TR ANSPO RT SY ST E M S T E L E M A T IC S T S T '02 TR A N SP O R T z.45, nr kol. 1570 II INTERNATIONAL CONFERENCE________________ P O LITEC H N IK I ŚLĄ SKIEJ 2002
marine transport system, optim al ship route Bernard W IŚ N IE W S K I1
PR O BL EM S O F W E A T H E R R O U T E N A V IG A T IO N O F V E SSE L IN T H E O CEAN
Ocean route recommendations for some vessels of the Polish Steamship Company were prepared on the basis of digital hydrological and meteorological data and programs for determining time optimum routes. The isochrone method and the theory of graphs were used for route planning. As an example, a voyage o f the m/v Pomorze Zachodnie is presented.
P R O B L E M Y N A W IG A C JI N A TR A SA C H ZA L EŻN Y C H OD PO G O DY D LA ST A T K Ó W O C EA N IC ZN Y C H
Zaprezentowano problematykę wyznaczania trasy minimalno - czasowej dla statku w podróży oceanicznej. Na przykładzie podróży m/v Pomorze Zachodnie przedstawiono rezultaty opracowania rekomendacji trasy przekazywanych z ośrodka lądowego armatora - Polska Żegluga Morska.
1. IN TR O D U C TIO N
There are tw o basic problem s in m arine navigation that m ight be form ulated as questions:
- W here am I, i.e. w hat is my position and how accurate is it?
- How should the ship be steered to reach the destination in the m ost econom ical way?
The form er problem has been solved satisfactorily by satellite system s o f ship positioning (GPS, D G PS) fo r the purpose o f steering a vessel along an ocean route. T he latter question still constitutes a problem to be solved due to varying environm ental conditions in w hich a ship sails, regarded as a control target. O bviously, sailors and ship navigators have always been interested in choosing the m ost advantageous sailing route. T he B ritish A dm iralty issues seasonal m aps for shipping know n as R outing C harts. T hese are continually updated and used at present by ship captains for program m ing an ocean voyage and sailing.
Nowadays the preparation o f an ocean voyage cannot be lim ited to the specifying o f a seasonal route. As w eather conditions change, a ship w ill be sailing along a route different from the planned one. T o this end the ship w ill use com puter program s for optim um route determination based on current w eather forecasts and consult a route w ith an appropriate land-based centre, etc.
The sequence o f voyage p lanning is as follow s:
Institute o f Navigation, Maritime University o f Szczecin, Waty Chrobrego 1-2, 70-500 Szczecin, Poland bwis@wsm.szczecin.pl
Institute o f Marine Science, University o f Szczecin, W ąska 13, 71-434 Szczecin , Poland
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seasonal route
- route allow ing for cu rrent w eather forecasts - reception o f facsim ile m aps, com puter program s for ro u te optim isation
route recom m ended by specialised routing centres, e.g. O ceanroutes, N avitech, M etroute, P S C ’s Ship R outing Centre.
Several subjects are interrelated in the problem s o f ocean route optim isation:
- w eather co nditions (availability and quantity o f inform ation, its reliability)
vessel as a control target (sea-keeping qualities, diversity o f vessel types, different types o f cargo)
system s o f com m unications, search and rescue, V TS s u rv e illa n c e ,...
sh ip o w n e rs’ requirem ents (voyage prom ptness, m axim um loading states, navigation in d ifficult areas - ice conditions, icing, currents).
W eath er routing aim s at:
- o b jective navigational, hydrological and m eteorological calculations as w ell as data processing
satisfying the conditions for the safety o f navigation, vessel and cargo
allow ing fo r voyage m inim um -tim e, m inim um fuel consum ption indicator, avoidance of w eather dam age
forecasting w eather conditions and determ ining vessel m ovem ent conditions depending on its structural qualities and loading state.
R esearch m ethods used in solving the problem s listed above are the follow ing:
solving non-determ inistic and stochastic processes (weather) - spectrum o f wave param eters, forecasting areas affected by w ind, w aves, ic in g ,...
- solutions offered by the control theory (characteristics o f ship m otion in high seas and w ind, fuel consum ption c u r v e s ,...)
m athem atical m odelling, calculus o f variations, and optim isation principles (dynamic program m ing using the isochrone m ethod, graph theory, B ellm an ’s optim isation principles, P on try ag in ’s m a x im u m ,...).
