3D-visualization of fairway margins, vessel hull versus ...119781/FULLTEXT01.pdf · the world leading software when working with 3D-visualization of marine information. It is used

Bachelor’s Thesis in Geomatics

Examiner: Stig-Göran Mårtensson

DEPARTMENT OF TECHNOLOGY AND BUILT

ENVIRONMENT

3D-visualization of fairway margins, vessel hull

versus depth data

Kerim Genel & Jörgen Andersson

Geomatics Programme

June 2007

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Foreword

This bachelor thesis is produced by Kerim Genel and Jörgen Andersson, students at the

University of Gävle, Geomatics programme. The Geomatics programme belongs to the

Department of Technology and Built environment at the University of Gävle. The

assigner for this thesis is the Swedish Maritime Administration. Supervisor from The

Swedish Maritime Administration has been Anders Åkerberg. Examiner and supervisor

from the University of Gävle is Stig-Göran Mårtensson.

We would like to thank some persons with all the help we have received. Stig-Göran

Mårtensson with his expertise as a teacher, supervisor and examiner. All help from

Anders Åkerberg and his knowledge in this subject. Help to find an interesting subject,

Lars Jakobsson from the Swedish Maritime Administration. For a fast kick-start we

would like to thank Ulf Olsson with his knowledge in hydro geographic information.

Gävle June 2007

Kerim Genel Jörgen Andersson

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Abstract

Fledermaus is software where different kind of analysis with spatial data can be done.

The main area where to use Fledermaus is related to hydrographical surveys. This study

is aimed to test and analyse the way Swedish Maritime Administration (Sjöfartsverket)

uses Fledermaus. Through step by step explaining how to do when measuring sea bed

conditions from a vessel, this text is possible to use as a manual for the applications that

are mentioned in this report.

Another thing that is treated is the squat effect that belongs to vessel dynamic motions.

Test of visualization that concerning squat in Fledermaus is done, but with a negative

result when squat in a perspective to show motions in height that can be up to about a

metre is very hard in a terrain model of thousands of metres. By further tests by arranging

the input data, several interesting diagrams have been created through Microsoft Excel

where graphs show that the depths are affecting the squat effect. This is showed in same

diagram but with two different scales to show the relationship between how a point at the

vessel moves in height compared to the depth under the vessel when the vessel is

navigating in the sea.

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Sammanfattning

Fledermaus är en programvara där olika analyser med rumsliga data kan genomföras.

Största användningsområdet är att använda Fledermaus till mätningar som är relaterade

till sjömätning. Den här studien är inriktad till att testa och analysera applikationer som

Sjöfartsverket använder sig av i Fledermaus. Genom att steg för steg förklara hur

Fledermaus ska användas när bottenförhållanden ska mätas sett från ett fartyg, så blir

texten även möjlig att använda som en manual till de applikationer i Fledermaus som är

nämnda i denna rapport.

Det andra som behandlas är squateffekten som tillhör ett fartygs dynamiska rörelser. Test

av visualisering som behandlar squat i Fledermaus är genomförd, dock med negativt

resultat då squat i ett perspektiv med att visa rörelser i höjd som kan uppgå till runt en

meter är väldigt svårt i en terrängmodell som sträcker sig tusentals meter. Dock genom

vidare tester genom behandling av indata, har flertalet intressanta diagram skapats genom

Microsoft Excel där kurvor visar att djupet inverkar på squateffekten. Detta visas genom

att i samma diagram fast med två olika skalor visa förhållandet mellan hur en punkt på

båten rör sig i höjd jämfört med att djupet under fartyget ändras då fartyget gör fart

genom vattnet.

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Table of contents

FOREWORD ................................................................................................................................... 3

ABSTRACT ..................................................................................................................................... 4

SAMMANFATTNING ................................................................................................................... 5

1 INTRODUCTION ................................................................................................................ 10

2 METHODS AND MATERIALS ......................................................................................... 11

2.1 MÄLAREN....................................................................................................................... 11

2.2 IVS 3D AND FLEDERMAUS ............................................................................................. 12

2.3 GPS ................................................................................................................................ 13

2.4 RTK - GPS ..................................................................................................................... 14

2.5 SWEPOS ....................................................................................................................... 15

2.6 REFERENCE SYSTEMS ..................................................................................................... 15

2.6.1 The Lake Mälaren height reference system .......................................................... 16

2.7 MULTIBEAM SONAR ....................................................................................................... 16

2.8 MRU (MOTION REFERENCE UNIT) ................................................................................. 17

2.9 BIGGEST REPRESENTATIVE SHIP IN A FAIRWAY .............................................................. 17

2.10 SQUAT EFFECT ................................................................................................................ 18

3 THE SOFTWARE FLEDERMAUS ................................................................................... 19

3.1 INPUT DATA .................................................................................................................... 19

3.2 ADD A VESSEL/ROUTE .................................................................................................... 20

3.3 ADD IMAGE/CHARTS IN FLEDERMAUS ............................................................................ 23

3.4 PROFILE VISUALIZATION ................................................................................................ 24

3.5 VISUALIZE DISTANCES IN FLEDERMAUS ......................................................................... 25

3.5.1 Offsets ....................................................................................................................... 25

3.5.2 Distance setup in Fledermaus ................................................................................. 27

3.5.3 Alternative distance possibilities in Fledermaus................................................... 28

3.5.4 Contouring ............................................................................................................... 29

3.6 VISUALIZATION ALTERNATIVES IN FLEDERMAUS ........................................................... 29

3.7 ARRANGE DATA TO VISUALIZE SQUAT FACTORS IN DIAGRAMS ....................................... 32

4 DISCUSSION ....................................................................................................................... 35

4.1 FLEDERMAUS ................................................................................................................. 35

4.2 INVERTED VALUES IN VESSEL MANAGER ........................................................................ 35

4.3 DISTANCE CALCULATIONS IN FLEDERMAUS ................................................................... 36

4.4 SQUAT VISUALIZATION IN FLEDERMAUS ........................................................................ 36

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4.5 SQUAT TEST RESULTS .................................................................................................... 37

4.6 GPS AND SECURITY ....................................................................................................... 38

REFERENCES ............................................................................................................................. 39

RECOMMENDED READING ................................................................................................... 40

