International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 3

Number 1

March 2009

Modernization of Maritime DGPS in Poland

M. Dziewicki

Maritime Office, Gdynia, Poland

1 INTRODUCTION

Most of mariners use Global Navigation Satellite

Systems (GNSS) as a primary means of navigation.

Currently available GNSS does not fulfil the re-

quirements of IMO with respect to accuracy and in-

tegrity. The use of IALA maritime DGNSS does ful-

fil these requirements. International maritime

standards exist for both: onboard receiver and land

based DGNSS service. The system has been widely

adopted as the international maritime standard for

providing differential corrections to GNSS. The

IALA DGPS beacon systems were installed in many

countries over the period 1993-2000 and now be-

came obsolete. The Radio-navigation (presently e-

Navigation) Committee concluded that there is a re-

quirement to recapitalise national systems. It is po-

tentially a good reason to re-organise the system for

the benefit of existing users and to enhance DGNSS

capabilities taking into account technical innova-

tions. At the same time some countries are consider-

ing submission of their DGNSS services to IMO as

components of the World Wide Radio Navigation

System.

2 IALA OPTIONS

The key system of secure marine navigation and ac-

curate hydrographic survey is reliable radionaviga-

tion service. The IALA Radio-navigation Committee

has assessed the current and potential use of the

DGNSS system and concluded that there is a re-

quirement to continue existing service and to mod-

ernise the system and develop enhanced GNSS ca-

pabilities as well as alternative technologies to meet

the requirements of IMO Resolution A.915(22) .

There are several alternatives to the IALA beacon

system for the transmission of differential correc-

tions and safety related information. There are

methods of providing enhanced services, like e-

Loran, Eurofix, EGNOS, AIS, Real Time Kinematic

(RTK) or pseudolites. Their related basic features

and a subjective cost are listed in Tab. 1., [ 2].

ABSTRACT: Some new techniques and functionality adopted for modernization of national DGPS systems

by maritime administrations in Europe are presented. Any solution adopted must meet international require-

ments: IMO standards and IALA e-NAV Committee recommendations. The results of DGPS Re-

capitalization Meeting in Gdynia 2008 are presented. Modernization and re-engineering of maritime DGPS

must take into account backward compatibility with existing onboard receivers as well as future trends to-

wards e-Navigation. Operational and legal status of the Polish DGPS network is also mentioned in this con-

text.

Table 1. Alternative techniques for IALA DGNSS

__________________________________________________________________________________________________________

System Accuracy Coverage Instant warning Cost Maritime standard

Integrity/Continuity Provider/user

__________________________________________________________________________________________________________

IALA DGNSS 1-3 m local/regional Yes/High Moderate/low yes

EGNOS 5-10 m regional/global Yes/High Very high/low no

AIS 1-20 m local Can be/Moderate Low/low yes

Pseudolites sub-meter local Yes/Moderate High/moderate no

Eurofix 2-10 m regional Yes/High low/moderate no

RTK sub-meter local Can be/Low Moderate/high no

__________________________________________________________________________________________________________

The simplest modernization option may be re-

placement of existing equipment with new dedicated

hardware Reference Stations and Local Integrity

Monitors (RSIM). This solution could limit the po-

tential for future development. Additionally modern-

ization of DGNSS should be considered in the con-

text of position-fixing requirements for e-

Navigation.

The future need could be providing additional

messages relating to Galileo, GPS L2C/L5 and

GLONASS M should be taken into account.

Other possibilities include:

− Software Reference Stations and Integrity Moni-

tors (RSIM)

− Virtual Reference Station (VRS),

− SBAS (EGNOS, WAAS) Integration

Above options are explored further in IALA Rec-

ommendation R-135, [3].

Finally IALA members are encouraged to:

− Recapitalize existing DGNSS systems prior to

their obsolescence, noting the advice given in R-

135,

− Consider the options for replacement systems,

with reference to the documents listed below,

− Share information regarding studies carried out

and specifications of replacement solutions, and

report progress to IALA,

− Investigate potential future developments com-

patible with the development of shore based e-

Navigation architecture,

− Investigate techniques for adding value to trans-

missions, such as transmission of safety related

information and/or backup positioning capabili-

ties, [1].

3 DGPS RE-CAPITALIZATION MEETING IN

GDYNIA

The meeting “DGPS re-capitalization”, was hosted

in May 2008 by Maritime Office Gdynia, in Gdynia.

The development of a strategy for future implement-

ing of local and regional augmentation systems was

noted. The response of representatives at the meet-

ing indicate that most administrations providing

DGNSS services are undertaking re-capitalisation or

are planning such activities based also on co-

operation with National Geodetic Networks.

− Sweden is currently studying options for soft-

ware RSIM solutions and transmissions of VRS

data via MF beacon system taking into account

also geodetic network SWEPOS.

− Germany is planning to implement DGNSS re-

capitalization plan by creating RAAS and VRS

based on national network operated from national

centre of control. The new concept of “moving

centre of system accuracy” was presented. Also a

new type of MF transmitting antenna (NTA) was

presented. Germany also announced a feasibility

study to investigate the addition of Ranging sig-

nals (R-Mode) on MF beacon and AIS carri-

ers, [1].

− Scotland referred to the common UK and Ireland

studies of DGPS replacement options which con-

cluded that the lowest risk option for the GLAs

would be hardware replacement, although the

flexibility provided by the software option would

better meet emerging requirements and should

not be ruled out .The GLAs have tendered for

new RSIM equipment, which may be fulfilled by

either hardware or software solution, [1].

− Russia is testing broadcast of DGlonass and

DGPS corrections via AIS system in Golf of Fin-

land.

