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1 INTRODUCTION

Satellite Based Augmentation Systems (SBAS) are

designed to augment global navigation system

constellations by broadcasting additional signals from

geostationary (GEO) satellites. The basic scheme is to

use a set of ground monitoring stations to receive

GNSS signals that are processed in order to estimate

satellite (position and clock) and ionospheric errors

which are also applicable to users within the service

definition area. Once these estimations have been

computed, they are broadcast in the form of

“differential corrections” by means of SBAS

geostationary satellite(s). Some integrity data are also

broadcast along with these correction messages for the

GNSS satellites that are in the view of this network of

monitoring stations what increases the confidence that

a user can have in the satellite-based positioning

solution.

Figure 1.SBAS architecture

EGNOS is the satellite-based positioning service

over Europe which provides better accuracy with

respect to GPS standalone position. In addition,

EGNOS provides Integrity, which can be suitable for

safety critical applications in the maritime sector.

EGNOS Performance Along Finnish Coast

R. González

, E. Lacarra

, M. López

& K. Heikonen

EGNOS Satellite Services Provider, Madid, Spain

European GNSS Agency, Prague, Czech Republic

Finnish Transport Infrastructure Agency, Helsinki, Finland

ABSTRACT: The purpose of this article is on one side to inform Maritime community about the ongoing

activities adopted for the provision of EGNOS (European Geostationary Navigation Overlay Service) L1

maritime service and IEC standardisation process to produce a new IEC (International Electrotechnical

Commission) standard for SBAS maritime receivers and on the other side, to demonstrate the benefits of the

SBAS system in Europe, EGNOS (European Geostationary Navigation Overlay Service) in high latitudes to

Maritime community.

http://www.transnav.eu

the International Journal

Marine Navigation

and Safety of Sea Transportation

Volume 15

Number 3

September 2021

DOI: 10.12716/1001.15.03.07

552

2 EGNOS L1 MARITIME SERVICE

The European Commission, EC (EGNOS owner), the

GNSS Agency, GSA (EGNOS Services Programme

Manager), the European Satellite Services Provider,

ESSP (EGNOS service provider) and the European

Space Agency, ESA (EGNOS design agency) are

working in close collaboration to provide an EGNOS

L1 maritime service for “Harbour entrances, Harbour

approaches and Coastal waters” and for “Ocean

Waters” over Europe.

The EGNOS L1 Maritime service aims at providing

pseudo-range corrections, associated ranging integrity

and alert information to GPS L1 signals to let

shipborne receivers compute an enhanced navigation

solution with respect to GPS standalone, meeting

operational requirements included in in the IMO

Resolution A.1046 (27) for maritime navigation in

ocean waters, harbour entrances/approaches and

coastal waters over European coastal and inland

waters. EGNOS L1 Maritime service is planned by

2023 when the IEC SBAS test standard is expected to

be ready. The service will include performance

monitoring reporting and provision of Maritime

Safety Information (MSI) as well.

EGNOS L1 performance (accuracy, availability,

continuity, integrity, time to alarm, coverage) was

analysed concluding that EGNOS L1 meet the

operational requirements stated in International

Maritime Organization (IMO) Resolution A.1046 (27)

for “Harbour entrances, Harbour approaches and

Coastal waters” and for “Ocean Waters” over Europe.

Assessment is ongoing to define the potential servicer

area for the EGNOS L1 maritime service, which plans

to cover most of European coast and inland waters.

Moreover, GNSS campaigns on board vessels (such as

the one presented in section 6 of this paper) along

European coasts have been carried out to demonstrate

the EGNOS benefits in real environmental conditions

and potential and common vessels.

The service provision scheme required to

guarantee the required service level is under

definition, and was presented in the European

Maritime Radionavigation Forum (EMRF) to maritime

authorities. This service plans to include an EGNOS

Maritime Safety Information (MSI) service to mariners

and a potential establishment of specific working

agreements between the EGNOS Service Provider and

any national competent authority.

