African Satellite

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Telecommun Syst (2013) 52:121137DOI 10.1007/s11235-011-9464-x

Development and characteristics of African SatelliteAugmentation System (ASAS) network

D.S. Ilcev

Published online: 15 June 2011 Springer Science+Business Media, LLC 2011

Abstract This paper reports on an African Satellite Aug-

mentation System (ASAS) Space and Ground Segments asan integration part of Global Satellite Augmentation Sys-

tem (GSAS) for enhanced Traffic Control and Management

(TCM) globally at sea, on the ground (road and railway ve-

hicles) and in the air. The ASAS network can be used as

solely systems for covering and providing TCM and Safety

and Security service for entire African Continent and Mid-

dle East region, according to the International Maritime Or-

ganization (IMO), its Global Maritime Distress and Safety

System (GMDSS) and International Civil Aviation Orga-

nization (ICAO) recommendations and requirements. Since

1995 few commercial Regional Satellite Augmentation Sys-

tem (RSAS) networks have been projected and developed toutilize Communication, Navigation and Surveillance (CNS)

service for Maritime Traffic Control (MTC), Land Traffic

Control (LTC) and Air Traffic Control (ATC), including for

improved Safety and Security in all transportation systems.

The proposed Space Segment of Geostationary Earth Orbit

(GEO) constellation and Ground Segment of ASAS network

are discussed, and areas examined where further investiga-

tions are needed. Specific issues related to these challenges

are concluded and a set of solutions is proposed to maxi-

mize the availability of ASAS network capacity to the user

applications.

Keywords ASASGSASCNSRSAS GEOGNSS

GPSGLONASSWAASEGNOSMSASCNSO

SDCM SNASGAGANTABGMSGCSGES

LSASCMGCSMGC

D.S. Ilcev ()Mangosuthu University of Technology (MUT), 133 Bencorrum,183 Prince Street, Durban 4001, South Africae-mail:[email protected]

Acronyms

ADSS Automatic Dependent Surveillance SystemASS Augmentation Standards Service

ASTB African Satellite Test Bed

ATC Air Traffic Control

AVAS African VHF Augmentation System

CES Coast Earth Station

CMGC Coastal Movement Guidance and Control

CNS Communication, Navigation and Surveillance

CNSO Civil Navigation Satellite Overlay

CRS Coast Radio Station

DC Differential Corrections

DC Differential Corrections

DGPS Differential GPS

DME Distance Measuring Equipment

DOP Dilution of Precision

DSC Digital Selective Call

DST Department of Science and Technology

DST Department of Science and Technology

EGNOS European Geostationary Navigation Overlay

System

FAA Federal Aviation Administration

GAGAN GPS/GLONASS and GEOS Augmented

Navigation

GAS Ground Augmentation System

GBAS Ground-based Augmentation System

GCS Ground Control Stations

GEO Geostationary Earth Orbit

GES Ground Earth Station

GIC GNSS Integrity Channel

GMDSS Global Maritime Distress and Safety System

GMS Ground Monitoring Station

GNSS Global Navigation Satellite System

GRS Geostationary Ranging Station

GRS Ground Radio Station
mailto:[email protected]:[email protected]


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122 D.S. Ilcev

GSAS Global Satellite Augmentation System

ICAA Integrity, Continuity, Accuracy and

Availability

ICAO International Civil Aviation Organization

IGP Ionospheric Grid Points

ILS Instrument Landing System

IMO International Maritime Organization

LAA Local Augmentation Area

LAS Local Augmentation System

LGS Light Guidance System

LSAS Local Satellite Augmentation System

LTC Land Traffic Control

LVAS Local VHF Augmentation System

MSAS MTSAT Satellite-based Augmentation System

MTC Maritime Traffic Control

NDB Non-Directional Beacons

NMS Navigation Management System

NPA Non-Precision Approach

NSI National Space Institute

PA Precision Approach

PVT Position, Velocity and Time

RAIM Receiver Autonomous Integrity Monitoring

RCS Radar Control Station

RDDI Radio Direction Distance Information

RDI Radio Direction Information

RFP Request for Proposal

RGIC Ranging GIC

RR Reference Receiver

RSAS Regional Satellite Augmentation System

Rx Receivers

SBAS Satellite-based Augmentation System (ICAO

nomenclature)

SDCM System of Differential Correction and

Monitoring

SMGC Surface Movement Guidance and Control

SNAS Satellite Navigation Augmentation System

TAB Transport Augmentation Board

TCC Traffic Control Centers

TCM Traffic Control and Management

TCS Terrestrial Communication SubsystemTTN Terrestrial Telecommunication Networks

VHF Very High Frequency

VOR VHF Omnidirectional Ranging

VPR Voice Position Reports

WAA Wide Augmentation Area

WAAS Wide Area Augmentation System

WADGNSS Wide Area Differential GNSS

WMS Wide Master Station

WRS Wide Reference Station

1 Introduction

The first generation of the Global Navigation Satellite Sys-

tem (GNSS) infrastructure are represented by old funda-

mental solutions for Position, Velocity and Time (PVT) of

the satellite navigation and determination systems such as

GPS and GLONASS for the US or Russian (former-Soviet

Union) military requirements, respectively. The GPS andGLONASS are first generation of GNSS-1 infrastructures

giving positions to about 30 metres, using simple GPS re-

ceivers onboard chips or aircraft, and they therefore suffer

from certain weaknesses, which make them impossible to be

used as the sole means of navigation for ships, particularly

for land (road and railway vehicles) and aviation applica-

tions. In this sense, technically GPS or GLONASS GNSS-1

systems used autonomously are incapable of meeting civil

maritime, land and especially aeronautical mobile very high

requirements for integrity, position availability and determi-

nation precision in particular and are insufficient for certain

very critical navigation and flight stages [7,9].Because these two systems are developed to provide

navigation particulars of position and speed on the ships

bridges or in the airplane cockpits, only captains of the ships

or airplanes know very well their position and speed, but

people in Traffic Control Centers (TCC) cannot get in all

circumstances their navigation or flight data without ser-

vice of new CNS facilities. Besides of accuracy of GPS

or GLONASS, without new CNS is not possible to pro-

vide full TCM in every critical or unusual situation. Also

these two GNSS systems are initially developed for military

utilization only, and now are also serving for all transport

civilian applications worldwide, so many countries and in-ternational organizations would never be dependent on or

even entrust peoples safety to GNSS systems controlled

by one or two countries. However, augmented GNSS-1 so-

lutions of GSAS were recently developed to improve the

mentioned deficiencies of current military systems and to

meet the present transportation civilian requirements for

high-operating Integrity, Continuity, Accuracy and Avail-

ability (ICAA). These new operational CNS solutions are

the US Wide Area Augmentation System (WAAS), the Eu-

ropean Geostationary Navigation Overlay System (EGNOS)

and Japanese MTSAT Satellite-based Augmentation System

(MSAS), and there are able to provide CNS data from mo-biles to the TCC.

