International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 6

Number 3

September 2012

377

1 INTRODUCTION

Marine transport development causes the increase of

the intensity of ships traffic and ships dimensions.

The navigational risk increase requires more sophis-

ticated methods of its assessment. Marine accidents

such as grounding are very rare and serious safety

analysis should also include incident (near misses)

analysis. The incident analysis is very important fac-

tor in navigational safety analysis due to the inci-

dents are usually not reported. Probability of the

ships grounding is one of the most important factors

influencing the navigational safety [2]. Based on the

data from HELCOM in 2008, there were 60 reported

groundings in whole Baltic Sea, and 32 of them

were reported in the south western Baltic Sea. As it

is shown on Figures 1 and 2, in 2009 the number of

reported groundings decreases to 38, but still about

half of them were reported in south-western Baltic

Sea.

Figure 1 Grounding accidents between (2000-2009) in south-

western Baltic Sea

Figure 2 Grounding accidents between (2000-2009) in Baltic

Sea

Incidents Analysis on the Basis of Traffic

Monitoring Data in Pomeranian Bay

L. Gucma & K. Marcjan

Maritime University of Szczecin, Poland

ABSTRACT: In this paper preliminary analysis of grounding incidents was presented for the future use in

navigational safety management system development. The analysis is focused on the area of Pomeranian Bay.

Grounding incidents model is created with use of AIS data. The distance of vessel from the dangerous depth

and draught/depth ratio was considered as the main factors of navigational incident in presented model.

378

Figure 3 Ships groundings on southern Baltic, analysed area [4]

Presented in this paper analysis of grounding in-

cidents is devoted to the Pomeranian Bay area exact-

ly the area between 13

00’E - 15

00’E and 54

00’N - 55

’

N. This area extends between Born-

holm, Rügen and the approach to Świnoujście. It

may be considered as costal area, where some places

have relatively low depth. Those are depicted in

Figure 4. Regions with depth of 10 m or less extends

around the Rügen Island, around Bornholm close to

Polish and German shore and also north of approach

to Świnoujście.

Figure 4 Map of selected area with isobaths.[5]

2 MODEL DETERMINING THE GROUNDING

INCIDENTS

Model used for determining the grounding incidents

on selected area. The model is based on AIS data,

from where static and dynamic data allow one to de-

termine the information on the ship and its positions.

Application written in C# [3] consists of three sec-

tions:

1 First section decodes data retrieved from the AIS

and records the routes of vessels navigating with-

in the analysed area. Data is segregated and writ-

ten to the appropriate database tables. Vessels of

6m depth or more are taken into account.

Figure 5 Database table with AIS dynamic data.

2 Second section examines individual positions of

the vessel in terms of distance from depths. The

depths of less than 140% of vessel’s draught are

taken into account. Then the lowest depth, and

the smallest distance to this depths is recorded.

Figure 6 A diagram of lowest depth and distance selection.

3 Third section is a model of positions extrapola-

tion. On the basis of dynamic data this part of

programme is searching for the previous position

(φ(t0), λ(t0)) and following position (φ(tn), λ(tn))

of the vessel in vicinity of the dangerous depth.

Both positions are taken into account only if the

time difference between them and the reference

position (φ(tr), λ(tr)) is less than 6 minutes. Ex-

trapolation algorithm calculates every second po-

sition and the distance from the depth between

the previous, reference and the following posi-

tion. The result is a position of a vessel that is the

closest to the smallest depth in vicinity of the ves-

sel.

379

∑

⋅−

⋅+⋅+=

kkr

jji

VCOG

iVCOG

)sin(

λλ

(1)

∑

⋅−

⋅+⋅+=

kkr

jji

VCOG

iVCOG

)cos(

ϕϕ

(2)

where:

– latitude in time t

between previous position and

reference position of the vessel,

– longitude of position number i between previous

position and reference position of the vessel,

COG

– Course Over Ground in time t

- speed of the vessel in time t

r – number of extrapolated positions between previ-

ous position and reference position of the vessel.

dCOG

ttCOGCOG

⋅−+= )(

(3)

ttVV

⋅−+= )(

(4)

3 RESULTS

The result of the analysis of grounding incidents on

the area between 13

00’E - 15

00’E and 54

00’N -

’

N within 6 month time period (1

January

2008 – 30

June 2008) were 230 grounding inci-

dents calculated by the algorithm. Figure 7 is pre-

senting analysed area with marked vessel position

divided due to the ratio D/T. The 10m and 12m iso-

baths are shown, to mark the places with low depth.

All the ports and their surroundings were excluded

from the examined area.

Figure7 Grounding incidents on selected area from 01.01.2008

to 30.06.2008

The ratio of vessel draught to the depth of the wa-

ter is shown in figure 8. 42 vessels were passing

close to the depth which was lower than their

draught. The other 188 vessel were close to the

depth which might have been a problem to pass it

safe.

Figure 8 Number of vessels close to depth with assigned ratio

D/T

Generally there were 3 ships that were passing

the dangerous depth with distance of 2 cables or

less. It must be remembered that the distance is

measured between the calculated depth and the posi-

tion of vessel’s antenna. The actual distance from

the depth could have been lower than 2 cables. All

the distances of the ship to the depth are depicted in

figure 9. According to experts the distance of 0,7

Nm can be interpreted as a safe distance, but taking

into account the conditions of open water, getting so

close to a dangerous depth contours can be regarded

as an unjustified risk situation or a grounding inci-

dent.

Figure 9 Number of vessels approaching to dangerous depth

with assigned distance.

3 3

33 33

0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1 1,2 1,3

Distance from the depth

Distance [Nm]

No. of grounding incidents

380

Length of most of the vessels which had ap-

proached close to dangerous depths is between 101m

and 160m. Most vessels length range extends be-

tween 101m and 120m, these are vessels of draught

(5-7m). Such depth are mainly found in coastal are-

as. It means it is very likely that some surroundings

of ports aren’t sufficiently cut off.

Figure 10 Number of grounding incidents based on vessel

length.

4 CONCLUSIONS

Presented results of grounding incidents constitute a

valuable source of information about the areas with

low water depth around which vessels are passing

with dangerous distances. The incident places ob-

tained by presented model are very close to the

grounding accidents on analyzed area (Fig.3). Ob-

tained results will be used in navigational safety

management system development, which is de-

scribed in [1]. There is still some work to be done to

verify models results but partially verification of the

results presented, is overlapping positions of calcu-

lated grounding incidents to real groundings, in the

examined area.

REFERENCES

Gucma L., Marcjan K. 2011. The Incident Based System of

Navigational Safety Management of on Coastal Areas. Pro-

ceedings of the 8th International Probabilistic Workshop.

Szczecin.

Przywarty M. 2008. Models of Ships Groundings on Coastal

Areas. Journal of Konbin Vo-lume 5, Number 2 / 2008.

Versita, Warsaw.

ECMA International. 2006. C# Language Specification (4th

ed.).

HELCOM. 2009. Report on shipping accidents in the Baltic

Sea area during 2009.

http://maps.helcom.fi/website/mapservice/index.html

http://www.io-warnemuende.de/topography-of-the-baltic

sea.html

22 22

100

Vessel LOA

Vessel length [m]

No. of grounding incidents