APPENDIX A................................................................................................................................ 41

APPENDIX B ................................................................................................................................ 45

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List of figures

Figure 1. Location of Lake Mälaren in Sweden. ............................................................... 11

Figure 2. Part of Lake Mälaren. ........................................................................................ 12

Figure 3. A GPS satellite. .................................................................................................. 14

Figure 4. Multibeam sonar. ............................................................................................... 16

Figure 5. Depth increase by yaw. ...................................................................................... 17

Figure 6. Squat. ................................................................................................................. 18

Figure 7. Vessel Manager. ................................................................................................. 20

Figure 8. The setup in the vessel manager. ....................................................................... 21

Figure 9. Vessel alternatives. ............................................................................................ 22

Figure 10. Picture of the tanker model used in Fledermaus. ............................................. 23

Figure 11. To switch on or switch of the chart over the 3D-image use the option mask out

areas. .......................................................................................................................... 24

Figure 12. Profile visualization. ........................................................................................ 24

Figure 13. Offset locations on vessel BW Helen. Offset locations are presented in a true

relationship to one and another, but the outline of the ship is only for illustration. .. 26

Figure 14. Widgets and the bounding coords line visible. ................................................ 27

Figure 15. Distance visualization. ..................................................................................... 28

Figure 16. Distance visualization. ..................................................................................... 29

Figure 17. Visualization of main view of the vessel and the profile at the bottom. .......... 30

Figure 18. Visualization at the top is the new view that is locked to the vessels direction.

Middle visualization is the main view and at the bottom the distance monitor. ....... 31

Figure 19. A draped terrain model and usual charts by the side of the 3D-model. ........... 31

Figure 20. Offsets are analysed from this area. White line is the route from a vessel. ..... 32

Figure 21. Squat diagram at different speeds on the route Södertälje – Köping by the

vessel BW Helen. ...................................................................................................... 34

Figure 22. Offset 1 relationship (11-12 knots). ................................................................. 41







Figure 29. Offset 8 relationship (11-12 knots)...................................................................44

Figure 30. Timetable…………………………………………………………… ………45

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List of tables

Table 1. Offset lengths from the reference point. ............................................................. 26

Table 2. Results from Excel after arranging data. Shows different offset heights in

different depths ......................................................................................................... 33

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1 Introduction

The Fairway Department (Farledsavdelningen) of the Swedish Maritime Administration

(Sjöfartsverket) owns a license of the software Fledermaus produced by IVS, Canada.

The main purpose of this software is to examine and to quality control depth information

collected from different hydrographical surveys. In the software there are several 3D-

visualization functions, one of which is to simulate vessel traffic by having a vessel at

right scale and simultaneously observe the conditions of the sea bed when the vessel is

navigating in a fairway. The technique used to follow the vessel in the fairway is

maintained by coordinate sensors on the body of the vessel; during navigation real time

calculations give information about distances to the surroundings. Information given by

Fledermaus this way can be used to analyse and alert about vessel margins to the sea bed.

An important effect influencing the margins is the squat effect. This effect has been

known for long, but has been very difficult to observe to desired accuracy until now with

modern technique. Equipping the vessels with coordinate sensors like GPS-antennas and

observing in RTK-mode, gives a possibility to obtain position at accuracy of a few

centimetres.

The software Fledermaus gives the Swedish Maritime Administration a new tool to

analyse vessel depth data. An evaluation of the possibilities to observe distances to

surroundings by the software is a part of this bachelor’s thesis, particularly the squat

effect.

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2 Methods and materials

2.1 Mälaren

Mälaren is the third largest lake in Sweden. The lake drains into the Baltic Sea (Figure 1).

It has an east-west extent of approximately 120 kilometres, an area of approximately

1140 km2 and a content of fresh water of approximately 14.3 billion m

3. The mean depth

is calculated to 12.8 metres and the greatest measured depth is 66 metres.

Figure 1. Location of Lake Mälaren in Sweden.

Mälaren is a fresh water supply for approximately 2 million people, particularly for the

city of Stockholm (Stockholm vatten). For that reason regular samples of the water

quality are taken because of its use for drinking water. Large amounts of water from

Mälaren are used by people and factories in the surroundings but the level of water is well

maintained by four larger rivers draining into the lake.

An accident, at great danger for the environment, on the lake or close to it, would have a

great impact. Substances like oil or diesel can not be removed or dissolved and will for a

long time be found in the water cycle. Therefore a continuous development on the

shipping security should be aimed at, such as double hull and traffic surveillance.

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Figure 2. Part of Lake Mälaren.

The shipping on Mälaren mainly use the lock in Södertälje because the other lock in

Hammarby has a limited capacity and can not allow large conveyance of goods. The

marine fairway in Mälaren starts at the lock in Södertälje and ends at the ports in Västerås

and Köping. The most important goods that are transported to the ports in Mälaren are

cement, petroleum products, pulpwood/chips and lime/plaster. Manure, grain, iron, steel

and general mixed cargo are the most important products that are transported from the

ports. The ports of Västerås and Köping are the eleventh biggest ports in Sweden and

they are handling about 80 % of the total transported cargo in Mälaren. In the year of

1992 the transported cargo amount was 3.4 million tonnes. At the year of 2000 the

amount had increased to 4.7 million tonnes (SOU 2006:94).

2.2 IVS 3D and Fledermaus

The company Interactive Visualization Systems (IVS) was founded in 1995. The

Headquarter is located in Fredericton in Canada, with offices in the United States and in

the United Kingdom.

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Their main objective of the company is to produce interactive 3D-visualization software

for ocean mapping, realized through their main product; the software Fledermaus.

Fledermaus is used to explore and analyse great amounts of information and has become

the world leading software when working with 3D-visualization of marine information. It

is used in different kinds of projects all over the globe, and is used for commercial,

academic and military purposes.