In the presentation o f w orks in progress (bibliography [1-6]), it is w orth em phasising that au th o r’s theoretical solutions have proved useful in operational recom m endations o f ocean routes for P o lish S team ship C om pany vessels (PSC). As a resu lt o f m any years o f experience gained by the P o lish m erchant fleet, the P olish S team ship C om pany and Szczecin M aritime U niversity have established a ship routing centre. In its operational system th e centre recom m ended routes to vessels in the N orth A tlantic and N orth P acific O ceans. T h e author’s route selection program s w ere used, m aking use o f digital hydro-m eteorological data o f the GTS netw ork. T h e isochrone m ethod and route selection b ased on the graph theory w ere used in the program s. F or daily com m unications w ith the ships recom m endations and calculation results w ere prepared.
2. M ETH O D S A N D A N E X A M PLE
O ne good exam ple o f ideal co-operation betw een the P S C ’s ship routing centre and vessels w as the daily elaboration o f recom m endations for a voyage o f th e m /v Pomorze Z achodnie from V entspils to M ontreal, on w hich the vessel saved 37.3 hours as com pared to a
traditional seasonal route in particular w eather conditions that prevailed in the N orth Sea and North A tlantic (betw een 24.04. and 03.05. 1998).
The m otor vessel P om orze Z achodnie left the port o f V entspils on 20 A pril w ith a cargo o f steel heading for M ontreal. D ue to the cargo, the vessel, shipow ner’s operating departm ent and chief n av ig ato r’s office w ere asked consulted. T he vessel was recom m ended, if possible during the voyage route planning, to avoid seas higher than 5 m com ing from abeam ; it was said that the vessel could reduce speed w hen the characteristic w ave hc>3m com ing from ahead; that the vessel should n o t proceed by itself through ice covering m ore than 50% o f the area, etc.
In April 1998 on several occasions before the voyage o f the m /v Pom orze Zachodnie, waves in the N orth A tlantic exceeded 10 m (data from wave analyses and forecasts) and for this and other reasons the vessel and centre exchanged in great detail w eather and operating data. The vessel encountered in the B altic Sea conditions average in that season o f the year, w hilst in the North Sea the conditions w ere w orse than average ( -5 ° to 6°B). T he m ost im portant decision in the first leg o f the voyage was taken on 21/22. A pril before the Skagen light vessel was passed. T he decision w as based on w ind and waves forecasts for the N orth A tlantic up to 120 hours in advance. T he forecasts indicated that high seas (to 9m ) w ould develop m ainly in latitudes o f approx. 50° N orth. T he route recom m ended then w ent through P entland Strait across the A tlantic along approx. 60°N latitudes, w here the expected w inds were to blow from astern. It was also know n that practically the route by Belle Isle to St Law rence Bay w ould be closed and that vessels w ould have to avoid the lim it o f pack ice and spreading icebergs in way o f N ew foundland. O ther essential inform ation w as sent to the vessel when detailed forecasts w ere confirm ed and the vessel was about to go through P entland Strait on 24 April.
Following an alternative seasonal route, it w ould still have been in the N orth Sea before entering routes in the E nglish Channel. Spreading iceberg lim its before N ew foundland up to 48°N 043°W m ade it necessary to test routes to 46°N 046°W (F ig .l).
Fig. 1. A chart o f ice conditions in the area o f Newfoundland on 24 April 1998. Source: Ice Patrol
Characteristic wave is observed by lookouts onboard a vessel. Its height is similar to the significant wave (hi/3) and statistically, the probability o f its occurrence in the wave area is equal to 9%.
D uring all the subsequent days the vessel was sending to the C entre current data on its position, w eather, conditions, possibly its speed-dow n table, w hereas th e C entre delivered recom m endations in the form displayed below in T able 1.
