1 INTRODUCTION

Different stages should be considered in the design of

harbours involving diverse tools. As described in the

methodology to design a navigation channel provided

by PIANC [4], a concept design is initially selected

based on guidelines. This first design can then be used

as a basis to develop a more detailed design which

consist of refining the initial one using more accurate

input data. At this stage, a real time simulator is a

useful tool to reproduce the behaviour of the vessels

in specific hydro-meteorological conditions and to

assess the operational limitations of the selected

design based on nautical expertise as well as

feedback from pilots.

Real time simulations are also used extensively to

evaluate the accessibility of larger ships using existing

access channels, as for example is the case for ships

calling the port of Antwerp [2]. Specific critical

locations can be examined and the results of the

simulations can be used to propose solutions to tackle

those bottlenecks by for example proposing additional

AtoN (Aids to Nagivation). Full mission bridge

simulators can also be used for the improvement of

vessel traffic services and personnel training to

improve safety of navigation as presented by Senčila

et al. [7].

The level of realism of simulations relies mainly on

the accuracy of the mathematical manoeuvring model

and of the hydro-meteorological model which are

used to reproduce the behaviour of a specific ship in

specific environmental conditions. The degree of

realisms can differ significantly. For example, the

bottom of a waterway could be represented as a flat

hard surface, but could also be represented as an

irregular surface composed of mud with varying

density properties (e.g. [8]). Although it is common

practice to use state of the art mathematical models

and complex post-processing techniques to implement

accurate hydro-meteorological data as described by

Nautical Access Study Based On Real Time Bird’s Eye

View Simulations

M. Mansuy

, M. Candries

& K. Eloot

Ghent University, Ghent, Belgium

Flanders Hydraulics Research, Antwerpen, Belgium

ABSTRACT: Real time ship manoeuvring simulations are a valuable source of information in the detailed

design phase of nautical studies. The feedback of pilots, which is not available for fast time simulations that are

carried out by a computerized autopilot, is an important asset in the evaluation of the feasibility of ship

manoeuvres. However, real time simulations are significantly more expensive in that realistic 3D visuals are

needed so that the pilot can immerse himself in a sailing environment. Modelling and generating such 3D views

is time consuming and requires expensive hardware and special skills. Real time simulations that offer only a

2D bird’s eye view for the execution of manoeuvres by pilots, can sometimes be used as a cheaper and faster

alternative. This paper presents a case study that evaluates the nautical access to two harbours and discusses

some of the advantages and disadvantages of a real time bird’s eye view setup

http://www.transnav.eu

the International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 15

Number 1

March 2021

DOI: 10.12716/1001.15.01.04

Donatini et al. [1], it is difficult for a pilot or a client to

perceive this level of complexity. Indeed, the core of

the simulator is hidden behind its walls and the

fidelity of the visual setup can sometimes have a more

significant influence on the user immersion [5].

An important advantage of full mission bridge

simulators is the integration of the human factor but

this involves challenges to guarantee a good

immersion of the user. Therefore, it is important to

reproduce the ship bridge as completely as possible

with all the monitors and controls that could be found

in real-life [3]. The pilot can then interact with this

interface and displace the ship in an environment with

the same level of easiness/difficulty as in reality. The

visualization of the environment above the waterline

is the main aid for the pilot to position the ship. Most

simulators reproduce the environment in 3D and

display it in front or around the pilot. However,

depending on the level of details and the size of the

environment, the development of this three-

dimensional environment can have a significant

impact on the cost and preparation time of a project.

This paper describes the use of real time

simulations that are carried out to assess the

operational limits of two ports within a limited time

frame. In order to reduce time and cost, the study was

carried out using a specific two-dimensional bird’s

eye view setup to represent the outside view on the

harbour as an alternative to a 3D view which can be

found on most common full mission bridge

simulators.

Section 2 explains how these real time simulations

were set up. Section 3 presents the criteria which were

used to evaluate the safety of entrance and exit

manoeuvres and discusses the results. The advantages

and disadvantages of the 2D view in comparison to a

3D view are discussed in section 4. In Section 5,

finally, the conclusions are given.

