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1 INTRODUCTION
Ship navigation and operational activities at sea need
meteorological and hydrographic information to
enhance safety and efficiency. On the other hand,
besides observations collected from data buoys,
marine meteorological information services rely on
weather observation reports from ships to increase
the data density and thus service quality.
Automatic Identification System (AIS) is a radio
communication system which operates in the
maritime VHF band [1]. It is designed to facilitate
ship-to-ship and ship-shore data exchange. The
purpose stated by the International Maritime
Organization (IMO) is "to improve the safety of
navigation by assisting in the efficient navigation of
ships, protection of the environment, and the
operation of Vessel Traffic Services (VTS)"[2]. As
required by the Safety of Life at Sea Convention
(SOLAS), carriage and operation of a Class A
shipborne equipment of AIS is mandatory for vessels
over 300 tonnage on international voyage and vessels
over 500 tonnage on domestic voyage [3]. So far,
major applications of AIS include the collision
avoidance between ships, coastal vessel monitoring,
and vessel traffic management. Such applications rely
on the autonomous and continuous sending of static,
dynamic, and voyage-related data about ships, using
self-organized time division multiple access
(SOTDMA) protocol. To be specific, each AIS-fitted
vessel reports its identifications, ship/cargo type,
destination, position, speed, course, heading, etc., at
adaptively varying intervals. If needed, short safety-
related messages, which allow the exchange of
format-free ASCII-text, may be sent and read via the
mandatory functions of the Minimum Keyboard and
Display (MKD) of class A AIS.
AIS-Assisted Service Provision and Crowdsourcing of
Marine Meteorological Information
S.J. Chang, C.H. Huang & S.M. Chang
National Taiwan Ocean University, Keelung, Taiwan
ABSTRACT: Ship navigation and operational activities at sea need meteorological and hydrographic
information to enhance safety and efficiency. Besides observations collected from deployed data buoys, marine
meteorological information services rely on weather observation reports from ships to increase the data density
and thus service quality. Automatic Identification System (AIS), adopted internationally to facilitate ship-ship
and ship-shore data exchange, has developed into communication links between ship/shore and buoys with
many potential applications. This paper presents AIS applications designed and implemented for marine
meteorological information services in a long-term project initiated by the Central Weather Bureau of Taiwan.
Achievements of this initiative include: versatile service delivery via shore-based AIS network to shipborne
application platforms such as smart phones, remote controllable moving weather data collection, and assisted
sharing of weather observation reports from ships. Typhoon forecast and warning is one of the key applications
implemented for this region.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 13
Number 1
March 2019
DOI: 10.12716/1001.13.01.05
64
Benefits of AIS have encouraged more and more
non-SOLAS vessels, such as fishing boats and
pleasure crafts, to carry either class A transceivers,
class B transceivers [4] or simply AIS receivers. AIS
Aids to Navigations (ATON) or data buoys fitted
with AIS become common. Such widespread
installations have triggered even more innovative
applications.
AIS may use binary messages for transmission of
Application-Specific Messages (ASM), either
addressed to a specific AIS station or broadcasted.
The technical characteristic and the structure of the
AIS ASMs are specified in [1], while the content and
format are to be tailored to different applications. The
format of ASM can be defined for international or
regional use, and identified by a Function
Identification (FI) in the message. International ASMs
are defined by IMO. In 2010, IMO approved a
guidance on the use of AIS ASM, including 17
message formats recommended for international use
[5]. Table I lists the IMO defined AIS ASM with
potential application in marine meteorological
services.
Table 1. Weather-related AIS ASMs defined by IMO
_______________________________________________
FI Message Name
_______________________________________________
21 Weather observation report from ship
22 Area notice – broadcast
23 Area notice – addressed
26 Environmental
29 Text description – broadcast
30 Text description – addressed
31 Meteorological and Hydrographic data
_______________________________________________
However, not only the generation and
transmission of ASMs but also the display of
transmitted information require dedicated software
and suitable equipment, which is not included in
standard AIS or other shipborne equipments such as
the Electronic Chart Display and Information System
(ECDIS). To propose specific presentation and
display standards for AIS ASMs was considered
premature, therefore IMO only provided some
examples, and states that the portrayal of AIS ASM
should conform to the concept of operation
envisioned for e-navigation [6]. It is expected that AIS
ASM "will become means to achieve many of the core
objectives of e-navigation."[6]
Based on the ASM mechanism of AIS, an
operational system of systems is developed for
service provision and crowd-sourcing of marine
meteorological information[7]. This is achieved in an
AIS-Weather project initiated by the Central Weather
Bureau (CWB) of Taiwan and carried out by the ENC
Center, Department of Communications, Navigation
and Control Engineering, National Taiwan Ocean
University (NTOU) from 2012 to 2015. Targeted
coverage include coastal Taiwan waters and the
routes of cross Taiwan Strait vessels.
Details of the system and services are described in
the following sections.
