International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 1

Number 3

September 2007

237

Usage AIS Data for Analyzing Ship’s Motion

Intensity

K. Naus, A. Makar & J. Apanowicz

Polish Naval Academy, Gdynia, Poland

ABSTRACT: In preliminary unit of report were introduced order, structure and format of VDM code sended

by the AIS VHF data link. Described the process of decoding combination of binary chains sentences describe

from ITU R M. 1371.In principle unit analyse of ships intensity of movement in Gulf of Gdańsk used coded

isoline on background of map as well as transverse intersection on a approach to harbour of Gdynia. Authors

presented new generated and used method of processing of regular GRID net - designed to description of

spatial expansion of ship intensity of movement. Authors circumscribed method of utilizations the

VerticalMapper software Systemu to calculation the izoline of even ships intensity of movement, intersections

of transverse, as well as principles of visualizations coded isoline on background of the map, according the

author's software.

1 INTEGRATED NAVIGATION

The state of safety at sea can be rate towards vision

range of movement of ships and surface units. All

information about the ships movement in

dependence of location of sea area is possible to

obtain used various methods of observation, with the

help of the AIS system. The description of

movement of ships, acquisition in the AIS, refer to

geographical position, courses, construction

parameters of ship as well as kind of transportation,

should be presented in figure of simplified diagram:

space /time. Diagrams these illustrate ships density

of movement under specified sea area, on which they

shift ships. Multi-criteria analyzes of such diagrams

lets the possibility of improvement of organization

human activity at sea which can create threat for

ships movement, the human life and sea

environment.

2 AIS DATA DECODING METHODS

Determined, that in aim of creation of diagrams of

ships movement intensity, the AIS data will be

converted to files of type: *.mif, *.mid as well as

*.txt . The first two files be used become in

programme GIS - MapInfo to display position and

information descriptive fixes of monitored ships,

however third file - in programme MI Vertical

Mapper to transfer in the GRID to describe the

spatial expansion of analysed parameter (the

intensity of movement of ships).

Realized above mentioned, was worked out

specialist software attend to conversion of files from

AIS data, which be coded fin accordance ITU – R.

M. 1371, to files type: *.mif, *.mid, and *.txt.

The decoding and interpreting process compose

of three leg:

− transformation in binary chains mark chains,

which represent it,

238

− the organization in packets of message the binary

chains peaceably from ITU – R.M. 1371,

− the mapping of organized guided packets of

message on suitable information.

It below example - mark chain and transformed

binary chain was presented. Figure this is the visual

help, which can facilitate the understanding of

process of decoding of AIS message. Line astern on

left hand drawing 10 entitled “Bit positions VDM” is

information about accurate position - binary chain of

message the information about bit exact position.

However line astern after right side entitled “The

binary representation of sign” it motion the

information about binary representation of message.

The median line astern contains next the signs of

chain of message. Decoding VDM chain has begun

for first sign in chain. There in this case sign is “1”,

and answering him binary chain “000001”. The fix

of individual bits of binary chain has be presented on

left hand as value since 1 to 6.

Second sign of chain “P” the binary chain

represents “100000”. The fix of individual bits of

binary chain has be presented in left line astern as

value since 7 to 12. The same the process follows for

every sign of chain of message.

Fig. 1. Example - mark chain and transformed binary chain

(IEC 2002)

Bits 1-6 = Identifier for this message

000001 = message 1 (Reference Annex E of

ITU-R M.1371-1:2000 to interpret following

bits 7-168.)

Bit 7-8 = Repeat Indicator

2 = message repeated twice

Bits 9-38 = MMSI number of broadcasting unit

000000000000000000000001111111 = 127

Bits 39-42 = Navigational status

0000 = underway using engine

Bits 43-50 = Rate of turn (equation used)

00000101 = +1.1 degrees/minute

Bits 51-60 = Speed over ground

1001100100 = 61.2 knots

Bit 61 = Position accuracy

0 = low (greater than 10 meters)

Bits 62-89 = Longitude in 1/10000 minutes

0000111101111111010010010000 =

27 degrees 5 minutes East

Bits 90-116 = Latitude in 1/10000 minutes

000001011101000101000010000 =

5 degrees 5 minutes North

Bits 117-128 = Course over ground in 1/10

degrees

001110111111 = 95.9 degrees true

Bits 129-137 = True Heading

101011111 = 351 degrees true

Bits 138-143 = UTC second when report

generated

110101 = 53 seconds past the minute

Bits 144-147 = Regional Application

0000 = no regional application

Bits 148 = Spare

Bit 149 = RAIM Flag

0 = RAIM not in use

Bit 150-168 = Communications State

00 = UTC Direct

001 = 1 frames remaining until a new slot

is selected, UTC hour and minute follow,

01111001000100 = 01111:0010001 = 15 : 17 UTC

Bits 167-168 not used for UTC Sub-message

Table 1. Messages 1, 2, and 3 (position reports) (ITU 2001)

Parameter

Number

of bits

Description

Message ID

Identifier for this message 1, 2

or 3

Repeat

Indicator

Used by the repeater to indicate

how many times a message has

been repeated.

