International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 3
Number 2
June 2009
121
1 INTRODUCTION
The European Union recognises the great potential
of inland navigation as an alternative transport mode
for freight transport. Facing tremendous capacity
and environmental problems in the land transport
modes, in particular road transport, the European
transport policy consequently has a great interest in
developing inland waterway transport to become a
real alternative whilst keeping the environmental
burden to a minimum [www.iris-europe.net].
The continuous information of user’s position is
one of the most important factors, which determines
the safety of the user in the transport, on inland
waterways also. The requirements towards
radionavigation are well defined for the maritime
world (sea navigation, coastal navigation etc.) in the
IMO (International Maritime Organization)
resolution A.915(22). As the IMO is not responsible
for inland waterways, and these requirements are not
binding, the new performance requirements must be
created. The most comprehensive approach for the
inland navigation community is the project
MARUSE. For traffic management and information
the following requirements have been identified:
absolute accuracy – 3 m, alert limit – 7.5 m, time to
alarm – 10 s, integrity risk (per 3 hours) –10
–5
,
availability (% per 30 days) – 99.8, continuity
(%/3hours) – 99.97 [Amlacher et al. 2007]. The
accuracy requirement of 3 m has been confirmed in
real time operations, e.g. for the matching of the
radar image with the Electronic Navigation Chart
(ENC).
Moreover the coordinates of actual position must
be sent to other ship’s devices and different kind of
land stations. That’s why the user’s position on
inland waterways must be fixed continuously by
specialized electronic position–fixing systems –
satellite navigation systems (SNS), the differential
mode of these systems, satellite based augmentation
systems (SBAS) and terrestrial radionavigation
systems [Januszewski J. 2007].
2 SATELLITE NAVIGATION SYSTEMS AND
THEIR DIFFERENTIAL MODE
A presently (December 2008) unique, fully
operational and global system is the American GPS
(Global Positioning System – Navstar) and its
differential mode DGPS. Experience has shown that
stand alone GPS system does not provide sufficient
accuracy for a reliable operation of the system.
Many maritime administrations have implemented a
DGPS service in their waters to improve safety and
efficiency of navigation [Hoppe M. et al. 2005]. At
present more than 300 DGPS reference stations have
operational status; and this number is still increasing
[ALRS 2008/09]. In this paper these stations are
called IALA DGPS.
For maritime users (channel and coastal
navigation, harbour approach) the IALA DGPS
stations are situated at seashore, for inland
navigation the additional stations must be installed
inland in properly chosen places.
Satellite and Terrestrial Radionavigation
Systems on European Inland Waterways
J. Januszewski
Gdynia Maritime University, Gdynia, Poland
ABSTRACT: The usefulness for all sea users of Satellite Navigation Systems (SNS), Satellite Based
Augmentation Systems (SBAS) and Automatic Identification System (AIS) is well known. The possibility,
actual and future, of the utilization of all these systems on European inland waterways, GPS augmented by
IALA DGPS reference stations, GPS augmented by European SBAS – EGNOS from direct Signal–in–Space
(SIS) and GPS augmented by EGNOS from re–transmission over AIS, is presented in this paper. The
operational systems, such as the German network IALA DGPS and DoRIS, and planned system such as
GALEWAT, MARGAL, MUTIS and MARUSE are described also.
122
The provision of DGPS corrections can be
realized in two different ways:
− IALA DGPS network covering all inland
waterways of the chosen region or the territory of
the country,
− the distribution of the DGPS corrections via AIS
base stations.
The first solution became realized in Germany.
The two IALA DGPS stations were located in
Helgoland and in Gross Mohrdorf, which cover the
German Bight and the German part of the Baltic
Sea, respectively. These stations and the third,
planned in Zeven, will provide good coverage of the
harbour entrances of the great three German rivers –
Elbe, Ems and Weser. This IALA DGPS stations
network became extended for four stations – Bad
Abbach (Bavaria), Iffezheim (Baden-Württemberg),
Koblenz (Rhinelad-Palatinate) and Mauken
(Sachsen-Anhalt), which permitted coverage for all
of Germany. The range of these stations over land is
approximately 250 km [Hoppe M. et al. 2005].
