2 Types of Navigation Celestial Radio Navigation The use of the stars, sun and time to calculate positionsRadio NavigationLand based e.g. Loran CSatellite Based e.g. GPSTypes of NavigationCelestialCelestial navigation is the art and science of finding one's geographic position by means of astronomical observations, particularly by measuring altitudes of celestial objects – sun, moon, planets, or stars.Radio Navigation – Land – Loran CThe LORAN-C system was developed in the 1950s. Current land-based radio navigation system operating in the 90 kHz to 110 kHz band. Loran-C is a pulsed hyperbolic system that provides 0.25 nm predictable accuracy, m repeatable accuracy, 95% confidence and 99.7% availability. Loran-C is the federally provided radio-navigation system for civil marine use in U.S. coastal waters. The U.S. Coast Guard is responsible for system operation and maintenance in the U.S. and certain overseas locations. Loran-C provides coverage for the continental U.S. and its coastal waters, the Great Lakes, and most of Alaska. Many other countries are also involved in the providing of Loran-C (or Loran-like) services, or are in negotiations with their neighbors to expand coverage. These countries include India, Norway, France, Ireland, Germany, Spain, Italy, Russia, China, Japan, the Philippines and others.Radio Navigation – Space – GPSA satellite navigation system based on 24 or more satellites orbiting the earth at an altitude of 12,000 miles and providing very precise, worldwide positioning and navigation information 24 hours a day, in any weather.
3 History of Satellite Navigation TRANSIT / TSIKADADNSSTimationSystem 621BNAVSTAR GPSGLONASSHistory of Satellite NavigationTRANSITTransit was the first operational satellite navigation system. Developed by the Johns Hopkins Applied Physics Laboratory, the system was intended as an aid to submarine navigation. The Transit system allowed the user to determine position by measuring the Doppler shift of a radio signal transmitted by the satellite. The user was able to calculate position to within a few hundred meters as long as the user knew his altitude and the satellite ephemeris.The system has several drawbacks. First, the system is inherently two dimensional. Second, the velocity of the user must be taken into account. Third, mutual interference between the satellites restricted the total number of satellites to five. Thus, satellites would only be visible for limited periods of time. These drawbacks pretty much eliminated aviation applications and severely limited land-based applications.TSIKADAIn 1965 the USSR Navy begun developing a satellite navigation system very similar to TRANSIT, called TSIKADA. The system consisted of 12 cosmos satellites in a 1000 km orbit with a period time of 105 minutes. Each TSIKADA satellite continuously transmited two frequencies (150 and 400 MHz), but the higher frequency was unmodulated and was only used for the correction of the ionospheric influence.Defence Navigation Satellite System (DNSS)Developed in 1972 by the Naval Research Laboratory (NRL), Timation, was never really deployed and used,; however, it was used as a model for satellite-based navigation systems . In 1973, the US Air Force developed a DNSS (Defense Navigation Satellite System) combining their own System 621B with Timation. This gave birth to the NAVSTAR (Navigation System with Timing And Ranging) GPS Program.NAVSTAR GPSThe NAVSTAR GPS system is a satellite-based radionavigation system developed and operated by the U.S. Department of Defense (DOD). The NAVSTAR system permits land, sea, and airborne users to determine their three-dimensional position, velocity, and time 24 hours a day, in all weather, anywhere in the world with a precision and accuracy. The NAVSTAR systems performs another function besides positioning and time transfer. Starting with satellite vehicle 8, Navstar satellites carry nuclear explosion detection equipment. The GPS Nuclear Detection (NUDET) system is a joint program between the U.S. Air Force and the Department of Energy. The NUDET system replaces the older VELA system in enforcing the nuclear Non-Proliferation Treaty (NPT) and the Limited Test Ban Treaty (LTBT).GLONASSThe GLONASS global satellite navigation system is a further development of the TSIKADA system. The drawbacks of the TSIKADA system, i.e. the availability of two dimensional positions only with an accuracy of +/- 500 m (at 95 % probability), no velocity information and poor system timeliness made the development of a new positioning system necessary. GLONASS was developed at about the same time as GPS. This paralleled the evolution of two similar global navigation systems based on satellites. A satellite navigation system was also needed in the former USSR to enhance all military operations.