2 2D BIRD’S EYE VIEW SIMULATOR

2.1 Objectives of the study

In order to assess the accessibility levels of new

designs for the ports of Ténès and Annaba in Algeria,

a simulation study was commissioned by Laboratoire

d’Études Maritimes (LEM) and executed by ISL

Ingénierie together with the Maritime Technology

Division at Ghent University (UGent) and Flanders

Hydraulics Research (FHR). Different manoeuvres of

entry and exit of the ports (total number of 50) were

simulated with bulk carriers, container ships and

general cargo ships of different sizes in the most

critical hydro-meteorological conditions (two for each

port) in order to determine the maximum allowable

size of the vessels calling to both ports and the

operational limits.

2.2 Manoeuvring simulator

The simulations were carried out on one of the full

mission manoeuvring simulators at Flanders

Hydraulics Research dedicated for maritime studies

and training. This maritime simulator is composed of

a ship bridge with a 225° aerial view projected on

screens as shown on Figure 1. The 3D view displayed

outside the windows of this ship bridge requires some

3D designing work and large graphics resources

which would have been too time consuming and

would have significantly increased the cost of the total

study presented in this paper. In order to save some

time and to restrict the overall cost of the project, it

was proposed to the client to carry out the simulations

using a two-dimensional bird’s eye view. Hence, no

3D visuals needed to be prepared and the screens

displaying the outside view on the ship bridge were

turned off. Instead, the environment was displayed on

a monitor located in front of the pilot, as shown in

Figure 2.

During the simulations, the pilot can visualize the

contour of the ship moving in the 2D representation of

the port, the coastline and the boundaries of the

approach channel (when available). Other information

such as wind direction and speed, ship’s speed and

under keel clearance are displayed as well.

Figure 1. Manoeuvring simulator for maritime studies

(Flanders Hydraulics Research, Belgium).

Figure 2. 2D bird’s eye view of the Port of Ténès as seen by

the pilot on the simulator.

2.3 Port environment

The part of the port above the water level is

represented by a simplified 2D aerial view on the

simulator bridge, as shown in Figure 2. The

environment that is shown includes the layout of the

port, the coastline and the specific mooring areas for

different types of vessels. The approach channel was

also displayed for the port of Annaba. No approach

channel was designed for the port of Ténès. The part

under water is modelled in 3D based on a bathymetric

model implemented in the simulator for each port, as

shown in Figure 3 for the port of Ténès. This part

under the waterline is not shown to the pilot during

the real time operations, but is used for the post-

simulation analysis.

Figure 3. Bathymetry of the port of Ténès. From deep

(green) to shallow zones (red).

Figure 4. Current field in the extreme hydro-meteorological

condition at the entrance of the harbour of Ténès (harbour

new design in white).

Wave induced vertical motions were not simulated

as they were considered to have a limited impact on

the manoeuvres, especially in comparison to the

impact of the wave induced currents on the horizontal

motions. A second reason is the fact that only a top

view is used so vertical motions would not enhance

the level of fidelity of the simulations as would be the

case in a traditional 3D visual environment.

The currents modelled in the two ports are mainly

generated by the annual swell. Two current

conditions, referred as moderate and extreme in the

next sections, were implemented in the simulator for

each of the two ports. These data were provided in the

form of current velocity vector fields, as shown in

Figure 4 and Figure 5. Wind conditions of force 6 to 9

Beaufort were included as well.

Figure 5. Current field in the extreme hydro-meteorological

condition at the entrance of the harbour of Annaba (harbour

new design in white, access channel in red).

2.4 Ship models

For this study, four standard manoeuvring models

from the FHR database were selected and scaled to

represent the 6 design vessels as described in Table 1.

ASD tug boats were modelled based on the

communicated towing capacities of the ports (see

Table 2).

Table 1. Design vessels characteristics implemented in the

simulator.

_______________________________________________

Characteristics Container Bulk Cargo

Ténès/Annaba ship carrier vessel

_______________________________________________

DWT (ton) 20000/30000 30000/60000 20000/30000

LOA (m) 184/218 181/235 170/193

LPP (m) 177.1/209.8 173.1/224.8 162.3/184.3

B (m) 28.7/30.2 27/34 24.9/27.8

T (m) 10/11.1 10.6/13.5 10.4/11.9

Bow thrusters 800 - -

(kW)

Frontal wind 924/1079 431/691 415/531

areas (m²)

Lateral wind 3098/4074 1411/2334 1228/1595

areas (m²)

_______________________________________________

Table 2. ASD tug characteristics implemented in the

simulator.