These three RSAS are integration segments of the GSAS

network and parts of the interoperable GNSS-1 architec-

ture of GPS and GLONASS and new GNSS-2 of the Eu-

ropean Galileo and Chinese Compass, including Inmarsat

CNSO (Civil Navigation Satellite Overlay) and new project

of ASAS infrastructure. The additional three GNSS-1 net-

works in development phase are the Russian System of Dif-

ferential Correction and Monitoring (SDCM), the Chinese


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Development and characteristics of African Satellite Augmentation System (ASAS) network 123

Fig. 1 GSAS networkconfiguration. Courtesy ofmanuscript for book:Aeronautical CNS by Ilcev [9]

Satellite Navigation Augmentation System (SNAS) and In-dian GPS/GLONASS and GEOS Augmented Navigation

(GAGAN). Only remain something to be done in South

America and Australia for establishment of the GSAS in-

frastructure globally, illustrated in Fig.1.

The RSAS networks are based on the GNSS-1 signals for

augmentation, which evolution is known as the GSAS net-

work and which service provides an overlay function and

supplementary services. The future ASAS Space Segment

will be consisted by existing GEO birds, such as Inmarsat-

4 and Artemis or it will implement own satellite constella-

tion, to transmit overlay signals almost identical to those of

GPS and GLONASS and provide CNS service. The SouthAfrican firm IS Marine Radio, as designer of the Project will

have overall responsibility for the design and development

of the ASAS network with all governments in the region.

2 GNSS applications

The RSAS infrastructures are available globally to enhance

current standalone GPS and GLONASS system PVT perfor-

mances for maritime, land (road and railway) and aeronau-

tical transport applications. User devices can be configured

to make use of internal sensors for added robustness in thepresence of jamming, or to aid in vehicle navigation when

the satellite signals are blocked in the urban canyons of

tall city buildings or mountainous environment. In the simi-

lar sense, some special transport solutions, such as maritime

and especially aeronautical, require far more CNS accuracy

and reliability than it can be provided by current military

GPS and GLONASS GNSS-1 space infrastructures [9,10].

Moreover, positioning accuracy can be improved by re-

moving the correlated errors between two or more satellites

GPS and/or GLONASS Receivers (Rx) performing rangemeasurements to the same satellites. This type of Rx is in

fact Reference Receiver (RR) surveyed in, because its geo-

graphical location is precisely well known. In such a man-

ner, one method of achieving common error removal is to

take the difference between the RR terminals surveyed posi-

tion and its electronically derived position at a discrete time

point. These positions differences represent the error at the

measurement time and are denoted as the differential cor-

rection, which information may be broadcast via data link

to the user receiving equipment. In this case the user GPS

or GLONASS augmented Rx can remove the error from its

received data.Alternatively, in non-real-time technique GNSS solu-

tions, the differential corrections can be stored along with

the users positional data and will be applied after the data

collection period, which is typically used in surveying ap-

plications [8].

If the RR or Ground Monitoring Station (GMS) of the

future ASAS service coverage is within of the mobile users,

the mode is usually referred to as local area differential, sim-

ilar to the US Differential GPS (DGPS) for Maritime appli-

cations. In this way, as the distance increases between the

users and the GMS, some ranging errors become decorre-

lated. This problem can be overcome by installing a net-work consisting a number of GMS reference sites through-

out a large geographic area, such as a region or continent

and broadcasting the Differential Corrections (DC) via GEO

satellites. In such a way, ASAS network has to cover entire

African Continent and the Middle East region.

Therefore, all GMS sites connected by Terrestrial Tele-

communication Networks (TTN) relay collected data to one

or more Ground Control Stations (GCS), where DC is per-

formed and satellite signal integrity is checked. Then, the


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124 D.S. Ilcev

GCS sends the corrections and integrity data to a major

Ground Earth Station (GES) for uplink to the GEO satellite.

This differential technique is referred to as the wide area

differential system, which is implemented by GNSS system

known as Wide Augmentation Area (WAA), while another

system known as Local Augmentation Area (LAA) is an im-

plementation of a local area differential, The LAA solution

is an implementation for seaports and airport including forapproaching utilizations. The WAA is an implementation of

a wide area differential system for wide area CNS maritime,

land and aeronautical applications, such as Inmarsat CNSO

and the newly developed Satellite Augmentation WAAS in

the USA, the European EGNOS and Japanese MSAS [10].

These three operational systems are part of the world-

wide GSAS network and integration segments of the future

interoperable GNSS-1 architecture of GPS and GLONASS

and GNSS-2 of Galileo and Compass, including CNSO as

a part of GNSS offering this service via Inmarsat-3/4 and

Artemis spacecraft. The author of this paper for the first time

is using more adequate nomenclature GSAS than Satellite-

based Augmentation System (SBAS) of ICAO, which has to

be adopted as the more common designation in the field of

CNS [6].

As discussed earlier, the current three RSAS networks in

development phase are the Russian SDCM, Chinese SNAS

and Indian GAGAN, while African Continent and Middle

East have to start at the beginning of 2011 with develop-

ment ASAS project. In this sense, development of forth-

coming RSAS projects in Australia and South America will

complete Augmented CNS system worldwide, known as an

GSAS Network [8].Three operational RSAS together with Inmarsat CNSO

are interoperable, compatible and each constituted of a net-

work of GPS or GLONASS observation stations and own

and/or leased GEO communication satellites. Namely, the

Inmarsat CNSO system offers on leasing GNSS payload,

while the European system EGNOS, which will provide pre-

cision to within about 5 metres is operational from 2009.

In fact, it also constitutes the first steps towards forthcom-

ing Galileo, the future European system for civilian global

navigation by satellite. The EGNOS system uses leased In-

marsat AOR-E and IOR satellites and ESA ARTEMIS satel-

lite. Thus, the US-based WAAS is using Inmarsat satellitesand Japanese MSAS is using its own multipurpose MTSAT

spacecraft, both are operational from 2007 and 2008, respec-

tively. Although the global positioning accuracy system as-

sociated with the overlay is a function of numerous technical

factors, including the ground network architecture, the ex-

pected accuracy for the US Federal Aviation Administration

(FAA) WAAS will be in the order of 7.6 m (2 drms, 95%)

in the horizontal plane and 7.6 m (95%) in the vertical plane

[4,8].

3 Status and weaknesses of the current CNS system

Business or corporate shipping and airways companies have

used for several decades HF communication for long-range

voice and telex communications during intercontinental sail-

ing and flights. Meanwhile, for short distances mobiles have

used the well-known VHF onboard ships and VHF//UHF

radio on aircraft. In the similar way, data communicationsare since recently also in use, primarily for travel plan and

worldwide weather (WX) and navigation (NX) warning re-

porting. Apart from data service for cabin crew, cabin voice

solutions and passenger telephony have also been devel-

oped. Thus, all mobiles today are using traditional electronic

and instrument navigations systems and for surveillance fa-

cilities they are employing radars.

The current communication facilities between ships and

MTC are executed by Radio MF/HF voice and telex and

VHF voice system; see Previous Communication Subsys-

tem in Fig.2. The VHF link between ships on one the hand

and Coast Radio Station (CRS) and TCC on the other, mayhave the possibility to be interfered with high mountainous

terrain and to provide problems for MTC. The HF link may

not be established due to lack of available frequencies, high

frequency jamming, bad propagation, intermediation, unsta-

ble wave conditions and to very bad weather, heavy rain or

thunderstorms.

