IEC 63135:2018

IEC 63135 ®
Edition 1.0 2018-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Maritime navigation and radiocommunication equipment and systems –
Automatic identification systems (AIS) – SAR airborne equipment – Operational
and performance requirements, methods of test and required test results

Matériels et systèmes de navigation et de radiocommunication maritimes –
Systèmes d'identification automatique (AIS) – Équipement aéroporté SAR –
Exigences d'exploitation et de fonctionnement, méthodes d'essai et résultats
d'essai exigés
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 21 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 16 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - webstore.iec.ch/advsearchform IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 67 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
IEC Just Published - webstore.iec.ch/justpublished

Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Catalogue IEC - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
Application autonome pour consulter tous les renseignements
Le premier dictionnaire en ligne de termes électroniques et
bibliographiques sur les Normes internationales,
électriques. Il contient 21 000 termes et définitions en anglais
Spécifications techniques, Rapports techniques et autres
et en français, ainsi que les termes équivalents dans 16
documents de l'IEC. Disponible pour PC, Mac OS, tablettes
langues additionnelles. Egalement appelé Vocabulaire
Android et iPad.
Electrotechnique International (IEV) en ligne.

Recherche de publications IEC -
Glossaire IEC - std.iec.ch/glossary
webstore.iec.ch/advsearchform
67 000 entrées terminologiques électrotechniques, en anglais
La recherche avancée permet de trouver des publications IEC et en français, extraites des articles Termes et Définitions des
en utilisant différents critères (numéro de référence, texte, publications IEC parues depuis 2002. Plus certaines entrées
comité d’études,…). Elle donne aussi des informations sur les antérieures extraites des publications des CE 37, 77, 86 et
projets et les publications remplacées ou retirées. CISPR de l'IEC.

IEC Just Published - webstore.iec.ch/justpublished Service Clients - webstore.iec.ch/csc
Restez informé sur les nouvelles publications IEC. Just Si vous désirez nous donner des commentaires sur cette
Published détaille les nouvelles publications parues. publication ou si vous avez des questions contactez-nous:
Disponible en ligne et aussi une fois par mois par email. sales@iec.ch.

IEC 63135 ®
Edition 1.0 2018-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Maritime navigation and radiocommunication equipment and systems –

Automatic identification systems (AIS) – SAR airborne equipment – Operational

and performance requirements, methods of test and required test results

Matériels et systèmes de navigation et de radiocommunication maritimes –

Systèmes d'identification automatique (AIS) – Équipement aéroporté SAR –

Exigences d'exploitation et de fonctionnement, méthodes d'essai et résultats

d'essai exigés
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 47.020.70 ISBN 978-2-8322-6258-0

– 2 – IEC 63135:2018 © IEC 2018
CONTENTS
FOREWORD . 7
1 Scope . 9
2 Normative references . 9
3 Terms, definitions, symbols and abbreviated terms . 9
3.1 Terms and definitions . 9
3.2 Symbols and abbreviated terms . 10
4 General requirements . 11
4.1 General . 11
4.1.1 Overview . 11
4.1.2 Capabilities of the AIS . 11
4.1.3 Transmitter shutdown procedure . 11
4.2 Modes of operation . 11
5 Performance requirements. 11
5.1 Composition . 11
5.2 Time and position . 12
5.2.1 Source for UTC . 12
5.2.2 Source for AIS position reporting . 12
5.3 User interface . 12
5.4 Identification . 12
5.5 Information . 13
5.5.1 Information provided by the AIS SAR airborne station . 13
5.5.2 Information reporting intervals . 13
5.5.3 AIS station reporting capacity . 14
5.6 Permissible initialization period . 14
5.7 Technical characteristics . 14
5.8 Alarms and indications, fall-back arrangements . 14
5.8.1 Built-in test equipment . 14
5.8.2 Alarm messages . 14
5.8.3 Status messages . 16
6 Technical requirements . 18
6.1 General . 18
6.2 Physical layer . 19
6.2.1 General . 19
6.2.2 Transmitter parameters. 19
6.2.3 Receiver parameters . 21
6.3 Link layer . 21
6.3.1 General . 21
6.3.2 Link sublayer 1: medium access control (MAC) . 22
6.3.3 Link sublayer 2: data link service (DLS) . 22
6.3.4 Link sublayer 3: link management entity (LME) . 22
6.4 Network layer . 24
6.4.1 General . 25
6.4.2 Setting of operating channels . 25
6.5 Transport layer . 25
6.6 Presentation interface . 25
6.6.1 General . 25