In addition, vessels should be equipped with type

approved receivers for SBAS L1 in order to ensure the

required operational performance for maritime

community. For that, EC requested CEN / CENELEC

to support the development of a test standard

regarding SBAS L1 receivers for maritime

applications, which will be covered in a new part

standard in IEC 61108 series. The IEC standardisation

process has started in February 2020, and is expected

to be completed by 2023.

3 SBAS STANDARDISATION FRAMEWORK FOR

SHIPBORNE RECEIVERS

Currently, IALA G-1152, [2], states that “IMO

recognises GNSS as part of World Wide Radio

Navigation System (WWRNS) only for ocean areas

where required performance levels which can be

achieved without using augmentation systems [e.g.

IMO Circular SN.1/Circ.329]”. Besides, GNSS

standalone positioning such as GPS, GALILEO,

GLONASS, Beidou and IRNSS are not suitable by

themselves for Harbour entrances, harbour

approaches and coastal waters.

According to IALA Guidelines for SBAS maritime

Service, G-1152 [2], SBAS systems are needed to

achieve the performance levels required (i.e. accuracy

and integrity) for harbour entrances/approaches and

coastal waters in IMO Res. A.1046(27), [9], in which

the freedom to manoeuvre is limited. Therefore, SBAS

systems are particularly needed where there is no

back-up infrastructure (i.e. DGPS/ DGLONASS) or in

poorly covered environments.

Supporting this last necessity, it has been

published that as of June 30th 2020, all Nationwide

Differential GPS System (NDGPS) service has been

discontinued in favour of SBAS system in accordance

with the Nationwide Differential GPS System

(NDGPS) Federal Register Notice USCG-2018-0133,

[1]. Apart from the United States of America,

Australia and Japan have recently discontinued their

radio beacon DGNSS service. The United Kingdom

and Ireland have stated that their DGPS service will

cease in 2022. DGPS is no longer deemed a necessary

augmentation for close harbour approach.

IMO MSC.401(95), [10], and IEC 61108-4

(Shipborne DGPS and DGLONASS maritime radio

beacon receiver equipment), [6], allow the use of

augmentation signals in shipborne receivers but there

is no standard for its implementation. Most of recent

maritime GNSS receiver models are SBAS compatible

but they could present important differences in their

performance since they are not certified according to a

specific test standard.

An IEC 61108 standard for SBAS receiver

equipment should be published in order to ensure a

safe use of Satellite Based Augmentation Systems by

all shipborne receivers. IEC 61108 is a collection of

IEC standards for "Maritime navigation and radio-

communication equipment and systems - Global

navigation satellite systems (GNSS)". IEC has

published International Standards for the following

GNSS systems: 61108-1, [3], for GPS, 61108-2, [4], for

GLONASS, 61108-3, [5], for Galileo and 61108-5, [7],

for BDS, and launched a new proposal 1108-6, [8], for

IRNSS. In addition, IEC has published International

Standard 61108-4, [6], for DGPS and DGLONASS,

which are ground-based Augmentation systems based

on an enhancement to primary GNSS constellations

(GPS and GLONASS).

A new IEC 61108 is planned to be developed to

include the minimum performances for SBAS L1

maritime GNSS receivers to be fulfilled by the

receiver equipment in order to be compliant with the

IMO Res. A.1046(27) [9] operational requirements for

harbour entrances, harbour approaches and coastal

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waters, along with the methods of testing and

required test results.

At this point, two initiatives are currently working

to support this standardisation process:

− First, the GNSS Space Agency (GSA) and the

European Commission (EC) have launched the

MARESS (MAritime Receiver SBAS

Standardisation) project, where ESSP, BNAE,

CEREMA, University Gustave Eiffel will be

working during 2021 in the production of technical

documentation to support the International

Electrotechnical Commission (IEC)

standardisation.