_______________________________________________

Port Tug Bollard pull Engine power Mode

_______________________________________________

Ténès fore 20 ton 1100 kW Push or pull

aft 40 ton 2x1400 kW Push or pull

Annaba fore 40 ton 2x1400 kW Push or pull

aft 40 ton 2x1400 kW Push or pull

_______________________________________________

For each simulation, 2 tugs (one attached to the

fore part of the ship and one attached to the stern

most of the time) were provided and controlled by the

operator, as shown in Figure 6, under the orders of the

experienced pilot.

Figure 6. Console dedicated to control 4 tug boats from the

instructor room.

Moored vessels models have also been added to

the 2D bird’s eye view in order to add more realism to

the actual situation and available space, especially

during a mooring manoeuvre in the port basins.

2.5 Pilots

The real time simulations were carried out by 4

different Flemish pilots(Flemish pilotage DABL)

during 4 days (one different pilot each day) to check

the accessibility level of the critical configurations

which were defined while setting up the protocol for

the simulations. The pilots are familiar with the

simulators at FHR and in particular with port to river

entry/exit manoeuvres with vessels of the same size as

the design vessels.

The last three days were organized in the presence

of the client LEM, ISL and Direction des Travaux

Publics (DTP). The last day, two Algerian pilots also

performed a number of simulations and shared their

local experience and navigational habits with the

Flemish pilots.

3 MANOEUVRING ASSESSMENT

3.1 Methodology

After each simulation, the pilot is invited to the

control room to discuss the scenario being tested and

sometimes there is an exchange of opinions. The track

of the ship is shown to the pilot on the operator screen

together with the bathymetry, wind vectors and

current vectors, as shown in Figures 3 to 5. The pilot

then assigns two marks out of 6 points to the

manoeuvre according to an evaluation grid as shown

in Table 3. It should be noted that the reserve reflects

the safety margin available as estimated by the pilot,

while the degree of difficulty reflects the level of

stress and concentration of the pilot. When a run is

not acceptable, measures are discussed with the pilots.

The nautical expert takes into account the pilot

feedback and gives a conclusion on the accessibility

level (acceptable or not acceptable) after a more

detailed analysis of all the post-processed trajectories

and time series of the control parameters (ship’s

velocity, rudder angles, use of tugs power, current

velocities etc…). This analysis is discussed internally

and reported to the client with conclusions.. The pilots

were instructed to use the tugs only when necessary.

The use of the tugs was not imposed, but they were

made available for each simulation. The assistance of

the tugs was discussed during the analysis of the

simulations and specified in the protocol.

Table 3. Protocol and results of the simulated entrance (In)

and exit (Out) manoeuvres in moderate (Mod.) and extreme

(Extr.) hydro/meteo conditions presented in section 3.2 with

BC = Bulk Carrier, CN = Container Ship.

_______________________________________________

Simulation protocol Results

Pilots Nautical

feedback expert

_______________________________________________

Port Vessel Dir. Cond. Reserve Difficulty Access.

/6 /6 level

Ténès CN In Mod. 2 2 Acc.

Ténès BC In Mod. 1 1 Acc.

Ténès BC In Extr. 2 2 Acc.

Ténès BC Out Extr. 2 2 Acc.

Annaba BC In Ext. 3 3 Not acc.

Annaba CN In Extr. 1 2 Acc.

Annaba BC Out Extr. 1 1 Acc.

_______________________________________________

3.2 Analysis of entrance and exit manoeuvres

The main results and observations of the simulations

are presented in this section through examples of

simulated entrance and exit manoeuvres in both ports

highlighting the use of the 2D bird’s eye view.

Some general observations can first be made.

Depending on the vessel type and dimensions,

different levels of accessibility were obtained. The

container ship is equipped with a bow thruster which

allows for more manoeuvres without requiring the

assistance of tugs, whereas the bulk carrier and

general cargo vessels require the use of tugs most of

the time. Bulk carriers and general cargo are also less

manoeuvrable. The container ships, on the other hand,

can be more challenging to control in strong wind

conditions due to the larger windage areas.

An approach in longitudinal current is easier than

an approach in cross current. As the current at the

port entrance is directed from southeast (cf. Figure 4),

the pilots tried to approach the port from the

northwestern side, almost perpendicular to the jetty as

shown in Figure 7, in order to sail in the opposite

direction of the current flow. However, during the

manoeuvre it can be noticed that the ship encounters

some difficulties while turning to enter the harbour

because the current on the stern counteracts with the

turning moment of the ship. Powerful tugs are

therefore required to assist the ship in its turning

manoeuvre, thus allowing to pass safely the harbour

entrance. This manoeuvre was not possible in extreme

conditions with a bulk carrier.