The second solution became realized in Austria,
via the DoRIS (Donau River Information Services)
system. 23 DoRIS base stations are installed along
the Danube, two of them are augmented with DGPS
functionality and distribute the corrections over the
neighbouring base stations to the users onboard
ships. The distribution of these two stations, called
AIS DGPS, is such that the distance between the
user and the nearest DoRIS station is less than 90
km always. The AIS DGPS stations produce the AIS
message type 17, according to the ITU–R M.1371–1
standard, which includes the DGPS correction data.
Over the AIS radio data channel this message is
broadcast every 10 seconds. The DoRIS system has
been operational since 2006 year with no major
outages.
Nowadays the GLONASS (Russian system)
cannot be a continuous position fixing system (the
number of operational satellites is less than nominal
24 continually). The new system – Galileo,
sponsored by the European Union, is under
construction as the European contribution to the next
generation of satellite navigation [Spaans J. 2008],
but these two systems are already taken into account,
in this paper also. The new navigation satellite
system (NSS) actually built by China, called
Compass, was not taken into account.
The number of satellite (ls) which can be used for
to fix ship’s position first of all depends on masking
elevation angle H
min
of the receiver and the number
of satellites fully operational at given moment. If the
angle H
min
increases, the number ls decreases. As the
most important European inland waterways are at
geographical latitudes 40–60°N, we can pose the
question – what is or what will be the geometry
(elevation angle and satellite azimuth, in particular)
of two the most important SNSs – GPS and Galileo
in this part of Europe.
Table 1. Distribution (in per cent) of satellite elevation angles (H) in open area for Galileo system (GAL) and GPS system (GPS) at
different observer’s latitudes (φ)
__________________________________________________________________________________________________________
φ [
o
] System Elevation angle H [
o
]
0-10 10-20 20-30 30-40 40-50 50-60 60-70 70-80 80-90
__________________________________________________________________________________________________________
40-50 GAL 23.0 16.7 14.3 11.8 9.9 8.5 7.6 6.1 2.1
GPS 22.2 16.9 14.9 12.1 10.1 8.7 7.2 5.8 2.1
50-60 GAL 23.0 19.7 14.5 11.8 9.3 8.2 6.4 4.8 2.3
GPS 24.1 19.3 14.8 11.3 10.1 7.8 6.1 4.1 2.4
__________________________________________________________________________________________________________
Table 2. Distribution (in per cent) of satellite azimuths for different masking elevation angles (H
min
) for Galileo system (GAL) and
GPS system (GPS) at different observer’s latitudes (φ)
__________________________________________________________________________________________________________
φ [
o
] H
min
[
o
] System Satellite azimuth H [
o
]
0–45 45–90 90–135 135–180 180–225 225–270 270–315 315–360
__________________________________________________________________________________________________________
0 GAL 8.7 19.5 11.1 10.8 11.1 11.1 19.0 8.7
GPS 7.1 20.3 11.3 11.0 11.0 11.9 20.0 7.4
40-50 5 GAL 7.0 20.7 11.4 10.8 11.4 11.4 20.4 6.9
GPS 5.6 21.3 11.6 11.1 11.0 12.4 21.4 5.6
15 GAL 4.6 22.4 11.7 10.7 11.6 11.8 22.2 5.0
GPS 3.4 22.7 12.1 11.2 10.8 12.7 23.6 3.5
0 GAL 10.0 17.4 12.0 10.4 11.1 12.1 17.1 9.9
GPS 8.9 17.6 12.3 11.1 11.1 12.4 17.3 9.3
50-60 5 GAL 8.6 18.2 12.3 10.5 11.4 12.6 17.8 8.6
GPS 7.1 18.5 13.0 11.4 11.4 13.0 18.3 7.3
15 GAL 4.0 20.7 13.6 11.4 12.2 14.1 20.3 3.7
GPS 2.7 20.3 14.6 12.2 12.3 14.3 20.9 2.7
__________________________________________________________________________________________________________
123
The distribution (in per cent) of satellite elevation
angles (H) in two latitude zones, 40–50°N and 50–
60°N (containing mentioned above waterways) for
both systems is presented in the Table 1. We
recapitulate that:
− the distributions of angle H values in all zones for
both systems are practically the same,
− for both systems in all zones about half of
satellites are visible below 30°, while the
percentage of satellites visible above 70° is less
than 10.