4 GPS Multiple series of satellites provide the current constellation Newer satellites have better clocks and are able to continue operating automatically without contact from the ground stationsContinual replenishment of the satellites is ongoingGPSCurrent ConstellationThe currently operational GPS satellites are designated BLOCK II, BLOCK IIA and BLOCK IIR. The BLOCK II satellites, space vehicle numbers (SVN) 13 through 21, are the first full scale operational satellites developed by Rockwell International. Block II satellites were designed to provide 14 days of operation without contact from the Control Segment (CS). The Block IIs were launched from February 1989 through October 1990.The BLOCK IIA satellites, SVNs 22 through 40, are the second series of operational satellites, also developed by Rockwell International. Block IIA satellites were designed to provide 180 days of operation without contact from the CS. During the 180 day autonomy, degraded accuracy will be evident in the navigation message. The Block IIAs were launched November 1990 through November The design life of the Block II/IIA satellite is 7.3 years; each contain four atomic clocks: two Cesium (Cs) and two Rubidium (Rb); and have the Selective Availabilty (SA) and Anti-Spoof (A-S) capabilities. The Block II/IIA satellites were launched from Cape Canaveral Air Force Station, Florida, aboard the Delta II medium launch vehicle (MLV).The BLOCK IIR satellites, SVNs 41 through 62, are the operational replenishment satellites developed by Lockheed Martin and will carry the GPS well into the future. Block IIR satellites are designed to provide at least 14 days of operation without contact from the CS and up to 180 days of operation when operating in the autonomous navigation (AUTONAV) mode. Full accuracy will be maintained using a technique of ranging and communication between the Block IIR satellites. The cross- link ranging will be used to estimate and update the parameters in the navigation message of each Block IIR satellite without contact from the CS. The design life of the Block IIR satellite is 7.8 years; each contains three Rb atomic clocks and have the SA and A-S capabilities. Launching of the Block IIRs began in January 1997.
5 GPS Current Status Full constellation in operation Continuing replenishment of old satellitesSome satellites have lasted well outside of their design lifeGPS Current StatusGPS has been in full operation since 17th July 1995 and continues to provide a global navigation service free of charge. The GPS programme is set to continue with is primary aim to continuing supporting US Military and Security operations. The constellation is being constantly replenished to replace failed or failing satellites. On November 6th 2004, GPS IIR-13 was launched, this was built by Lockheed Martin and took the constellation to 30 satellites. This satellite was launched to replace one which has been in orbit since well beyond its calculated life expectancy.The figure shows the current performance of GPS – Horizontal Accuracy 95%.
6 GLONASS Russian global satellite navigation system Very similar to GPS conceptFull Constellation expected in 2007GLONASSAs in GPS the GLONASS system was designed as a military navigation system to provide global continuous and precise 3D positioning and velocity determination in real-time. The aims were:The navigation solution should be available in real-time for an unlimited number of users.There should be no means to identify the user while working with the navigation signals.In addition the system should provide a good jamming resistance.These requirements led to the above concept of GLONASS.HistoryThe work on the GLONASS satellite positioning system started in the early 70's as a big collaboratory project involving NPO of Applied Mechanics, Russian NII of Space Devices, and the Russian Institute of Radio Navigation and Time as chief designers. Broad-scale planning, design and experimental works on the system elements were followed by the step-by-step deployment. The first spacecraft were launched into orbit in Further deployment of the satellite constellation continued at a rate of 1-2 launches a year.The preoperational phase lasted from 1982 until In this time 10 Block I spacecrafts were launched. In the operational phase, 6 Block IIa satellites were launched between 1985 and 1986, 12 block IIb satellites between 1987 and 1988 and 31 block IIv satellites between 1988 and Since May 1987 GLONASS has been used in the Earth's rotation parameters (ERP) determination service.During the 1990‘s the system went into decline, this was partly to do with the changes in the Russian political structure, but also to do with the poor quality of the satellites. Many satellites failed suring this time.