Figure 7. Entrance of the port of Ténès of a bulk carrier with

tug assistance in moderate conditions (vessel in purple, fore

tug in orange and aft tug in white).

Figure 8. Entrance to the port of Ténès of a bulk carrier with

a large drift angle due to current in extreme hydro-

meteorological conditions.

To enter the port of Ténès with a bulk carrier in

extreme conditions, one of the pilots requested to try

an approach with a cross current to evaluate the drift

generated by the current flow. Figure 8 shows that the

pilot anticipates first the effect of the south east

current by sailing to the north east direction and then

let the ship drifting for about 100 m. The pilot corrects

his heading just before the entrance of the port, which

is then protected from cross current. During this

manœuvre it is important to feel the effect of current

accurately. During the simulation, the pilot requested

to optimize the view on the 2D screen to have a more

detailed view on the ship relative to the northern jetty

and he had to use the radar and draw lines to

visualize the drift motion of the ship which was

difficult to estimate on the 2D bird’s eye view. In

reality or in a 3D environment the pilot would have

more reference points to feel the ship drifting.

In moderate hydro-meteorological conditions, an

entrance manoeuvre under cross current is also

acceptable when a container ship is approaching

parallel to the jetty and counteracting the drift due to

current and wind with sufficient safety margins when

passing the harbour entrance (100 m from the

southern jetty), as shown in Figure 9. Tugs were used

to assist the ship in the manoeuvre to turn to the

mooring area. A collision can be noticed during the

mooring manoeuvre, but the pilot claimed that in

reality visual reference points would have helped to

position the ship more accurately and would have

allowed to prevent the collision. This part of the

trajectory could not be exploited since the level of

realism of this manoeuvre was not sufficient

according to the skipper. Note that this example is

only used to illustrate a limitation of the simulation

setup and has no consequences on the accessibility

assessment which focuses on the approach

manoeuvres.

Figure 9. Entrance to the port of Ténès of a container ship

with a large drift angle due to current and wind in

moderate conditions (vessel in purple, fore tug in orange,

aft tug in white).

The entrance of the port of Annaba follows an

access channel. In extreme hydro-meteorological

conditions, the pilot is using the current effect, shown

in Figure 10, and sails very close to the boundaries of

the channel (i.e. 6 m was measured from the vessel to

the channel boundary), as shown in Figure 10.

However, the distance from the ship to the jetty

(about 45 m) is accurately controlled since the pilot

has a clear view on the channel boundaries on the 2D

bird’s eye view. In reality, the pilot would see this

only on an electronic chart or on the radar. This

example shows that the current field and the

bathymetry need to be well known by the pilot in

those hydro-meteorological conditions.

Figure 10. Entrance of the port of Annaba of a bulk carrier in

extreme hydro-meteorological conditions (vessel in purple,

aft tug in white, access channel dredged to – 17 m in red).

After a couple of runs with a container ship in

extreme conditions, the pilots recommended to

approach the harbour entrance from the south and let

the ship drift in the current field toward the north by

setting a NNW heading to pass the second jetty and

then turn toward the harbour, shown in Figure 11.

Those observations can be used to provide

recommendations for the training of pilots.

Figure 11. Entrance of the port of Annaba of a container ship

in extreme hydro-meteorological conditions (vessel in

purple, aft tug in white, access channel dredged to – 17 m in

red).

To exit the port of Ténès, since bulk carriers and

cargo vessels are not equipped with bow thrusters,

tugs are used to help the pilot in order to move away

from the quay against current and wind, as shown in

Figure 12. This manoeuvre was successfully

performed on the simulator and the fidelity of the 2D

bird’s eye view in combination with the tug console

was sufficient. It may be noted that the exit

manoeuvre is not as difficult as the entrance

manoeuvre since the ship can accelerate and reach

enough speed and space to manoeuvre.

Figure 12. Exit of the port of Ténès of a bulk carrier in

moderate hydro-meteorological conditions (vessel in purple,

fore tug in orange, aft tug in white).

Figure 13. Exit of the port of Annaba of a bulk carrier in

extreme hydro-meteorological conditions (vessel in purple,

fore tug in orange, aft tug in white, access channel dredged

to – 17 m in red).