2 THE SYSTEM AND SERVICES
2.1 The Shore-side System and Network
AIS-Weather uses AIS data link to provide service,
therefore needs AIS shore stations to broadcast
weather information, receive weather reports from
ships and to remotely control operation parameters
such as reporting interval of installations onboard
cooperating vessels. The shore stations installed are
mainly Type 3 AIS ATONs conforming to IEC 62320-
2. Fig. 1 illustrates the system architecture on the
shore-side.
Figure 1. System architecture on the shore-side.
Each broadcast site (BS) consists of an AIS
transceiver, i.e. the AIS ATON, and a serial-to-
Ethernet device server, thus connected to a Regional
Control Monitor (RCM) located in CWB via internet
or intranet. For each connected BS, RCM collects the
messages received by the AIS transceiver, and
controls the transmission of AIS ASMs according to
the schedule and priority set by the Met/Hydro
Central Control (MHCC). RCM is also responsible for
monitoring the status and operations of each BS, and
handles the retransmission or reconnection
accordingly. The status of each RCM is in turn
checked by MHCC. Along with the MHCC software,
there is a web/application server for accessing the
system configuration, management and operation
monitoring functions with web browsers. Fig.2,
which is captured from the web page of the MHCC
web site, shows the broadcast sites established up to
2015. Coverage area of each site shown in red color is
the convex hull of AIS ship positions received within
latest 6 minutes (adjustable), as an indication of
possible service area at that moment. An online list of
status codes, with explanation and suggested actions,
is provided for users to recognize whether the point
of failure or anomaly is at the BS transceiver or the
network connection.
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Figure 2. Realtime coverage and status of the broadcast
sites.
2.2 The Shipboard System and End-User Application
This marine meteorological information service may
be accessed onboard vessel via shipborne AIS
equipment or wherever there is an internet
connection. A mobile application (AIS-weather APP)
can be downloaded and run on smart phones or
tablets. Both Android and IOS are supported. For the
APP to connect to the shipboard AIS equipment, a
converter is required to convert the NMEA/RS-
422/RS-232 serial to Wi-Fi. This APP will check its
connection to the shipborne AIS and the internet.
Even if the AIS data link is not available, it may still
connect via internet to a server and receive all the
broadcasted information as well as APP updates.
In previous design, AIS-Weather APP comes with
a reduced set of electronic navigational charts
covering Taiwan waters in the web map tile service
(WMTS) format[8]. New design has replace the map
tiles with map data in vector format. Using the
electronic chart as background, the APP displays the
received marine meteorological data graphically as
selectable overlay layers. The own ship symbol is also
displayed according to the data decoded from the
dynamic position reports transmitted by the own
ship. Fig.3 illustrates the APP's display of the own
ship symbol, information layer selections, as well as
the switching between DAY/NIGHT color tables and
UTC/Local Time. The language of user interface is
automatically switched between Traditional Chinese
and English according to the locale settings of the
mobile device. In Fig.3, the APP was connected to the
server in NTOU, that's why the own ship is located
on land. The setting panel beside the map display can
be shown or hidden via the home button. A tool
panel for measuring relative range/bearing and
cursor coordinate is accessed via the "arrow and plus"
button, as shown in Fig.4. In addition to its location,
time of the delivered marine meteorological
information is essential for users to interpret and use
that information correctly. Therefore, a sliding time
bar, as shown in the upper right corner of Fig.4, is
designed to control visibility according to the valid
time of the data, which may be an observation with
some age or a forecast. Touching the "i" button as
shown in the lower right corner of Fig.4 slides in (and
out) an information panel for the data point that user
pick on the map, e.g. the data buoy as shown in Fig.5.
Figure 3. AIS-weather APP showing the map display,
setting panel.
Figure 4. AIS-weather APP showing the measurement tool
and the time bar.
Figure 5. AIS-weather APP with the information panel
showing data of the selected buoy site (highlighted in red).
Each underlined data item in the information
panel, such as the average wind speed and water
temperature, links to a chart of the data received in
the past few hours to indicate the tendency.
2.3 Protocols, Messages and Data Sources
Among the AIS ASMs implemented in AIS-Weather
to provide marine meteorological services, those
defined by IMO for international use are listed in
Table II.
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Table 2. IMO-defined AIS ASMs Implemented in AIS-
Weather
_______________________________________________
FI Message Name Data Sources
_______________________________________________
21 Weather observation Shipborne weather stations
report from ship
26 Environmental Tidal water level
observations and
predictions
31 Meteorological and Data buoy observations:
Hydrographic data wind, wave, current, water
temperature, air
temperature and pressure
_______________________________________________
Data broadcast using FI 31 are hourly
observations collected from offshore data buoys.
When broadcast after the quality control process, the
data age can easily become over 1 hours. In response
to user needs regarding the timeliness and forecast
information, two more regional AIS ASM messages
are designed and implemented in AIS Weather,
namely "Regional Wind Forecast" and "Typhoon
Warning".