7 GLONASS Current Status GLONASS programme to continueReplenishment of satellites is underwayFuture of the system is assured for military and civilian purposesGLONASS Current StatusThe following is a summary of some of Russia's plans for the GLONASS constellation:A new launch of 3 satellites is scheduled for 26 December One of these will be a GLONASS-M and the other two will be the older model satellite. GLONASS satellite numbers 712, 796 and 797 will be placed into slots 1, 7 and 8 of plane 1 of the constellation. This will bring the total number of GLONASS satellites in orbit to 14. Eleven satellites are now operational, including the first GLONASS-M (launched in December 2003) that has been set healthy just recently.The Russian Aerospace Agency has the approval of the Russian government to continue a long-term plan for the period , during which time it plans to reconstitute a GLONASS constellation of 24 satellites. Russia plans to have 18 operational satellites by the end of 2007 and 24 operational satellites by the end of 2010.The GLONASS-M satellites have two civil signals and have an expected life of 7 years. In addition to the one currently in orbit and the one scheduled for launch on 26 December, 7 more have been ordered for production.
8 GPS / GLONASS Initial Design Differences GPS GLONASS Nominal No. of Satellites24Operational Satellites (end of 2000)928Orbital Planes3 (seperated by 120o)6 (separated by 60o)Satellites per orbital plane8 (equally spaced)4 (unequally spaced)Orbital Radius25510 km26560kmInclination of orbital planes64.8o55oRevolution Period~11h16~11h 58 minNominal EccentricitySignal Separation TechniqueFDMACDMAReference SystemPZ-90WGS-84Time ReferenceUTC (SU)UTC (USNO)GPS/GLONASSFDMA = Frequency Division Multiple AccessCDMA = Code Division Multiple AccessA GLONASS receiver distinguishes the signals from different satellites by frequency, a GPS receiver uses unique codes (Gold Codes) to distinguish between satellites.
9 Current Use of Satellite Navigation MarketsAviationMaritimeRoadRailLBSProfessionalCurrent Use of Satellite NavigationAlthough the systems of today were primarily designed for military use, a variety of civilian applications have developed. Making use of the freely available signals from space has meant that many industries, people and jobs now rely on the use of satellite navigation. Below is a list of some of the current applications for Satellite Navigation.TransportThe current GPS system is currently being used for logistic purposes to aid the tracking and delivery of cargoes. It is also being used as a safety tool for the tracking of vessels while at see. Perhaps the most challenging environment is its use in the aviation industry, with the aid of augmentations to increase accuracy, continuity and integrity this is becoming a realityLeisureThe largest market for civilian GPS uses is the leisure one, a variety of receivers are available, to aid navigation while outdoors, at sea or flying light aircraft. It is also becoming increasingly integrated with mobile phones for the provision of Location Based ServicesMilitaryAs GPS was primarily designed for military use, it is still an integral part of the modern military today, used in a variety of tracking and targeting applicationsEngineeringGPS revolutionised the way in which many engineering disciplines operate, the offshore industry finds is particularly useful for oil rig siting and general navigation. Other industries to benefit are surveying, construction, structural monitoring and archaeology.ScienceWith its capability to provide continuous positioning it is possible to monitor natural processes using the satellite system. Data can be collected around geological faults and volcanoes to aid studying and potentially prediction. Meteorological predictions have also benefited from the measurement of atmospheric delays on the radio signals.
10 Space Based Augmentation Systems Space Based Augmentations Systems (SBAS)The term SBAS can also mean Satellite Based Augmentation Systems. The terms Space/Satellite are commonly interchangeable.
