543

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

& V. Antón

GSA, European Global Navigation Satellite Systems Agency, Prague, Czech Republic

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.

545

− 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

546

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

547

SBAS capability is included in 89% of the non-SOLAS

satellite navigation devices. EGNOS is explicitly

mentioned in 75% of the datasheets or user manuals

of these equipment.

Figure 6. Percentage of SBAS compatible devices within

non-SOLAS navigation equipment

Figure 7. Percentage of non-SOLAS navigation equipment

which mention EGNOS

5.2 AIS Equipment Survey

5.2.1 SOLAS

There are 17 AIS devices authorised for being used

onboard SOLAS vessels, from 14 different brands. The

number of SBAS capable devices increased in 2019

with a slight decrease in 2020. This decrease should be

further analysed in the coming years since it

corresponds solely to one device. The number of

SOLAS authorised AIS devices is very limited to yield

statistical conclusions without an extended period of

analysis.

The evolution in the last four years can be seen in

Figure 8. To be highlighted that 12 out of 17 devices

are SBAS/EGNOS compatible, however, EGNOS is

only mentioned in the datasheets or user manuals of 7

products.

Figure 8. SBAS compatible device evolution in AIS SOLAS

equipment

Almost a 65% of the authorised manufacturers to

supply AIS SOLAS equipment have at least one SBAS-

enabled receiver within their products portfolio. The

SBAS capability is included in 71% of the onboard AIS

SOLAS devices. EGNOS is explicitly mentioned in the

41% of the datasheets or user manuals of these

equipment.

Figure 9: Percentage of SBAS compatible devices within AIS

SOLAS equipment

Figure 10. Percentage of AIS SOLAS equipment which

mention EGNOS

5.2.2 Non-SOLAS

The datasheets of 70 AIS devices for non-SOLAS

vessels were analysed, from 26 different brands.

Excluding discontinued products, it was observed

that the number of shipborne AIS devices available in

the market for non-SOLAS vessels increased in the

last year to reach a total of 64 available devices in the

market. The evolution in the SBAS capability depicted

in Figure 11 shows a steadily growth over the past

four years.

In this case, only 20 out of 64 devices are

SBAS/EGNOS compatible and EGNOS is explicitly

mentioned in the datasheets or user manuals of 11

products.

Figure 11. SBAS compatible device evolution in AIS non-

SOLAS equipment

548

Even though the number of AIS non-SOLAS

devices which are SBAS compatible increases every

year, the percentage is still low. The SBAS capability

is included in 31% of the AIS non-SOLAS devices.

EGNOS is explicitly mentioned in the 17% of the

datasheets or user manuals of these equipment.

Figure 12: Percentage of SBAS compatible devices within

AIS non-SOLAS equipment

Figure 13: Percentage of AIS non-SOLAS equipment which

mention EGNOS

5.2.3 Inland AIS

The datasheets of 30 inland AIS devices, from 19

different brands were analysed. Excluding

discontinued products, there are 10 out of 27 devices

which are SBAS/EGNOS compatible and 7 of them

explicitly mention EGNOS in the datasheets or user

manuals.

Figure 14: Percentage of SBAS compatible devices within

inland AIS equipment

Figure 15: Percentage of inland AIS equipment which

mention EGNOS

5.3 Portable Pilot Units Survey

The assessment of PPUs is based on 19 products

available in the market in 2020. Most of them, 18, are

SBAS/EGNOS compatible and EGNOS is mentioned

in 15 products. In percentage, this compatibility can

be seen in the following figures.

Figure 16: Percentage of SBAS compatible PPUs

Figure 17: Percentage of PPUs which mention EGNOS

5.4 Dynamic Positioning Survey

This section covers other maritime positioning

equipment, not included in the previous categories,

which is used in maritime applications, such as,

dynamic positioning or marine surveying.

A total of 29 devices were analysed, being a 100%

of them SBAS/EGNOS capable. EGNOS is explicitly

mentioned in 20 of them.

549

Figure 18: Percentage of SBAS compatible devices

within DP systems

Figure 19: Percentage of DP equipment which mention

EGNOS

6 CONCLUSIONS

Many GNSS receivers currently available on the

market are able to receive and process EGNOS

messages and can be used to support numerous

applications. As a result of using EGNOS, a better

position performance can be obtained.

