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
6
Identifier for this message 1, 2
or 3
Repeat
Indicator
2
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
30
MMSI number
Navigational
status
4
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
19
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
10
10
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 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