− Second, CEN, the European Standardisation

Committee through its Technical Committee 5

dedicated to Space has created the Working Group

8 (CEN/CLC JTC5 /WG 8) of SBAS receiver

performance for maritime applications in

September 2020. In this group, MARESS project’s

outputs will be presented to commonly agree on

the draft of IEC-61108 Part 7 for SBAS receiver

equipment, which will be submitted to IEC

Technical Committee 80 (Maritime navigation and

radiocommunication equipment and systems).

The New Work Item Proposal IEC 61108-7

standard was submitted to IEC TC80 in February

2021, starting the international process. The ballot is

open until beginning of June 2021 and thus, National

bodies interested and with representation in IEC are

encouraged to vote in favour with participation. This

ballot will be a key milestone since it is required to

pass the approval criteria in terms of participation and

positive support in order to continue with the process.

Figure 2. Tentative plan for standardisation process

As presented in Figure 2, the approval of the New

Work Item Proposal (NWIP) IEC 61108-7 standard for

SBAS is expected to be approved in Q2 2021. When

the New Work Item Proposal is approved, the IEC

standardisation process within IEC Technical

Committee 80 group will start.

Assuming that the NWIP is approved considering

the support expected for several countries, by June the

first meeting of the European Working Group

CEN/CLC JTC5 /WG 8 is planned to discuss the

inputs provided by MARESS Project, which would

include an outline of the IEC standard and the

proposal for the definition of the minimum

performances for SBAS L1 on GNSS Maritime

receivers. Later in Q3 2021, the first meeting of IEC TC

80 could be held presenting the draft agreed within

CEN/CLC JTC5 /WG 8. Finally, in 2022 a Committee

Draft for IEC 61108-7 standard is expected to be under

assessment within IEC TC 80. Note that these dates

are tentative milestones; the final plan will be

scheduled by IEC TC 80.

4 MARITIME REQUIREMENTS BASED ON IMO

RESOLUTION A.1046 (27)

EGNOS L1 maritime service is fully characterised by a

list of performance parameters derived from the list in

IMO Res. A.1046 (27), [9], (see Table 1) which are

Signal Availability, Horizontal Accuracy 95%,

Position update rate, Service Coverage, Service

Continuity and Time To Alarm for “Harbour

entrances, Harbour approaches and Coastal waters”

and for “Ocean Waters”.

Table 1. Operational requirements based on IMO A.1046

(27), [9]

_______________________________________________

Ocean Harbour entrances/

Waters approaches and

coastal waters

_______________________________________________

Horizontal 100m 10m

Accuracy 95%

Signal Availability 99.8% 99.8%

Service continuity - 99.97%

(over 15min)

Position update rate 2s 2s

Time to Alarm

Maritime 10s

Safety

Information

as soon as

practicable

System coverage Adequate

Adequate

_______________________________________________

Generation of integrity warnings in cases of system

malfunctions, non-availability or discontinuities.

Taking into account the radio frequency environment,

the coverage of the system should be adequate to

provide position-fixing throughout this phase of

navigation.

This paper focuses in the requirements of accuracy,

signal availability and continuity. EGNOS provides a

service performance compatible with this 2s update

rate. The compliance to update rate shall be

demonstrated by the receiver/equipment

manufacturers. The receivers used in this assessment

were configured to provide an update rate of 1

second.

5 GNSS PERFORMANCE ASSESSMENT ALONG

FINNISH COAST ON BOARD MASTERA OIL

TANKER

A GNSS campaign was performed along the Gulf of

Finland in order to analyse the EGNOS performance

in the border of Northeast EGNOS coverage area. Two

kinds of receivers were configured to use SBAS. Then,

this paper presents the results of a maritime receiver

and a high-end receiver. The EGNOS performance

results were compared with respect to the GPS

standalone solution, to evaluate the improvement of

EGNOS for maritime community. The performance

obtained with those receivers was compared with the

operational requirements defined in the IMO

Resolution A.1046 (27), [9], (Table 1) to assess the

feasibility of EGNOS for ocean waters, coastal waters

and harbour entrances/approaches, being beneficial

for maritime community over the Finnish coast.

