Maritime University of Szczecin
Akademia Morska w Szczecinie
2010, 20(92) pp. 60–66 2010, 20(92) s. 60–66
Using NMS-90 simulator for ship accidents reconstruction
Wykorzystanie symulatora NMS-90 w procesie rekonstrukcji
wypadków morskich
Wiesław Juszkiewicz
Maritime University of Szczecin, Faculty of Navigation, Institute of Marine Traffic Engineering Akademia Morska w Szczecinie, Wydział Nawigacyjny, Instytut Inżynierii Ruchu Morskiego 70-500 Szczcin, ul. Wały Chrobrego 1–2, e-mail: w.juszkiewicz@am.szczecin.pl
Key words: simulation, ship accidents, safety at sea Abstract
Simulators are useful in very wide field of current life. Very important is to know their advantages and disadvantages. One of the most important of navigational simulator using is deck officers training. Possibilities of using real collision situations for officers training can seriously improve knowledge about deck officers behavior in dangerous situations. Analysis of the possibility of using the NMS-90 simulator for ship’s collision reconstruction was the aim of experiment. Some problems of recorded data accuracy and simulator possibilities influence on accident reconstruction process are described in this paper.
Słowa kluczowe: symulacja, awarie statków, bezpieczeństwo na morzu Abstrakt
Symulatory są obecnie szeroko wykorzystywane w wielu dziedzinach życia. W związku z tym bardzo istotną kwestią jest znajomość zarówno ich wad, jak i zalet. Jedną z dziedzin, w których wykorzystuje się symulatory nawigacyjne, jest szkolenie oficerów pokładowych. Wykorzystanie w trakcie symulacji sytuacji nawigacyj-nych, w których doszło do kolizji statków, powinno znacząco wpłynąć na poznanie sposobu zachowania się nawigatorów, jak i przebiegu procesu podejmowania przez nich decyzji w trudnych sytuacjach nawigacyj-nych. Istotą przeprowadzonego w symulatorze eksperymentu było sprawdzenie możliwości wykorzystania symulatora NMS-90 do rekonstrukcji wypadków morskich. W artykule przedstawione zostały wybrane pro-blemy związane z wpływem dokładności zarejestrowanych danych źródłowych oraz możliwości samego sy-mulatora, związanych z dokładnością rekonstrukcji sytuacji kolizyjnych.
Introduction
Basic tasks set for navigational-radar simulators consist in exploiting their possibilities both in the navigators training process and in research works. Technological progress enables more and more excellent modeling phenomena presented in the process of the simulation. The interactivity of ac-tions taken in simulators and the huge data sets recording possibility are very important. But very important are also possibilities of multiply repeat-ing created scenarios and gettrepeat-ing results in relative-ly short time.
The attempt of reconstruction of m/v “Ziemia Lodzka” and m/v “Vertigo” collision was taken in the experiment carried out in the NMS-90
simula-tor. This accident was chosen on the basis of analy-sis of material gathered in the process of salvage proceedings because it was precisely described in official documents and the mathematical model of bulk carrier available in simulator database.
Simulator NMS-90 principles
The NMS-90 simulator was designed to meet the needs of training both Maritime University students and deck officers in the scope of the operation of radar and ARPA devices. Carried out simulations are very similar to real situations. The place of exercises can be chosen in restricted or an open sea area. The instructor can use one of the set of recorded coastlines or build by himself.
Up to 60 targets can be controlled by the instructor from his console and 3 own ships motion simulated separately at the same time. Many different navigational conditions can be simulated, for example:
– own ships’ and targets’ positions, true courses and speeds;
– ships’ characteristics influencing echo size (ship’s length, width, height, radar cross section, depth);
– simplified dynamic target characteristics;
– programmed target tracks (up to 600 waypoints). Programmed scenarios can take place both in open sea and near chosen coastline. They can be also improved by hydro meteorological conditions (winds, currents, rain etc.) and different emergency states can be also additionally simulated.
The NMS-90 simulator consists of the instructor console and three separate ship’s bridges. Every bridge is equipped with steering console, steering gear, the main equipment board and radar / ARPA devices.
The main navigational equipment is ARPA. It is used for obtaining both navigational and anti-collision information. The simulator is equipped with following ARPA devices:
– bridge no 1: FAR-2815 Furuno and DB-7 Norcontrol (Fig. 1),
– bridge no 2: Krupp-Atlas 9800 Series,
– bridge no 3: DB-10 Norcontrol and Rascar 3400M Sperry.