Fledermaus is available in three different versions. The first one is Fledermaus Standard

which is a 3D-visualization system. The purpose of this version is to open and explore

digital elevation models, and different kind of images such as charts. The images can be

geo-referenced so they are displayed in the correct location. The second version is

Fledermaus professional, it is based on Fledermaus Standard but include a couple of

applications for analysis. Examples of which are route planning and real time

visualization. The route planning application is used to visualize different routes for

vessels or similar objects. With the real time visualization application the position of a

vessel can be monitored in the 3D-scene. This can also be used to display multiple

vehicles. Distances from the vessel to the sea bed or to another vessel can also be

displayed. The last version is iView3D. It is a viewer for files that has been created in

Fledermaus. This version is free and includes the main view window from Fledermaus; it

makes it possible for users that do not have access to Fledermaus to explore scenes that

are created in Fledermaus.

2.3 GPS

GPS was developed by the US military under the name Navstar GPS (Navigation System

by Time and Ranging a Global Position System). The GPS system comprises

approximately 30 satellites (Figure 3) in 6 orbits. The fundamental idea of GPS is to

provide positions all over the Earth.

From the beginning the US military overlaid a disturbing code on the civil GPS-signal,

the reason was that they did not want civil users and armed forces to have the same

possibility as they did to high accuracy. The disturbing code, the SA (Selective

Availability) worsens the accuracy to 70 – 100 metres compared to 10 – 15 metres

nominal.

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Other GNSS (Global Navigation Satellite System) are available. Russia has a system

called GLONASS, and Europe a system that is not yet in use named Galileo.

Figure 3. A GPS satellite.

The GNSS technology is based on distance measurements between receivers and

satellites. The distance measurements are based on the time it takes for the signal to travel

from the satellite to the receiver. The Earth model GPS is using is the reference ellipsoid

WGS 84 (World Geodetic System).

2.4 RTK - GPS

Real Time Kinematic (RTK) is a recent technology where positions by GPS can be

obtained in real time through transfer of data from a single station, or a network, to a

moving station (a rover). The position of the transmitting station (stations) must be

known, and then by receiving data, the position of the rover is obtained in real time at

accuracy close to that of the reference station (stations). In case of a single-station setup, a

high accuracy is maintained on distances up to 20 kilometres between the reference

station and the rover. In case of a network, high accuracy is maintained up to 60-70

kilometres (www.swepos.com). In both cases, the limitation in distance between a

reference and a rover is due to the difference in atmospheric conditions at participating

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stations and particularly how the atmosphere is modelled in each case. To be able to use

the Network-RTK service the user needs an advanced geodetic two frequency GPS-

receiver. Communication equipment is required; at present it is a GSM-connection. The

equipment has several connection abilities, for an example built-in modem, modem

connected by Bluetooth or cable, or by a usual GSM-telephone connected to the

equipment. (www.swepos.com)

In this thesis we only discuss the network case, called Network-RTK, and the network

providing the service is the SWEPOS.

2.5 SWEPOS

SWEPOS is a nation wide network of permanent reference stations for GPS observations.

Operation and maintenance of the network is run by the Swedish National Land Survey

(Lantmäteriet). The operating central is located in Gävle. The network consists of

approximately 100 stations all of which participate in providing data for the Network-

RTK service, available in almost all of Sweden. Data between the stations are transmitted

by telephone lines with a modem and protocol TCP/IP.

2.6 Reference systems

Reference systems are needed to place geographical information in some kind of

structure. Most countries have their own reference systems developed after their needs

and situation. Sweden has recently changed the national reference system to a new system

called SWEREF 99. This was done in January 2007. SWEREF 99 is the Swedish

realization of ETRS 89, which is a global three-dimensional reference system, defined by

the 21 fundamental points in the national net of permanent reference stations for GPS

(Lantmäteriet). SWEREF 99 is close to WGS 84.

To this reference system a new geoid model has been developed (SWEN05LR) making it

possible to obtain heights in a height system called RH 2000.

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2.6.1 The Lake Mälaren height reference system

The first height system in Sweden was established between the years of 1886 and 1905

and is denoted RH 00. This system is still in use in Stockholm and that is why this is

important to know when it comes to water levels in Mälaren. Lake Mälaren has it own

height system by the name MVY 2000 Mälaren (average water surface). This system has

a zero level that is 384 centimetres below RH 00 (SOU 2006:94 page 54). MVY 2000 is

used as height reference. Transformation of ellipsoid at heights to MVY 2000 Mälaren is

done by SWEN05LR and RH 2000 with current supplement corrections (Blom et al.

2006). The information about the level of the water surface can be found from SMHI.

2.7 Multibeam sonar

Sea beds are surveyed by for instance multibeam sonars. Regular sonars measure the

water depth directly under the vessel while multibeam sonars measures over a large area

on both sides of the vessel (Figure 4). This is possible because the multibeam sonar sends

out acoustic signals in different directions. The multibeam measures and records the time

it takes for the signal to travel from the transmitter to the sea bed and back to the

transmitter. The coverage area on the sea bed is dependent of the water depth. The

coverage area is approximately two to four times larger then the water depth (NOAA).

The result from the survey with the multibeam sonar is a 3D-image of the sea bed.

Figure 4. Multibeam sonar.

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2.8 MRU (Motion Reference Unit)

An MRU unit gives pitch, roll and heave information (attitude changes) of a vessel. It is

important that the unit is mounted at the centre of the vessel. This information can be

used alone or be complemented by GNSS information to keep track of the vessel at sea.

With observations recorded by the MRU it is possible to reproduce in Fledermaus every

movement of the vessel. MRU gives information about yaws as in Figure 5.

Figure 5. Depth increase by yaw.

2.9 Biggest representative ship in a fairway

There are regulations for all fairways of what size of ships that are allowed to pass

through. In the report (Sjöfartsverket, CT-beslut nr 2/00) from the Swedish Maritime

Administration they declare “Biggest representative ship: The size of ships in the fairway

often existing type, which can use the fairway. The biggest representative ship should

from the security perspective take notice of the fairways width and out markings”. A new

fairway should when constructed be dimensioned for the sizes of the ships that will be

navigating in the fairway. Several kinds of guidelines on this matter are presented in

PIANC documents (www.pianc.org), which is an international hydrographical

organisation.

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2.10 Squat effect

Squat is a dynamic motion that arises when vessels hull moves through water, squat is

increasing in shallow waters. Small boats rise relative to the water surface at higher

speeds. But vessels draught gains relative to the water surface when speed increases (See

Figure 6). The factors involved are under keel clearance (UKC), speed and the hull form

(NOAA). Squat seems to be very dependent on the depth where the vessel is, as is

presented later in this report.