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5.1 Characteristics of GNSS data campaign

The characteristics of this GNSS data campaign in

maritime domain were:

− Route: the vessel, Mastera, departed from Porvoo

(Finland) to Primorsk (Russia) then until Naantali

(Finland). Afterwards, the vessel went from

Naantali (Finland) to Primorsk (Russia) being two

days stopped close to Uusimaa waiting for orders

(adrift) and finally arrived at Porvoo (Finland).

− Time framework: the vessel departure was on

01.11.2019 and arrived on 14.11.2019 at Porvoo.

− Vessel: Mastera. This is a Finnish Aframax crude

oil tanker operated by Neste Shipping. This

icebreaking tanker transports crude oil year-round

from the Russian oil terminal in Primorsk to Neste

Oil refineries in Porvoo and Naantali.

https://www.neste.com/

Figure 3. Mastera oil tanker

Figure 4. GNSS data collection path

The equipment installation consisted of two GNSS

MFMC high-end receivers and a maritime receiver

connected to a GNSS MF antenna.

Additionally, a RF signal recorder was connected

to the same GNSS MF antenna to log the same RF L1

signal as the rest of the GNSS receivers.

RF L1 signal recorded during the maritime

dynamic data campaign was replayed in the maritime

receiver to obtain GPS standalone solution. It has to be

stressed that the SIS recorder capability is only of five

days (from November 1st to 6th 2019).

After the GNSS data campaign, high-end receiver’s

output files were post-processed using high precision

techniques to obtain the real followed route.

5.2 Methodology of computing

The activity for the GNSS performance assessment

consists of three general lines:

1. Real position. It was obtained in post-processing

using high precision techniques (PPP, Precise Point

Positioning) with the GNSS data obtained by the

receiver. Figure 5 describes the flow of data

through different tools to obtain the precise path of

the Mastera vessel in order to compute GNSS

performance.

It is stressed that both high-end receivers are with

the same configuration. One is the back-up of the

other one.

2. SBAS Navigation solution. This was computed

directly with the GNSS maritime receiver. The

computation of the performance analysis is done

using internal Analysis Tools developed by ESSP.

Figure 5 summarises the process of the

methodology followed.

3. GPS-only solution. RF L1 signal recorded during

the maritime dynamic data campaign was

replayed in the maritime receiver to obtain GPS

standalone solution. It has to be stressed that this

recorded scenario only lasts five days (from

November 1st to 6th 2019).

SBAS/GPS-

only PVT

solution

Real path

Analysis Tool

Maritime

receiver

L1 RF Raw Data

MFMC Raw

Data

PPP tool

HNSE SV monitored HDOPC/N0

Figure 5. Process of GNSS PVT solution

5.3 GNSS performance analysis

GNSS performance analysis is based on the position

solution obtained with some GNSS receivers installed

in the vessel:

− a high-end receiver;

− a maritime receiver.

Besides, the RF L1 signal in space recorded during

almost six days on-board was replayed in the

following receivers in order to analyse their GNSS

performance:

− a maritime receiver (to analyse GPS position

solution);

− a high-end receiver (to analyse GPS position

solution).

5.4 EGNOS signal in space

EGNOS signal availability refers to the percentage of

time during which reliable information is provided by

the system within the specified area of service. Thus,

EGNOS 1046 Signal Availability assesses the

percentage of time the EGNOS signal in space is

provided by the GEOs according to messages that can

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be processed by an SBAS receiver aligned with the

receiver guidelines.

EGNOS broadcasts through two operational GEO

satellites. This redundancy benefits EGNOS receivers

which can instantaneously GEO switch and therefore,

EGNOS signal availability is calculated as the

combined signal availability of both operational

EGNOS GEO satellites.

EGNOS signal unavailability happens when there

is a simultaneous signal in space outage in both

EGNOS GEO satellites.

During the whole period of Mastera vessel trip

(November 2019) the operational EGNOS GEO

satellites were PRN 123 and PRN 136.