The current navigation possibilities for recording and

processing Radio Direction Information (RDI) and Radio

Direction Distance Information (RDDI) between vessels and

TCC or MTC centre are performed by ground navigation

equipment, such as the shore Radar, Racons (Radar Beacon)

and Passive Radar Reflectors, integrated with VHF CRS fa-

cilities, shown by Previous Navigation Subsystem in Fig. 2.

This subsystem needs more time for ranging and secure nav-

igation at the deep seas, within the channels and approach-

ing to the anchorages and ports, using few onboard type of

radars and other visual and electronic navigation aids.

The current surveillance utilities for receiving Radar

and VHF Voice Position Reports (VPR) and HF Radio

Data/VPR between ships and TCC can be detected by Radar

and MF/HF/VHF CRS. This subsystem may have similar

propagation problems and limited range or when ships are

sailing inside of fiords and behind high mountains Coastal

Radar cannot detect them; see the Surveillance Subsystem

in Fig. 2. The very bad weather conditions, deep clouds

and heavy rain could block radar signals totally and on the

screen will be blanc picture without any reflected signals, so

in this case cannot be visible surrounded obstacles or traf-

fic of ships in the vicinity, and the navigation situation is

becoming very critical and dangerous causing collisions.

On the contrary, the new Communication CNS/MTM

System utilizes the communications satellite and it will

eliminate the possibility of interference by very high moun-

tains, see all three CNS Subsystems in Fig. 2. At this point,


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Fig. 2 Current and newCNS/MTM system. Courtesy ofmanuscript, Maritime CNS byIlcev [7]

satellite voice communications, including a data link, aug-

ments a range and improves both the quality and capac-

ity of communications. The WX and NX warnings, sail-

ing planning and NAVAREA information may also be di-

rectly input to the Navigation Management System (NMS).

The new Navigation CNS/MTM System is providing im-proved GPS/GLONASS navigation data, while Surveillance

CNS/MTM System is utilizing augmented facilities of GPS

or GLONASS signals. Thus, if the navigation course is free

of islands or shallow waters, the GPS Navigation Subsys-

tem data provides a direct approaching line and the surveil-

lance information cannot be interfered by mountainous ter-

rain or bad weather conditions. The display on the screen

will eliminate misunderstandings between controllers and

ships Masters or Pilots [7].

The current communication facilities between aircraft

and ATC can be executed by traditional VHF/UHF and HF

voice (radiotelephone system), see the Present Communica-

tion Subsystem in Fig.3. The VHF voice link between air-

craft on one the hand and Ground Radio Station (GRS) and

TCC on the other, may have the possibility to be interferedwith high mountainous terrain. Moreover, the HF link may

not be established due to lack of available frequencies, be-

cause many users are working on the same frequency band,

intermediation, unstable wave conditions and to very heavy

rain or thunderstorms.

The current navigation possibilities for recording and

processing RDI and RDDI between aircraft and ATC are

performed by ground landing navigation equipment, such

as the Instrument Landing System (ILS), VHF Omnidirec-


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126 D.S. Ilcev

Fig. 3 Current and newCNS/ATM system. Courtesy ofbook: Global Mobile SatelliteCommunications by Ilcev [9]

tional Ranging (VOR) and Distance Measuring Equipment

(DME), illustrated by the Present Navigation Subsystem in

Fig.3. This subsystem needs more time for ranging and se-

cure landing, using an indirect way of flying in a semicircle.

The current surveillance utilities for receiving Radar and

HF Voice signals between aircraft and TCC are detected bySurveillance Radar and Ground HF Stations, respectively.

This subsystem may have similar HF voice communica-

tions problems or when airplanes are flying behind high

mountains they cannot be detected by Radar, see the Present

Surveillance Subsystem in Fig.3.

The issues of new CNS/ATM systems shown in Fig. 3for

Communication, Navigation and Surveillance have the sim-

ilar improved impacts introduced in the previous Maritime

CNS/MTM system [9].

4 Development of ASAS network

As stated earlier, the basic GPS and GLONASS service

fails to meet the high-operating ICAA requirements that are

needed by many civilian mobile users. In order to meet the

requirements for better ICAA of GPS or GLONASS over

African Continent and Middle East is necessary to design

the ASAS network. The ASAS service will improve the

ICAA requirements of the basic GPS or GLONASS signals

and allows them to be used as a primary means of ships

navigation at coastal waters and precision approach to the

anchorages and for en-route flight of airplanes, Precision

Approach (PA) and Non-Precision Approach (NPA) in the

African and Middle East coverage area [9].

To start with realization of the project it will be neces-

sary to form Augmentation Standards Service (ASS) and to


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establish Transport Augmentation Board (TAB). The TAB

team together with IS Marine Radio, as a designer of ASAS

project, will be responsible for providing the leadership role

in engineering, realization and coordination the operational

implementation of existing and emerging modern satellite

CNS technologies into the African Continent and the Mid-

dle East region. The TAB team has to be instrumental in the

project and development of the criteria, standards and proce-dures for the use of unaugmented and as well an augmented

GNSS signals by the ASAS and Local Satellite Augmen-

tation System (LSAS). If there is not developed yet some

RSAS network, it can be also used Local VHF Augmenta-

tion System (LVAS) for seaports and airports also known as

a current DGPS developed in US for Coast Guard MTC.

4.1 Overview of ASAS Project

Among the GNSS-1 elements and characteristics stan-

dardized by the ICAO board the complements to GPS or

GLONASS augmented solutions are as follows:

(a) Regional RSAS ProjectIn this paper, the use of the

ICAO nomination Satellite-based Augmentation Sys-

tem (SBAS), which appear in the classification of the

acronyms, will be replaced by Regional Satellite Aug-

mentation System (RSAS) as better convenient nomen-

clature. The RSAS complementary information is dif-

fused by GEO satellite by means of a pseudo-GPS or

GLONASS signals and covers a wide geographical area

of GSAS systems, such as ASAS project for entire

African Continent and Middle East region.

(b) Local LSAS ProjectThe Local Satellite Augmen-

tation System (LSAS) nomenclature also convenientmuch better than Ground-based Augmentation System

(GBAS) nomination of ICAO. The complementary in-

formation is valid over a limited area, such as seaport or

airport and can use satellite diffusion to provide connec-

tion between mobiles and TCC. In similar instances, the

local scenario can employ LVAS diffused by using VHF

Radio system, similar to the US DGPS.

On this basis, the TAB team has to launch the development

of regional ASAS, whose objective has ultimately to pro-

vide one single navigation system over the whole Africa and

Middle East. The ASAS program has to be a combination of

ground and space equipment to augment the standard posi-

tioning service of the GPS or GLONASS. It has to be de-

signed as a milestone of the next generation civil maritime,

land and aviation CNS service. However, the fundamental

mission of ASAS is to provide a primary means of improved

navigation for maritime and also for land and aeronautical

applications.