The Squat effect has for a long period of time been a phenomenon that is known. The

problem has been to measure and perceive it. Now with new technologies it can be

examined but few have presented a good way to illustrate the squat effect. The new

technology used to measure squat better is GPS Network-RTK. With GPS Network-RTK

the position can be obtained within a few centimetres in real time. This phenomenon will

in future be very important to know how it works. Large cargo ships can examine and

plan their route before they leave the harbour. Thereafter the cargo companies can save

money when they can calculate the route better and load more goods.

Figure 6. Squat.

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3 The software Fledermaus

This chapter is describing typical applications that can be done in Fledermaus. The

chapter is created in such a structure that the reader can use it as a guideline for the

software.

3.1 Input data

From our assigner, the Swedish Maritime Administration, we have received a lot of data

to use for tests and analysis.

For the digital bathymetric model, where all depths are available for the fairway in

Mälaren, an sd-file based on a raster with squares of 6 by 6 metres has been made

available. From this file all distance calculations can be done to a vessel in the same area.

The vessel is also available in sd-file that originally was a CAD-drawing of a tanker. This

information is really not necessary for making analyses, but it gives a realistic

visualization of the vessel in Fledermaus.

A lot of files that covers several routes in Lake Mälaren by the vessel BW Helen are

available. The basic format for these files is NMEA with a string header ($C&C). The

string header is followed by the name of the vessel, time, position, course, pitch, roll and

height: $C&C,BWHelen,08:10:10,1604421.62,6564915.91,354.27,0.04,-0.64,0.08. All

data must be comma separated when used in Fledermaus. Mentioned files are used every

time a visualization of a recorded route is requested in Fledermaus. Some additional files

with all offset heights on a route are available making it possible to show diagrams of

how the squat effect is affected by the under keel clearance (UKC) to the sea bed (See

chapter 3.7).

Charts are also available, they are used for different visualization alternatives (See

chapter 3.3). The charts can also be draped over the digital bathymetric model to get 3D-

charts.

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3.2 Add a vessel/route

Before the visualization of a vessel in Fledermaus is possible, first the sd-file with the

information about the sea bed should be opened. The first thing to accomplish is to

choose the menu data and add vessel. In the lower parts of Fledermaus are now several

options for vessel visualization visible. The three different flaps; vessel, distances and

tools contain options for the visualization. The flap vessel has three groups with following

titles; vessel setup, vessel model, and display. The flap distances handle options that

concern different kinds of distances. On the flap tools you find the three categories;

history, profile and prediction.

In order to add a vessel, first the vessel manager of Fledermaus has to be started. The

vessel manager is found under the option display. The upper left corner of the window

shows which vehicles are active. On the right side, beneath data acquisition, is the vessel

data that Fledermaus imports displayed. The lower left side have the alternatives;

setup/preferences, load points of interest, playback controls, ROV simulator and setup

beacons (Figure 7). The first step to add a vessel is to choose setup/preferences. New

alternatives for the vessel are now opened in a new window. The four alternatives;

vehicle information, serial port setup, output projection and navigation logging are now

presented. The serial port setup is used in order to collect data from the serial port from a

vessel in progress in real time. Projection is used to choose which projection that should

be used.

Figure 7. Vessel Manager.

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The first step is to state which kind of the three stream formats that shall be chosen. The

option custom is used when a navigation package is connected to the system. The data to

custom is similar to NMEA but custom makes it possible to use several vessels

simultaneous. Custom and NMEA collect various information directly from the data.

PLO is a binary data format. The data consist of different information such as vehicle and

positioning information. PLO includes support for up to ten vehicles. The data format

custom is produced to resemble the NMEA, but it supports a standard NMEA message

string that could be data from a navigations program such as WinFrog. The vessel

manager is not supporting data from different serial ports at the same time. This is the

only way, apart from PLO, to have several vessels running at the same time. In such case

use the option custom since real time data is not available.

As string header $C&C is typed in and the name BWHelen is typed in at vehicle 1, this

information has to be the same as in the data file (Figure 8). The last alternative in this

window is the depth offset. The depth offset is used to adjust the height of the vessel in

related to the zero level / water level in the 3D-environment. After clicking at the OK

button the vessel manager returns. To import the file that the vessel manager should

collect data from, choose the playback control button. After the choice of navigation file

click OK and return to the vessel manager.

Figure 8. The setup in the vessel manager.

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If you want to see if the vessel manager is collecting data from the navigation file, choose

the alternative show processed messages. If everything is correct the data is shown in

data acquisition. If you want to collect data in real time, then click on the start serial port

nav button. To see the real time data in data acquisition, choose show raw messages. In

update rate suitable update speed is typed in. Everything is now set in the vessel manager

but do not close the window because the vessel manager continues to collect navigation

information from the data file only when it is open. It is possible to minimize the window.

Return to the main window of Fledermaus. In the flap vessel -vessel setup click on the

activate button. Fledermaus is now starting to collect information from the vessel

manager (Figure 9).

Figure 9. Vessel alternatives.

Fledermaus can automatically follow a vessel in the 3D-environment when clicking on

the options button that is recovered in vessel –display. In the new window, choose lock

main view to vessel.

There are four different alternatives of vessel models to use for visualization. These

alternatives can be found in vessel model. The four different vessel models are;

basicROV, cube, cylinder and custom. An sd-model is used for the tanker. In order to

show the model in Fledermaus custom is chosen in type. To collect the vessel model click

on the load custom model button and choose the vessel model file (figure 10). The model

now shown does not have the right dimensions. The right dimensions should be typed in

at the options size. In our case 126 18 25 are typed in and this stands for a vessel that is

126 metre long, 18 metre wide and 25 metre high.

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Figure 10. Picture of the tanker model used in Fledermaus.

3.3 Add image/charts in Fledermaus

In order to show images simultaneously with the 3D-depth data, make sure that your 3D-

depth data file is opened. The most interesting with images in Fledermaus is to visualize

charts that overlap the depth data. Charts that should be imported to Fledermaus have to

be geo-referenced. The image and the depth data must be in the same reference system. In

our case charts are available over the whole fairway between the cities of Södertälje and

Köping in the Lake Mälaren.

