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1 INTRODUCTION
The maritime sector was one of the first communities
that recognized and exploited the opportunities and
advantages provided by Global Navigation Satellite
Systems (GNSS). In fact, the introduction of GNSS
represented a great revolution in the maritime
domain.
It is acknowledged that GNSS have become the
primary means of obtaining Position, Navigation and
Timing (PNT) information at sea. Most of the ships in
the world, even in the recreational and leisure field,
are equipped with GNSS receivers. At the beginning,
GNSS was only used as a means to know the current
position; at present, GNSS receivers are connected
and integrated with other equipment such as
Integrated Bridge Systems, ECDIS, ARPA, GMDSS,
AIS, LRIT or VDR. In this sense, GNSS has become the
positioning source to implement additional
functionalities.
Accuracy is one of the main requirements when
talking about maritime positioning. Nowadays
maritime users can take advantage of augmentation
systems such as differential GNSS or SBAS/EGNOS,
as they provide an adequate answer, especially in
Evolution of SBAS/EGNOS Enabled Devices in Maritime
M. López
1
& V. Antón
2
1
GSA, European Global Navigation Satellite Systems Agency, Prague, Czech Republic
2
ESSP, European Satellite Services Provider, Madrid, Spain
ABSTRACT: The maritime sector was one of the first communities that recognized and exploited the
opportunities and advantages provided by Global Navigation Satellite Systems (GNSS). In fact, GNSS have
become the primary means of obtaining Position, Navigation and Timing (PNT) information at sea. Most of the
ships in the world are equipped with GNSS receivers.
GPS provides the fastest and most accurate method for mariners to navigate, measure speed, and determine
location. However, its performance can be enhanced by taking advantage of augmentation systems such as
differential GNSS or Satellite-Based Augmentation Systems (SBAS/EGNOS), especially in terms of accuracy.
Direct access to EGNOS in vessels can be achieved through EGNOS-enabled navigation receivers and EGNOS-
enabled AIS transponders.
This paper provides an analysis of the number of onboard devices, mainly devoted to navigation purposes, and
AIS transponders which are SBAS compatible. In addition, other equipment using GNSS positioning in the
mari
time and inland waterways domains are also considered for the analysis of SBAS compatibility, including
inland AIS, Portable Pilot Units (PPUs) and Dynamic Positioning (DP) equipment. A first survey was done in
2017 to have an overview of the percentage of SBAS enabled devices available in the maritime market [8]. Since
then, the analysis has been yearly updated to understand the market evolution in terms of SBAS compatibility
and its main results are summarised in this paper.
http://www.transnav.eu
the
International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 15
Number 3
September 2021
DOI: 10.12716/1001.15.03.06
544
terms of accuracy. The first step is to have a receiver
compatible with these services.
Therefore, the objective of this paper is to present
an assessment done covering the last four years to
estimate how many GNSS shipborne devices available
in the market are SBAS ready.
1.1 What is EGNOS?
Satellite navigation systems provide positioning and
timing services over wide geographical areas
(typically continental or global coverage) with high
accuracy performance. However, a number of events
may lead to positioning errors. Satellite-Based
Augmentation Systems (SBAS) are designed to
augment the global navigation constellations by
broadcasting additional signals from geostationary
(GEO) satellites. EGNOS (European Geostationary
Navigation Overlay Service) is the European SBAS
providing an augmentation service to the Global
Positioning System (GPS) and to Galileo in a future.
EGNOS has been designed to broadcast a GPS-like
ranging signal in Europe with embedded corrections,
providing improved performances over GPS. With
EGNOS, all compatible navigation receivers can
benefit from enhanced accuracy, availability and
continuity over GPS.
The EGNOS coverage area is Western Europe, but
could be readily extended to include other regions
within the broadcast area of the geostationary
satellites, such as Africa or Eastern Europe.
In addition to EGNOS, there are other SBAS
around the world with similar characteristics and
compatible among them. Figure 1 presents the
coverage of the different SBAS systems in the world.
Figure 1. SBAS indicative service areas [4]
The main objective of the EGNOS Open Service
(EGNOS OS) is to improve the achievable positioning
accuracy by correcting several error sources affecting
the GPS signals. The corrections freely transmitted by
EGNOS geostationary satellites contribute to mitigate
the ranging error sources related to satellite clocks,
satellite position and ionospheric effects. The EGNOS
OS minimum accuracy is specified in the table 1 [2].
Focusing on the maritime domain, EGNOS is able
to provide, over its coverage area, the same type of
information offered by a DGNSS service (i.e.
differential corrections and system integrity
information). This information can be used to improve
the accuracy in the position and to protect users
against potential system failures.