The functions have to be provided by RSAS missions are:

DGPS corrections (to improve accuracy), integrity monitor-

ing (to ensure that errors are within tolerable limits with

a very high probability and thus ensure safety) and rang-

ing (to improve availability). Therefore, separate differen-

tial corrections are broadcasting by RSAS to correct GPS or

GLONASS satellite clock errors, ephemeris and ionospheric

errors. At this point, Ionospheric corrections are broadcast-

ing for selected Ionospheric Grid Points (IGP), which are

lattice points of a virtual grid of lines of constant latitude

and longitude at the height of the ionosphere.The ASAS network will integrate the Space Segment

of own constellation developed by South African Govern-

ment or leased Inmarsat-3 and Artemis GNSS satellite pay-

loads, and the Ground Segment, which consists in a primary

and secondary GMS, GCS, GES and Traffic Control Centre

(TCC) to attain improved availability, accuracy and integrity

beyond the standard GPS or GLONASS GNSS constella-

tions [8].

The TAB team, IS Marine Radio with partners from Rus-

sia and Ukraine, NovAtel, Leica and research institutions

such as National Space Institute (NSI) together with South

African Department of Science and Technology (DST), hasto perform all feasibility studies and research for develop-

ment of regional ASAS prototype including participating in

the early tests of an experimental ASAS. This team with

TAB has to analyze the accuracy of the experimental system

when it will be used to provide guidance to ships and aircraft

performing approaches on the four coasts of the African

continent. Feasibility studies will include a few performance

tests of alternative ionospheric correction and integrity algo-

rithms (error boundings).

On the other hand, TAB will assist to establish perfor-

mance demands for the ASAS and provide technical data

to other teams that will evaluate contractor responses to the

ASAS Request for Proposal (RFP). After the contract award,

TAB will assist in the transfer of technology project to the

prime contractors. The TAB team has also to provide techni-

cal advice to the contractors on the ASAS design in the areas

of performance and safety since the contract award, and has

also to be involved in the design, modeling prototype and

simulation of ASAS availability performance. The all insti-

tution parties of ASAS will be used in sensitivity analyses

to help determination of optimal mix and location of land

resources, such as GMS and GES, and to determine the im-

pacts of design changes that alter equipment performance

or location. It will be also used as a tool to demonstrate to

air traffic planners the behavior of a space navigation sys-

tem (i.e., orbiting sensors) and to help also to determine

operational strategies for dealing with low performance ar-

eas [10].

At first has to be established the African Satellite Test

Bed (ASTB) that includes the all above mentioned parties,

then minimum 55 ATSB GMS over African continent and

both existing Inmarsat GES in a ground uplink centre Maadi

in Egypt and Jeddah in Saudi Arabia. In addition, it is neces-

sary to establish one GES in Senegal, one in Kenya and one


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128 D.S. Ilcev

in South Africa or to utilize service of the existing CSIR

Satellite Centre [8].

The TAB can initiate a 3-phase developmental approach

to complete the ASAS network:

1. Phase 1 (20112012)Will start with initial ASAS com-

missioned with 44 GMS, 5 GCS uplinks, 5 GES and 3

leased GEO satellites. In the next stage will be upgraded

GMS infrastructures to maximum 55 and perhaps can be

provided own GEO satellites. The ASAS ground network

will enable wide civilian Maritime deep sea and coastal

navigation including approaching to anchorages and sea-

ports, while for Land application will enable precise nav-

igation facilities for road and rail vehicles and for Aero-

nautical solutions will provide en-route navigation, mo-

bile terminal navigation and NPA. In addition, this sys-

tem will support Category I PA within a limited coverage

area as well.

2. Phase 2 (20122015)Will initiate with full ASAS in-

frastructures and with additional GMS up to 55. Redun-

dant coverage of the entire initial ASAS operational re-

strictions will be removed. The ALAS ground structures

will be deployed at major African seaports and airports.

Precisely surveyed ground stations with multiple GPS re-

ceivers and processors will be established, including one

or more pseudolites and VHF data link-supports Cate-

gory II/III PA locally at all runway ends of an airport.

An additional approach lighting system will be deployed,

the Cat I precision approach and where higher availabil-

ity is required than ASAS network can provide. In the

proper manner, the reduction of ground-based NAVAIDS

infrastructure, such as VOR and Non-Directional Bea-

cons (NDB) will be initiated, and the added 2nd and 3rd

civil radio frequencies will improve GPS robustness and

ICAA.

3. Phase 3 (20152018)To continue reducing ground-

based NAVAIDS, when VOR and DME will support only

operations along principal air routes and NPA at many

airports. Furthermore, the ILS will support PA at high-

activity airports for ATC and Management. Full constel-

lations of GPS/GLONASS with 2nd and 3rd civil fre-

quency band available for ASAS/ALAS have to be mod-

ified accordingly to: Dual-frequency avionics to mitigate

unintentional jamming and complete phase-out of all on-

airport NAVAIDS (VOR, NDB).

4.2 ASAS system configuration

The ASAS will be designed and implemented as the pri-

mary means of satellite CNS for aviation routes in corridors

over African Continent and Middle East region, control of

airports approachings and managing all aircraft and vehi-

cles movements on airports surface. In this sense, it will

also serve for maritime course operations such as ocean

crossings, navigation at open and close seas, coastal navi-

gation, channels and passages, approachings to anchorages

and ports, and inside of ports, and for land (road and rail-

ways) solutions. It was intended to provide the following

services [10]:

(1) The transmission of integrity and health information on

each GPS or GLONASS satellite in real time to en-

sure all users do not use faulty satellites for navigation,

known as the GNSS Integrity Channel (GIC).

(2) The continuous transmission of ranging signals in addi-

tion to the GIC service, to supplement GPS, thereby in-

creasing GPS/GLONASS signal availability. Increased

signal availability also translates into an increase in Re-

ceiver Autonomous Integrity Monitoring (RAIM) avail-

ability, which is known as Ranging GIC (RGIC).

(3) The transmission of GPS or GLONASS wide area dif-

ferential corrections has, in addition to the GIC and

RGIC services, to increase the accuracy of civil GPS

and GLONASS signals. Namely, this feature has been

called the Wide Area Differential GNSS (WADGNSS).

The combination of the Inmarsat overlay services and

Artemis spacecraft will be referred to as the ASAS network

illustrated in Fig. 4. As observed previous figure, all mo-

bile users (3) receive navigation signals (1) from GNSS-1 of

GPS or GLONASS satellites. In the near future can be used

GNSS-2 signals of Galileo and Compass satellites (2). These

signals are also received by all reference GMS terminals of

integrity monitoring networks (4) operated by governmen-

tal agencies in many countries within Africa and Middle

East. The monitored data are sent to a regional Integrity and

Processing Facility of GCS (5), where the data is processedto form the integrity and WADGNSS correction messages,

which are then forwarded to the Primary GNSS GES (6). At

the GES, the navigation signals are precisely synchronized

to a reference time and modulated with the GIC message

data and WADGNSS corrections. The signals are sent to

a satellite on the C-band uplink (7) via GNSS payload lo-

cated in GEO Inmarsat and Artemis spacecraft (8), the aug-

mented signals are frequency-translated to the mobile user

on L1 and new L5-band (9) and to the C-band (10) used for

maintaining the navigation signal timing loop. The timing

of the signal is done in a very precise manner in order that

the signal will appear as though it was generated on board

the satellite as a GPS ranging signal. The Secondary GNSS

GES can be installed in Communication CNS GES (11), as

a hot standby in the event of failure at the Primary GNSS

GES. The TCC ground terminals (12) could send request

to all particular mobiles for providing CNS information by

Voice or Data, including new Voice, Data and Video over

IP (VDVoIP) on C-band uplink (13) via Communication

payload located in Inmarsat or Artemis spacecraft and on

C-band downlink (14) to mobile users (3). The mobile users


9/18


Fig. 4 ASAS networkconfiguration. Courtesy of book:UnderstandingGPSPrinciples andApplications by Kaplan(modified by authors) [10]