Fig. 1. The view of NMS-90 simulator – bridge no. 1 Rys. 1. Symulator NMS-90 – widok mostku nr 1
The NMS-90 simulator enables to set the main radar parameters: gain, range, Sea-Clutter, Rain- -Clutter, radar shadow sectors, radar impulse time characteristic or antenna height. There are also possibilities to simulate many types of marine radars and weather conditions influencing radar work.
The basic characteristics of radar echoes from different objects depend on their size, the height and their property of reflecting radar waves. Pro-grammed radar parameters and its working condi-tions have a serious influence on the characteristics of radar clutters. One should be particularly taken into consideration: the object can be not detected if it stays in the area of strong clutters.
Every coastline has the alterable depth chart where it is possible to place up to 3000 sounding values, as well as the chart of currents, with the maximum number of 300 programmable vectors. A possibility of simulating weather conditions also exists (e.g. force and direction of the wind, state of the sea, currents, atmospheric falls). Placing up to 500 navigational marks defined by their position, size, and, if necessary, racon signal is also possible.
Navigational situation simulation principles in NMS-90
Before the exercise programming begins, the instructor must choose the mathematical model of the ship. Individual models of different vessel types are in the database of the simulator.
In the case of the discussed reconstruction a model of the bulk carrier was chosen for the simulation, because this mathematical model parameters are the most similar to the both collided vessels parameters.
The parameters of the main model of bulk carrier are:
– total length: 174.0 m, – breadth: 31.1 m, – draught: 12.0 m, – displacement: 54 600 t, – full ahead speed: 14.8 knots.
Additionally it is possible to make some changes of basic model parameters if needed.
In the second step of simulation programming process, the instructor must adjust appropriate parameters which are essential to carry it out.
The most important stages of navigational sce-nario programming process are:
– the choice of the appropriate coastline;
– ship’s parameters programming, this function allows selection of an appropriate mathematical model and its parameters;
– the choice of the way of ship’s steering (from the instructor console, on the basis of the pro-grammed route or from the navigational bridge). In the first mode all manoeuvres are carried out systematically on the basis of their execution time. In this case factors which have the influence on the accuracy of reconstruction are:
the different technique of steering or the syn-chronization of carrying individual manoeuvres out; the automatic mode requires from the instructor implementing turn points and values of ship’s courses, speeds, turn rates, speed rates etc. It is possible to choose the mode of way-points coordinates calculating;
– programming of extrinsic factors (hydrometeo-rological conditions, currents and tides charac-teristics, wind, blasts of wind, rainfall, etc.); – programming of radar parameters.
Accident description
The collision took place in the area close to the Agersoe Flak (Fig. 2). That is a narrow area where two navigational routs (T and H) join together. South going vessels have to change their course about 50 degree to starboard to follow Route T (Deep Water route direction). So it is very impor-tant to proceed in the proper side of appropriate center line.
Fig. 2. VTS Great Belt area – the collision position [1] Rys. 2. Pozycja kolizji – obszar nr 2 nadzorowany przez VTS Great Belt [1]
During the accident there was calm weather with good visibility (3–4 NM). There was 1.5 knots north going current.
Both ships collided in the Great Belt were manned in accordance with the Minimum Safe Manning Certificate and their officers held the re-quired statutory certificates. “Vertigo” (Fig. 3b) had a mixed crew of Rumanian and Philippine citizens and “Ziemia Lodzka’s” (Fig. 3a) crewmembers were all Polish citizens.
a)
b)
Fig. 3. Ships participating in collision: a) m/s “Ziemia Lodzka”, b) m/s “Vertigo”
Rys. 3. Statki biorące udział w kolizji: a) m/s „Ziemia Łódzka”, b) m/s „Vertigo”
The engines and the steering equipment of the two vessels were fully functioning.
“Vertigo” was equipped with two radars, one of which with ARPA, and AIS. The equipment was fully operational.
“Ziemia Lodzka” was also equipped with two radars, with ARPA, and AIS, which were fully operational.
There is no indication that any technical failure or any failure of the bridge equipment has influ-enced the circumstances leading to the collision.
