GIS-Based Technology of Ship Routing in Ice

Igor Stepanov, Igor Stepanov, Sergey Frolov, Sergey Frolov, Sergey Klyachkin, Sergey Klyachkin, Yury ScherbakovYury Scherbakov

(Arctic & Antarctic Research (Arctic & Antarctic Research Institute, St. Petersburg, Institute, St. Petersburg, Russia)Russia)

The fourth meeting of the International Ice Charting Working Group (IICWGThe fourth meeting of the International Ice Charting Working Group (IICWG) )

St.Petersburg, Russian Federation, April 7-11, 2003St.Petersburg, Russian Federation, April 7-11, 2003

The general principles for selection of the The general principles for selection of the

optimal ship route in iceoptimal ship route in ice total ice concentration is minimum; quantity of young ice forms (in autumn-winter) and

melting stages of ice (in spring-summer) are maximum; minimum hummock and ridge concentration and

increased ice fracturing are observed; prevailing orientation of discontinuities in the ice cover

(fractures, cracks and leads) coincides with the general course of convoy motion;

depths correspond to the navigation safety requirements for the given ship

AtAt winter-spring navigation (January-May) winter-spring navigation (January-May) the selection of the easiest transit variant is the selection of the easiest transit variant is determined in general by:determined in general by:

drifting ice edge position; extent of development of flaw polynyas; distribution of dynamically active zones (ice pressures

or discontinuities in the ice cover) in the ice massif

The computer system concept is based on The computer system concept is based on

the following main principles:the following main principles: as a design environment capable to ensure a full-value

functioning of the prototype, the geographical information system (GIS) was selected;

remote sensing data from satellites present the main source of ice information;

a criterion of the optimal route is minimum transit time for navigation of a convoy of ships;

calculation of speed (transit time) is made taking into account a possible ice cover redistribution during the period of marine operation

Generalized functional scheme of the system prototype for selecting an optimal ship transit route

in ice

Preparation of the satellite ice chartPreparation of the satellite ice chart

expert assessment of the uniform ice cover areas, their classification and identification (interpretation of satellite images);

delineation of boundaries of the ice cover uniform areas (contouring) with the formation of a digital set of contour coordinates;

creation of an object containing a set of contour coordinates and attributive characteristics of the uniform ice area

The electronic ice chart (shape-file) based on the satellite image processing is formed

Usage of the numerical model of ice cover Usage of the numerical model of ice cover evolutionevolution

Principal blocks of the modelPrincipal blocks of the model::

forecast of the sea thermal state and dynamics (both in the absence and presence of the ice cover);

forecast of the thermal growth and dynamics of the ice cover

Models of ship motion in iceModels of ship motion in ice

Model for prediction of leading icebreaker(s) speeds;

Model for prediction of escorted ship(s) speeds

Model of leading icebreaker motion:Model of leading icebreaker motion: empirical-statistical model of the quantitative empirical-statistical model of the quantitative

assessment of ice navigation difficultyassessment of ice navigation difficulty

Two blocks of the model:a transfer from the general distribution of ice cover characteristics in the transit area, which is fixed on the composite ice charts to the distribution of ice cover characteristics directly along the transit route determined by a selective character of ship motion in ice;an assessment of the influence of ice cover characteristics with which the ship interacts on the efficiency of its navigation expressed through its motion speed in a uniform ice zone

Model of the escorted ship motion:Model of the escorted ship motion: the analytical model based on the the analytical model based on the

mathematical description of the physical mathematical description of the physical processes accompanying the ice-ship processes accompanying the ice-ship

interactioninteraction

The characteristics of the conditions of safe ice navigation:Safe speed – the maximum ship transit speed in ice at which no

damage of hull structures occurs under the action of ice loads.Attainable speed – the maximum speed a ship can develop when

moving under the given ice conditions at a given shaft power regardless of whether maintaining such speed by ship leads to ice damages of the hull structures or not.

Speed limit – the maximum ship speed prescribed by the ice passport that it could develop moving in ice without hull damage; it is determined as the least of the safe and attainable speeds.

Calculation of the convoy speed:Calculation of the convoy speed:

The expected convoy speed is defined as the least value among the known speeds of the leading icebreaker and the escorted cargo ship moving along the channel

The criterion of the optimality of the The criterion of the optimality of the navigation variant: the minimum time navigation variant: the minimum time

expenditureexpenditure

The example of the model system usage for The example of the model system usage for selecting the optimal ice navigation routeselecting the optimal ice navigation route

The icebreaker of “Yermak” type (capacity is 30 Mwt) and one tanker of “Aframax” type;March 1988;The Sea of Japan, Tatar Strait

The electronic chart of ice conditions. The electronic chart of ice conditions. March 20, 1988March 20, 1988

Prognostic chart of ice conditions. Prognostic chart of ice conditions. March 21, 1988March 21, 1988

Prognostic chart of ice conditions. Prognostic chart of ice conditions. March 22, 1988March 22, 1988

The scheme of ice routing using the prognostic ice The scheme of ice routing using the prognostic ice chart and the calculation of time expenditures for chart and the calculation of time expenditures for

the selected variantthe selected variant

The calculation resultsThe calculation results::

The average speed: western route – 6.9 kn., eastern route – 6.0 kn.

Total time expenditure: western route – 32.15 hrs, eastern route – 40.35 hrs.

Thus, the western route is recognized as the optimal one because it allows the convoy to economize about 8 hours.