To import the charts choose in the menu file and import –import image. The charts are

now centred over the whole main window. To get the correct geographical position of the

chart, click on the geo-ref button at the right side of the window. To limit the chart to

areas where it is overlapping depth data, choose the alternative mask out areas. This

option is available at the bottom when the chart is marked in the file list. To mask the

chart, click on the compute mask button in the options area. The fairways sea bed is now

visualized in 3D on the chart (Figure 11).

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Figure 11. To switch on or switch of the chart over the 3D-image use the option mask out

areas.

3.4 Profile visualization

Depth data and a vessel have to be loaded before profile visualization can be performed.

Choose the option profile visible in the flap tools. The standard profile is a 20 metre

cross-track of the sea bed and is locked to the centre of the vessel. To get the profile in

along-track, set the rotate angle to 90 degrees, making it possible to visualize the sea bed

condition in front of the vessel as well as behind it. If a profile length of 200 metre is

typed in, then a vessel length of 126 metre will result in possibilities to visualize 37 metre

of the sea bed in front of and behind the vessel. The remaining profile is recovered

directly beneath the vessel (Figure 12).

Figure 12. Profile visualization.

There are several options to consider if the button advanced is used. In order to show the

vessel in the shape of a rectangle in profile, choose the option visible. Our values at left

and right are -63 and +63 respective by because of the vessel length of 126 metre. Top of

the vessel is given the value 3. This value is not important for the visualization, it only

changes the position of the rectangle with respect to the water level. The value of the

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bottom is typed in as -5.5 which correspond to the draught. The rectangle can also be

shown directly with the vessel in the 3D-scene if the option show rectangle in scene is

chosen. In the advanced dialog the option show distances that refers to the profile and

show distances in scene referred to the 3D-visualization. If a horizontal line appears in

the profile with length information it is the information for the distance to the

geographical position where the vessel can hit the sea bed. This information is only

visible for the line direction that collects information to the profile.

The water level can be visible in the profile when the option visible is enabled. The water

level consists of a thicker line than the scale lines. The profile is depending on the line

that is beneath the vessel. This line is only visible if the vessel is at the top of the rank to

the left. The scale of the profile is changeable but our recommendation is to lock the

profile to a suitable scale. Viewers of the profile can easily get confused because a

permanent distance can vary heavily when the scale is not locked. We conclude that this

method is appropriate when the distance to the sea bed should be visualized during the

route of the vessel. The big disadvantage is that the corresponding profile is based on the

thin line width and not on the vessel width.

3.5 Visualize distances in Fledermaus

3.5.1 Offsets

The positions of BW Helen are available in the SWEREF 99 coordinate system. These

coordinates have been transformed to SWEREF 99 by using three GPS-receivers, and

every position has been stored for every second. All offsets are with respect to an origin,

a reference point. The reference point is located 0.25 metre above the water surface

(unloaded vessel), the distance to the keel is 6.8 metre and the location on the vessel is in

the front of bridges centre line.

To be able to know all the offset values in Fledermaus the software Geo (Swedish

software used for arranging and analysing surveyed information.) is used. In Geo all the

offsets coordinates from one position are entered. The values from the offsets in Geo

26

show a good relationship between all offsets. The reference point in Geo is also inputted

to be able to calculate all distances from the reference point (Figure 13).

Figure 13. Offset locations on vessel BW Helen. Offset locations are presented in a true

relationship to one and another, but the outline of the ship is only for illustration.

The biggest uncertainty factor with the results is to know where all offsets are along the

vessel. This is because Fledermaus calculate all values from the centre of the vessel, but it

is calculated from the reference point that is located at the bridge in the centreline of the

vessel. The difference between these locations is about 25 metres. Thereafter this value is

taken care of for in the offset positions in Fledermaus (Table 1).

Table 1. Offset lengths from the reference point.

Left/right from centre

(m) Prow/stern

from centre (m) Offset height

(m)

Offset 1 0 59.601 -9.94

2 0 -48.097 -10.01

3 -6.501 21.903 -9.88

4 6.496 21.903 -10.04

5 -6.503 -4.003 -9.9

6 6.494 -4.003 -10.06

7 -3.504 -25 -9.95

8 3.494 -25 -10.03

27

3.5.2 Distance setup in Fledermaus

The digital bathymetric model of the fairway and the vessel should be opened in

Fledermaus before starting analysing distances. The true position of the vessels in height

is the hardest to configure truthful in Fledermaus distance analyses. The ways to do this

are the following: When the vessel is at the beginning of the planned route, the bounding

coords are opted to be visible to be able to get an appreciation in height related to the

water surface. In the vessel manager a height offset for the vessel is chosen to 4.5 metres.

After this the height widgets (Figure 14) must be configured to fit the water line at the

vessel. Now the bounding coords are visible along the waterline at the vessel.

Approximately should the draft now be 5.5 metres in Fledermaus, but this is only for our

data. If vessel or digital terrain model are changed all parameters are different. As

mentioned before, this is the hardest to setup in Fledermaus to get it near the truth when

visualizing distances.

Figure 14. Widgets and the bounding coords line visible.

Under the flap vessel – distances is where all distances obtained from Geo should be

typed in. The distance type should be set to vertical. Under local offset all the values from

Table 1 are inserted. The warning distance is set to 1 metre (Figure 15). When any of the

offsets are within 1 metre to the sea bed the offset line that is visible from the hull to the

sea bed become thick and changed to red colour.

28

Figure 15. Distance visualization.

3.5.3 Alternative distance possibilities in Fledermaus

One of the software applications available in Fledermaus is RoutePlanner. Vessel routes

can be created with RoutePlanner, but also cable and pipe planning on the sea bed.

Another application is DMagic which is used to drape charts over bathymetric models.

On charts there is a black line indicating the fairway. With RoutePlanner new lines can

be created. When a new route is finished it is saved as an sd-file. The file is then opened

in Fledermaus with a bathymetric model and a vessel model. The height of this line is set

to zero by clicking on set heights and then type in the value zero and choose OK. Mark

the vessel in the list at the lower left and choose the flap distances. The distance type

should be Line object (+/-). As target object is the file that contains the information of the

line that is created, e.g. shoreline created with RoutePlanner etc. The result of this is that

the distance from the vessel to the line is presented in real time (Figure 16).

