roll periods Tr of the vessel
coincides to the encounter period Te of the waves,
Figure 2, i.e.
where
44
r
is the roll radius of gyration with respect
to an axis parallel with the x-axis through the centre
of gravity,
44
A
is the roll added moment and
t
GM
is
the transverse metacentric height (the parameter
which has most influence on the roll period). M is
the mass, ρ is the density of seawater and
∇
is the
displaced volume of the ship. U is the ship’s speed,
T
0
is the wave period and β is the wave heading
angle.
Parametric rolling resonance conditions occur
when the natural roll periods of the vessel is equal to
half of the encounter period of the waves, Figure 2.
Fig. 2. Ranges of roll resonance
Furthermore, the vessel should be travelling with
a small heading angle to the predominant wave
direction (head or stern seas), wavelength should be
comparable to ship length, wave height should be
large and the roll damping characteristics of the
vessel should be low (low speed).
3.3 Slamming / green water
Wave impact typically occurs in the bow section of
the ship, at flat bottom sections, and at the upper
bow flare. For modern containerships slamming may
also occur at the stern section due to flat bottom
design. The impact loads are highly concentrated in
a very short time period and may result in damage of
local structure and accentuate structural vibration
throughout the hull, also known as whipping. Its
severity will depend on ship speed, wave height and
71
wave length as well as the design of the bow
sections, wet deck height forward and deadrise. The
probability of slamming to occur can be formulated
as [Faltinsen, 1990]
where V
cr
is the threshold velocity, σ
v
2
is the
variance of the relative velocity, d is the distance
from waterline to the slamming point and σ
r
2
is the
variance of the relative motion.
The green water problem arises when a ship is
sailing in heavy weather conditions and encounters
waves exceeding the freeboard level. The deck is
then wetted and the term “green water” refers to the
shipped water on deck, Figure 3. In most green water
incidents, the shipped water will not have any
destabilizing/damaging effect. However, in some
cases the amount of shipped water can be so large it
causes damage to deck equipment and cargo as it
could flood damaged compartments and cause
reductions in stability. The probability of green
water on deck to occur can be written as [Faltinsen,
1990]
where d
f
is the freeboard distance and σ
r
2
is the
variance of the relative motion.
Fig. 3. Green water load on a ship
4 MODELLING AND IMPLEMENTATION
4.1 Algorithms and data structure
A set of algorithms (appendix) for the MSC 707
parameters have developed for WeatherView
TM
.
The algorithms are based on general ship infor-
mation, the ship’s natural roll period and the wave
data obtained from the forecast in WeatherView
TM
.
The required inputs and details in data flow are
described in the Appendix.
4.2 Layout and interfaces
A graphical user interface has been proposed as a
“Condition Display” to provide relevant information
on the ship’s response under the predicted
environmental conditions, Figure 4. This interface
enables the OOW to view the environmental
conditions and the ship’s predicted response in
heave, pitch and roll. The polar diagram utilises a
roll down menu to show the selected phenomena (or
all) of the user’s choice. It also displays the ship’s
GZ curve to give an indication of whether the natural
roll period is higher or lower than the calculated
value. Finally, the ship’s course and speed will be
shown – as default from route calculations or by
user’s choice. This enables the OOW to watch
effects of course and/or speed changes on the polar
diagram.
Fig. 4. Condition display
5 FULL SCALE TEST
5.1 Ship and route
The test was conducted on a container ship m/v Olga
Maersk (3000 TEU) en route from Felixstowe (UK)
to Kingston (Jamaica) in April 2007, Figure 5. The
route was chosen on basis of the current weather
forecast to follow a rhumb line. Under way, weather
routing information and guidance was obtained from
the Danish Meteorological Institute (DMI).
Fig. 5. m/v “Olga Maersk” and route. Screenshot of Weather
View
TM
on 16. April 2007 at 1205 UTC. The northerly route is
the planned route and the southerly is based on advice from
weather routing service
72
5.2 Configuration set-up
A trial version of WeatherViewTM was installed on
a laptop and weather forecast was downloaded twice
a day. The ship’s motion was recorded by a Xsens
MTi motion sensor [Xsens Motion Technologies,
www.xsens.com] that was connected to a laptop and
placed at the bow section. The sensor recorded
accelerations and rate of turn in x, y and z directions
and provided direct output of roll, pitch and yaw.
The sensor was calibrated when alongside quay in
Felixstowe by using the calibration method as
advised by Xsens. The sensor was calibrated to
follow a coordinate system defined by ship’s
movements (positive x direction towards the bow,
positive y direction towards starboard and positive z
direction up).