Fig. 5 ASAS space segment.Courtesy of book: GlobalMobile SatelliteCommunications by Ilcev [9]

are able to send augmented CNS data on L-band uplink (15)

via the same spacecraft and L-band downlink (16). The TCC

sites are processing CNS data received from mobile users by

Host and displaying on the surveillance screen their current

positions very accurate and in the real time (13). Therefore,

the ASAS will be used as a primary means of navigation

during all phases of traveling for all mobile applications [ 6].

The ASAS space constellation could be formally con-

sisted in the 24 operational GPS and 24 GLONASS satellites

and of 2 Inmarsat and 1 Artemis GEO satellites. The GEO

satellites downlink the data to the users on the GPS L1 RF

with a modulation similar to that used by GPS. Information

in the navigational message, when processed by an ASAS

Rx, allows the GEO satellites to be used as additional GPS-

like satellites, thus increasing the availability of the satellite

constellation. At this point, the ASAS signal resembles a

GPS signal origination from the Gold Code family of 1023

possible codes (19 signals from PRN 120-138).

An ASAS ground segment consists of a network of cer-

tain GMS cites that monitor the satellite signals and send

their observations to one or more GCS, which generate the

augmentation message. This is in turn sent to uplink GES,

which transmit it to the navigation transponders on board the

GEO spacecraft payload.

Finally, these satellites broadcast the ASAS message to

the mobile users at the L1 or 1575.42 MHz GPS frequency.

The ASAS signal is modulated on a GPS look-alike sig-

nal using a spread-spectrum code thus providing an ASAS

pseudo range measurement. This means that, with slightly

modified equipment, GPS or GLONASS users can receive

integrity and more accurate position information. In such

a way, the ranging signals improve Dilution of Precision

(DOP) and RAIM.

In fact, the ASAS signal will be modulated with a 250 b/s

data message containing GPS health information, vector po-

sition corrections and ionospheric mapping terms. This data

message separates ASAS from normal GPS or GLONASS

by increasing integrity (satellite health), improving the accu-

racy (vector corrections) and also enhancing the availability

(additional pseudo range) of the System. The ASAS network


10/18

130 D.S. Ilcev

Fig. 6 ASAS space and groundsegments. Courtesy ofmanuscript for book:Aeronautical CNS by Ilcev [9]

improves accuracy in two ways by reducing the range mea-

surement error by sending differential corrections for each

satellite and by adding new ranging signals thereby improv-

ing the geometry [9,10].

The vector corrections include fast corrections contain-

ing the satellite clock error; long-term corrections contain-ing more slowly varying errors of satellite location and iono-

spheric corrections (Van Dierendonck). The fast corrections

are sent every 10 to 12 seconds and only one correction

per satellite is sufficient for the entire ASAS coverage area.

Long-term and ionospheric corrections are sent much less

frequently (about every 2 minutes) as they do not vary much

over the entire ASAS network. The GEO satellites reduce

the need to update these corrections as rapidly as a normal

GPS or GLONASS satellite.

4.3 ASAS space segment

The ASAS Space Segment can be designed by using own

project of GEO satellite constellation, what is more expen-

sive solution, or by leasing existing GEO Inmarsat-3 and

Artemis spacecraft. The operational system can use 3 GEOsatellites: Inmarsat-3 AORE at 15.5W; Inmarsat-3 IOR at

position 64E, and ESA Artemis at 21.5E over equator, il-

lustrated in Fig.5. The navigation payloads on these GEO

spacecraft are essentially bent-pipe transponders, so that a

data message uploaded to a satellite is broadcast to all users

in the GEO broadcast area of the satellite over entire African

Continent and the Middle East region, see Fig.6. The ASAS

system can use service of existing Geostationary Ranging

Station (GRS) infrastructures and to implement a wide trian-


11/18


gular observation base for ranging purposes with the stations

located in Aussaguel (France), Kourou (French Guiana) and

Hartebeeshoeck (South Africa) [4,8].

In general, navigation payloads of GEO spacecraft for

augmentation systems must fulfill 2 key roles:

(1) Transmission of a spread-spectrum timing and ranging

signal on 1 or 2 navigation L-band RF;

(2) Relay in near-real-time of data originated on the groundand for use in user Rx to improve performance (reliabil-

ity, accuracy) with GPS and GLONASS signals.

As mentioned earlier, GEO is able to augment the perfor-

mances of GPS and GLONASS by providing a separate

ranging channel to transmit integrity and correction data.

This concept dates back to the late eighties and has evolved

to its current form known as RSAS. In this sense, RSAS data

will allow GNSS to meet the stringent reliability, availability

and integrity requirements set by MTC and ATC. Land users

will also be able to improve in positioning accuracy by Land

Traffic Control (LTC) for road and railway applications [1].In response to improve this need, Inmarsat decided to em-

bark a new navigation transponder to support RSAS func-

tions on its last generation of GEO Inmarsat-4 at the begin-

ning of 2005, which it is now developing to provide new

broadband services and which can be used for ASAS space

segment as well. Throughout the evolution of the RSAS con-

cept, Inmarsat played an active role in GNSS. In November

1990, it decided to include navigation transponders on its

third generation of GEO satellites, Inmarsat-3, developed to

provide the space capacity needed by WAAS and EGNOS.

Inmarsat-3 satellites alone, however, do not give sufficiently

redundant coverage for EGNOS and WAAS systems to offer

operational services throughout their respective service ar-

eas. In fact, more GEO will be necessary to assure a proper

replenishment policy when the Inmarsat-3 birds terminate

their operational life [2].

In the meantime, the US made a commitment to support

civil applications of GPS including the modification of fu-

ture generations of spacecraft to meet civil requirements.

The GPS modernization initiatives will make two new civil

signals available: a second signal at 1227.60 MHz (L2) and

a third civil signal at 1176.45 MHz (L5) RF. Moreover,

in 2004 FAA expressed its intention to have the L5 signal

also available on GPS augmentation satellites planed to be

launched in 2005 for civil aviation safety-of-life and secu-

rity services and other precision positioning and navigation

applications [6].