Refer to § 4.6.1; 0 - 3; default =

0; 3 = do not repeat any more

User ID

MMSI number

Navigational

status

0 = under way using engine, 1 =

at anchor,

2 = not under command,

3 = restricted manoeuvrability,

4 = Constrained by her draught;

5 = Moored;

6 = Aground;

7 = Engaged in Fishing; 8 =

Under way sailing;

9 = reserved for future

amendment of Navigational

Status for HSC;

10 = reserved for future

239

amendment of Navigational

Status for WIG;

11 - 14 = reserved for future

use; 15 = not defined = default

Rate of turn

ROT[AIS]

127 (–128 (80 hex) indicates not

available, which should be the

default). Coded by ROT[AIS] =

4.733 SQRT(ROT[IND])

degrees/min

ROT[IND] is the Rate of Turn

(720 degrees per minute), as

indicated by an external sensor.

+ 127 = turning right at 720

degrees per minute or higher;

- 127 = turning left

at 720 degrees per minute or

higher

SOG

Speed over ground

in 1/10 knot steps

(0-102.2 knots)

1023 = not available,

1022 = 102.2 knots or higher

Position accuracy

1 = high (< 10 m; Differential

Mode of e.g. DGNSS receiver)

0 = low (> 10 m;

Autonomous Mode of e. g.

GNSS receiver or of other

Electronic Position Fixing

Device); default = 0

Longitude

Longitude in 1/10 000 min

(±180 degrees,

East = positive,

West = negative.

181 degrees (6791AC0 hex) =

not available = default)

Latitude

Latitude in 1/10 000 min

(±90 degrees,

North = positive,

South = negative,

91 degrees (3412140 hex) = not

available = default)

COG

Course over ground in 1/10° (0-

3599). 3600 (E10 hex) = not

available = default;

3601 – 4095 should not be used

True Heading

Degrees (0-359)

(511 indicates not available =

default).

Time stamp

UTC second when the report

was generated (0-59,

or 60

if time stamp is not available,

which should also be the default

value, or 62 if Electronic

Position Fixing System operates

in estimated (dead reckoning)

mode, or 61 if positioning

system is in manual input mode

or 63 if the positioning system

is inoperative)

Reserved for

regional

applications

Reserved for definition by a

competent regional authority.

Should be set to zero, if not

used for any regional

application. Regional

applications should not use zero

Spare

Not used. Should be set to zero

RAIM-Flag

RAIM (Receiver Autonomous

Integrity Monitoring) flag of

Electronic Position Fixing

Device;

0 = RAIM not in use = default;

1 = RAIM in use)

Communication

State

Total number of

bits

168

3 PRINCIPLE OF THE SHIPS MOVEMENT

INTENSITY DIAGRAMS CREATION

In programme implemented the algorithms to

determination of number of ships spending in sub-

area (formed with division of inspected area on

smaller fragments - point of grid net) in time definite

slice. Parameter this be described as value definite in

node of GRID net. It was determined in result of

analysis of mutual location next intervals of ships

cruses and intervals limiting the individual point of

GRID net.

Processed application possesses following main

window (cardinal port).

In this picture - PC window the strainer cores

(filters) are to sharp-tuning of individuals selection

ships as well as the editorial ports (window) fixable

to the parameters of net GRID. Strainer cores permit

on of individuals selection ships according to:

− MMSI number,

− type,

− dimensions,

− the velocity of motion (speed),

− draught,

giving in this the way the possibility of constructing

the GRID net with expansions of intensity of

movement chosen group of individuals ships. The

size and resolution of net be established in window

"the parameters of GRID net ”. It influence on

resolution, appointive from grid in programme

VerticalMapper, isoline of analysed parameter and

the same on quality their display in programme

MapInfo.

240

Fig. 2. Main window – programme cardinal port

It below represented the example - file of *.txt

type with calculated value of node GRID net.

ncols

nrows

xllcorner

yllcorner

cellsize

18.00000000

54.00000000

0.00027778

NODATA_value 0

0 0 0 0 2 0 0 0 0 0

0 0 0 0 0 1 0 0 0 0

0 0 0 0 1 0 0 1 0 0

0 0 0 0 0 0 0 2 0 0

0 0 0 0 0 3 0 0 0 0

0 0 0 2 0 0 1 0 0 0

0 0 2 0 0 0 1 0 0 0

0 0 2 0 0 0 0 1 0 0

2 2 0 0 0 0 0 1 0 0

0 0 0 0 0 0 0 0 1 0

Fig. 3. The trajectories of passenger ships in one week period

241

Fig. 4. The analysis of passenger ships movement intensity with

speed above two knots (kn) from 24.IV.2006 to 06.IX.2006

Fig. 5. The analysis of tankers movement intensity with speed

above two knots (kn) from 24.IV.2006 to 06.IX.2006

242

Fig. 6. The analysis of ships movement intensity on

section

from 24.IV.2006 to 06.IX.2006

4 CONCLUSION

The safety at sea describes the state of sea

environments, objects in movement as well as the

organization and principle of realization of human

activity at sea. The diagrams of ships movement

intensity should permit on quantitative qualification

of security - safety level, connected directly with

kind of area as well as exploited thereon with types

of ships at sea. It should facilitate the guidance of

tests the relating of local regulation, among other

things: the principles of ships movement, especially

determination of ships distances, principle of passing

and crossing each other on the NavArea fairways.

REFERENCES

IEC, Maritime navigation and radiocommunication equipment

and systems – Digital interfaces - Part 100: Single talker

and multiple listeners - Extra requirements to IEC 61162-1

for the UAIS, 2002.

ITU, Technical characteristics for a universal shipborne

automatic identificationsystem using time division multiple

access in the VHF maritime mobile band - M.1371, 2001.