The distribution (in per cent) of satellite azimuths
for masking angle H
min
= 0°, H
min
= 5° and H
min
=
15° for both systems at different observer’s latitudes
is shown in the Table 2. We can say:
− distributions of satellite azimuths for both
systems are practically the same at given angle
H
min
,
− the number of satellites in different azimuth’s
intervals depends on the observer’s latitudes for
both systems,
− at latitudes 40°
to 60°, independently of H
min
,
the
number of satellites with azimuth from interval
315–045°
are for both systems less than from
intervals 045–090° and 270–315° considerably.
It means that position accuracy depends on river or
canal orientation and the form of shoreline. The
distributions in the tables 1 and 2 are the results of
the calculations made by using author’s simulating
program. The detailed results were presented among
other things in [Januszewski J. 2004] and
[Januszewski J. 2005].
Nowadays on inland waterways the 3D position
nevertheless can be obtained in almost all cases,
because the GPS spatial segment consists of 31
satellites fully operational.
3 SATELLITE BASED AUGMENTATION
SYSTEMS
The Satellite Based Augmentation Systems (SBAS)
as Wide Area Augmentation System (WAAS),
Multi-functional Transport Satellite Based
Augmentation System (MSAS) and European
Geostationary Navigation Overlay System (EGNOS)
are adequately accessible in USA, Canada, Japan
and Europe [Prasad R., Ruggieri M. 2005]. The C/A
codes used by all these systems belong to the same
family of 1,023-bit Gold codes as the 37 PRN codes
reserved by the GPS system.
The EGNOS system will provide three services:
− open service (free access but without guarantee),
− commercial data distribution (with guaranteed
service),
− safety of life (almost real time integrity), and this
service will be the most interesting for all users of
European inland waterways, certainly.
The EGNOS user segment is composed of a GPS
and/or GLONASS receiver and EGNOS receiver.
The two receivers are usually embedded in the same
user terminal. As the receiver can process the
message in a 6-second duty cycle the integrity time
to alarm is limited to the duty cycle time.
EGNOS will be fully operational in April 2009; it
is designed for a wide number of applications,
including transport on inland waterways. For the
users of European inland waterways the problem of
the visibility appears in the EGNOS system owning
to the three geostationary satellites (GEO) – two
operational: Inmarsat–3–F2 Atlantic Ocean Region–
East (AOR–E) and Inmarsat–3–F5 Indian Ocean
Region–West (IOR–W) located at longitudes
015.5
O
W and 025
O
E, respectively and one with
status industry test transmissions – Artemis at
021.5
O
E. The 3 current EGNOS C/A codes are 120,
126 and 124 respectively [Kaplan, E.D.,Hegarty,
C.J. 2006].
Due to the environment along the shoreline of the
rivers/canals, the risk of losing line-of-sight to GEO
satellites is quite high. Obstacles could be
mountainous terrain, high buildings, big bridges, or
other technical structures (e.g. harbour area, locks).
4 TERRESTRIAL RADIONAVIGATION
SYSTEMS
Terrestrial radionavigation system Loran C (Long
Range Navigation) is a low frequency electronic
position fixing system using pulsed transmissions at
100 kHz. Groundwave ranges of from 800 to 1200 n
miles are typical, depending upon transmitter power,
receiver sensitivity, and attenuation over the signal
path.
On European inland waterways two Loran C
chains (6731 and 7499) can be used with three lines
of positions: 6731−X, 6731−Z and 7499−X in
France and northwest Germany, in particular. As the
location of all European Loran C System
(Ex−NELS) transmitters are designed for the sea
user (Norway Sea and North Sea) first of all, this
system cannot be taken into account in the
navigation on great European rivers such as the
Rhine and Danube.
Eurofix is an integrated radionavigation and
communication system, which combines Loran C
and DGPS by sending differential satellite
corrections to users as time, modulated signal
information. At present four Ex−NELS, Boe and
Vaerlandet (Norway), Sylt (Germany), Lessay
(France), stations transmit Eurofix corrections only,
124
additionally the number of user’s receivers is very
small. That’s why this system cannot be used on
inland waterways.
