International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 1

Number1

March 2007

Modernization of Satellite Navigation Systems

and Theirs New Maritime Applications

J. Januszewski

Gdynia Maritime University, Gdynia, Poland

ABSTRACT: The last years gave a rise to many important changes in the operational status and practical

exploitation of satellite navigation systems (SNS) GPS & GLONASS, differential mode of these systems

(DGPS, DGLONASS) and Satellite Based Augmentation Systems (SBAS) as EGNOS or WAAS. Therefore

the modernization of these systems as new satellites, new civil signals, new codes, new monitoring stations

etc. and the details about new systems under construction as Galileo, Compass and IRNSS, the problem of

interoperability and new maritime applications are presented in this paper.

1 SATELLITE NAVIGATION SYSTEMS

TODAY AND IN THE FUTURE

The last years gave a rise to many important changes

in the operational status and practical exploitation of

satellite navigation systems GPS and GLONASS, in

particular, differential mode of these systems and

Satellite Based Augmentation Systems. These chan-

ges include improvements to the ground support seg-

ment, and augmentation to provide differential servi-

ces and to support Search and Rescue (SAR) service.

1.1 GPS system

GPS system consists of three segments: the Space

Segment, the Operational Control Segment (OCS)

and the User Segment.

The current (March 2007) GPS constellation

consists of 30 satellites under Full Operational

Capability (FOC) – 15 Block IIA, 12 Block IIR and

3 Block IIR–M. Satellite PRN24/SVN24 is usable

since August 30, 1991; nearly 16 years ago!

The first satellite, GPS Block IIR–M,

PRN17/SVN53, incorporating civil code C at L2

and, a modernized military signal with enhanced

security the M–code at L1 & L2, has been operating

since December 16, 2005. For the first time the new

M−code was successfully acquired and tracked by

Raytheon Company of El Segundo, California; this

news was announced November 6, 2006. The M–code

provides enhanced accuracy, encryption, and anti–

jamming capability for authorized users.

The next 5 satellites IIR–M will be launched in

2007 or later.

After Block IIR–M the “follow–on” satellites will

be Block IIF. The IIF spacecrafts will broadcast the

same 6 signals, which are transmitted by current

Block IIR–M satellites and additionally a new third

civil signal at 1,176.45 MHz (L5 carrier). The first

GPS Block IIF satellite can be launched in 2008.

The Block IIF SV is designed for a life of 12

years with a mean mission duration (MMD) of 9.9

years, its autonomous operations are for up to 60

days, body dimensions: 248 x 202 x 178 cm, other

parameters – increased disposal capability, uplink

rate 1 or 2 kbps, downlink data rate: up to 1.9 Mbps.

In OCS the satellite signals are tracked from six

U.S. Air Force monitor stations and from six

monitor stations operated by the National

Geospatial–Intelligence Agency (NGA) of the

Department of Defence. Boeing has successfully

completed live demonstration of a newly architected

six Air Force monitor stations, which, when fully

operational, will control the 32 GPS satellites now in

orbit as well as that will join the fleet in the coming

months.

The twelve–station network allows the system

operators to watch each satellite from at least two

monitor stations at all times. Five more NGA–

operated monitor stations will be added to the actual

network in the future (Misra, P & Enge, P. 2006).

Satellite IIF upgrade will be compatible with OCS

architecture. After modernization this segment will

be characterized by the following parameters: total

constellation space vehicle contract available using

crosslinks, time accuracy offset reduced, enhanced

navigation planning capability, 50% reduction in

operator workload, comprehensive maintenance and

support infrastructure. Boeing is building 12 GPS

Block IIF satellites under contract from the GPS

Wing, U.S. Air Force Space and Missile Systems

Center, and expects to deliver the first satellite in

2007 or later.

The GPS III program was conceived to reassess

the entire GPS architecture as it has involved to its

present state and determine the correct architecture

to lead into the future. This program has two main

goals: reduce the government’s total ownership costs

and provide sufficient architectural flexibility to

satisfy evolving requirements through 2030. GPS III

with the next generation satellites is expected to

provide significant increase in position, velocity and

time (PVT) accuracy, high level of continuity and

signal availability, greater timing accuracy, a system

integrity solution (GPS II is without integrity service),

autonomous navigation, a high data capacity

intersatellite crosslink capability, and higher signal

power to meet military antijam requirements.