11 Space Based Augmentation Systems Space-Based Augmentation Systems or SBAS broadcast correction signals from satellites. Three main systems are underdevelopment by the USA, Europe and Japan, named WAAS, EGNOS and MSAS respectively.WAAS, EGNOS and MSAS have networks of stations on the ground which receive signals from the U.S. Government's GPS satellites. These ground stations, rather than sending corrected positioning signals to users via beacon stations, instead send signals up to their own proprietary satellites, which in turn transmit the signals back to individual WAAS/EGNOS/MSAS-capable receivers on Earth.Like radio beacon differential signals, Space-Based Augmentation System differential signals are freely accessible to anyone with appropriate equipment.Instead of calculating range corrections, which are applicable to only local geographic regions, WAAS, EGNOS and MSAS determine the value of each separate source of error. This facilitates more uniform corrections.WAASEGNOSMSAS
12 Europe - EGNOS Europe - EGNOS The smaller figure distinguishes two EGNOS Service Areas. The larger area is the area over which EGNOS will provide accurate ranging and therefore enhancements to the availability and continuity of EGNOS. This area is called the Geostationary Broadcast Area (GBA).The smaller area covers the airspace of the States of the European Civil Aviation Conference (ECAC) and is called the ECAC area. Within this area, EGNOS will provide all three services: differential corrections to improve accuracy, ranging to increase availability and continuity as well as integrity for safety.The full EGNOS service will be available in the ECAC or “core” area because the RIMS network will cover that region. Further RIMS networks will be required outside ECAC if other regions in the GBA wish to obtain the complete service. The ETG is discussing this with partners in Africa and the Middle East, for example. Full accuracy enhancement will not occur over the rest of the GBA, because accurate differential corrections require a network of reference stations throughout the area to be served. Also, the integrity degrades outside the core area, because a network of integrity monitoring stations would be required for the detection of satellites which are out of performance limits.The larger figure shows the Horizontal Accuracy (95%) of using GPS and EGNOS together. Overall the coverage over Europe is estimated to give 4m accuracy.
13 US - WAAS Designed for Aviation Industry Enhanced Accuracy, Integrity and ContinuityInitial Operating Capability (IOC) July 2003US - WAASBackgroundWAAS provides the additional accuracy, availability, continuity and integrity necessary to enable users to rely on GPS for all phases of flight. WAAS significantly improves safety by providing near-precision approach capability at almost all runway ends in the National Airspace System that currently do not have this capability. Unlike conventional land-based navigation aids, WAAS provides vertical guidance through all phases of flight. This enables the system to provide a level of safety that was unavailable until now.How WAAS WorksWAAS works by having a network of precisely surveyed ground reference stations collecting GPS satellite data. This data is sent through leased ground communications lines to master stations which analyze the information and prepare a WAAS correction message for broadcast to pilots and other users. The WAAS correction message is broadcast to aircraft and other users through leased transponders on commercial geosynchronous (GEO) communication satellites. To use WAAS in an aircraft, receivers which can receive and interpret the WAAS correction to GPS are used. WAAS receivers have been developed by industry and are currently available for sale.WAAS CommissioningOn July 10, 2003, the U.S. WAAS was commissioned by the FAA over most of the continental United States, adjacent oceanic regions, and much of Alaska, and is the only SBAS currently certified for instrument flight rules (IFR) operations in the world. On this date, aviation users were able to use WAAS as a navigation aid for enroute and lateral navigation/vertical navigation (LNAV/VNAV) approaches. Using the nearly 700 LNAV/VNAV approaches that have been developed so far, pilots could safely descend to 350 ft. above the runway threshold with the vertical guidance provided by WAAS. In September 2003, the first of the near precision approaches (known as LPV) were provided where pilots could safely descend to a 250 ft. decision height.
14 Japanese MSASJAPANESE MTSAT Satellite Based Augmentation System (MSAS)In parallel with Europe and the United States, Japan is developing a geostationary overlay called the MTSAT Satellite Based Augmentation System (MSAS). MSAS is based on an aeronautical package to be flown on the Multi-functional Transport Satellite (MTSAT), which also has a meteorological mission. MSAS is planned for launch during 2005.MSAS is distinct from EGNOS and WAAS, because it will include two-way voice and data communication. This communication capability will be used to provide Automatic Dependent Surveillance (ADS). Specifically, MSAS is based on the ICAO FANS concept including: GNSS for navigation; and the Aeronautical Mobile Satellite Service (AMSS) for two way voice/data including ADS.The GNSS augmentation function provided by MSAS consists of a GPS overlay signal, wide area differential information and GNSS integrity broadcast. Improved integrity, availability, continuity of service and accuracy to the GPS Standard Positioning service for civil aviation will be achieved using MSAS as a geostationary platform for the navigation transponder. The system will also need to have a capability to exchange GIC information with other GNSS augmentation systems.