5 AUTOMATIC IDENTIFICATION SYSTEM
Automatic Identification System (AIS) is a ship
borne radio data system continuously broadcasting
ship identification number (ID), its position, course
and speed, and other data to all nearby ships and to
shore side infrastructure on a common VHF radio
channel. On inland waterways, the data transmission
is based on the “Vessel Tracking and Tracing
Standard for Inland Navigation” published by the
Central Commission for the Navigation on the Rhine
(CCNR) and by the European Commission in 2007.
This standard describes the so called “Inland AIS”
which guarantees 100% compatibility with the mari-
time AIS system while extending AIS to the needs
of inland waterway transportation [Amlacher C. et
al. 2007].
Inland ships, which are equipped with AIS, can
utilize the information transmitted from other ships
by AIS to improve the traffic image surrounding a
traffic situation.
We can distinguish two different applications of
AIS in inland navigation:
− for navigation support on board,
− for traffic information and traffic management
services.
The AIS transponder as a key element for RIS
needs to be installed onboard ships, as well as in
base stations on shore. A transponder unit generally
comprises three main functional elements, of which
one is a Global Navigation Satellite System (GNSS)
module with the capability of applying differential
GPS or EGNOS corrections to the measurements
[Trögl J. et al. 2004].
Based on the data of AIS exchange, the
visualization of traffic information on an ENC, so
called Tactical Traffic Image (TTI) is enabled. This
TTI supports the skipper in his nautical maneuvers.
6 INTEGRATED SYSTEMS
Accuracy of the ship’s position is a functional
requirement for inland waterways operations.
However without integrity information the data
received from GPS system and/or DGPS system can
only be used with restrictions. Integrity is the ability
to provide users with warnings within a specified
time when the system should not be used for
navigation. Although this may be acceptable for
some users, it is not acceptable for other users.
The provision of integrity information by the
GPS constellation is however not foreseen in the
near future, because only the next generation’s
satellites block III is expected to provide, among
other things, a system integrity solution. Satellites of
the nearest block IIF will be without integrity.
Therefore, the need of integrity is evident.
Nowadays this kind of information can be obtained
from EGNOS, and in the future from Galileo. That’s
why information about the position and integrity can
be assured by the integrated systems with these two
systems mentioned above.
A discussion of the usefulness of Galileo system
for the inland waterways two planned services, Open
(OS) and Safety of Life (Sol), will be very
interesting for the users. Galileo will provide
increased performance through the use of dual (L1 +
E5a) or triple (L1 + E5a + E5b) frequency
observations as well as improvements in safety
through the provision of an integrity message.
− The five possible integrated systems and their
most important parameters are presented in the
Table 3. Let us discuss each parameter:
− GPS integrity. As this integrity is assured by the
system EGNOS, it takes place for all integrated
systems, except the combination GPS/Galileo,
− Galileo integrity. It is assured by all integrated
systems in which one of the systems is Galileo,
− improved RAIM (Receiver Autonomous Integrity
Monitoring); as above,
− redundant system; as above,
− redundant augmentation. It is assured by these
systems, in which the EGNOS corrections reach
the user’s receiver through AIS,
− system failure tolerance. It is assured by all
integrated systems in which one of the systems is
Galileo,
− robustness to interference; as above.
AIS DGPS provision is fully operational in
Austria, Slovakia has a pilot system in operation and
Bulgaria, Croatia, France, Hungary, Romania,
Serbia and Ukraine are currently preparing
implementation of similar systems [Amlacher C.,
Trögl J. 2008].
Several projects utilizing NSS, SBAS and AIS in
RIS are already realized in Europe with several more
prepared as follows.
6.1 GALEWAT project
The GALEWAT (Galileo and EGNOS for
Waterway Transport) project, founded by the
European Space Agency (ESA) Advanced Research
Telecommunications program ARTE–5, aims the
realization of a first step towards the introduction of
EGNOS and finally Galileo into the upcoming River
Information Services (RIS) all across Europe.