There are more alternatives as; distance to pick point, object, line object and fixed point

in Fledermaus, but we have not examined these options.

29

Figure 16. Distance visualization.

3.5.4 Contouring

By using the alternative contouring in the tools menu, contour lines are created. The

contour lines should in this case be created on the bathymetric model. The lines can be

created with certain equidistance, but also a specific contour line can be added by using

the single elevation alternative. A line can represent a shoreline on both sides of the

fairway. This can be useful because now the distances from the vessel to the shoreline can

be presented in the 3D-scene. Another useful application for this is to make a contour line

for a specific depth. For example, if the draft for the vessel is 5.6 metres, a contour line

for 5.5 metres is created. Use Line object (+/-), now the distance monitor shows a

distance to places where it is to shallow for the vessel. See chapter 3.5.3 for illustration of

Line object (+/-).

3.6 Visualization alternatives in Fledermaus

Different kind of visualizations can be performed in Fledermaus. When visualization and

analyses are done at the same time it is desirable to present several data at the same time

in Fledermaus. For this a new view is opened where we lock the vessel to its direction.

Locking the view to a vessel direction in the main window of Fledermaus is not possible.

The main view is useful when moving around the scene and the view is not locked to the

vessel. Below this information the distance monitor is visible and shows all offsets and

30

their directions. A profile can be shown as described in chapter 3.4. To lock the vessel in

the new view, choose show view. Choose display-options and pick both of the

alternatives lock new view to vessel and lock view direction to vessel direction (figure

18). In order to look at the vessel from a stern point of view and to get the centre of the

view to the hull, type in offset values to 0 -100 -9.5. These values are depending on

individual settings and they are according to our settings and the type of vessel that are in

use. The reason for doing this is to be able to visualize the vessel’s UKC.

Figure 17. Visualization of main view of the vessel and the profile at the bottom.

A lot of information makes use of the monitor’s total area. There are different ways to

eliminate this. First, and maybe the best way, is to use two monitors and show the hole

working area on both. Another way is to select one monitor and use a high resolution, e.g.

1600 x 1200 pixels. When increasing the resolution, more can be visualized on the same

screen size. Both cases require a powerful computer equipped with a powerful graphics

card.

31

Figure 18. Visualization at the top is the new view that is locked to the vessels direction.

Middle visualization is the main view and at the bottom the distance monitor.

Something that enhances a public presentation is the use of draped charts. This is done in

the DMagic. Draped charts do some times have difficulties to show all height levels, thus

for analysis it is better to use the usual 3D-view. An example of a draped chart can be

seen in Figure 19.

Figure 19. A draped terrain model and usual charts by the side of the 3D-model.

32

3.7 Arrange data to visualize squat factors in diagrams

To be able to see different kind of relationships between squat and UKC, all data must be

reprocessed and rearranged. Our primary goal is to show the relationship between the

squat effect and the depth to the sea bed.

The input data comes in NMEA format, offset height data is in Excel with all eight

offsets in position and height. To be able to show a relationship two factors are missing,

namely; the distance from the offset at the hull to the sea bed and the speed. The

unknown distance is calculated by using the Fledermaus software Cross check. In Cross

check it is possible to open the digital bathymetric model over the sea bed and thereafter

open a text file with the route with vessels positions. In this case every offset has the

same area to be able to compare the results. Fledermaus was used for looking at the

bathymetric model to find an area where the vessel is navigating and the sea bed are

changing in height (Figure 20).

Figure 20. Offsets are analysed from this area. White line is the route from a vessel.

The area that was found is presented in Figure 20. In this area UKC can differ from 2.5 to

13 metres. The coordinates in Fledermaus was taken and searched in coordinate files by

using Excel to find the same area.

Now there are four factors that are needed that should be available: position, speed, UKC

and offset height.

33

Table 2. Results from Excel after arranging data. Shows different

offset heights in different depths

UKC (m)

Offset height

(m)

Speed

(knots)

10.62 -7.07 11.47

9.61 -7.08 11.45

8.34 -7.09 11.40

7.26 -7.11 11.42

6.83 -7.12 11.37

6.67 -7.13 11.40

6.41 -7.14 11.34

6.09 -7.15 11.34

5.63 -7.17 11.32

Now three factors for every offset are important. The fourth factor position does not need

to be available in the table, because when the right area is chosen the position does not

affect the diagrams. In Table 2, the UKC, offset height and speed are available. With this

information a diagram showing the relation between UKC and speed can be presented.

Our tests to arrange data to get a view over the squat effect related to depth shows that

there is a relationship between depth and offset movements in height. It clearly shows

that there is a correlation between the two factors. 8 diagrams are created for all offsets to

see the same relations but those are in the same area. These diagrams are in Appendix A.

The two first diagrams in Appendix A show the relations at the prow and stern (offset 1

and offset 2). Here it is clear that the prow is deeper than the stern, which is the case that

is known with the squat effect. When the vessel squats the water under the keel is passing

very fast to fill the space behind the keel. This is more visible and powerful in shallow

areas related to the vessel speed.

Data are available at eight locations (offsets) at vessel BW Helen. A diagram is created in

Excel to illustrate the draughts in different speeds. All input data had to be reduced by

calculates the average draught in intervals by 0.5 knots.

34

SQUAT of BW Helen in Lake Mälaren

-7,25-7,20-7,15-7,10-7,05-7,00-6,95-6,90-6,85-6,80-6,75-6,70-6,65

0.00

- 0.

5

1.01

- 1.

5

2.01

- 2.

5

3.01

-3.5

4.01

- 4.

5

5.01

- 5.

5

6.01

- 6.

5

7.01

- 7.

5

8.01

- 8.

5

9.01

- 9.

5

10.0

1 - 1

0.5

11.0

1 - 1

1.5

12.0

1 - 1

2.5

13.0

1 - 1

3.5

14.0

1 - 1

4.5

15.0

1 - 1

5.5

Speed in knots

Dra

ug

ht

in m

ete

r

Prow

Stern

Figure 21. Squat diagram at different speeds on the route Södertälje – Köping by the vessel

BW Helen.