Table 1 A recommendation sent to the vessel
fm : p o l s t e a m - o c c a n t r a m p , s z c z c c in to : m a s t e r m /v p o m o r z e z a c h o d n i c
r e c o m m e n d e d r o u t e f o r V o = 1 3 . 7 w .:
L a t [n ] L o n g [ w ] t im e [h ] d i s t a n
5 8 .4 2 8 .5 0 0 . 0 0 0 . 0 0
5 8 .4 2 9 .5 0 2 .3 8 3 1 .1 7
5 8 .4 2 1 1 .5 0 7 .2 4 9 3 .5 1
5 8 .4 2 1 2 .5 0 9 .5 9 1 2 4 .6 8 5 8 .4 2 1 3 .5 0 1 1 .9 8 1 5 5 .8 6 5 7 .4 2 1 9 .5 0 2 6 .9 3 3 5 4 . 8 2 5 6 .4 2 2 4 .5 0 3 9 .5 2 5 2 8 .0 6 5 4 .4 2 3 1 .5 0 5 9 .3 6 7 9 3 . 4 2 5 2 .4 2 3 6 .5 0 7 5 .2 5 1 0 0 7 .7 6 5 1 .4 2 3 8 . 5 0 8 2 .9 4 1 1 0 2 .6 8 5 0 .4 2 4 0 .5 0 9 0 .7 6 1 1 9 8 .8 8 4 8 .4 2 4 3 . 5 0 1 0 4 .1 5 1 3 6 6 .0 7 4 6 .0 0 4 6 . 0 0 1 1 8 .2 2 1 5 5 0 .4 7
E x p e c te d c o n d i t i o n s in r o u te :
tim e L a t L o n g c o u r s e V s w a v e h e ig h t / a n g l e
0 . 0 0 5 8 .4 2 8 . 5 0 2 7 0 1 3.1 1 .8 0 5 3 4 . 0 0 5 8 .4 2 1 0 .3 0 2 7 0 1 2 .8 2 .1 0 4 8 8 .0 0 5 8 .4 2 1 2 .0 9 2 7 0 1 3 .3 2 .2 0 9 8 1 2 .0 0 5 8 .4 2 1 3 .5 0 2 5 2 1 3 .2 1 .6 0 4 9 1 6 .0 0 5 8 . 2 6 1 5 .2 5 2 5 2 1 2 .9 1 .9 0 2 4 2 0 .0 0 5 8 .1 1 1 6 .5 7 2 5 2 1 2 .7 2 .1 0 0 1 2 4 . 0 0 5 7 .5 5 1 8 .3 4 2 5 2 1 3 .4 1.1 0 2 0 2 8 . 0 0 5 7 .3 7 2 0 .1 6 2 4 9 1 3 .7 0 .3 0 5 0 3 2 . 0 0 5 7 .1 8 2 1 .5 1 2 4 9 1 3 .6 0 .5 0 5 4 3 6 . 0 0 5 6 .5 9 2 3 .2 5 2 4 9 1 3 .6 0 .7 0 8 2 4 0 . 0 0 5 6 .3 9 2 5 . 0 0 2 4 3 1 3 .3 1 .7 0 8 2 4 4 . 0 0 5 6 .1 6 2 6 . 2 4 2 4 3 1 3 .0 2 .2 0 7 2 4 8 . 0 0 5 5 .5 4 2 7 . 4 0 2 4 3 1 1 .9 3 .3 0 5 9 5 2 .0 0 5 5 .3 3 2 8 .5 4 2 4 3 1 1 .6 3 .9 0 6 7 5 6 .0 0 5 5 .1 0 3 0 .1 5 2 4 3 1 3 .0 1 .8 0 4 6 6 0 .0 0 5 4 .3 7 3 2 .0 3 2 3 6 1 3 .7 0 . 4 0 3 2 6 4 . 0 0 5 4 .0 7 3 3 . 2 0 2 3 6 1 3 .6 0 .8 0 5 8 6 8 . 0 0 5 3 .3 6 3 4 .3 6 2 3 6 1 3 .5 1 .3 0 9 1 7 2 . 0 0 5 3 .0 7 3 5 .4 9 2 3 6 1 3 .2 1 .9 0 7 4 7 6 . 0 0 5 2 .3 6 3 7 .0 2 2 3 0 1 2 .6 2 .3 0 4 1 8 0 .0 0 5 2 .0 5 3 8 .0 5 2 3 0 1 2 .4 2 .8 0 5 7 8 4 .0 0 5 1 .3 4 3 9 .0 7 2 3 1 1 2 .5 4 .3 1 1 3 8 8 . 0 0 5 1 . 0 1 4 0 . 1 2 2 3 1 13.1 4 .5 1 4 6 9 2 . 0 0 5 0 .3 0 4 1 .0 8 2 2 4 1 3.1 3 .6 1 2 0 9 6 . 0 0 4 9 . 5 2 4 2 .0 5 2 2 4 1 3 .3 4 .5 1 6 9 1 0 0 .0 0 4 9 . 2 0 4 2 . 5 5 2 2 4 1 1 .4 6 .5 1 2 4 1 0 4 .0 0 4 8 . 4 9 4 3 . 3 9 2 2 4 1 0 .5 6 .8 1 0 6 1 0 8 .0 0 4 8 . 0 0 4 4 . 2 4 2 0 8 1 2 .4 4 . 6 1 1 5 1 1 2 .0 0 4 7 . 1 6 4 5 . 0 0 2 0 8 1 2 .6 3 .8 1 0 3 1 1 6 .0 0 4 6 .3 1 4 5 . 3 6 2 0 8 1 2 .7 3 .5 101 1 1 8 .2 2 4 6 . 0 0 4 6 . 0 0
2 5 . 0 4 w a v e c e n t r e a t 5 0 n / 3 8 w m o v in g E S E , c o n d it i o n s e x p e c t e d o n o u r r o u t e 2 8 . 0 4 w ith
to w a r d s 4 0 n 2 0 w 2 7 .0 4 . D e t e r i o r a t io n o f w e a t h e r 6 m w a v e c e n t r e a t 4 8 n / 3 8 w .