Table 1. EGNOS OS Horizontal and Vertical Accuracy
_______________________________________________
Accuracy Definition Value
_______________________________________________
Horizontal Corresponds to a 95% confidence 3m
bound of the 2-dimensional position
error in the horizontal local plane for
the Worst User Location
Vertical Corresponds to a 95% confidence bound 4m
of the 1-dimensional unsigned position
error in the local vertical axis for the Worst
User Location
_______________________________________________
EGNOS accuracy performance, as shown in
Table 1, is in line with DGNSS one (<5m (95%) - IALA
Guideline 1112 [13]). Therefore, SBAS can be
considered as a means to complement DGNSS
services.
2 ONBOARD GNSS RECEIVERS - SOLAS
CONVENTION
The SOLAS Convention [11] is the reference to be
consulted to understand what kind of navigation
equipment can be found onboard vessels. The SOLAS
Convention is considered as the most important of all
international treaties concerning the safety of
merchant ships. Chapter V within SOLAS Convention
deals with safety of navigation; it identifies navigation
safety services which should be provided by
Contracting Governments and sets forth operational
provisions applicable in general to all ships on all
voyages. Of special interest is Regulation 19 within
chapter V, which establishes the carriage requirements
for shipborne navigational systems and equipment.
2.1 Satellite Navigation Equipment
According to that Regulation [6], all ships irrespective
of size are required to be fitted with a GNSS receiver.
This could be a GNSS receiver which might or might
not be equipped to receive differential corrections,
since the carriage of a DGNSS receiver or an SBAS
enabled receiver is not mandatory. The question is:
Does a simple GPS receiver fulfil the IMO
requirements in all navigation phases?
The most common system used as primary means
of navigation is GNSS, however currently available
GNSS do not fulfil IMO requirements in regards to
accuracy and integrity in all the navigation phases.
IMO Resolution A.915(22) [6] recognises that
differential corrections can enhance accuracy (in
limited geographic areas) to 10 m or less (95%) and
also offer external integrity monitoring. In this sense,
this Resolution mentions the following techniques
that can improve the accuracy and/or integrity of GPS
and GLONASS by augmentation:
Differential correction signals from stations using
the appropriate maritime radionavigation
frequency band between 283.5 and 325 kHz for
local augmentation.
Craft or receiver autonomous integrity monitoring.
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Integrated receivers combining signals from GPS,
GLONASS, LORAN-C and/or Chayka (a Russian
terrestrial radionavigation system, similar to
LORAN-C).
Wide area augmentation systems using differential
correction signals from geostationary satellites
such as EGNOS for Europe, WAAS for the United
States and MSAS for Japan.
A more recent IMO Resolution, A.1046(27) [7] on
the “Worldwide Radionavigation System” refers to
Chapter V of the SOLAS Convention, Regulation 13,
when talking about navigation in harbour entrances,
harbour approaches and coastal waters. At the same
time, IMO Res. A.1046 [7] establishes that: where a
radionavigation system is used to assist in the
navigation of ships in such waters, the system should
provide positional information with an error not
greater than 10 m with a probability of 95%. It is
important to note that this is a requirement to be
accomplished by the radionavigation system.
The broadcast of differential corrections,
understood as aids to navigation to be provided by
maritime authorities, is not mandatory. It is up to the
Contracting Governments to decide to provide this
service based on the volume of traffic and the degree
of risk. Hence, when navigating in waters without a
maritime DGNSS service, it is of special interest the
access to SBAS corrections or even as a backup when
this DGNSS service is provided. According to the
GSA report on user needs [12], EGNOS can provide
solutions in areas where IALA beacons are not
deployed or coverage is sparse and there is high
traffic density.
2.2 AIS onboard devices
Automatic Identification System (AIS) is an
autonomous and continuous broadcast system,
operating in the VHF maritime mobile band. The
objective of AIS is to exchange navigation data such as
vessel identification, position, course, speed, etc.
between participating vessels and shore stations.
Section 4.1.1 of the IALA Guideline 1082 [5] is
devoted to shipborne AIS, that is, Class A and Class B
devices. According to that Guideline and the AIS
Technical Standards (ITU-R M.1371), Class A
equipment complies with the IMO AIS performance
standards. Whilst the Class B are compatible with
Class A, they are not fully compliant with IMO
requirements and report less frequently than Class A.
AIS uses an absolute referencing system to
determine position. This position is normally derived
from a GNSS receiver. AIS Class A devices can obtain
position information from an internal GNSS receiver
or from the vessel’s primary GNSS receiver. However,
Class B equipment only uses the AIS internal GNSS
sensor to obtain the position information.
According to the SOLAS Convention, AIS carriage
(Class A) is mandatory for ships of 300 gross tonnage
and upwards engaged on international voyages and
cargo ships of 500 gross tonnage and upwards not
engaged on international voyages and passenger ships
irrespective of size. In addition, EU Directive
2002/59/EC [3] states that fishing vessels with a length
of more than 15 metres overall shall be fitted with an
AIS (Class A) which meets the performance standards
drawn up by the IMO.
AIS devices are also used in inland waterways.
being compatible with IMO’s maritime AIS standards
and considering specific requirements for inland
navigation which are gathered in the Inland AIS
standard [15].