The GPS III satellite constellation characteristics

are not defined yet. Two ongoing studies are

exploring two different solutions: an innovative

three–plane constellation (as in GLONASS and

Galileo systems) and the traditional six–plane

constellation used in the current GPS. The first GPS

III satellite launch is planned for year 2013 or later

and Full Operational Capability for year 2030

(Kaplan, E.D. & Hegarty, C.J. 2006).

According to a different unofficial source,

SVN23, an old Block IIA satellite decommissioned

in 2004, might be recommissioned as PRN32. This

may seek to test the ability of current GPS receivers

to handle more than 31 PRN numbers. PRN code 32

is permitted but has not been used since 1993.

1.1.1 Differential mode

As existing GPS and GLONASS could not fulfil

all institutional and technical demands, the maritime

administrations of the countries all over world have

implemented a radiobeacon DGNSS service to

improve safety and efficiency of navigation in their

coastal waters. It was necessary to expand the

existing radiobeacon network at the coast with

additional stations to cover all inland waterways.

That’s why the number of beacons (stations)

transmitting DGPS corrections has been increased in

last years considerably (Table 1). In 2001 there were

138 beacons with status operational, 80 with status

on trial, 15 planned, in 2006 these numbers were

234, 57 and 11 adequately. At present the beacons

are localized in 41 countries, the greatest number of

beacons operational are in USA (39), Japan (27),

China (21), and India (19); Table 2. Additionally 6

stations are without status, e.g. Jaroslawiec in Poland

(position, frequency of DGPS corrections,

identification number of transmit station, and

nominal range only). In Europe there are 73

operational and 25 on trial maritime differential

beacons (ALRS. 2001–2006).

Table 1. The numbers of stations transmitting DGPS

corrections in the period 2001÷2006 [1]

Year

(volume)

Number of stations

Operational On trial Planned Total

2001 (8)

138

233

2002 (8)

162

244

2003 (2)

189

288

2004 (2)

208

288

2006 (2)

234

302

Until recently, there was only one set of RTCM

Special Committee 104 messages to support both

code and carrier–based Local–Area DGPS services.

This message set has evolved over time (1.0, 2.0,

2.1, 2.2); version 2.3 (published in 2001), is the most

recent.

In February 2004 SC–104 has published the latest

edition of its version, called 3.0 for differential

Global Navigation Satellite System (GNSS)

services. This standard supports very high accuracy

navigation and positioning through a broadcast to

mobile GNSS receivers, which allows the receivers

to compensate for errors that exist in satellite

positioning without augmentation. This latest edition

includes an interoperable definition for Network

Real–Time Kinematic (Network RTK).

1.2 GLONASS system

As with GPS, GLONASS is on the way to

modernization of the system. Apart from the signals

in the L1 band, GLONASS system has already

established a second civil signal at L2 upon launch

of the first GLONASS–M satellite in 2003. Three

last satellites GLONASS–M, 715, 716 and 717, were

launched December 25, 2006. These satellites are

placed on orbit II. A third civil signal at L3 band

(1,190–1,212 MHz range, near GPS L5), is expected

to start in 2008 aboard GLONASS–K satellites. In

addition to transmitting navigation–message data,

the two new signals will also transmit GLONASS

integrity and GLONASS wide–area differential

correction information to enhance the accuracy and

reliability of the navigation services (Kaplan, E.D. &

Hegarty, C.J. 2006).

The current GLONASS status is far away from its

nominal numbers (24) because the actual (March

2007) GLONASS constellation consists of 9

satellites under Full Operational Capability (FOC).

10 additional space vehicles are on orbit but have

been temporarily switched off and are currently not

broadcasting any signals (www.glonass-ianc.rsa.ru).