The Inmarsat-4 satellite navigation payload is a dual-

channel bent-pipe transponder that converts two C-band (C1

and C5) uplink signals from one GES to two downlink sig-

nals in two separate bands. In such a way, Inmarsat designed

its Inmarsat-4 navigation transponder to be, as far as possi-

ble, backward compatible with the existing RSAS and suit-

able for the future RSAS projects. It also recognized that

Fig. 7 EGNOS professional ESA 1 and Personal-Nav 400 Rx.Courtesy of WebPages: EGNOS Test Bed User Equipment fromInternet [4]

dual user downlink RF are an important advance over the

current Inmarsat-3 satellite augmentation capabilities.However, the satellite communication design had to re-

spect the technical constraints imposed by the Inmarsat-

4 space segment primary communications mission. In the

proper manner, the Inmarsat-4 navigation payload will trans-

mit satellite navigation signals at the GPS L1 and L5 fre-

quencies and allow the real-time relay from a single ground-

monitoring network of integrity and accuracy augmentation

data for orbiting GNSS constellation [8].

The L1 and L5 downlink signals can be received in in-

tegrated L1/L5 GPS/RSAS receiver (Rx), see two Rx pro-

totypes. The ASAS users will have at their disposal a few

models of multimodal prototype Rx units. The multimodalprototypes will enable users to carry out few tests on the

ASAS system: static and/or dynamic platform testing; user

ASAS Rx validation and system performance demonstration

comparison with reference position: geodetic marks (static),

trajectography data (dynamic), such as the model of EGNOS

Rx ESA 1 prototype shown in Fig.7(A).

The ASAS Standard Rx will be also developed to verify

the Signal-In-Space (SIS) performance. In the meantime a

set of prototype user equipment has been manufactured for

civil maritime, land and aeronautical applications. That pro-

totype equipment will be used to validate and eventually cer-

tify ASAS for the different applications being considered. Insuch a way, a handheld personal receiver (like a cell phone)

would use satellite navigation to avoid traffic jams in city

centres, find the nearest free parking space, or even the near-

est pizza restaurant in an unfamiliar city, as shown in the

Personal-Nav 400 in Fig.7(B).

Precise position via the Internet and ASAS system will be

possible anytime after completing and testing the ASAS net-

work, thanks to the SIS technology developed by the ESA.

This technology combines the powerful capabilities of satel-


12/18

132 D.S. Ilcev

Fig. 8 ASAS ground segments.Courtesy of manuscript forbook: Aeronautical CNS byIlcev [9]

lite navigation and the Internet. As a result, the highly ac-

curate navigation information that comes from the ASAS

SIS will be available on the Web in real time over the Inter-

net [2].

5 ASAS ground segment

The ASAS service will correct GNSS-1 signals from the

24 GPS and 24 GLONASS orbiting satellites, respectively,

which can be in error because of satellite orbit and clock

drift or signal delays caused by the atmosphere and iono-

sphere, or can also be disrupted by jamming.

The ASAS network, shown in Fig. 8, can be based on

55 GMS spread over entire Africa and Middle East (see red

cubes), 5 GCS (see red circles) and 5 GES (see red trian-

gles), covering large area and monitors GPS data. The GCS

and GES sites will be located in South Africa, Saudi Arabia,

Kenya, Egypt and Senegal, see prototype of WAAS ground

monitoring station in Fig. 9(A). In such a manner, signals

from GPS are received and processed at 55 GMS, which

are distributed throughout the African territory and linked to

form the ASAS network. In this instance, each of this pre-

cisely surveyed monitoring reference station receives GPS

signals and determines if any errors exist, while 5 GCS col-

lect data from these GMS reference terminals, assess signal

validity, compute all corrections and create the ASAS cor-

rection message [6].Furthermore, data from the GMS are forwarded to the

GCS, which process the data to determine the differential

corrections and bounds on the residual errors for each mon-

itored satellite and for each IGP. The bounds on the resid-

ual errors are used to establish the integrity of the rang-

ing signals. Hence, the corrections and integrity information

from the GCS are then sent to each GES and unlinked along

with the GPS navigation message to the GEO communica-

tion satellite. The GEO downlinks this data to the users via


13/18


Fig. 9 RSAS ground stations.Courtesy of WebPages:WAAS from Internet [4]

the current GPS L1 frequency with GPS type modulation

[9,10].

Therefore, the message is broadcasting on the same fre-

quency as GPS to receivers that are within the broadcast

coverage area of the entire ASAS network. In fact, these

three GEO communications satellites also act as an addi-

tional navigation constellation providing supplemental sig-

nals for position determination. Each satellite covers a part

of the hemisphere, except for both Polar Regions. The user

receiver, installed aboard a boat, ships, land vehicles or air-

craft, combines the GPS signals with the ASAS message to

arrive at a more accurate position. Otherwise, each ASAS

ground-based station or subsystem configuration communi-

cates with TCC infrastructure via terrestrial landline [6].

The GMS is a special ground reference station with an-

tenna and adequate equipment located at a precisely sur-

veyed position, as shown in Fig.9(A). The ASAS network

will use 55 GMS, while the current WAAS configuration

uses only 25 Wide Reference Stations (WRS) spread over

the entire territory of the Continental US, covering as well

as eastern Canada [3]. The WRS infrastructure continuously

receives and collects GPS data for various satellites and then

sends the data to their Wide Master Station (WMS), which

interpret the data from each WRS and calculate the errors

and health of each satellite [4]. The ASAS network will

use 5 GCS, while WAAS uses only two WMS calculate

observed satellite errors for the entire WAAS network and

then forward these corrections to a primary GES. The GES

receives GPS corrections and transmits them to GEO satel-

lites using a ground uplink system on the GPS L1 frequency,

while the next generation of GPS will provide L5 as well [5].

The GEO satellite receives corrections and forwards

them to users, who are equipped with special Rx equipment,

as shown in the Raytheon GPS/WAAS Rx 2 in Fig. 9(B).

The WAAS satellite signal type is compatible with GPS or

GLONASS systems, so new RSAS-enhanced GPS receivers

will not be much more expensive than unaugmented GPS re-

ceivers (possibly 50 US$ or more). Thus, some type of GPS

receivers or chart plotters can be upgraded with RSAS spe-

cial hardware modem or software without additional cost,

by contacting the manufacturer to be converted for RSAS

signal utilization [11]. The GPS signal can be received

by integrated GPS/RSAS Rx for processing pseudorange,

pseudorange-rate and accumulated Doppler measurements.

These measurements control the phase and frequency (code

and carrier) of the corresponding signal generator, SG-L1

and SG-L5, to generate two individually controlled uplink

signals. Inmarsat plans to develop prototype equipment for

proper navigation signal generation and control that will be

used for the ground and in-orbit test campaign in order to

conduct end-to-end system tests [2].

6 LSAS System configuration

The LSAS is intended to complement the ASAS service us-

ing a single differential correction that accounts for all ex-

pected common errors between a local reference and mobileusers. The LSAS will broadcast navigation information in

a localized volume area of seaport or airport using satellite

service of ASAS network or any of mentioned RSAS net-

works developed in Northern Hemisphere.