125
Table 3. The integrated systems and their parameters.
__________________________________________________________________________________________________________
Systems GPS Galileo Improved Redundant Redundant System Failure Robustness to
Integrity Integrity RAIM System Augmentation Tolerance Interference
__________________________________________________________________________________________________________
GPS, EGNOS SIS
GPS, EGNOS SIS,
EGNOS through AIS
GPS, Galileo
GPS, Galileo, EGNOS SIS
GPS, Galileo, EGNOS SIS,
EGNOS through AIS
Among others, the following topics are subject to
the GALEWAT project [Abwerzger C. et al. 2005]:
− identification of user requirements related to AIS
and EGNOS service parameters for transport
efficiency, waterway transport in particular,
− replacement of conventional RIS local differential
GPS stations by direct reception of the EGNOS
signal in shipboard transponders,
− bridging outages of the EGNOS SIS by
retransmitting the EGNOS differential corrections
and integrity data via AIS base stations in areas
without direct EGNOS reception,
− analysis and validation of EGNOS, integrated
into the AIS transponder concept, being capable
to meet the user and service requirements.
The GALEWAT is composed of five segments:
− ship, several ships, all equipped with standard
equipment (AIS transponders with GPS and
DGPS receivers), one additionally with extended
equipment which allows the position fixes in
different modes (GPS stand alone, GPS + IALA
DGPS, GPS + EGNOS SIS, GPS + EGNOS
AIS),
− shore, mainly comprises two AIS base stations
which must receive the EGNOS signal (with the
differential corrections) from GEO satellites and
then broadcast re–formatted EGNOS information
via the AIS data link,
− regional, terminals located nearby strategic
points, which are connected to several shore
elements to gather tactical traffic information of
the area,
− operator, e.g. national control center storing all
traffic information provided by RIS in a large
database,
− external, which consists fundamentally of web
interface where external users can retrieve
relevant traffic information of the area.
The public demonstrations of this system in
Vienna (Austria), Lisbon (Portugal) and Constanta
(Romania) have already been successfully executed.
6.2 MARGAL project
The MARGAL project, prepared by Kongsberg
Seatex (Norway) and eight European concerns, is
based on AIS technology to monitor vessels and to
deliver EGNOS differential corrections and integrity
warning to applications where direct reception signal
is not possible [Kristiansen K. et al. 2005].
This project is a harmonized and seamless
solution for maritime navigation for European ports
and inland waterways. The project MARGAL has
shown that changes to the actual version (2.3) of
RTCM message format and to the AIS handling of
message 17 (RTCM message) are needed to meet,
respectively, the accuracy requirements for new
services and the time to alarm requirements. The
current EGNOS and the future Galileo integrity
services can be utilized in operational applications
like remote pilotage and queue systems for ports and
locks [www.margal.net].
6.3 MUTIS project
MUTIS (Multimodal Traffic Information Services)
is a project within the ARTES (Advanced Research
in Telecommunications Systems) 3 program of ESA.
This project is aiming at the study of the feasibility
of the introduction of satellite based communication
LEO (Low Earth Orbit) into the upcoming RIS
across Europe [Trögl J. et al. 2004].
The demonstration within MUTIS will focus in
the Danube waterway from Vienna in Austria to
Constantia in Romania on the length of
approximately 1700 km. A vessel is equipped with
necessary facilities as EGNOS receiver, PC and
LEO & GSM communication. In this way the vessel
transmits every 15 minutes own position obtained
from GPS system and EGNOS system over a LEO
service provider to database & control station.
Position information and data from/to the vessel will
be transmitted to/from this station via several
channels:
− GSM as a terrestrial wireless system,
− GLOBALSTAR as “big LEO” satellites system,
− IRIDIUM as alone satellite system,
− THURAYA as a low-cost GEO satellite system.
6.4 MARUSE project
The MARUSE project, part of the EU 6
th
framework
programme, was realized in the years 2005–2007.
The main objective of this project is to demonstrate
126
Galileo differentiators and the benefits of using
Galileo and EGNOS in maritime and inland
waterways applications. The technology
development consists of two major elements: a user
terminal and a local infrastructure
[www.maruse.org].