Russian officials predict that GLONASS system

performance will equal that of GPS system by 2008

with 18 satellite constellation and the frequency of

launches would increase over the next years to

provide a 24 satellite constellation and Full

Operational Capability (FOC) by 2010−2011.

Russia’s president Putin decreed on 18 January 2006

to speed up the GLONASS program and made

additional budgets available.

Table 2. The numbers of stations transmitting DGPS

corrections in different countries in 2006 (ALRS. 2001–2006)

Country

Station status

Total

Operational

On trial

Planned

Australia

–

Canada

–

China

–

India

–

Japan

–

Norway

–

Spain

USA

1.3 Galileo system

The European Commission, together with the

European Space Agency (ESA) and European

industry, is building up a European Satellite

Navigation System under name Galileo. This system

will be controlled by civil authorities and be inter–

operable with GPS and GLONASS. It will provide

real–time position-ing and timing services at

different levels of accuracy, integrity, and

availability. Other than existing satellite navigation

systems, Galileo is suitable system for safety critical

applications, such as landing aircraft, guiding cars,

tracking hazardous materials, and controlling rail

traffic (Seeber, G. 2003).

Construction of the first of the two Galileo

ground control centers at Oberpfaffenhofen, near

Munich, in Germany, began on November 7, 2006.

The 16 milion euro complex will employ 100

engineers and controllers. The second center will

situated at Toulouse in France.

Galileo plans to provide four types of navigation

services and a search and rescue service (p.4.2):

− Open Service (OS): Accessible to all without user

fees; like GPS Standard Positioning Service

(SPS), but claimed to be better. The OS will

provide positioning, velocity, and timing

information, this service is suitable for mass–

market applications, such as in car navigation, is

also suitable with integration in mobile tele-

phones;

− Commercial Service (CS): Fee based service

offering assured level of performance, including

service availability;

− Public Regulated Service (PRS): Fee based

service intended for government agencies and

military applications requiring a higher level of

protection. Controlled access (the PRS signals

will be encrypted, authorized users only) with

high integrity and availability, and interference–

resistant signals;

− Safety of Life (SoL): Fee based service aimed at

transport applications with high integrity.

Authentication of signal, certification and

guarantee of service, to comply with the

requirements of the IMO and International Civil

Aviation Organization (ICAO).

At present the first Galileo test satellite, GIOVE–

A, is in orbit, with control administrated through its

manufacturer’s – Surrey Satellite Technology Ltd. –

headquarters in Guildorf, United Kingdom. Launch

of the second test satellite, GIOVE–B, is now set for

2007. The Galileo In–Orbit Validation (IOV) phase

is planned to start at the end of 2008 with four

satellites and achieve FOC in 2012.

Galileo is not yet in operation but already the so–

called evolution program for the second generation

is planned to start in 2007 or later. Galileo II could

arrive somewhere around 2020 and is expected to

introduce new modernization elements analogous to

the steps made by its counterparts GPS and

GLONASS (Hein, G. et al. 2007).

1.4 Compass system

Compass is the SNS planned in China. The will of

this country is to develop own global navigation

system. This system will provide two navigation

services: an open service for commercial customers

and an “authorized” positioning, velocity, and timing

communications service. Spatial segment will

consist of 27 MEO, 3 Geosynchronous (GSO) and 5

GEO satellites.

Each satellite transmits the same four carrier

frequencies for navigational signals. These signals

are modulated with a predetermined bit stream,

containing coded ephemeris data and time, and

having a sufficient bandwidth to produce the

necessary navigation precision without recourse to

two–way tran-smission or Doppler integration.

The three GEO satellites (080°E, 110°E, 140°E)

were placed into orbit between 2000 and 2003. The

launch of two last GEO (058.75°E, 160°E)

scheduled for early in 2007, is expected to cover

China and parts of neighboring countries by 2008,

before being expanded into global system.

The first version of Compass was called Beidou.

Compass can be operational in 2012 if the political

statements are brought into reality (Hein, G et al.

2007), (Kaplan, E.D. & Hegarty, C.J. 2006).