5.3 Recorded data
The following parameters were recorded for
analysis:
− Ship motion (roll, pitch, heave acceleration),
course, speed and position.
− Engine RPM and kW, torque on propeller shaft.
− Fuel consumption pr. day.
− Environmental information.
Observations, table 1 were combined to a set of
time-series which were used to validate results from
calculations performed in WeatherView
TM
.
5.4 Validation
The following data were validated from observa-
tions:
− Ship’s response in current sea state: Roll and
pitch calculations were compared to observations
from motion sensor while heave motion was
derived from acceleration in z-direction and
compared to calculations in WeatherView
TM
.
− IMO MSC707 parameters were calculated for
various observations and compared to those
shown in WeatherView
TM
.
− Suggestions for optimized route was compared to
the route actually sailed. Comparison parameters
were speed and fuel consumption.
6 RESULT ANALYSIS
6.1 Setup
During the voyage numerous observations were
made, example:
Time
UTC
Latitude Longitude Course Speed
water
Speed
ground
1205 38°07'4N 33°01'0W 238° 23.8 knots 23.3
knots
Wind
direction
Wind
speed
Waves
direction
Waves
height
Swell
direction
Swell
height
220° 9.1 m/s 200° 3.0 m 200° 3 m
Engine
RPM
Torque Actual kW Average
kW
Fuel
consump.
95.0 2944x
10
3
kN
28.90x
10
3
kW
28.51x
10
3
kW
5.47 t/h
(average)
The motion sensor was set to record all ship’s
motion during the voyage. The observed data was
used to verify response calculations made in
WeatherView
TM
, example Figure 6.
The MSC 707 parameters shown on polar
diagrams were manually calculated for each observa-
tion and compared to those shown in
WeatherView
TM
, example Figures 7 and 8.
3175
3177
3179
3181
3183
3185
3187
3189
3191
3193
3195
-3
-2
-1
0
1
2
3
3175 3177 3179 3181 3183 3185 3187 3189 3191 3193 3195
-0. 4
-0 . 35
-0. 3
-0 . 25
-0. 2
-0 . 15
-0. 1
-0 . 05
0
0. 05
0.1
Calculated pitch compared to observed
Fig. 6. Comparison of response
73
Fig. 7. Calculated synchronous roll zone on polar diagram
Fig. 8. Polar diagram from WeatherView
TM
6.2 Results of analysis
The results of the analysis shows
− Agreement of observed and calculated response.
− Some errors in polar diagrams shown in
WeatherView
TM
. Errors occurred at random and
included roll zones and environmental data.
Due to nature of environmental conditions the test
results are not sufficient to give a full validation of
the system and further testing regarding sensitivity
and program structure is considered necessary.
7 CONCLUSIONS
Functionalities for prediction of slamming, green
water, synchronised and parametric roll have been
proposed for an advanced shipboard information and
decision-making system to support safe and efficient
ocean passage planning. A test system with proposed
functionalities has been developed on the software
platform of WeatherView
TM
. Relevant graphical and
numerical outputs are presented.
The system has been tested on board an
A.P. Møller-Maersk container ship for evaluation
purposes. It is argued that the proposed functional-
ities are capable to provide valuable information to
the OOW in ocean passage planning. Results from
the sea trial indicates further testing and development
of the system is required to determine that
sufficiently accurate and reliable outputs can be
obtained.
ACKNOWLEDGEMENTS
The authors are grateful to Jeppesen Marine (a
Boeing company) for assistance in implementing the
proposed added functionalities in a test version of
WeatherViewTM. A.P.Møller-Maersk is appreciated
for offering full scale-test to take place on board m/v
“Olga Maersk”.
REFERENCES
O.M. Faltinsen. “Sea Loads on Ships and Offshore Structures”.
Cambridge University Press, 1990.
IMO. “Guidance to the Master for Avoiding Dangerous
Situations in Following and Quartering Seas”. IMO MSC
Circ. 707. Maritime Safety Committee 65
th
session, 1995.
J.J.Jensen et al. ”Estimation of ship motions using closed-form
expressions”. Ocean Engineering 31, 2004.
Xsens Motion Technologies.”Software Documentation and
Development Kit”, 2007.
APPENDIX
The slamming and green water predictions are based
on calculated using simple closed form functions
[J.J.Jensen et al.,2003].
The wave spectra used is a generalized
JONSWAP spectrum formulated by the wave
frequency ω, the significant wave height H
1/3
, the
mean wave period T
S
and the peak enhancement
factor γ.
Algorithms and data structure for the MSC 707
parameters is shown in Figure 9 Synchronous Roll,
10 Broaching / Surfriding, 11 Parametric roll and 12
High Wave Group Encounter .