PRN

136

PRN

123

Figure 6. EGNOS operational satellites (November 2019)

The EGNOS monitoring information shows that

the EGNOS signal in space availability was 100%

during the whole data campaign period, which meets

the 99.8% EGNOS signal in space availability

requirement.

The EGNOS service continuity was 100% during

the data campaign period meeting the 99.97% over a

period of 15 minutes of IMO Res. A.1046 (27) [9], since

no service interruption occurred during that period.

5.5 EGNOS / GPS standalone position availability

EGNOS as a radio-navigation system has a

particularity which is EGNOS GEO satellites

broadcast messages over the GEO satellite footprint

(Figure 6) but EGNOS can be used only within the

Message Type 27 service area. EGNOS is a regional

augmentation system that provides ionospheric and

satellite corrections for Europe.

Therefore, EGNOS position availability is the

percentage of time an user is able to compute a

position based on EGNOS.

Table 2 shows the percentage of time the receiver

is computing the position solution using EGNOS and

GPS standalone.

N. B. GPS standalone performance assessment for

Maritime receivers is only between 01.11.2019 16:15

UTC and 06.11.2019 19:43 UTC (5 days) due to the

capacity of the Signal recording equipment.

Analysing these results, it can be concluded that:

− EGNOS position availability was 100% for both

receivers.

− No EGNOS position continuity events were

detected during the data campaign period.

Table 2. Position availability obtained using EGNOS and

using GPS standalone

_______________________________________________

EGNOS Position GPS standalone

Availability [%] Position Availability

_______________________________________________

DOY High-end Maritime High-end Maritime

receiver receiver receiver receiver

_______________________________________________

305 100 100 100 100

306 100 100 100 100

307 100 100 100 100

308 100 100 100 100

309 100 100 100 100

310 100 100 100 100

311 100 100 100 --

312 100 100 100 --

313 100 100 100 --

314 100 100 100 --

315 100 100 100 --

316 100 100 100 --

317 100 100 100 --

318 100 100 100 --

_______________________________________________

5.6 EGNOS / GPS accuracy

Horizontal Accuracy is the 95% percentile of the

Horizontal Position Error (HPE) distribution. HPE is

the 2D radial error of the instantaneous measured

position by the GNSS receiver respect to the true

instantaneous position.

Table 3 compares the horizontal accuracy between

the user performance obtained using EGNOS and GPS

standalone.

Table 3. HPE (95%) obtained using EGNOS and using GPS

standalone

_______________________________________________

EGNOS HPE GPS standalone HPE

95% percentile [m] 95% percentile [m]

_______________________________________________

DOY High-end Maritime High-end Maritime

receiver receiver receiver receiver

_______________________________________________

305 1.179 0.869 4.073 1.444

306 0.935 0.791 3.284 1.809

307 0.970 0.792 1.653 1.222

308 0.970 0.747 2.103 1.638

309 1.023 0.835 1.738 1.307

310 0.967 0.841 2.235 2.000

311 0.950 0.907 1.832 --

312 0.956 0.718 3.818 --

313 0.873 0.762 3.312 --

314 1.000 0.786 3.527 --

315 1.057 0.808 3.860 --

316 0.911 0.784 1.208 --

317 0.870 0.792 1.228 --

318 1.049 0.872 1.688 --

_______________________________________________

TOTAL 0.971 0.815 3.149 1.551

_______________________________________________

Table 3 presents daily HPE (95%) quite close to 1m

when using EGNOS solution against GPS standalone,

in particular, there is a global HPE (95%) for the 13

days using the maritime receiver, of 0.815m whereas

the global value for the same receiver reproducing the

recorded RF L1 signal to compute GPS standalone

solution during 5 days is 1.551m. In contrast, the high-

end receiver shows more extreme results: 0.971m of

HPE (95%) when using EGNOS solution against

3.149m when using GPS standalone solution.