2 REGIONAL AND SATELLITE–BASED

AUGMENTATION SYSTEMS

In addition to the mentioned above global satellite

navigation systems two regional systems are also

being developed by Japan and India, QZSS and

IRNSS respectively:

− Quasi–Zenith Satellite System (QZSS) will serve

as enhancement for GPS. The constellation

consists of three satellites inclined in elliptic

orbits with different orbital planes in order to pass

over the same ground track. QZSS and GPS will

be fully interoperable, the first QZSS satellite will

be launched in 2008;

− Indian Radionavigation Satellite System (IRNSS)

is an independent seven satellites constellation

that will be built and operated by India. This

system will seek to maintain compatibility with

other GNSS and augmentation systems of the

region and is planned to provide services for

critical national applications.

Nowadays Satellite Based Augmentation Systems

(SBAS) are the following:

− the European Geostationary Navigation Overlay

Service (EGNOS) would supplement GPS (and

perhaps GLONASS in the future) by reporting on

the reliability and accuracy of the signals. The

system started its initial operations in July 2005,

and is intended to be certified for use in safety of

life applications in 2008;

− the Wide Area Augmentation System (WAAS)

augments GPS over North American territory to

provide the additional accuracy, integrity, and

availability needed to enable users to rely on GPS

for safety–critical applications;

− the Multifunctional Transport Satellite Augmen-

tation System (MTSAT) in Japan is used for

meteorological observations and communication

services following a multi–mission concept. Two

satellites were launched in 2005 and 2006;

− GAGAN. The GPS and GEO Augmented Navi-

gation system is India’s SBAS for the south Asian

region. This system is under construction.

GAGAN will eventually expand into IRNSS;

− NIGCOMSAT. With its Nigerian Communica-

tions Satellite, Nigeria is the first African country

planning to enter the field of GNSS by

transmitting two L–band signals in L1 and L5;

(Kaplan, E.D. & Hegarty, C.J. 2006).

3 SATELLITE NAVIGATION SYSTEMS

INTEROPERABILITY

In the agreement on the promotion, provision and

use of Galileo and GPS satellite–based navigation

systems and related applications signed by United

States of America and European Community summit

on June 26, 2004 in Ireland among other things we

can read that both parties recognize that:

− the US operates a satellite–based navigation sys-

tem known as GPS, a dual use system that pro-

vides precision timing, navigation, and position

location signals civil and military purposes,

− the European Community is developing and plans

to operate a civil global satellite navigation, tim-

ing and positioning system, Galileo, which would

be radio frequency compatible with GPS and in-

teroperable with civil GPS services at user level,

− civil GPS and Galileo, if radio frequency com-

patible and interoperable at the user level, could

increase the number of satellites visible from any

location on the Earth,

− the International Maritime Organization (IMO)

established international standards and other

guidance applicable to the use of global SBAS for

maritime navigation.

Table 3. Comparison of satellite navigation systems

Parameter GPS GLONASS Galileo

time base

GPS system time

GLONASS system time

Galileo system time

related system time

UTC

USNO

UTC

TAI

geodetic datum

WGS–84

PZ–90

GTRF

satellite signal division

CDMA

FDMA

CDMA

The Russian government has stated that, like GPS

system, GLONASS is a dual–use system and there

will be no direct user fees for civil users. Russia are

working with the European Union and the United

States to achieve compatibility between GLONASS

& Galileo and GLONASS & GPS, respectively. As

in the case with GPS/Galileo interoperability, key

elements to achieving interoperability are compatible

signal structure, geodetic coordinate reference frame,

and time reference frame (Table 3).

Nowadays GPS and GLONASS are not interop-

erable, even if there are GPS and GLONASS inte-

grated receivers on the market, e.g. Javad Navigation

System Gyro–4T, NovAtel OEMV–2–RT2. The first

has 20 channels and its signal tracked are L1/L2

GPS, L1/L2 GLONASS and WAAS, while the

second can have 72 channels, signal tracked are L1

C/A, L2C, carrier phase (CP), L1 and L2

GLONASS, SBAS (GPS Receiver Survey. 2007).