6.6.2 Optional automatic input of sensor data . 26
6.6.3 High speed input/output ports . 27
7 Test conditions . 29
7.1 Normal and extreme test conditions . 29
7.1.1 Normal test conditions . 29
7.1.2 Extreme test conditions . 29
7.2 Standard test environment . 30
7.3 Additional test arrangements. 30
7.3.1 Arrangements for test signals applied to the receiver input . 30
7.3.2 Encoder for receiver measurements . 30
7.3.3 Waiver for receivers . 30
7.3.4 Impedance . 30
7.3.5 Artificial antenna (dummy load) . 31
7.3.6 Facilities for access . 31
7.3.7 Modes of operation of the transmitter. 31
7.4 Common test conditions for protection from invalid controls . 31
7.5 Measurement uncertainties . 31
8 Test signals . 32
8.1 Standard test signal number 1 . 32
8.2 Standard test signal number 2 (TDMA) . 32
8.3 Standard test signal number 3 (TDMA) . 32
8.4 Standard test signal number 4 (PRBS) . 32
8.5 Standard test signal number 5 (PRBS) . 32
9 Power supply, special purpose and safety tests . 33
10 Environmental tests . 33
11 Operational tests . 33
11.1 Identification and operating modes. 33
11.1.1 Autonomous mode . 34
11.1.2 Polled mode . 34
11.1.3 Addressed operation . 35
11.1.4 Transmission retry . 35
11.1.5 Broadcast operation. 36
11.1.6 Multiple slot messages . 37
11.2 Information . 37
11.2.1 Information provided by the AIS . 38
11.3 Initialization period . 38
11.3.1 Method of measurement . 38
11.3.2 Required results . 38
11.4 Transceiver protection . 38
11.4.1 Method of measurement . 38
11.4.2 Required results . 38
11.5 Alarms and indicators, fall-back arrangements . 38
11.5.1 Monitoring of functions and integrity . 38
11.5.2 Monitoring of sensor data . 39
12 Physical tests . 41
12.1 TDMA transmitter . 41
12.1.1 Frequency error . 41
12.1.2 Carrier power . 42

– 4 – IEC 63135:2018 © IEC 2018
12.1.3 Slotted transmission spectrum . 42
12.1.4 Modulation accuracy . 43
12.1.5 Transmitter output power characteristics. 44
12.2 TDMA receivers . 44
12.2.1 Sensitivity . 44
12.2.2 Error behaviour at high input levels. 45
12.2.3 Co-channel rejection . 46
12.2.4 Adjacent channel selectivity . 46
12.2.5 Spurious response rejection . 47
12.2.6 Intermodulation response rejection and blocking . 49
12.2.7 Blocking or desensitisation . 50
12.2.8 Transmit to receive switching time . 51
12.2.9 Immunity to out-of-band energy . 52
12.3 Conducted spurious emissions . 52
12.3.1 Spurious emissions from the transmitter . 52
12.3.2 Spurious emissions from the receiver . 53
13 Specific tests of Link layer . 53
13.1 TDMA synchronisation . 54
13.1.1 Synchronisation test using UTC . 54
13.1.2 Synchronisation test using UTC with repeated messages . 54
13.1.3 Synchronisation test without UTC, semaphore . 55
13.1.4 Synchronisation test without UTC . 55
13.1.5 Reception of un-synchronised messages . 55
13.2 Synchronisation and jitter accuracy . 55
13.2.1 Definition . 55
13.2.2 Method of measurement . 56
13.2.3 Required results . 56
13.3 Data encoding (bit stuffing) . 56
13.3.1 Method of measurement . 56
13.3.2 Required results . 56
13.4 Frame check sequence . 56
13.4.1 Method of measurement . 56
13.4.2 Required results . 56
13.5 Slot allocation (channel access protocols) . 56
13.5.1 Network entry . 56
13.5.2 Autonomous scheduled transmissions (SOTDMA) . 57
13.5.3 Scheduling of other reporting intervals . 57
13.5.4 Safety related/binary message transmission . 58
13.5.5 Transmission of static data with Message 24A (ITDMA) . 58
13.5.6 Transmission of static data with Message 5 (ITDMA) . 59
13.5.7 Assigned operation . 59
13.5.8 Group assignment . 61
13.5.9 Fixed allocated transmissions (FATDMA). 64
13.5.10 Randomisation of message transmissions . 65
13.6 Message formats . 65
13.6.1 Received messages . 65
13.6.2 Transmitted messages . 65
14 Specific tests of Network layer . 66
14.1 Dual channel operation – Alternate transmissions . 66