15 India - GAGAN GPS and GEO Augmented Navigation 1 Geostationary SatelliteIndia based Ground Reference StationsInteroperability with EGNOS, MSAS & WAASGAGANIndia plans to have its own satellite-based augmentation system, named GAGAN, an abbreviation for GPS and Geo Augmented Navigation system. The Airports Authority of India and the Indian Space Research Organisation signed a memorandum of understanding in August 2001 for jointly establishing the GAGAN system. But the first satellite which will provide the space platform for the augmentation system is scheduled to be launched in As with the other augmentation systems, GAGAN too will have to pass through an experimental phase before it is declared operational. Once up and running, GAGAN will bridge the gap between the European EGNOS and the Japanese MSAS systems.ISRO's GSAT-4 satellite, currently scheduled for launch in , will carry the satellite transponder for broadcasting the GAGAN's correction signals. On the ground, eight reference stations are planned for receiving the signals from the GPS and GLONASS satellites. The Mission Control Centre will be based in Bangalore, as will the uplink station.Once GAGAN is operational, it is likely to improve air safety over India, increase the traffic which can be handled by individual airports, and make more airports open to routine flights. There are 449 airports and airstrips in the country. The AAI manages 92 airports and 28 civil enclaves at defence airfields. According to the AAI website, only 34 instrument landing systems have been installed. With GAGAN, aircraft will be able to make precision approaches to any airport in the coverage area.
17 EGNOS ESA European Commission EUROCONTROL System Design Development Qualification & Technical ValidationEuropean CommissionLand User RequirementsSatellite CommunicationsUser EquipmentEUROCONTROLCivil Aviation RequirementsOperational Testing and ValidationEGNOSThe European Geostationary Navigation Overlay Service (EGNOS) is Europe’s first foray into satellite navigation. It is being developed by ESA under a tripartite agreement between the EC, the European Organisation for the Safety of Air Navigation (Eurocontrol) and ESA. Several service providers are supporting the development programme with their own investments.EGNOS will complement the military-controlled GPS and GLONASS systems. It will disseminate, on the GPS L1 frequency, integrity signals giving real-time information on the health of the GPS and GLONASS constellations. Correction data will improve the accuracy of the current services from about 20 m to better than 5 m. The EGNOS coverage area includes all European states and can be readily extended to include other regions within the coverage of the two Inmarsat geostationary satellites being used. The third satellite, ESA’s Artemis, reached its operational position in January 2003.EGNOS will be the first stimulus for European-led navigation services and will as such pave the way for the Galileo services. EGNOS has been developed under the ESA Artes 9 programme, this does not include the operating costs. For civil aviation use, EGNOS complies with ICAO global standards. It is also expected to cover multi-modal transport and many other non-transport applications.An EGNOS System Test Bed (ESTB) broadcasting an EGNOS test signal has been available since early ESTB provides an opportunity for validating new application developments in a realistic environment. It comprises a space segment of two transponders aboard the Inmarsat-III Atlantic Ocean East and Indian Ocean satellites, a ground segment with a number of reference stations (RIMS) throughout Europe and beyond, a processing centre and uplink facilities integrated into Inmarsat Earth stations.EGNOS is a joint project of the European Space Agency (ESA), the European Commission (EC) and Eurocontrol, the European Organisation for the Safety of Air Navigation. It is Europe’s contribution to the first stage of the global navigation satellite system (GNSS) and is a precursor to Galileo, the full global satellite navigation system under development in Europe.EGNOS is the first step in the European contribution to the Global Navigation Satellite System, and a fundamental stepping-stone towards Galileo, Europe's own Global Navigation Satellite System. EGNOS is an augmentation system to the GPS (Global Positioning Satellite) and GLONASS satellite navigation systems, which provides and guarantees navigation signals for aeronautical, maritime and land mobile Trans-European network applications.Satellite broadcasting through geostationary satellites (GEOs) has proved to be an efficient strategy for avionic applications and other modes of transport. For some applications though, GEO broadcasting may have some limitations because building obstacles in cities or rural canyons can interfere with the GEO reception.