According to the EGNOS OS SDD [2], the EGNOS

OS horizontal minimum accuracy, corresponding to a

95% confidence bound of the 2-dimensional position

error in the horizontal local plane for the Worst User

Location, is 3 meters. Nevertheless, the observed

errors are usually lower than this upper bound [1].

Therefore, the accuracy requirement established in

IMO Res. 1046 [7] about navigation in harbour

entrances, harbour approaches and coastal waters

with an error not greater than 10 m with a probability

of 95% is fulfilled by far when the GNSS receiver is

EGNOS enabled. It is also important to remark that

IMO Resolution A.915(22) [6] considers SBAS/EGNOS

as one of the techniques that can improve the accuracy

of GPS.

To take advantage of this improved accuracy,

direct access to EGNOS in vessels can be achieved

through:

− EGNOS-enabled navigation receivers:

94% of the GNSS-based equipment authorised to

be used in SOLAS vessels are SBAS/EGNOS

compatible. Concerning the GNSS-based

equipment used in non-SOLAS vessels, the 89% of

devices are SBAS/EGNOS compatible.

− EGNOS-enabled AIS transponders:

71% of the AIS devices authorised to be used in

SOLAS vessels are SBAS/EGNOS compatible. This

percentage is lower in the AIS non-SOLAS devices,

around 31%.

In addition to navigation receivers and AIS

transponders, there are other types of devices which

take benefit of SBAS/EGNOS for their operation. This

is the case of PPUs and DP systems.

EGNOS is usually activated in PPUs to obtain a

better accuracy in specific operations such as the

entrance and navigation through locks or in docking

and turning manoeuvres. This is especially useful

when visibility is reduced and big vessels require

access to ports with difficult entrance.

EGNOS is also used in DP systems, mainly as a

free of charge back-up system to other paid

augmentation services.

Choosing SBAS/EGNOS-enabled receivers leads to

an accurate position information. The advent of new

standardised receivers, following common

implementation guidelines will lead to an

improvement in safety in navigation and an

enhancement of those services based on position

information.

REFERENCES

1. EGNOS: https://egnos-user-support.essp-

sas.eu/new_egnos_ops/position_error, last accessed

2020/11/10.

2. EGNOS OS SDD: EGNOS Open Service (OS) Service

Definition Document v2.2User Technology Report.

(2020).

3. EU Directive 2002/59/EC: Directive of the European

Parliament and of the Council of 27 June 2002

establishing a Community vessel traffic monitoring and

information system. (2002).

4. GNSS: User Technology Report. , GSA (2020).

5. IALA: An Overview of AIS. (2016).

6. International Maritime Organization: Revised maritime

policy and requirements for a future Global Navigation

Satellite System (GNSS). (2001).

7. International Maritime Organization: Worldwide

Radionavigation System. (2011).

8. Lopez, M., Anton, V.: SBAS/EGNOS Enabled Devices in

Maritime. TransNav, the International Journal on

Marine Navigation and Safety of Sea Transportation. 12,

1, 23–27 (2018). https://doi.org/10.12716/1001.12.01.01.

9. MED Database: https://portal.med.emsa.europa.eu/, last

accessed 2020/11/10.

10. RadioComunicaciones:

http://apps.fomento.gob.es/RadioComunicaciones/, last

accessed 2020/11/10.

11. SOLAS: International Convention for the Safety of Life

at Sea. (1974).

12. GSA: Report on Maritime and Inland Waterways user

needs and requirements. GSA-MKD-MAR-UREQ-

229399 Issue/Revision: 2.0 Date: 01/07/2019

13. IALA: Guideline 1112. Performance and monitoring of

DGNSS Services in the Frequency band 283.5 - 325 KHz.

Edition 1.0. May 2015

14. CCNR: List of approved Inland AIS equipment in

accordance with the Rhine Vessel Inspection

Regulations. 21.12.2018

15. UNECE: International Standard for Tracking and

Tracing on Inland Waterways (VTT). Ref.: ECE/TRANS/

SC.3/176/Rev.1. 2015

16. IMPA: Guidelines on the design and use of Portable

Pilot Units. 2016