One of four demonstrations took place at the
Danube Iron Gate I (two locks) in Serbia in June
2007. GPS differential corrections are transmitted
via the AIS data link (AIS Msg.17). The vessel is
equipped with a Maritime User Terminal utilizing a
standard AIS transponder augmented by a
GPS/GLONASS positioning element and a digital
compass for a determination of vessel heading. The
AIS transponder system is linked to an ECDIS
viewer providing the skipper with the TTI and the
integrity information. In the future the vessel’s
position will be fixed by a third NSS – Galileo
[Christiansen S.E. et al. 2007].
7 CONCLUSIONS
− the measurements realized within the framework
of several European projects showed the full
usefulness of SNS, SBAS and AIS on inland
waterways, particularity the great European rivers
Rhine and Danube,
− as the distribution of satellite azimuths of each
SNS depends on observer’s latitude, the position
accuracy of the ship sailing with high river coast
on both sides depends on its geographic location
also,
− the results obtained from measurements using
EGNOS signals (GALEWAT project) showed
that GPS augmented by EGNOS from SIS can be
a good candidate for inland waterway safety–
critical applications with required accuracy below
10 m, high system availability, and protection
level below 25 m,
− the use of AIS to broadcast EGNOS data
(GALEWAT project) is not introducing any
significant degradation of performance compared
to the EGNOS performance directly obtained
with the SIS (DoRIS project),
− IALA DGPS reference stations situated today at
seashore first of all can be installed and used
inland, e.g. four stations already installed in
Germany,
− the actual projects, e.g. MARGAL, MARUSE,
include the implementation of software defined
vessel’s receivers making a smooth transition
from EGNOS to Galileo possible,
− integrity of the systems built around and the
needs of inland navigation can be assured by
these integrated systems only, one of which is the
present EGNOS system, and in the future Galileo
system also.
REFERENCE
Admiralty List of Radio Signals. 2008/09. The United Kingdom
Hydrographic Office, vol.2.
Abwerzger, G. et al. 2005. Galileo and EGNOS for Waterway
Transport – The GALEWAT Project, The European
Navigation Conference GNSS 2005, Munich.
Amlacher, C. et al. 2007. Evolution of Positioning Services for
Inland Waterways, European Journal of Navigation, vol. 5,
no 4.
Amlacher, C., Trögl J. 2008. Experiences with DGNSS
provision for River Information Services, The European
Navigation Conference GNSS 2008, Toulouse.
Christiansen, S.E. et al. 2007. Introduction of Galileo in
Maritime and Inland Waterway Applications, The
European Navigation Conference 2007, Geneva.
Hoppe, M., Bober, S. & Rink, W. 2005. DGNSS Service for
Telematic Applications on Inland Waterways, 18
th
ION
GNSS, Long Beach.
Januszewski, J. 2004. Terrestrial and Satellite Radionavigation
Systems in Maritime Area, The European Navigation
Conference GNSS 2004, Rotterdam.
Januszewski, J. 2005. Geometry and Visibility of Satellite
Navigation Systems in Restricted Area, Institute of
Navigation, National Technical Meeting, San Diego (CA).
Januszewski, J. 2007. Modernization of satellite navigation
systems and theirs new maritime applications.
TransNav’2007, Gdynia.
Kaplan, E.D. & Hegarty, C.J. 2006. Understanding GPS
Principles and Applications, Artech House,
Boston/London.
Kristiansen, K. et al. 2005. Introduction of Galileo in Maritime
Applications – The MARGAL Project, The European
Navigation Conference GNSS 2005, Munich.
Prasad, R.& Ruggieri, M. 2005. Applied Satellite Navigation
Using GPS, Galileo, and Augmentation Systems. Artech
House, Boston/London.
Spaans, J. ENC-GNSS 2008, The European Navigation
Conference, European Journal of Navigation, vol. 6, no 2.
Trögl, J. et al. 2004. EGNOS and LEO for Telematics
Applications in the Inland Waterway Segment – Project
MUTIS, The European Navigation Conference GNSS 2004,
Rotterdam.
www.iris-europe.net
www.maruse.org
www.margal.net