As stated earlier, the ASAS network will consist 55 GMS

(Reference Stations), 5 GCS (Master Stations) and 5 GES

(Gateways), which service has to cover entire African Con-

tinent and Middle East region. Inside of this coverage the

ASAS network will also serve to any other customers at sea,

on the ground and in the air users who need very precise

determinations and positioning, such as:

1. Maritime (Shipborne Navigation and Surveillance, Sea-floor Mapping and Seismic Surveying);

2. Land (Vehicleborne Navigation, Transit, Tracking and

Surveillance, Transportation Steering and Cranes);

3. Aeronautical (Airborne Navigation and Surveillance and

Mapping);

4. Agricultural (Forestry, Farming and Machine Control

and Monitoring);

5. Industrial, Mining and Civil Engineering;

6. Structural Deformations Monitoring;


14/18

134 D.S. Ilcev

Fig. 10 CMGC subsystem.Courtesy of paper, SatelliteCNS for MaritimeTransportation AugmentationSystem (MTAS), by Ilcev [7]

7. Meteorological, Cadastral and Seismic Surveying; and8. Government/Military Determination and Surveillance

(Police, Intelligent services, Firefighting); etc.

However, all above fixed or mobile applications will be able

to use ASAS or any RSAS service directly by installing new

equipment known as augmented GPS receivers (Rx), and so

to use more accurate positioning and determination data. In

Fig.4is illustrated scenario that all mobiles and GMS di-

rectly are using not augmented signals of GPS or GLONASS

satellites. To provide augmentation will be necessary to pro-

cess not augmented signals in GCS, to eliminate all errors

and produce augmented signals. In this stage any RSAS orASAS network standalone will be not able to produce aug-

mented service for seaports, airports or any ground infras-

tructures. Meanwhile, it will be necessary to be established

some new infrastructure known as an LSAS, which can pro-

vide service for collecting augmented data from ships, land

vehicles, airplanes or any ground user. The navigation data

of mobiles can be processed in the TCC cites and shown

on the surveillance screen similar to the radar display and

can used for traffic control system at the see, on the ground

and in the air. This scenario will be more important for es-

tablishment MTC or ATC service using augmented GNSS-1

signals from the ships or aircraft, respectively. In this sense,the LSAS network can be utilized for seaport known as a

Coastal Movement Guidance and Control (CMGC) and air-

port known as a Surface Movement Guidance and Control

(SMGC) [8,11].

6.1 Coastal Movement Guidance and Control (CMGC)

The new LSAS network can be implemented as a Coastal

Movement Guidance and Control (CMGC) system inte-

grated in the ASAS or any RSAS infrastructure. It is a

special maritime security and control system that enablesa port controller from Control Tower at shore to collect all

navigation and determination data from all ships and vehi-

cles, to process these signals and display on the surveillance

screens. On the surveillance screen can be visible positions

and courses of all ships in vicinity sailing areas, so they can

be controlled, informed and managed by traffic controllers

in any real time and space.

In this case, the LSAS traffic controller provide essential

control, traffic management, guide and monitor all vessels

movements in coastal navigation, in the cramped channel

strips and fiords, approaching areas to the anchorage and

harbours, ship movement in the harbours, including landvehicles in port and around the ports coastal environment,

even in poor visibility conditions at an approaching to the

port. The controller issues instructions to the ship Masters

and Pilots with reference to a command surveillance display

in a Control Tower that gives all vessels position informa-

tion in the vicinity detected via satellites and by sensors on

the ground, shown in Fig.10.

The command monitor also displays reported position

data of coming or departing vessels and all auxiliary land

vehicles (road and railways) moving into the ports sur-

face. This position is measured by GNSS, using data from

GPS/GLONASS and GEO satellite constellation. A con-troller is also able to show the correct ship course to Mas-

ters and sea Pilots under bad weather conditions and poor

visibility or to give information on routes and separation to

other vessels in progress. The following segments of CMGC

infrastructure are illustrated in Fig.10:

(1) GPS or GLONASS GNSS Satellite measures the vessel

or port vehicles exact position.

(2) GEO MSC Satelliteis integrated with the GPS position-

ing data network caring both communication and navi-


15/18


Fig. 11 SMGC subsystem.Courtesy of book: GlobalMobile SatelliteCommunications by Ilcev[6,9]

gation payloads, In addition to complementing the GPSsatellite, it also has the feature of communicating data

between the ships or vehicles and the ground facilities,

pinpointing the mobiles exact position.

(3) Control Tower is the centre for monitoring the traffic

situation on the channel strips, approaching areas, in the

port and around the ports coastal surface. The location

of each vessel and ground vehicle is displayed on the

command monitor of the port control tower. The con-

troller performs sea-controlled distance guidance and

movements for the vessels and ground-controlled dis-

tance vehicles and directions based on this data.

(4) Light Guidance System (LGS) is managed by the con-

troller who gives green light or red light guidance

whether the ship should proceed or not by pilot in port,

respectively.

(5) Radar Control Station (RCS) is a part of previous sys-

tem for MTC of ship movement in the channels, ap-

proaching areas, in port and around the ports coastal

environment.

(6) Very High Frequency (VHF) is Coast Radio Station

(CRS) is a part of RCS and VHF or Digital Selective

Call (DSC) VHF Radio communications system.

(7) Coast Earth Station (CES) is a main part of satellitecommunications system between CES terminals and

shore telecommunication facilities via GEO satellite

constellation.

(8) Pilot is small boat or helicopter carrying the special

trained man known as a Pilot, who has to proceed the

vessel to the anchorage, in port, out of port or through

the channels and rivers.

(9) Bridge Instrumentof each vessel displays the ship posi-

tion and course [7].

6.2 Surface Movement Guidance and Control (SMGC)

The new LSAS network can be also implemented as a Sur-

face Movement Guidance and Control (SMGC) system inte-

grated in the ASAS or any RSAS infrastructure. It is a spe-

cial aeronautical security and control system that enables

an airports controller from Control Tower on the ground

to collect all navigation and determination data from all air-

craft, to process these signals and display on the surveillance

screens. On the surveillance screen can be visible positions

and courses of all aircraft in vicinity flight areas, so they can

be controlled, informed and managed by traffic controllers

in any real time and space. In such a way, the LSAS traf-fic controller provide essential control, traffic management,

guide and monitor all aircraft movements in the vicinity of

the aircraft, approaching areas to the airport, aircraft move-

ment in airport, including land vehicles in airport and around

the airport, even in very poor visibility conditions at an ap-

proaching to the airport. Thus, the controller issues instruc-

tions to the aircrafts Pilots with the reference to a command

surveillance display in a Control Tower that gives all air-

craft position information in the vicinity detected via satel-

lites and by sensors on the ground, shown in Fig. 11.

The command monitor also displays reported position in-

formation of landing or departing aircraft and all auxiliaryvehicles moving onto the airports surface. This position is

measured by GNSS, using data from GPS and GEO ASAS

or RSAS satellites. An airport controller is able to show the

correct taxiway to pilots under poor visibility, by switching

the taxiway centreline light and the stop bar light on or off.

Otherwise, the development of head-down display and head-

up display in the cockpit that gives information on routes

and separation to other aircraft is in progress. The following

segments of SMGC are shown in Fig. 11:


16/18

136 D.S. Ilcev

(1) GPS or GLONASS Satellitemeasures the aircraft or air-

port vehicles exact position.

(2) RSAS is integrated with the GPS satellite positioning

data network. In addition to complementing the GPS

satellite, it also has the feature of communicating data

between the aircraft and the ground facilities, pinpoint-

ing the aircrafts exact position.