To exit the port of Annaba, the pilot needs to find

the best time to initiate the turn toward the exit, as

indicated in Figure 13. During the simulations, the

pilot managed to find the best spot by calculating his

turning rate and estimate the trajectory from the top

view. However, in reality this is trickier without

electronic equipment. Leading lights were

recommended by the pilots to position the ship from

the exit extremities of the harbour.

3.3 Recommendations for accessibility improvement

Based on the analysis of the ship trajectories and

pilots’ feedback, different recommendations have

been suggested and the main output consists of a

proposal for optimal approach trajectories and AtoN.

It is worth noting that the simulations were carried

out by several pilots, not all of whom were familiar

with the site conditions. This enabled several opinions

to be obtained on the complexity and the measures to

be adopted. The opinions of the different pilots turned

out to be quite similar which, thus giving credibility

to the assessments provided.

To enter the port of Ténès, two approach paths can

be considered according to the pilots' feedback. An

approach trajectory from the north, facing the current,

requires a 90° turn. It is then necessary to rapidly

reduce the vessel's rate of turn once aligned with the

jetty to avoid contact with the breakwater or jetty. In

extreme hydro-meteorological conditions, this

trajectory was validated only for container ships and

for general cargo vessels. For bulk carriers, it was

advised to approach the port parallel to the jetty,

which is less subject to drift due to the wind.

Container ships can approach the port aligned with

the jetty or from the north. It should be noted that

approaching from the north requires a good

knowledge of the current and adequate training. An

approach parallel to the coastline allows the vessel to

sail with a large drift angle for a considerable

distance, especially in strong winds.

To exit the port of Ténès, the drift due to wind

seems important and the current inside the harbour

requires the use of at least one tug. It is advisable to

align with the jetty as soon as possible.

The AtoN recommended for the port of Ténès are

shown on Figure 14. Vessels must navigate at least 150

m from the northern tip of the jetty in extreme

conditions to avoid being in a field of currents

reaching high velocities. It is recommended to place

two buoys in a 90° line with the jetty and at a distance

of 100 m from the extremity. The depth line at -12 m

should also be marked with buoys. This identifies the

direction of the current along the coastline and aligns

with the harbour entrance. This allows vessels to

safely approach as close as possible to the coastline to

anticipate drift due to the current in extreme

conditions when approaching parallel to the jetty.

At the entrance of the port, two 40-ton tugs are

needed to assist bulk and cargo vessels to enter the

port in extreme conditions. For ships wishing to

approach from the north by making a 90° turn, three

tugs are required to stop the ship's turn once it has

entered and align it with the jetty. Inside the port, two

40-ton tugs are needed to assist bulk carriers and

general cargo ships in their docking manoeuvre. The

exit can be carried out with only one tug hooked up to

the rear, even in extreme conditions.

Figure 14. AtoN proposed for the port of Ténès (green and

red buoys).

To enter the port of Annaba, no specific approach

path was suggested since the width of the access

channel is wide enough for safe navigation and the

orientation of the existing approach path seems

natural to pilots. It does not seem to be a priority to

add buoys to the access channel, in addition to the

buoys required from a regulatory point of view.

The AtoN recommended for the port of Annaba

are shown on Figure 15. The green buoy is located in

the extension of the northern jetty and delimits the

starboard side of the access channel. The red buoy is

perpendicular to the southern jetty and delimits the

port side of the access channel.

Figure 15. AtoN proposed for the port of Annaba (leading

lights, green and red buoys).

At the entrance of the port of Annaba, general

cargo vessels require the presence of a tug attached to

the stern of the ship with a power of at least 40 ton.

Bulk carriers require the assistance of at least two 40-

ton tugs for safe entry and exit. Finally, container

ships require only one tug to assist them in their entry

manoeuvre in average conditions and exit manoeuvre

in any conditions, two tugs are required in extreme

conditions. Inside the harbour, two 40-ton tugs are

needed to push the bulk carriers and cargo ships away

from the quay and to make a turning manoeuvre. In

addition, in extreme conditions, the tugs must assist

these ships in crossing the entrance channel to counter

the drift caused by the current. In the event of a NW 7

Beaufort wind, both tugs must assist all types of ships

to the quay.

4 EVALUATION OF THE SIMULATION SETUP

The analysis presented in Section 3 shows that it was

possible to investigate the level of accessibility of the

ports of Ténès and Annaba and its operational

limitations using just a 2D bird’s eye view simulator.