These receivers look like a unique “box” to the

user, but the truth is that there are two parallel

receivers, which process separated signals and

combine them in a manner that potentially still

improves user performance. As GLONASS signal

uses FDMA technology while GPS and Galileo use

CDMA signals a very intriguing memo regarding

GPS–GLONASS interoperability has appeared

recently. At the September 2006 meeting of the ION

GNSS Russian Federal Space Agency (RFSA) spoke

of CDMA as an “option” for GLONASS and added

the system “probably will be able to implement

CDMA signals” on the new third frequency, to be

added on GLONASS–K satellites during Phase 3 of

GLONASS modernization, and at L1. Receiver

operation in the GPS and Galileo mode is simpler

with CDMA. A GLONASS switch to CDMA would

make manufacture of combined receivers far easier.

The EU–U.S. agreement will allow precise

estimation of the Galileo/GPS time offset and

inclusion of it in each system’s navigation message.

The accuracy of this time offset modulo 1 second is

specified to be less than 5 ns with 2–sigma

confidence interval over any 24–hour period

(Kaplan, E.D. & Hegarty, C.J. 2006).

4 MARITIME APPLICATIONS

Marine navigation was the first to embrace satellite

navigation. Nowadays its market is maturing,

additionally it is not the largest market segment.

4.1 GPS system

Along with radios and radar, a GPS receiver is a

piece of standard equipment on any ship operating

far from shore. The number of GPS receivers

installed on the board depends on the different ship’s

parameters (type, deadweight, region of navigation

etc.) and can be equal 1, 2, 3 or even 4.

In Federal Radionavigational Plan published in

December 2005 we can read that the United States

Coast Guard is exploring accuracy enhancement and

the integration of Nationwide Differential Global

Positioning Service (NDGPS) with other navigation

sensors. Particular emphasis is being placed upon the

integration of NDGPS with Inertial Navigation

Systems (INS). Efforts are being conducted to

determine the ability of INS to enhance GPS/DGPS

navigation service, and to provide heading

information for ECDIS use. Increasing numbers of

WAAS receivers have emerged in the public market

place and are being used in the maritime regions.

Additionally the Coast Guard is developing a set of

analysis tools to allow performance evaluations of

navigation systems as GPS system, in particular, in

specific ports and waterways (FRP Plan 2005).

Automatic Identification System (AIS) is a

shipboard transponder system in which ships

continually transmit data to all other nearby ships

and shoreside authorities. AIS utilizes a unique self–

organizing ti-me–division multiple access (STDMA)

data communications scheme, which uses the precise

timing data in the GPS signals to synchronize

multiple data transmissions from many users on a

single narrowband channel. The time reference is

supplied by the precise timing in the GPS satellite

message. Thus GPS plays a critical role in AIS,

providing the time reference as well as positioning

data for each ship.

GAPS is a unique Global Acoustic Positioning

System based on Ixsea Oceano’s mastery of Inertial

Navigation System and acoustic Chirp modulation

techniques. For the first time, Acoustic, Inertial and

GPS measurements are merged in single process in a

common housing and provide an all–in one solution

(without external computer) for among other things

precise positioning of several underwater vehicles

and robust treatment of GPS drop–out and

insensitivity to GPS jumps. As GAPS is able to

position a subsea target fitted with any industry

standard transponder beacon, it can accept input

from any alternative GPS receiver (DGPS or RTK).

Accuracy is about 0.2 % of slant range.

The long period gravity wave measurement

system with arrayed buoys equipped with the

kinematic GPS is proposed, which provides the

precise propagational direction of the long period

gravity wave. New method for measurement wave

height and direction by installing point positioning

GPS receiver on a buoy placed in the open sea was

proposed in Japan. The scientists have showed that

the propagation direction of the wave could be

estimated accurately by applying the Multiple Signal

Classification method to the wave signal on the basis

of simulation and observation results when the

observation buoys installed with the GPS system

were arrayed in the double–triangle with this system

arrayed in the double–triangle formation and the

wave height could be measured in millimetre level.