Table 1. Ships’ particulars [2] Tabela 1. Podstawowe dane statków [2]
Parameter “Ziemia Lodzka” “Vertigo” Home Port Monrovia, Liberia Montego Bay, Jamajka
Call sign A8DQ4 6YRD5
Numer IMO 8418746 8417601
Type of ship Bulk carrier Bulk carrier
Construction year 1992 1986 Gross Tonnage 26 264.00 26 666.00 Net Tonnage 17 458 15 502 Lenght Overall [m] 179.97 164.24 Breadth [m] 28.00 26.00 Engine Power [kW] 5 415.00 5 034.00
On the 7 December 2005, shortly after midnight, the fully loaded bulk carrier “Ziemia Lodzka” was proceeding south in Route T in the Great Belt, and the fully loaded bulk carrier “Vertigo” was pro-ceeding north in Route H.
Both vessels were proceeding at normal sea speed, “Ziemia Lodzka” at about 12 knots and “Vertigo” at about 13 knots. Both vessels reported positions to VTS Great Belt when passing VTS reporting line.
When the vessels approached the narrow area off Agersoe Flak “Ziemia Lodzka” was positioned at the centre line of Route T and “Vertigo” was slightly offset to the west of the centre line of Route H (Fig. 4).
Fig. 4. AIS recorded information at 00:30:00 [2]
Rys. 4. Zapis sytuacji na podstawie informacji AIS z godz. 00:30:00 [2]
The vessels were on crossing courses with “Vertigo” bearing approximately 20° on the star-board bow of “Ziemia Lodzka”.
Navigational situation recorded on the AIS base information and both master intentions at 00:30 were presented in figure 5.
At 0036 hours the vessels collided in position = 55°12.29 N = 011°05.46 E. The port bow of
“Ziemia Lodzka” struck the starboard side of “Ver-tigo”. “Vertigo” suffered heavy structural damage in the starboard side and foundered at position = 55°13’N = 011°05’ E at 11 meters depth of water (Fig. 6).
Fig. 6. Collision between “Ziemia Lodzka” and “Vertigo” [2] Rys. 6. Moment kolizji między m/s „Ziemia Łódzka” i m/s „Vertigo” [2]
The superstructure of the vessel was above water level. The crew abandoned the vessel in lifeboat and was picked up by “Stena Carrier”. There were no injuries. “Ziemia Lodzka” suffered structural damages on port side of the bow and was anchored approximately 3 miles north of the collision position. There was no pollution caused by the collision (Fig. 7).
Analysis of reconstruction accuracy
Basing on this material three variants of simulation were carried out. Each of them used a different option of programming offered by the NMS-90 simulator.
Fig. 5. AIS recorded information at 00:33:00 [2]
Rys. 5. Zapis sytuacji na podstawie informacji AIS z godz. 00:33:00 [2]
“Ziemia Lodzka’s” master intention was to continue southwest in Route H. When passing buoy #33 he therefore executed a change of course to starboard, when the distance to “Vertigo” was 0.5–0.8 miles.
“Vertigo’s” master became in doubt of the intention of “Ziemia Lodz-ka”, and when “Ziemia Lodzka” was right ahead on a crossing course he executed a full turn to port.
This was approximately 15 seconds after the start of the turn of “Ziemia Lodzka”.
a)
b)
Fig. 7. Ships after collision [2]: a) “Vertigo”, b) “Ziemia Lodzka”
Rys.7. Statki po kolizji [2]: a) „Vertigo”, b) „Ziemia Łódzka”
The programmed variants were:
1. POSITION BASED option v. 1 (PBV1): scenario time and ship’s courses are calculated on the basis of its given positions and speeds; 2. POSITION BASED option v. 2 (PBV2): ship’s
courses and speeds are calculated on the basis of its given positions and scenario time;
3. TIME BASED option (TBV): the way points positions are calculated on the basis of given ship’s courses, speeds and simulation time. Results of the simulations differed from one another. Data coming Investigation Report of the Danish Division for Investigation of Maritime Accidents was the base of the simulation accuracy assessment.
Data sets of ships’ positions, courses, speeds, turn and speed rates were recorded and ships’ positions plotted (plot interval was 5 second) during simulations. These data sets and plots allowed to compare simulations with AIS data sets recorded by Great Belt VTS. Final phases all variants of simulations, made out on the basis of plotted ships’ tracks, are presented in figures 8–10.
Scenario 1 (PBV1) accuracy analysis
There was collision recorded during the simulation (Fig. 8).