The diagram illustrates the draught and the squat by BW Helen and is a view of the

draught conditions in the route Södertälje – Köping at different speeds. The vertical axes

have negative values because it shows the depth for the vessel from the water surface. An

interesting result in Figure 21 is that when speed increases, the draught height between

offset 1 and offset 2 are different compared to lower speeds. This means that the prow is

deeper than the stern when the vessel making speed in water and this is also related to the

depth. This needs more parameters to get a more truly result. A parameter that is

interesting in this kind of analyses is the depth at every place of the vessel. Squat is not

only dependent on speed, but also the depth and speed together. As the diagram tells now

is that the draught is bigger at 10 knots than at 15 knots. The result is true but a better

view over why it is like this should be by even presenting draught by speed and depth.

Next chapter shows a diagram when the data are shown with a depth factor.

One of the tasks behind this report is to examine the squat with some kind of visualization

method. We have managed to show that the squat is dependent of the UKC. For BW

Helen the squat effect tilt the vessel by approximately 30 cm from being idle to its full

speed at 15 knots.

35

4 Discussion

4.1 Fledermaus

We have used the software Fledermaus from IVS in Canada. We are aware of that

Fledermaus has much more applications and functions that we did not use. Our thoughts

and ideas about Fledermaus is from the experience that we got from the tests we have

done.

The first time Fledermaus was started we was full of expectations for the software, the

interesting part is that now after 8 weeks working with Fledermaus we are even more

interested in its potential and possibilities.

In some applications in Fledermaus a feeling appears that it is new software with

expectations for improvements in the future. But in the same time it is very hard to find

other software with the same potential for this matter. We think that Fledermaus is good

software today but will be better in every update. Examples for this are what are

mentioned in chapter 4.2 about the inverted values in vessel manager. One irritating thing

that we noticed is if many windows are opened in Fledermaus a problem can appear with

the lower part of the main Fledermaus view. The problems are that all information in the

lower part can be forced under the visible area of the screen, and it is hard to adjust.

We hope that IVS will continue their work with Fledermaus. We are certain about if they

do they will be leading the market with this software.

4.2 Inverted values in vessel manager

We have discovered that the last value in the vessel manager is inverted. The last value is

the height value from the route file that the vessel manager imports data from. Thus the

value is positive in the route file is Fledermaus changing it to a negative value and vice

36

versa. This is a finding of importance because the squat effect is depending on the height

value. We do not know why Fledermaus is changing the values.

4.3 Distance calculations in Fledermaus

Fledermaus is a very powerful tool to visualize and analyse data from maritime areas.

One interesting matter of distance measurements that we noticed are that when we have a

vessel navigating in Fledermaus we saw pitches and rolls. One question is when

measuring in real time the distance to the sea bed, if the values are taken care of the

pitches and rolls that are visualized. We believe that Fledermaus do but we have no proof

for that is the case. One even more interesting matter when pitches and rolls appear are

that nowhere is there any information that Fledermaus visualize this behaviour. We think

this is a new thing in the latest Fledermaus and it is not fully completed. The proofs we

have for this behaviour really exist is that we have rearranged the input data and managed

to see when arranged that pitches are rolls and vice versa.

The distance measurement in Fledermaus is an interesting application, but questions

appear in this. We think this is a good application, and we wonder about why some kind

of similar application is not in use today in vessels that often passing in shallow areas. It

can be used not only for the direct distance to the sea bed, but for several types of

distances. Here the imagination can help you come up with many kind of distance

measuring, for an example is the way that is mentioned in chapter 3.5.4.

4.4 Squat visualization in Fledermaus

In Fledermaus it is very hard to visualize the squat effect. We think that Fledermaus

needs some kind of new application that is created for squat visualization to do this. The

problem today with squat visualization in Fledermaus is because of the squat effect in real

world gains decimetres, it is huge for a big vessel but very small for Fledermaus to show

correctly.

37

4.5 Squat test results

In Appendix A, eight diagrams are shown. Those diagrams are related to the same area

that is visually chosen in Fledermaus. Offset 1 and 2 is interesting to look at in the same

time. It is visible that the prow is deeper (offset 1) than the stern (offset 2). We are aware

of that it should be more appropriate to make this analysis in more areas and with

different speeds.

We think that our results that we achieved when visualizing the relations between the

offsets, speed and UKC are good. But we also realize that our result is pretty limited and

are good for continuous future researches. We find the subject interesting and think that

researches that have the same kind of data that we have available can obtain good results

and even be much appreciated all over the world from companies and authorities.

Vessel cargo companies can save a lot of money with software applications that

calculates how deep a vessel drafts in the route before a journey. With this knowledge

they can load more and adjust the speed to the information they have of different areas. In

a wider perspective this can be a big breakthrough for the environment when it shows that

the results are fewer trips and maybe less average speed. But these are only thoughts in a

positive way, in the other hand it maybe shows that the cargo companies notice that they

can go faster but they not really load more cargo at the ships. The result higher fuel

consumption and it is worse for the environment.

Even the biggest representative ship as mentioned in chapter 2.9 is interesting in this

matter. In the future when research of squat is available, we think that documents that

declare the biggest ship in fairways can be changed when more knowledge of ships

behaviour is known. This will probably allow bigger ships in many fairways, but with

new restrictions in several areas. This restriction comes from the knowledge of the

biggest representative ships draft and squat values.

38

4.6 GPS and security

Everything has a limit, the question is where and when does technology stop to function.

When measuring the sea bed it costs a lot of money if the GPS-receiver stops to receive

signals. It is not good or if the signals from the satellites do not have the requested

accuracy. As Prasad & Ruggieri (2005) mention about GPS integrity: “The ability of a

system to provide timely warnings to users when the system should not be used for

navigation. In particular, the system is required to deliver to user and alert within the time

to alert when an alert limit is exceeded. The alert limit is the maximum error allowable in

the user computed position solution; the alert limit can be specified in horizontal alert

limit (HAL) and vertical alert limit (VAL)”. With integrity there is also an integrity risk.

“The probability during the period of operation that an error, whatever the source, will

result in a computed position error exceeding the alert limit, and that the user will not be

informed within the specified time-to-alert” (Prasad & Ruggieri 2005).