The measurements were realized in Osaka Bay

(Fujii, H. et al. 2003).

Many Ports and Harbors around the world are

experiencing tremendous growth and the number

and size of ships is increasing dramatically. Modern

ships have sophisticated bridge electronic systems

including radar, satellite and terrestrial navigation

systems and other navigation tools. Older ships may

have limited navigation equipment or the equipment

may not be working properly. Consequently harbor

pilots around the world often carry on their own

portable units with electronic chart displays. That’s

why a highly accurate positioning and heading

system suitable for both portable and permanent

installations, called PilotMate, was developed in

USA, for the Port of Long Beach (CA), in particular.

Determination of a ship’s position is based on DGPS

or KDGPS technologies. PilotMate system achevies

a position accuracy of better than 3 m. This allows

for accurate presentation of the position and

orientation of a ship, regardless of whether it is

moving forward, astern, sideways, or is dead in the

water (Gilow, G. et al. 2003).

4.2 Galileo system

The efficiency, safety and optimisation of marine

transportation are key issues. Satellite navigation is

becoming a fundamental tool for bringing innovation

and progress this sector and many other marine

activities such as fishing, oceanography and oil and

gas exploitation will also benefit from the

availability of Galileo services.

The Galileo system also contributes to the

international search and rescue service, enhancing

the worldwide performance of the current COSPAS–

SARSAT system. The actual positioning accuracy is

rather poor (typically about few kilometres) and

alerts are not always issued in real time. The Galileo

search and rescue service (SAR) will drastically

reduce the Time To Alert (from hour to minutes),

and the position of the distress beacon from

anywhere cross the globe will be determined to

within a few metres. So far restricted to a

professional type user community, there are some

200,000 COSPAS–SARSAT beacons in existence

today. It has been shown that the market will rapidly

grow to a few million beacons after the advent of

Galileo.

Therefore the Galileo SAR services will provide

enhanced service offerings, among other things, with

significant improvements (Kaplan, E.D. & Hegarty,

C.J. 2006):

− reduced detection, localization, and confirmation

delay,

− multiple satellite coverage to avoid terrain

blockage in severe conditions,

− new return–link service from Rescue

Coordination Center to the distress–emitting

beacon, thereby facilitating the rescue operations

and helping to identify and reject the false alarms,

− forward link via stand–alone payload,

− return link integrated into navigation messages on

L1, uplinked by the Galileo Ground Segment.

Finally this service will fulfill the requirements

and regulations of IMO, via the detection of

emergency position indicating radio beacons

(EPIRB) of GMDSS of ICAO via the detection of

emergency location terminals (ELT).

New project on maritime navigation, called

MARUSE, developed by Kongsberg, was presented

in 2006. The aim of this project is to introduce

Galileo and EGNOS in the maritime domain.

Demonstrations are held and planned for harbour

approach including docking, inland waterways and

intermodal transport. The key technical development

activities within MARUSE will be among other

things Maritime Galileo pseudolites, Galileo/GNSS

receiver prototype capable of tracking GSTB–V2

signal and Galileo Pseudolites (Spaans, J. 2007).

4.3 GLONASS system

The Russian government plans to add a new SAR

payload to the new GLONASS–K satellites. The

payload will relay the 406 MHz SAR beacon

transmissions that are designed to work with the

currently deployed COSPAS–SARSAT system. This

payload is similar in design and concept to the

payload planned for Galileo system (Kaplan, E.D. &

Hegarty, C.J. 2006).

5 CONCLUSIONS

− the GPS new civil signals, L2C and L5, will

provide many advantages, such as higher signal

strength, lower cross correlation, and improved

support for high sensitivity indoor applications;

− the Russian government are working with

European Union and United States to achieve

compatibility between GLONASS and Galileo,

and GLONASS and GPS, respectively;

− interoperability and effective synergy between the

GPS and Galileo systems is the key to a bright

future for satellite navigation;

− modernized system GPS, new systems Galileo

and Compass, and the increasing of the number of

GLONASS satellites will provide the new

possibility for the users, positioning in restricted

area and maritime applications, in particular.

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