Although the view is simplified, after several runs, a

learning curve could be observed and the manoeuvres

to be carried out were better anticipated, thus leading

to improved manoeuvring conditions. This is in line

with reality, where manoeuvres are entrusted to pilots

who know the site conditions well. Overall, the study

showed that it is possible to give recommendations

for harbour improvement and formulate

approach/exit guidelines using a 2D bird’s eye view

simulator.

However, feedback from the pilots indicated that

there are several disadvantages related to the use of a

2D bird’s eye view simulator. First of all, the

execution of the manoeuvres was considered more

difficult on the simulator compared to reality because

the 2D view does not allow the pilot to have good

visual reference points. This was especially true when

the pilot needed to pinpoint his position in the

harbour and when he needed to feel the drift due to

the current at the same time. Some runs with

unexpected collisions and missed approaches were in

the end omitted because the pilot’s feeling about the

realism of the manoeuvre was not satisfactory. This

led to a repetition of runs. .

A second disadvantage is due to a mismatch

between the setup using a 2D bird’s eye view

simulator and the setup found on a full mission

bridge simulator and onboard. Several pilots

remarked that they require a good overall view of the

ship bridge, rather than having to tweak a button as is

the case using a 2D bird’s eye view simulator (e.g. to

zoom in and zoom out, move, rotate, measure…),

because by the time they do, the ship has already

moved a couple of meters. With the 2D bird’s eye

view proposed in this study, this was only possible if

a second person would take care of the controls while

the first pilot would analyse the 2D screen into greater

detail. In reality, a helmsman is also taking care of the

controls while the pilot is giving orders. In reality,

other crew members would also support the pilot. On

the simulator, this means that more persons would

need to take part to the study thus leading to an extra

cost and a situation that is more challenging in terms

of planning and management. An alternative would

be that the operator would control the rudder and the

propeller, in addition to controlling the tugs, but this

can sometimes lead to human erroneous action due to

excessive cognitive load. As a consequence,

simulations may have to be terminated prematurely,

which in turn leads to repeat simulations.

In this study, two pilots could work together at the

end of the simulation campaign and the exercise was

noticeably easier when one pilot was giving orders to

the other one and the first one could focus on the 2D

bird’s eye view and the use of extra tools, such as the

radar. By drawing target lines, the pilot could

estimate the drift due to current. The operator could

also assist the pilot by adjusting the position and the

size of the 2D bird’s eye view for him.

The limitations of the simulation setup are brought

up by the pilots during the debriefing moment after

each simulation. When the limitations are clearly

identified at this instance, some repeat simulations are

necessary using some extra information (such as

bathymetry and current field) on display. It is

therefore preferable to foresee extra time while

planning simulations using such a 2D bird’s eye view

setup so that repeat simulations can be carried out

when necessary.

Most of those limitations can be tackled when

pilots are already familiar with simulators or the site

conditions. However, if a pilot has no experience

whatsoever on a simulator and has never experienced

the real situation, it is difficult to make a distinction

between what should be ascribed to a lack of fidelity

or to the pilot’s lack of experience. On the other hand,

if a pilot is too familiar with the simulator but has no

experience with the on-site conditions, his feedback

on the safety of the manoeuvre might be biased as the

level of stress during the simulation is less important

than in real life, especially if the level of immersion is

low. Therefore, it is important that the pilot feels

comfortable with the tool while simultaneously

experiencing a sufficient level of immersion. During

the study, both type of pilots (i.e. a pilot who had not

worked with a ship manoeuvring simulator before on

the one hand and a pilot who performs simulations

very regularly but who was not familiar with the site

conditions on the other hand) where present and it

could be noticed that both pilots were

complementary.

A 2D bird’s eye view can therefore be sufficient for

studies where the pilot knows the site conditions well,

but it is recommended to carry out the simulations

with more than one pilot present. In this way, they

can share opinions and help each other to manipulate

the tools. An advantage of having two pilots involved

in a study, is having two different opinions on the

manoeuvres that have been carried out. A

disadvantage of having two pilots involved is the

extra budget that needs to be taken into account.

However, this extra budget in general is relatively

small in comparison to the budget that is required to

generate complete 3D visuals of the environment in

which the simulations are carried out.