In the merchant shipping, security is a big factor to think about. Not only for the humans,

also for the environment with all kind off chemicals and oil that can be loaded at a vessel.

All technology safety systems onboard have been improved and they can help the human

and can sometimes be forgiving when the well known human factor comes in. As in the

case to construct a system that can visualize the squat effect, many things should be

improved. And in many cases an improvement at the environment should be noticed if

this could help the companies to load more gods, and fewer routes is needed. Maybe it

could be a help to the environment if more loads were loaded and the speed should be

lower when the skipper sees how little marginal it is for the vessel to the sea bed when it

squats. “Even the most advanced design that is created for improvement of security in

technology systems can create error sources, which under given circumstances can trigger

mishaps. Related to this and as a further ironical part is later the same design or

engineering model that is searching for improved security by automation leave to human

operators to adjust factors and events that is not can be reached by the automation. To the

picture it belongs that the management of such events and factors often enough demands

a considerable knowledge, to essential part also based on training and experience” (Jense

2005).

39

References

Blom, J. Jakobsson, L. & Olsson, U. (2006) Plan för undersökning av dynamisk

djupgåendeförändring för fartyg under gång i Mälaren med hjälp av

avancerad GPS (RTK), Rapport sjöfartsverket projektnummer 40045-0

Jense, G. (2005) Den relativa säkerheten om risk, säkerhet och sjöfart. Institutionen för

samhällsvetenskap, Växjö universitet. Rapport nr 25. ISBN 91-89317-29-

7, ISSN 1401-6346

Lantmäteriet (2005) Infoblad n:o 1 Nya Referenssystem

http://www.lantmateriet.se/upload/filer/kartor/geodesi_gps_och_detaljmat

ning/Nytt_referenssytem/Infoblad/info_blad-1.pdf 070606

NOAA, Modern Measurement of Vessel Squat and Settlement Using GPS

http://nauticalcharts.noaa.gov/csdl/htp/sas.html 070420

NOAA, Sidescan and multibeam sonar http://chartmaker.ncd.noaa.gov/HSD/wrecks.html

070425

PIANC, Rules and regulations http://www.pianc-aipcn.org/docs02/policy/rules-

regulations.doc 070606

Prasad, R. & Ruggieri, M. (2005) Applied Satellite Navigation Using GPS, GALILEO

and Augmentation Systems. ISBN 1-58053-814-2

Sjöfartsverket, http://www.sjofartsverket.se 070525

Sjöfartsverket, the Fairway Department (2000), Sjöfartverkets riktlinjer för

farledsplanering och farledsutmärkning. CT-beslut nr 2/00.

SMHI, http://www.smhi.se 070428

SOU 2006:94, Översvämningshot, Risker och åtgärder Mälaren, Hjälmaren och Vänern.,

ISBN 978-91-38-22646-9

Stockholm vatten, http://www.stockholmvatten.se 070419

SWEPOS, http://www.swepos.com 070421

40

Recommended reading

Andersson, T. & Torngren, J. (2004) Traditionell RTK och Nätverks-RTK en

jämförelsestudie, LMV-rapport 2004:16 ISSN 280-5731

Ekman, M. (2002) Latitud, longitud, höjd och djup. Kartografiska sällskapet. ISBN 91-

631-3170-6

Larsson, K. (2005) Mälarens vattennivå i ett framtida klimat; Water levels in lake

Mälaren in future climate scenarios, University of Uppsala, ISSN 1401-

5765

41

Appendix A

Relationship Offset 1

2

4

6

8

10

12

14

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Time in seconds

Depth

in m

etr

e

-7,3

-7,25

-7,2

-7,15

-7,1

-7,05

-7

-6,95

-6,9

-6,85

-6,8

Dra

ught in

metr

e Speed

(knots)UKC

Offset 1

Height

Figure 22. Offset 1 relationship (11-12 knots).


2

4

6

8

10

12

14

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Time in seconds

Depth

in m

etr

e

-7,3

-7,25

-7,2

-7,15

-7,1

-7,05

-7

-6,95

-6,9

-6,85

-6,8

Dra

ught in

metr

e Speed

(knots)UKC

Offset 2

Height


42


2

4

6

8

10

12

14

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Time in seconds

Depth

in m

etr

e

-7,3

-7,25

-7,2

-7,15

-7,1

-7,05

-7

-6,95

-6,9

-6,85

-6,8

Dra

ught in

metr

e Speed

(knots)

UKC

Offset 3

Height



2

4

6

8

10

12

14

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Time in seconds

Depth

in m

etr

e

-7,3

-7,25

-7,2

-7,15

-7,1

-7,05

-7

-6,95

-6,9

-6,85

-6,8

Dra

ught in

metr

e

Speed

(knots)

UKC

Offset 4

Height


43


2

4

6

8

10

12

14

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Time in seconds

Depth

in

me

tre

-7,3

-7,25

-7,2

-7,15

-7,1

-7,05

-7

-6,95

-6,9

-6,85

-6,8

Dra

ught

in m

etr

e Speed(knots)

UKC

Offset 5Height



2

4

6

8

10

12

14

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Time in seconds

Depth

in

me

tre

-7,3

-7,25

-7,2

-7,15

-7,1

-7,05

-7

-6,95

-6,9

-6,85

-6,8

Dra

ught

in m

etr

e

Speed(knots)

UKC

Offset 6Height


44


2

4

6

8

10

12

14

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Time in seconds

Depth

in m

etr

e

-7,3

-7,25

-7,2

-7,15

-7,1

-7,05

-7

-6,95

-6,9

-6,85

-6,8

Dra

ught

in m

etr

e

Speed(knots)

UKC

Offset 7Height



2

4

6

8

10

12

14

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Time in seconds

Depth

in

me

tre

-7,3

-7,25

-7,2

-7,15

-7,1

-7,05

-7

-6,95

-6,9

-6,85

-6,8

Dra

ught

in m

etr

e Speed(knots)

UKC

Offset 8Height


45

Appendix B

v.15 v.16 v.17 v.18 v.19 v.20 v.21 v.22 v.23

Introduction

Work with

Fledermaus

Researches/Analysis

Writing Report

Opponent work

Presentation work

Finishing of report

Presentation

Figure 30. Timetable.

46

Documents

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