14.1.1 Method of measurement . 66
14.1.2 Required results . 66
14.2 Regional area designation by serial sentence . 66
14.2.1 Method of measurement . 66
14.2.2 Required results . 66
14.3 Slot reuse . 66
14.3.1 Method of measurement . 66
14.3.2 Required results . 67
15 Specific tests of Transport layer . 67
15.1 Behaviour of NavStatus 14 reception . 67
15.1.1 Test of AIS SART message . 67
15.1.2 Test of MOB-AIS message . 68
15.1.3 Test of EPIRB-AIS message . 68
16 Specific presentation interface tests . 68
16.1 General . 68
16.2 Checking manufacturer's documentation . 68
16.3 Test of sensor input . 69
16.3.1 Test of GNS input . 69
16.3.2 Test of RMC input . 69
16.3.3 Test of DTM input . 70
16.3.4 Test of GBS input . 70
16.3.5 Test of VTG input . 71
16.4 Test of high speed output . 71
16.4.1 Method of measurement . 71
16.4.2 Required results . 71
16.5 High speed output interface performance . 71
16.5.1 Method of measurement . 71
16.5.2 Required results . 71
16.6 Test of high speed input . 72
16.6.1 General . 72
16.6.2 Test of VSD input sentence . 72
16.6.3 Test of SSD input sentence . 72
16.6.4 Test of EPV input sentence . 73
Annex A (informative) Block diagram of AIS SAR airborne station . 74
Bibliography . 75

Figure 1 – OSI layer model . 19
Figure 2 – Power versus time characteristics . 20
Figure 3 – Format for repeating four-packet cluster . 32
Figure 4 – Measurement arrangement for frequency error . 41
Figure 5 – Measurement arrangement for carrier power . 42
Figure 6 – Emission mask for slotted transmission . 43
Figure 7 – Measurement arrangement for modulation accuracy . 43
Figure 8 – Measurement arrangement . 45
Figure 9 – Measurement arrangement with two generators . 46
Figure 10 – SINAD or PER/BER measuring equipment . 48
Figure 11 – Measurement arrangement for intermodulation . 50

– 6 – IEC 63135:2018 © IEC 2018
Figure 12 – Measurement arrangement for blocking or desensitisation . 50
Figure 13 – Transmit to receive switching time measurement setup . 51
Figure A.1 – Block diagram of AIS SAR airborne station . 74

Table 1 – Integrity alarm conditions signalled using ALR sentence formatter . 15
Table 2 – Sensor status indications signalled using TXT sentence formatter . 16
Table 3 – Position sensor fall-back conditions . 17
Table 4 – Use of position accuracy (PA) flag . 18
Table 5 – Transmitter parameters . 20
Table 6 – Power versus time characteristics . 21
Table 7 – Receiver parameters . 21
Table 8 – Use of VDL messages . 23
Table 9 – Presentation interface access. 26
Table 10 – IEC 61162-1 sensor sentences . 26
Table 11 – AIS high-speed input data and formats . 27
Table 12 – AIS high-speed output data and formats . 28
Table 13 – Property identifiers . 29
Table 14 – Content of first two packets . 33
Table 15 – Fixed PRS data derived from Recommendation ITU-T O.153 . 33
Table 16 – Peak frequency deviation versus time. 44
Table 17 – Frequencies for inter-modulation test . 50

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MARITIME NAVIGATION AND RADIOCOMMUNICATION EQUIPMENT
AND SYSTEMS – AUTOMATIC IDENTIFICATION SYSTEMS (AIS) – SAR
AIRBORNE EQUIPMENT – OPERATIONAL AND PERFORMANCE
REQUIREMENTS, METHODS OF TEST AND REQUIRED TEST RESULTS

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 63135 has been prepared by IEC technical committee 80: Maritime
navigation and radiocommunication equipment and systems.
The text of this International Standard is based on the following documents:
CDV Report on voting
80/875/CDV 80/889/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 8 – IEC 63135:2018 © IEC 2018
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
MARITIME NAVIGATION AND RADIOCOMMUNICATION EQUIPMENT
AND SYSTEMS – AUTOMATIC IDENTIFICATION SYSTEMS (AIS) – SAR
AIRBORNE EQUIPMENT – OPERATIONAL AND PERFORMANCE
REQUIREMENTS, METHODS OF TEST AND REQUIRED TEST RESULTS

1 Scope
This document specifies the minimum operational and performance requirements, methods of
testing and required test results as applicable for automatic identification systems (AIS) VHF
data link (VDL) related parts of an AIS SAR airborne station. This document incorporates the
applicable technical characteristics of AIS SAR airborne equipment included in
Recommendation ITU-R M.1371 and takes into account the ITU Radio Regulations, where
applicable.
This document also specifies the minimum requirements for the interfaces to other equipment
suitable to be used as means of input and display data.
Attention is drawn on that other requirements specific for airborne equipment can exist and
are beyond the scope of this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 61162-1, Maritime navigation and radiocommunication equipment and systems – Digital
interfaces – Part 1: Single talker and multiple listeners
ITU-R Recommendation M.1371-5:2014, Technical characteristics for an automatic
identification system using time division multiple access in the VHF maritime mobile frequency
band
ITU-T Recommendation O.153, Basic parameters for the measurement of error performance
at bit rates below the primary rate
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp

– 10 – IEC 63135:2018 © IEC 2018
3.2 Symbols and abbreviated terms
For the purpose of this document, the following abbreviated terms apply.
AIS automatic identification system
AIS-SART AIS search and rescue transmitter
BITE built-in test equipment
BT bandwidth-time
COG course over ground
CommState communication state
NOTE 1 Communication state is defined in Recommendation ITU-R M.1371. It is used to organize the slot
allocation for SOTDMA or ITDMA.
EPFS electronic position-fixing systems
EPIRB-AIS emergency positioning indicting radio beacon AIS
ETA estimated time of arrival
EUT equipment under test
FATDMA fixed access time division multiple access
GMSK Gaussian minimum shift keying
IMO International Maritime Organization
ITDMA incremental time division multiple access
locating device group of devices including AIS-SART, EPIRB-AIS and MOB-AIS
MAC medium access control
MMSI maritime mobile service identity
MOB-AIS man overboard AIS device
NavStatus navigational status
NOTE 2 Navigational status is defined in Recommendation ITU-R M.1371. It consists of information that can be
input by the ship's crew to indicate whether the ship is underway, moored, etc.
NSS nominal start slot
NTS nominal transmission slot
PER packet error rate
PI presentation interface
RAIM receiver autonomous integrity monitoring
RATDMA random access time division multiple access
RF radio frequency
SI selection interval
SOG speed over ground
SOTDMA self organizing time division multiple access
UTC universal time co-ordinated
VDL VHF data link
VSWR voltage standing wave ratio
Rx Receive
Tx Transmit
4 General requirements
4.1 General
4.1.1 Overview
Requirements contained in Clause 4 are requirements not taken up in other clauses and are
verified by observation and inspection of documented evidence.
This document specifies the requirements for the AIS SAR airborne station. The AIS SAR
airborne station shall support search and rescue operations involving SAR aircraft.
4.1.2 Capabilities of the AIS
The AIS SAR airborne station shall be capable of providing to ships, and to competent
authorities, information from the SAR aircraft, automatically and with the required accuracy
and frequency, to facilitate accurate tracking. Transmission of the data shall be with the
minimum involvement of personnel.
4.1.3 Transmitter shutdown procedure
An automatic transmitter hardware shutdown procedure and indication shall be provided in
case a transmitter continues to transmit for more than 2 s. This shutdown procedure shall be
independent of software control.
4.2 Modes of operation
The system shall be capable of operating in a number of modes:
1) an "autonomous and continuous" mode for operation in all areas; this mode shall be
capable of being switched to/from one of the following alternate modes by a competent
authority;
2) an "assigned" mode for operation in an area subject to a competent authority responsible
for traffic monitoring such that the data transmission interval and/or time slots may be set
remotely by that authority;
3) a "polling" or controlled mode where the data transfer occurs in response to interrogation
from a ship or competent authority;
4) a "receive only" mode where the station does not transmit.
5 Performance requirements
5.1 Composition
The AIS SAR airborne station shall comprise (see Annex A):
1) a communication processor, capable of operating over a range of maritime frequencies,
with an appropriate channel selecting and switching method;
2) at least one transmitter and two TDMA receiving processes;
3) a means of processing data from an electronic position-fixing system which provides a
resolution of one ten thousandth of a minute of arc and uses the WGS 84 datum; an
interface (see 6.6.2) may be provided to input the position used for navigation;
4) a means to automatically input data from other sensors meeting the provisions as
specified in 5.5.1 2) may be provided;
5) a means of error checking the transmitted and received data (see Clause 6); and
6) built-in test equipment (BITE) as specified in 5.8.1.
The AIS SAR airborne station shall be capable of:

– 12 – IEC 63135:2018 © IEC 2018
7) providing information automatically and continuously to other AIS stations, without
involvement of personnel;
8) receiving and processing information from other AIS stations;
9) responding to high priority and safety related calls with a minimum of delay;
10) providing positional and manoeuvring information at a data rate adequate to facilitate
accurate tracking by a competent authority and other AIS stations (see 5.5.2).
5.2 Time and position
5.2.1 Source for UTC
The AIS shall be provided with an internal GNSS receiver as primary UTC source which is
required for synchronisation purposes and for position, COG and SOG.
NOTE UTC includes a provision for leap seconds.
The internal GNSS receiver shall meet appropriate requirements for position accuracy,
COG/SOG, acquisition, re-acquisition, receiver sensitivity, RF dynamic range, interference
susceptibility, position update, failure warnings, status indications and integrity flag.
If an external source of UTC is provided, it shall fulfil the requirement for synchronization
timing.
If date and time is not available and Message 4 or 11 is being received, the unit shall use
date and time from that message, and the seconds shall be omitted.
5.2.2 Source for AIS position reporting
...