C alculations perform ed at the shipow ner’s ship routing centre and inform ation exchange with the vessel w ere sent every day, therefore, thanks to constantly updated w eather forecasts and ship m otion ch aracteristics, the final route w as adjusted to the changing w eather conditions, and M aster follow ed the recom m endations.
Figures 2.1 - 2.8 below show the actual route o f the m /v P om orze Z achodnie in particular days.
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Figs.2.1.-2.8. Real and predicted positions o f the m/v Pomorze Zachodnie on the seasonal route against the distribution o f wave fields in the north Atlantic (24.04 - 01.05 1998r.)
In the above records o f real w eather data for each o f the eight days there arc m ore favourable conditions for navigation alone the actual v essel’s track than along the seasonal route starting at the E n g lish C hannel. T h e vessel m /v P om orze Z achodnie enters the ro u te in the North A tlantic on 24 A pril w ith seas one m etre high. On 26 A pril the vessel proceeds w ith NNE waves three m etres high, w hile on the seasonal route at that tim e the seas ranged from four to five m etres from N W . On 28 A pril the difference in w ave height is significant; in its actual position the vessel encountered tw o-m etre w aves (hc=2m ), w hereas at the predicted position on the seasonal route (28-29 A pril) the vessel w ould have proceeded through a field o f waves up to seven m etres high. On 29 and 30 A pril the vessel diverted south from the great circle
„giving w ay” to w aves 6 m etres high th at was m oving from the vicinity o f N ew foundland to NNE. T h at diversion southw ard was also necessitated by ice fields that had to be avoided, particularly concentrations o f icebergs in the area o f 48°N 045°W . On 30 A pril by daytime
the vessel sailed along the iceberg lim it, (initially to 47°N , then 46°N ) w hich was slightly shifted northw ard by w ind and waves from SW in late A pril (about 40M m ).
Finally the vessel gained on the actual route 37.3 hours in relation to the sim ulated tim e o f voyage along the seasonal route in those w eather conditions from 20 April to 1 M ay 1998.
The application o f optim al route calculation m ethod using the isochrone and digraph m ethods has proved successful in practice, supposedly thanks to the sm ooth co-operation betw een the centre and vessel, supported the vessel operator and personnel o f the P S C ’s C hief N avigator D epartment.
Figure 3 below outlines the m o st im portant section o f the discussed N orth A tlantic route.
Fig.3. A (rack covered by the m/v Pomorze Zachodnie
Other passages o f vessels in the N orth A tlantic and N orth Pacific recom m ended by the PSC ship routing centre in w hich this author and his colleagues participated, that m ade use of calculation program s and navigational analyses, have been docum ented in research m aterials and other publications [1, 2, 6]. T hey m ake up good exam ples o f w eather routing implemented in ocean shipping o f m erchant vessels.
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B IB LIO G R A PH Y
[1] W IŚNIEWSKI B., CHOM SKI J., DROZD A., „Rekomendacje tras statków na Atlantyku opracowane w ośrodku armatora PŻM ”, III Sympozjum Nawigacyjne Gdynia WSM 1999, s. 161-170.
[2] W IŚNIEWSKI B., CHOMSKI J., DROZD A., P. M EDYNA P., „Rezultaty operacyjnego prowadzenia statków PŻM na trasach oceanicznych z wykorzystaniem rekomendacji pogodowych”, V Konferencja
„Okrętownictwo, Oceanotechnika, Maszyny i Systemy Transportowe. Międzyzdroje 2000, s. 333-340.
[3] W IŚNIEWSKI B., „Optymalizacja drogi morskiej statku z uwzględnieniem warunków pogodowych”, WSM Szczecin 1986.
[4] WIŚNIEWSKI B., „Problemy wyboru drogi morskiej statku”, Wyd. Morskie, Gdańsk, 1991.
[5] W IŚNIEWSKI B., CHOMSKI J., „Zastosowanie grafu skierowanego do obliczeń optymalnej trasy statku", Zeszyt Naukowy W SM Szczecin nr 37, Szczecin 1990, s. 181-197.
[6] W IŚNIEWSKI B., CHOMSKI J„ DROZD A., MEDYNA P., „Rezultaty- operacyjnego prowadzenia m/v Ziemia Tarnowska na Północnym Atlantyku z wykorzystaniem rekomendacji pogodowych”, XI Międzynarodowa Konferencja Komitetu Geodezji PAN, Sekcja Naw-igacji. AMW Gdynia 1998, s.276-284
R eview er: Ph. D. Z bigniew Pietrzykowski