18 EGNOS Programme & Schedule Prior to EGNOS becoming operational, there are a series of testing phases to be completed. This phases are being completed using the EGNOS System Test Bed or ESTB system configuration. The ESTB system consists of space, ground and user segments. Ground segment The ground segment is made up of reference stations, processing centres, navigation land Earth stations (NLES) and a communications network.There are three different types of reference stations:Stations for geostationary orbit (GEO) ranging function(a signal similar to GPS) which are part of the Euridis ranging system.ESTB-specific reference stations There are ten stations that serve as data collection points for the GIC/WAD function and which use the existing reference station facilities of Racal Survey's SkyFix and NMA's SatRev systems. All the stations are equipped with a GPS/GEO receiver, a GPS/Glonass receiver, an atomic clock, computers with processing software, routers, dual-frequency antenna and an archiving device to store data. In addition these stations also transmit real-time data.Reference stations from the Mediterranean Test Bed (MTB) used to create Ground Integrity Channel (GIC) and Wide Area Differential (WAD) messages.Processing centres The ESTB system has two processing centres. These are responsible for:creating ranging, GIC and WAD messagesESTB data collection, archiving and post processingESTB system monitoring and controlGEO- and GPS-related data are processed in real time, while in this first stage the GLONASS performance assessment is limited to off-line analysis.Navigation Land Earth StationsTwo navigation land Earth stations (NLES) are used in the ESTB. The NLES located in Aussaguel, close to Toulouse (France), is part of the Euridis Ranging system and transmits through the INMARSAT III AOR-E satellite, while the other NLES, situated in Fucino (Italy), provides access to the INMARSAT IOR satellite.Space segmentThis is composed of navigation transponders on board the Inmarsat-III Atlantic Ocean Region East (AOR-E) and Inmarsat-III Indian Ocean Region (IOR) satellites. User segment Multiple ESTB user receivers are available on the market to test the system and perform demonstrations. In the context of the EGNOS Contract, a specific Test Bed User Equipment (TBUE) has been developed by Thales Avionic and is based on the existing TSO C129A family of products. The 15-channel receiver allocates two channels to GEO satellites and 13 to GPS; GLONASS capability will be added at a later stage. This segment also comprises a data recorder and a computer for navigation processing.
19 EGNOS System Architecture Satellites: Geostationary, GPS & GLONASS7 NLESArchitectureCurrent Status (Dec 04)All 4 Master Control Centres (MCC) have been deployed;All Navigation Land Earth Stations; (NLES) have been deployed;30 of the 34 RIMS are today deployed;All 3 EGNOS Geostationary satellites are transmitting successfully;EGNOS transmission/performances since Dec Daily transmissions since July 2004.SIS-2 performance qualification event planned in December 2004.EGNOS final functional qualification (IORR) planned end 2004.EGNOS performance qualification (PQR) planned Q4 MCC34 RIMSUsers
20 EGNOS Ground Segment MCC RIMS NLES EGNOS Ground Segment MCC The Master Control Centres process the data received from the RIMSRIMSThe Ranging and Integrity Monitoring Stations receive the signals from the GPS and GLONASS satellitesNLESThe Navigation Land Earth Stations aid the uplink of the data to the EGNOS satelliteRIMSNLES
21 EGNOS Measured Accuracies (Sept 5 2004) LisbonToulouseRomeBrusselsParisHNSE95%1.2m0.9m1.1m0.8m1.0VNSE1.7m1.4m1.3Recorded over a 24h periodLess than 1m horizontal accuracies recordedVertical accuracies of 1-2m (well below the 7.6m specificationEGNOS Measured AccuraciesRecorded over a 24h periodLess than 1m horizontal accuracies recordedVertical accuracies of 1-2m (well below the 7.6m specification
22 EGNOS Projects EGNOS Projects Examples: EGNOS/SISNET for public bus transportation (NAVOCAP, France; and also GMV, Spain)EGNOS dissemination through FM RDS in cars (TDF, France)EUROCOPTER (Helicopter Emergency Medical Services, Germany/France)EGNOS to support Precision Farming (Booz Allen, UK)DELTA hybridisation test in airports (M3 systems, France, and also at Sweden)EGNOS disseminations through DAB radios (BOSCH/ BLAUPUNKT, Germany)Internet EGNOS transmission: SISNET Pocket PC PDA receiver (Finish Geodetic Institute, Finland)EGNOS/SISNET to support blind pedestrian (GMV and ONCE Spain)