(3) Control Toweris the centre for monitoring the traffic sit-uation on the landing strip around the airports environ-

ment. The location of aircraft and vehicles is displayed

on the command monitor of the control tower. The con-

troller performs ground-controlled distance guidance

for the aircraft and vehicles based on this data.

(4) Stop Line Light System is managed by the controller,

who gives guidance on whether the aircraft should pro-

ceed to the runway by turning on and off the central

guidance line lights and stop line lights as a signal, in-

dicating whether the aircraft should proceed or not.

(5) Ground Surveillance Radar(GSR) is a part of previous

system for ATC of aircraft approaching areas, in airportand around the airport air environment.

(6) Very High Frequency (VHF) is Ground Radio Station

(GRS) is a part of ARC via VHF or UHF Radio com-

munications system.

(7) Ground Earth Station (GES) is a main part of satel-

lite communications system between GES terminals and

ground telecommunication facilities via GEO satellite

constellation.

(8) Aircraft Cockpitdisplays the aircraft position and routes

on the headwind protective glass (head-up displays) and

instrument panel display (head-down display) [6,9].

7 Conclusion

The current radios and traffic control are based on 1960s

technology. In fact, there is no radar coverage over the

ocean areas, so ship captains and aircraft pilots must re-

port their positions verbally by voice or have them automati-

cally sent through a relay station. For the controller, surveil-

lance equipment, primarily radar, detects the position of the

many moving ships, vehicles and aircraft in the traffic cov-

erage area. Otherwise, the radar monitoring the movement

of ships, aircraft and other vehicles spins much faster thanthose radars covering.

New tools, like satellite surveillance, have been devel-

oped as part of GSAS combined with surface radars, to help

the controllers to move increased number of vessels, air-

craft and land vehicles more safely through the transporta-

tion augmentation system environment. In the proper man-

ner, this additional navigational accuracy now available on

the ships bridge and aircraft cockpit will be used for other

system enhancements and for surface control in area of ports

and airports. This is the Automatic Dependent Surveillance

System (ADSS), currently being evaluated and which is tak-

ing advantage of this improved accuracy of traffic control

for all mobile applications. By the way, South Africa (SA)

is building fast Gauteng train and new Dube airport in

Durban not implementing CNS technology.

Using this enhanced chain, the new ASAS system of

GSAS with navigational message will improve the GPS orGLONASS signal accuracy from about 30 metres to approx-

imately 3 metres. For example, the current US WAAS sys-

tem provides 12 metres horizontal accuracy and 23 me-

tres vertical accuracy throughout the contiguous US. Un-

fortunately, to receive an ASAS signal, an ordinary GPS or

GLONASS receiver must be upgraded by hardware module

or software and be capable of receiving and decoding ASAS

signals.

In the future will be possible to integrate new satel-

lite systems in ASAS network such as already mentioned

Inmarsat-4 space configuration or new SA Space Constella-tion and forthcoming GNSS-2 systems.

Although the global positioning accuracy system associ-

ated with the overlay is a function of numerous technical

factors and ground network architecture, the expected accu-

racy for the ASAS will be in the order of 12 metres hori-

zontal accuracy and 23 metres vertical accuracy throughout

the contiguous Africa and Middle East region.

References

1. El-Rabbany, A. (2002). Introduction to GPS. Boston: Artech

House.

2. Grewal, M. S. et al. (2008). Global positioning systems, inertial

navigation, and integration. London: Wiley.

3. Group of Authors (2008). Website of Leica (www.leica-

geosystems.com) & NovAtel(www.novatel.com).

4. Group of Authors (2008). Website of EGNOS (www.esa.int),

WAAS (www.gps.faa.gov) GSAS.

5. Group of Authors (2009).MTSAT Update, NextSAT/10 CG, Japan

Civil Aviation Bureau. Tokyo: MSAS.

6. Ilcev, D. St. (2005). Global mobile satellite communications for

maritime, land and aeronautical applications. Boston: Springer.

7. Ilcev, D. St. (2009). Satellite CNS for Maritime TransportationAugmentation System (MTAS). In CriMiCo conference, IEEE

catalog numbers CFP09788, Sevastopol, Ukraine.

8. Ilcev, D. St. (2010). Maritime communications, navigation and

surveillance (CNS). Durban: DUT.

9. Ilcev, D. St. (2010). Aeronautical communications, navigation

and surveillance (CNS). Chichester: Wiley (manuscript).

10. Kaplan, E. D. (1996).Understanding GPS principles and applica-

tions. Boston: Artech House.

11. Prasad, R., & Ruggieri, M. (2005). Applied satellite navigation

using GPS, GALILEO, and augmentation systems. Boston: Artech

House.
http://www.leica-geosystems.com/http://www.leica-geosystems.com/http://www.novatel.com/http://www.novatel.com/http://www.esa.int/http://www.gps.faa.gov/http://www.gps.faa.gov/http://www.esa.int/http://www.novatel.com/http://www.leica-geosystems.com/http://www.leica-geosystems.com/


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D.S. Ilcev received two B.Eng. de-grees in Mobile Radio Engineeringand in Maritime Navigation fromthe Faculty of Maritime Studiesat Kotor of Podgorica University,Montenegro; received BSc. Eng.(Hons) degree in Maritime Com-munications from the Maritime Fac-ulty of University at Rijeka, Croatia;

and received M.Sc. degree in Elec-trical Engineering from the Facultyof Electrical Engineering, Telecom-munication department of Univer-sity at Skopie, Macedonia, in 1971,1986 and 1994, respectively. His

Doctoral dissertation in Satellite Communications, Navigation andSurveillance (CNS) was positive evaluated in 2000 by Telecommuni-

cation department of Faculty of Electrical Engineering Nikola Teslaof Belgrade University, Serbia.He also passed in Spring 1995 an on-site GMDSS training course onPoseidon simulator at Military Maritime Training Centre in Varna, Bul-garia. He holds the certificates for Radio operator 1st class (Morse); forGMDSS 1st class Radio Electronic Operator and Maintainer; for Mas-ter Mariner, and he was Reserve Staff in CNS of Former YugoslavArmy.Prof. Ilcev is currently working as a Research Professor in Space

Science at Mangosuthu University of Technology (MUT) in Durban,South Africa, and as Director for establishment of National Space In-stitute (NSI). His research concentrated over 45 years on all aspects ofRadio and Satellite CNS systems, networks, technology transfer, navi-gation and logistics, including safety and security in all transportationsystems.


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C o p y r i g h t o f T e l e c o m m u n i c a t i o n S y s t e m s i s t h e p r o p e r t y o f S p r i n g e r S c i e n c e & B u s i n e s s

M e d i a B . V . a n d i t s c o n t e n t m a y n o t b e c o p i e d o r e m a i l e d t o m u l t i p l e s i t e s o r p o s t e d t o a

l i s t s e r v w i t h o u t t h e c o p y r i g h t h o l d e r ' s e x p r e s s w r i t t e n p e r m i s s i o n . H o w e v e r , u s e r s m a y p r i n t ,

d o w n l o a d , o r e m a i l a r t i c l e s f o r i n d i v i d u a l u s e .

Documents

African Satellite