3 ADDITIONAL USES OF GNSS RECEIVERS
GNSS receivers are also included in several types of
systems to support marine operations. Portable Pilot
Units and Dynamic Positioning systems are two
esamples.
3.1 Portable Pilot Units
Pilots usually get on a vessel to support the captain in
order to carry out the necessary manoeuvres to
introduce that vessel in a port. To assist pilots in this
process there are technological aids, which use GNSS,
called Portable Pilot Units (PPUs).
PPUs can be defined as tools to be carried onboard
vessels by the pilots in order to support the decision
making process when navigating in confined waters
or visibility is compromised, for instance, at night or
under bad weather conditions.
IMPA Guidelines [16] on the design and use of
PPUs recommend DGNSS enabled positioning
devices (GBAS or SBAS based) as the minimum to
provide enhanced accuracy in the positioning.
3.2 Dynamic Positioning systems
Dynamic Positioning is the result of applying a
combination of techniques to automatically maintain
the position of a vessel to a desire point, with regard
to a fixed reference or to a moving object.
Several sensors are involved in this process,
including positioning sensors, motion sensors and
wind sensors. All of them provide information to be
used by the DP algorithms in order to calculate the
vessel's position and the magnitude and direction of
the forces to be applied to maintain the position.
DP systems’ applications (e.g. drilling, dredging,
survey,…) are increasing in the maritime industry.
Different types of ships are now being fitted with DP
systems to improve control and handling over vessels
at sea.
4 METHODOLOGY
Three phases have been followed to carry out the
survey:
1. Definition and scope
The scope of the analysis is focused on the satellite
navigation equipment and AIS devices approved
to be used in SOLAS and non-SOLAS vessels. In
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addition, inland AIS equipment, Portable Pilot
Units (PPUs) and Dynamic Positioning (DP) and
marine surveying equipment were also considered.
As a starting point, it was decided to gather the list
of receivers and their datasheets and user manuals.
2. Survey
The navigation receiver equipment and AIS
devices list taken as reference was extracted from
the database published by the Spanish Merchant
Marine, as can be found in the Spanish Ministry of
Transport website [10] and also from the MED
Database [9]. These inventories catalogue SOLAS
and non-SOLAS authorised devices including
brand, model and dates of homologation and
expiration for each equipment. Besides, the list of
approved Inland AIS equipment in accordance
with the Rhine Vessel Inspection Regulations [14]
was taken as reference.
A first survey was done in 2017 to have an
overview of the percentage of SBAS enabled
devices available in the maritime market. This
assessment was published in 2018 in the TransNav
Journal [8]. Since then, the analysis has been yearly
updated to understand the market evolution in
terms of SBAS compatibility.
3. Analysis
The analysis of the characteristics sheets,
brochures, owner’s manuals, webpages or
technical specifications of the listed receivers and
AIS devices has led to know if the device is SBAS
compatible and, among the SBAS compatible ones,
if EGNOS is explicitly mentioned.
5 SURVEY RESULTS
5.1 Satellite Navigation Equipment Survey
5.1.1 SOLAS
The number of satellite navigation devices
authorised for its use in SOLAS vessels increased in
the last year to reach a total of 32 available devices in
the market from 8 different manufacturers. The
evolution in the last four years can be seen in Figure 2.
To be highlighted that 30 out of 32 devices are
SBAS/EGNOS compatible, although EGNOS is
explicitly mentioned in the datasheets or user
manuals of 26 products.
Figure 2. SBAS compatible device evolution in SOLAS
satellite navigation equipment
It is important to note that 100% of the authorised
manufacturers to provide SOLAS GNSS-based
equipment have at least one SBAS-enabled receiver
within their products portfolio. The SBAS capability is
included in 94% of the satellite navigation devices
approved for SOLAS vessels. EGNOS is explicitly
mentioned in the 81% of the datasheets or user
manuals of these equipment.
Figure 3. Percentage of SBAS compatible devices within
SOLAS navigation equipment
Figure 4. Percentage of SOLAS navigation equipment which
mention EGNOS
5.1.2 Non-SOLAS
A total of 537 satellite navigation devices used in
non-SOLAS vessels, from 26 different brands, were
checked in this assessment. Leaving apart
discontinued products, the number of satellite
navigation devices available in the market for non-
SOLAS vessels increased in the last year to reach a
total of 346 available devices in the market. The
evolution in the SBAS capability depicted in Figure 5
shows a steadily growth over the past four years.
To be highlighted that 309 out of 346 devices are
SBAS/EGNOS compatible, although EGNOS is
explicitly mentioned in the datasheets or user
manuals of 259 products.
Figure 5. SBAS compatible device evolution in non-SOLAS
satellite navigation equipment
It is important to note that 96% of the non-SOLAS
navigation equipment manufacturers have at least one
SBAS-enabled receiver within their products. The