For the regional wind forecast, each two-slot
message with FI=34 and DAC=416 delivers 8 grid
data of wind force vectors. Therefore, feature
extraction and broadcast scheduling are designed for
ships to receive data of the whole area as soon as
possible, then incrementally increase the data
density.
ASM for typhoon warning is designed according
to CWB's warning sheet, which consists of two parts :
(1) current position, radius and wind force of the
typhoon; (2) forecast position, radius and wind force
of the typhoon in12h, 24h, 36h, and 48h. A two-slot
regional ASM are designed utilizing FI 22 "Area
Notice" linked with FI 29 "Text Description" to
broadcast the dynamic geospatial information and
the wind force values, respectively. When received by
the AIS-Weather APP, such linked pair of messages
are combined to present the typhoon warning. Fig. 6
shows two screen shots of shipboard AIS-weather
application running on an android smart phone.
These were captured when typhoon Soudelor was
approaching Taiwan.
(a) Regional wind forecast, observations from data buoys,
and warning of the approaching typhoon Soudelor
(b) data buoy observation within the radius of typhoon
Soudelor
Figure 6. Screen cpatures of the AIS-Weather APP during
typhoon warnings.
2.4 Automatic Reporting of Shipboard Weather
Observations
According to the standard ITU-R M.1371-5, Class B
shipborne AIS equipments using Carrier-sense time
division multiple access (CSTDMA) technique should
not transmit binary messages, i.e. message 8 or
message 6. Therefore, only ships fitted with Class A
AIS or Class B AIS using Self-organized time division
multiple access (SOTDMA) technique may
participate in the automatic reporting of shipboard
weather observation using AIS ASM. AIS-Weather
project provides a software platform that interfaces
with shipborne weather stations of the participating
vessels, encodes the output data into ASM (Type 8, FI
21), and control the automatic reporting via the
shipborne AIS transceiver. Shipboard weather
observation reports may also be entered manually via
the user-interface of the AIS weather APP. Manually
entered data are tagged when encoded into ASM, to
differentiate them from those automatically
generated. Shipboard weather reports received by the
coastal AIS network are automatically delivered to
the database of CWB for use in the analysis and
forecast. Fig.7 shows shipboard weather observation
reports from the participating vessels.
(a) wind speed reported from NTOU research vessel
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(b) Wind speed reported from a passenger ship
Figure 7. Shipboard weather observation reports received
at MHCC in CWB.
Shipboard weather reports broadcast via AIS may
be directly received by other vessels, which however
may be rather limited in range due to the antenna
height of shipborne AIS, hence reduce the usefulness
of the information. In order to make the most use of
such valuable data, a retransmission function has
been designed and implemented to automatically
have the received weather reports from ships re-
broadcasted to a suitably wider area via the shore-
based AIS network.
3 CONCLUSIONS
AIS-Weather services delivered from the shore-based
AIS network to the shipborne application include
quality-controlled observations of wind, wave,
current, air pressure, and sea surface temperature
data collected from offshore buoys, observed tides
from coastal tide stations, as well as inshore tidal
forecasts. These official source data are automatically
encoded into several internationally recognized
message formats, i.e. AIS ASM formats
recommended by IMO.
Service area of each AIS shore station is limited to
its VHF radio coverage. Therefore the distribution
and scheduling for data broadcast is designed to
deliver data contents throughout the AIS-network,
without overloading the VHF data links of AIS.
Besides international ASMs, regional ASMs are
designed to deliver services such as regional wind
field forecast and the Typhoon warnings, to meet
local user needs. To deliver these information
services with minimum radio resources requires
careful design in the data model, encoding, updating
management as well as the portrayal of the data.
The shipborne application platform may connect
to the shipboard AIS equipment and optional
shipborne weather instruments via Wi-Fi. Weather
observation reports may be automatically generated
or manually entered via the user interface, broadcast
via AIS, and received by shore stations as also by
other vessels within VHF radio range. Such crowd-
sourced observation data received by the shore
stations are not only delivered to the database of
CWB but also arranged by the AIS-weather network
to be re-broadcast to other areas of interest. The
timeliness and coverage of observation-related
information services are improved in this way.
All the above mentioned platform and services are
in operation, with increasing shipboard installations
and shore-based service coverage.
ACKNOWLEDGMENT
Authors would like to thank the Central Weather Bureau of
Taiwan for initiating AIS-Weather project and the
continuing support for the operation of the system and
service developed in the project.
REFERENCES
[1] Recommendation ITU-R M.1371-4, “Technical
characteristics of a universal shipborne automatic
identification system using time-division multiple
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[2] International Maritime Organization, resolution MSC.74
(69) Annex 3, Recommendation on Performance
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[3] International Electrotechnical Commission IEC 61993-2,
"Maritime navigation and radiocommunication
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systems (AIS) - Part 2: Class A shipborne equipment of
the universal automatic identification system (AIS) -
Operational and performance requirements, methods of
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[4] International Electrotechnical Commission IEC 62287-1,
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[5] International Maritime Organization IMO
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[6] International Maritime Organization IMO SN.1/
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2010
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