Another advantage of using simulations with a 2D

bird’s eye view is that adaptations can be applied

easily and quickly. Moreover, these simulations can

be run on any computer without requiring a lot of

computing power and without requiring a series of

display screens. For instance, small training

computers were suggested to the pilots of the port of

Lomé after a design study conducted at Flanders

Hydraulics Research, as shown in Figure 16 [9].

Figure 16. Example of a simple setup with a 2D bird’s eye

view.

3D visuals have become the standard on ship

manoeuvring simulators worldwide and they do

appear necessary in confined environment or in

scenarios where visibility is an important factor for

the safety of the manoeuvre (e.g. an inland navigation

vessel sailing under a bridge). The use of 3D views

could also be relevant when waves and vertical

motions are implemented in the mathematical model

[6].

Moreover, not all ports are equipped with

electronic AtoN (e.g. Portable Pilot Unit) and it is

possible that those devices do not function properly.

Therefore, visual AtoN, such as lights and buoys, are

necessary. Recommendations from simulations with a

2D bird’s eye view will only be able to provide an

approximate location for these visual aids. These

positions would need to be implemented in a 3D

environment to make sure that the visual aids are

clearly visible from the ship bridge.

One alternative to a 2D bird’s eye view would be

to provide a very simplified representation of specific

reference points in a 3D environment. However, the

poor level of details seen on the screens could give a

wrong impression about the quality of the study.

Some pilots will, for instance, feel better immersed

and will focus more easily on a realistic simulator and

some clients will also be more convinced by the

quality of the study by what he sees rather than what

is hidden in the core of the simulator.

No matter what level of detail is selected, there is

always a difference from the view in reality and it is

important that the level of fidelity, i.e. the limitations

of the realism of the simulation tool, is well known

during the analysis of the data and well reported to

the user and the client.

Nowadays technology allows to develop detailed

3D visuals relatively quickly and easily by virtue of

powerful computers, graphical cards and software

development. New technologies are now going

towards Augmented Virtual Reality and solutions for

which the outside view of the simulator would for

instance follow the eyes of the pilot. Similar to the

level of accuracy of a mathematical model (3 degrees

of freedom (DOF), 6 DOF, 6 DOF including bank

effects, 6 DOF including waves…), the cost and time

of the development of the visuals need to be

balanced with the required level of realism for the

purpose of a study and the public. As shown in the

overview in Figure 17, simulations using a 2D bird’s

eye view only could nevertheless have their place for

certain studies where the execution time and the

overall cost of the project are restricted.

3D view

+ ship bridge

2D view

+ computer

2D view

+ ship bridge

Cost

Time

simplified 3D view

+ ship bridge

Figure 17. Comparison of cost, time and realism of different

solutions for the visual representation of ship manoeuvring

simulations.

5 CONCLUSIONS

A study was carried out to evaluate the operational

limits of a concept design proposed for two harbours.

Real time simulations were carried out with

experienced pilots on a dedicated full mission bridge

maritime simulator at Flanders Hydraulics Research

using a 2D bird’s eye view setup as an alternative to

the common 3D views to optimize the timing and

budget of the study.

The use of a 2D view was sufficient to identify

bottlenecks and suggest solutions to improve the port

operations and except from the pilots experiencing

difficulty to be fully immersed in the environment,

the harbour design could be validated for the current

operational limits. As a consequence,

recommendations on required AtoN and training of

pilots were provided to the client who commissioned

this study.

The difficulties related to the lack of realism of the

simulations were fully identified and taken into

account in the analysis. The study shows that the

combination of experienced pilots and the use of 2D

bird’s eye view simulator can be used able to test a

design and to help to understand bottlenecks during a

study or a training.

The level of details and type of visuals (2D or 3D)

used to represent the outside view of the simulator

needs to be specified in the simulation report and the

level of realism of the simulator should be taken into

account and discussed in the analysis.

This study has shown that in spite of all these

developments, real time simulations using a 2D bird’s

eye view could be a valid option if budget and

execution time are a limiting factor. Nevertheless, it is

recommended to carry out these simulations with at

least two pilots with complementary experience (port

and simulation based).

ACKNOWLEDGEMENTS

This study was commissioned by Laboratoire d’Etudes

Maritimes (LEM, Algeria) and executed by ISL Ingénierie.

The authors thank the Flemish pilots (DABL) and the

Algerian pilots who shared their experience and contributed

significantly in the proposal of solutions to tackle the

accessibility bottlenecks of both ports.

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