To be more precise, it can be compared EGNOS

HPE (95%) against GPS standalone HPE (95%) exactly

for the same period (since 01.11.2019 at 16:15 UTC to

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06.11.2019 at 19:43:21 UTC) using the same Maritime

receiver and replaying the same RF L1 signal-in-space.

Table 4. HPE (95%) obtained using EGNOS and GPS with

maritime receiver since 01.11.2019 at 16:15 UTC until

06.11.2019 19:43:21 UTC

_______________________________________________

EGNOS solution GPS standalone

DOY HPE (95%) Max. HPE HPE (95%) Max. HPE

_______________________________________________

305 0.869 1.219 1.444 1.721

306 0.791 0.910 1.809 2.184

307 0.792 1.088 1.222 1.552

308 0.747 0.970 1.638 2.132

309 0.835 1.353 1.307 1.804

310 0.798 1.092 2.000 2.544

TOTAL 0.800 1.353 1.551 2.544

_______________________________________________

Table 4 shows the clear improvement of EGNOS

horizontal accuracy between 54% and 103% for the

case of the maritime receiver against GPS standalone.

Analysing these results, it can be concluded that:

− Percentiles at 95% of Horizontal position errors

were lower than 1.2 meters for both high-end and

maritime receivers in all days and usually lower

than 1 meter.

− EGNOS Horizontal accuracy (95%) was lower than

1.2 meters for both receivers, which is compliant

with 10 meters accuracy requirement in IMO Res.

A.1046 (27) [9] for “Harbour entrances, Harbour

approaches and Coastal waters” and for “Ocean

Waters”.

− EGNOS provides a clear improvement of

horizontal accuracy between 54% and 103% for the

case of the maritime receivers with regards to the

use of GPS standalone.

6 GENERAL CONCLUSIONS

Results from two receivers (one maritime and other

high-end receiver) on board the vessel that navigated

during thirteen days along the Gulf of Finland show

that:

1. The EGNOS signal in space availability was 100%

during the data campaign period meeting the

99.8% requirement of IMO Res. A.1046 (27), [9]. In

fact, the two GNSS receivers were able to track

EGNOS messages from both operational GEO

satellites (PRN123 and PRN 136) the 100% of time.

2. The EGNOS service continuity was 100% during

the data campaign period meeting the 99.97% over

a period of 15 minutes of IMO Res. A.1046 (27) [9],

since no service interruption occurred during that

period.

3. EGNOS position availability was 100% for both

GNSS receivers during the whole period.

4. EGNOS position continuity was 100% for both

receivers during the whole period since no EGNOS

position continuity events were detected during

the data campaign period.

It is noted that this continuity parameter is at

receiver level considering local effect, along

receiver and antenna characteristics.

5. 95th percentile of the Horizontal Position Error

meets the 10 meter requirement for “harbour

entrances, harbour approaches and coastal waters”

and the 100-meter requirement of “Ocean waters”

established in IMO Res. A.1046 (27), [9], with both

GNSS receivers.

EGNOS horizontal position accuracy is enhanced

between 54% and 103% with respect to GPS

standalone solution for the case of the maritime

receiver.

In consequence, the EGNOS performance observed

on board the oil tanker, Mastera, indicates that

EGNOS can support “Harbour entrances/approaches

and coastal/ocean waters” according to IMO Res

A.1046 (27) [9], meeting the 10 meters confidence level

at 95%, the signal-in-space availability requirement of

99.8% and the service continuity of 99.97%.

ACKNOWLEDGMENTS

We would like to express our gratitude to OSM Group AS

(Norwegian Oil Transport provider) and Väylä (Finnish

Transport Infrastructure Agency) to allow ESSP to perform

this GNSS data campaign in the Gulf of Finland and install

GNSS equipment in Mastera.

Finally, the authors would like to acknowledge the efforts

done by EC, GSA and ESA to work at programme level for

the future provision of EGNOS L1 maritime service.

REFERENCES

1. Federal Register Notice. , USCG-2018-0133 (2018).

2. Guideline G-1152. , SBAS Maritime Service (2019).

3. Maritime navigation and radio-communication