4 MODERNIZATION OF POLISH

RADIONAVIGATION

Maritime Office Gdynia (MOG) has established and

operates shore based/costal network to support

DGPS, RTK, and AIS systems. These were built

and organized to fulfill international IMO standards

and recommendations endorsed by IALA.

Table 2. Polish DGPS marine stations

__________________________________________________________________________________________________________

Table of DGNSS Stations Country: POLAND Date of last amendment: Sept 2008

__________________________________________________________________________________________________________

Station Identification Geographical Station in Integrity Transmitted Freq Bit

name Reference Transmitting Position operation Monitoring message types (kHz) Rate

Station(s) beacon Lat/ Lon (bps)

__________________________________________________________________________________________________________

Dziwnów 741 481 54°01’ N yes yes 9,3,7,16 283.5 100

742 14°44’ E

Rozewie 743 482 54°49’ N yes yes 9,3,7,16 301.0 100

744 18°20’ E

__________________________________________________________________________________________________________

Polish DGPS system has already been fully mod-

ernized during the period 2007-8, to meet all the re-

quirements set out in IMO Resolution A.915(22) for

Future GNSS. The hardware RSIM solution has

been adopted for the re-capitalisation, on grounds of

low cost and market availability. The conception is

based on a network of reference stations and remote

integrity monitors continuously operated via IT links

from a common control center..

The DGPS-PL system is composed of two refer-

ence beacon stations which are remotely operated

and controlled via wide area network from the Con-

trol Station located in Gdynia. Both existing refer-

ence stations RS Dziwnów and RS Rozewie are

equipped with two reference L1, L2 receivers, two

MSK modulators and dual LF beacon transmitters.

Local integrity monitors (RSIM model) are being

under permanent control via WAN from Central Sta-

tion in Gdynia. A dedicated server at the control

center continuously gathers operational information

from all sites. Thus living database of Regional Area

Corrections can be created in the future. There are

also plans to integrate marine system with a national

geodetic network EUPOS to transmit VRS data via MF

beacons

4.1 Integrity of DGPS-PL

To ensure signal availability at required level of

(99,5%) for single site beacon station, a redundancy

of major hardware is fundamental, therefore each RS

station is doubled and operation will continue in

case of a hardware failure. The set of RTCM mes-

sages and broadcast frequencies from Polish DGPS

beacon stations is shown in Table 2.

Quality of DGPS broadcast is being checked and

evaluated by local integrity monitors (RSIM). Addi-

tionally the range and signal availability will be

monitored by remote LF DGPS monitors. Daily re-

ports and data on availability of the system are gath-

ered in data base of Central Control server in Gdy-

nia.

4.2 Integrity Settings (IM)

It was recognised that certain integrity monitor

threshold settings are vital to the proper performance

of the RS station. IALA Recommendation R-121

contains the list of parameters and recommended

settings, [4]. The local integrity monitor continuous-

ly checks the quality of the own DGPS transmis-

sions by receiving and applying own corrections.

Thus the IM software monitors position accuracy,

signal availability (SNR), tracked satellites, GPS ge-

ometry (DOP), RTCM data correctness and quality,

as well as radiated signal level (SS). When alarm

condition is detected, an alarm message is immedi-

ately set for local response and switching to optional

equipment (secondary configuration) can happen.

Any IM message warning will automatically be

broadcast to all users/ships in the area within 10s.

5 RTK SERVICE

Permanent reference RTK station was established on

Peninsula Hel to cover Gdańsk, Gdynia ports and

approaching routes. Real Time Kinematics solution

using carrier-phase corrections has the enhanced ac-

curacy, but there are constraints imposed by the

bandwidth and spatial de-correlation. For single

RTK station, the range is up to 10-40 km (Table 3).

This is sufficient for hydrographical and engineering

applications in the Gulf of Gdańsk, can also be used

during docking phase in the ports. Station operation

is fully controlled via network from RL Gdynia,

however radio signal strength and position accuracy

is being monitored by IM receiver situated perma-

nently in the port of Gdynia. It is highly recom-

mended that in the near future RS-Hel will be incor-

porated into Polish geodetic RTK network ASG-PL .

In result the whole system would benefit of better

marine coverage and VRS technique would become

available along the Polish coastal zone.

Table 3. Characteristics of RTK RS-Hel

___________________________________________________

Name Receiver Corrections Radio- Options

RS- Hel type output transceiver

___________________________________________________

System Net R-5 RTCM 18, Satelline 3AS VRS

19,20, 21 Epic, simplex

Application GPS, Binary code UHF 2-10W RTK,

Glonass CMR, CMR+ range 10-40km DGPS

Frequency L1,L2,L5 1Hz 434.25 MHz +/-1MHz

Link Mode Network serial, RS com VPN

(LAN) NMEA

___________________________________________________

6 CONCLUSIONS

− Re-capitalization process of national DGNSS sys-

tems is well advanced, however IALA members

are at different stages of developing, concerning

available options versus budgetary constrains.

− All of new solutions must meet the need of exist-

ing users taking into account existing and future

IMO, IALA regulations.

− Re-capitalization of national DGNSS gives good

opportunity to modernize technique and function-

ality towards new e-Navigation requirements.

REFERENCES

1. IALA Working paper of e-NAV Committee, e-NAV5-13-07

“IALA DGNSS Modernisation”, 2008.

2. N. Ward, Paper for ENC GNSS 2006, “Options for Re-

engineering Maritime DGNSS”.

3. IALA Recommendation R-135, “On The Future of

DGNSS”, Edition 2, December 2008.

4. IALA Recommendation R-121, “Recommendation on the

Performance and Monitoring of DGNSS Services in the

Frequency Band 283.5 – 325 kHz”, December 2004.