Main differences between Investigation Report (IR) and simulation were:
– period of 19 second difference in arrival time to the last waypoint occurred during the simulation of “Ziemia Lodzka” track and 4 second in the simulation of “Vertigo” track;
– differences between simulated and recorded in IR vessels’ courses are: up to 29 (more to starboard) in the “Ziemia Lodzka” case and up to 20.3 (more to port) in the “Vertigo” case; – because of the manoeuvre execution delay
(mathematical models characteristic), vessels’ tracks were moved about 18 m for “Ziemia Lodzka” and 15 meters for “Vertigo”;
– the impact point was moved more toward “Vertigo” stern part (about 60 m difference) and collision angle value was calculated 5–15 less than reported by witnesses.
Fig. 8. “Ziemia Lodzka” and “Vertigo” collision reconstru-ction – recorded ships’ tracks in PBV1 variant of simulation Fig. 8. Rekonstrukcja kolizji m/s „Ziemia Łódzka” i m/s „Vertigo” – trasy statków zarejestrowane podczas symulacji w wariancie PBV1
Scenario 2 (PBV2) accuracy analysis
There was collision recorded during the simulation (Fig. 9).
Main differences between Investigation Report (IR) and the simulation were:
– differences between simulated and recorded in IR speeds and courses occurred both for “Vertigo” and “Ziemia Lodzka” (up to 1.54 kn);
– simulated vessels’ track are very similar to presented in IR;
– the impact point was moved about 20–30 m (the impact point is located close to “Vertigo” superstructure) and collision angle value was calculated 10–20 less than reported by witnesses.
Scenario 3 (TBV) accuracy analysis
Because of the time interval influence on the simulation accuracy the additional waypoint was added in this scenario.
There wasn’t collision recorded during the simulation (Fig. 10).
Main differences between Investigation Report (IR) and the simulation were:
– the first three waypoints’ positions for both vessels are calculated properly,
– two last waypoints’ positions for both vessels are calculated imprecisely,
– there are slight differences between recorded in IR and simulated tracks (up to 10 m),
– “Ziemia Lodzka” passed astern of “Vertigo” in the distance of 5 m.
Conclusions
According to data obtained from Investigation Report, three variants of “Ziemia Lodzka”–
“Vertigo” accident were programmed in NMS-90 simulator. Accuracy reconstruction analysis leads to the conclusion that the most accurate simulation was scenario based on waypoints’ positions and simulation time (PBV2).
Some differences raised between the simulation and reported data (speeds and courses are not exactly the same as really recorded by VTS) but the impact point and value of collision angle are very similar to those reported by witnesses.
In the course of the simulations main factors influencing the reconstruction process are deter-mined. They are, first of all, recorded data accuracy and simulator possibilities. One of the main simu-lator restrictions is a limited set of mathematical vessel models. Because of this, the used mathema-tical bulk carrier model demonstrated some own characteristics which were different from those of real vessels and, therefore, some differences between simulated and obtained from Investigation Report tracks were visible. There were some delays in ships’ manoeuvres execution registered.
Increasing simulation accuracy is possible due to a new mathematical model created specifically for every simulated vessel.
Research results lead to the main conclusion that it is possible to use navigational simulators for maritime collision reconstructions, but two basic conditions must be fulfilled. First of all data
Fig. 9. “Ziemia Lodzka” and “Vertigo” collision reconstruc-tion – recorded ships’ tracks in PBV2 variant of simulareconstruc-tion Rys. 9. Rekonstrukcja kolizji m/s „Ziemia Łódzka” i m/s „Ver-tigo” – trasy statków zarejestrowane podczas symulacji w wariancie PBV2
Fig. 10. “Ziemia Lodzka” and “Vertigo” collision recon-struction – recorded ships’ tracks in TBV variant of simulation Fig. 10. Rekonstrukcja kolizji m/s „Ziemia Łódzka” i m/s „Vertigo” – trasy statków zarejestrowane podczas symulacji w wariancie TBV
accuracy. Witnesses statements cannot be the base of calculation because of their ambiguity and low precision. Sometimes they are contrary to one another.
Research shows that enough accuracy data can be obtained from AIS but sometimes they are burdened with a bigger error. In the future VDR data could be more useful.
Reconstructed accidents can be a good exercise for navigators both for training and recognizing navigators’ behaviour in difficult situations.
References 1. www.imo.org
2. Division for Investigation of Marine Accidents. Danish Maritime Authority. 2006. “Vertigo” / “Ziemia Lodzka” Collision on 7 December 2005, www.dma.dk
Others
3. Norcontrol. 1985. NAVSIM NMS-90 Instructor’s quick reference manual.
4. Norcontrol. 1985. Norcontrol Simulation NMS-90 MK II, Instructor’s Reference Manual.