23 EGNOS SISNeT EGNOS SISNeT SISNeT combines the capabilities of satellite navigation and the Internet. The navigation information that comes from the EGNOS (European Geostationary Navigation Overlay Service) Signal-In-Space (SIS) is now available over the Internet and in real time via SISNeT.Specifically, SISNeT gives access to the wide-area differential corrections and the integrity information of EGNOS. The SISNeT project was undertaken by ESA during the second half of In August 2001, the first prototype of the system was set-up, and the SISNeT concept was successfully validated. Since February 2002, the system has been pre-operational, broadcasting an EGNOS-like signal through the Internet, as generated by the EGNOS System Test Bed (ESTB).Any user with access to the Internet (usually through wireless networks - GSM or GPRS) can access EGNOS through SISNeT, irrespective of the GEO visibility conditions. No EGNOS receiver is needed.The scientific and engineering communities can benefit hugely from SISNeT because they can exploit the ESTB (EGNOS System Test Bed) information simply via the Internet.The four main components of the SISNeT platform are:Base Station (BS) A PC computer connected to an EGNOS receiver through a serial port. Several software components are installed on the computer, so that EGNOS messages can be obtained and sent to a remote computer (called Data Server) in real-time.Data Server (DS) A high-performance computer, optimised for running server applications with many users connected at the same time. The DS functionality is implemented through a software application called SISNeT Data Server (SDS). This software receives the EGNOS messages from the BS and transfers them to the remote SISNeT users in real time. In addition, the SDS implements all the extra services (present and future) provided by the SISNeT system to the users.User Application Software (UAS) A software application, which design complies with the SISNeT User Interface Document specifications. The UAS obtains EGNOS messages in real time (1 message/s or 250 bit/s) from the DS. The UAS can also access and apply the present and future additional SISNeT services. Each concrete SISNeT-based application is characterised by specific processing and output interface stages, which provide the desired functionality and user interface to the UAS. The software can be embedded in different kinds of computers and electronic devices (e.g. Personal Data Assistants).Web Server The DS can store the received messages in a remote Web server via the FTP protocol, enabling future development of Web / WAP applications (accessible to the users through a Web browser or mobile device).
24 EGNOS Message Server 24h/24h Archive of EGNOS Messages Broadcast messages are stored in hourly text filesNew PossibilitiesEvaluation of EGNOS performanceAssessment of EGNOS at IGS SitesAble to post process data with conventional GPS receiversTest EGNOS enabled receiversEGNOS Message Server (EMS)Aiming at providing a 24h / 24h archive of EGNOS messages, ESA has launched a new service called EGNOS Message Server (EMS). The EMS service is accessible free-of-charge, using standard means (specifically, the FTP protocol). In practical terms, EMS is accessible by simply introducing an address in Internet Explorer or Netscape Web browsers. EMS stores the augmentation messages broadcast by EGNOS in hourly text files, which are organised over a pre-defined hierarchy of directories. All the information necessary to access EMS and exploit its data is explained in the EMS User Interface Document (UID). This document can be understood as a comprehensive EMS user guide, focusing both on developers of applications and also on general users wanting to simply browse the EMS archive. The ESA EMS service opens the door to new forms of synergy between the EGNOS system and the Internet. Some possible applications are:Interfacing simulation / analysis tools to EMS, being able to automatically evaluate the EGNOS performances over a given period.Combining GPS data from the IGS network sites with EGNOS messages got from EMS, being able to assess EGNOS performances at the location of the IGS sites. An interpolation process could easily derive performance maps covering Europe.Performing EGNOS tests using GPS-only receivers. Using GPS-only data and the EGNOS messages got from EMS, it is possible to apply the EGNOS corrections and integrity information on the post-processing stage.Test of EGNOS receivers. EMS data can be used offline to simulate the presence of the EGNOS Signal-in-Space, easing algorithm testing.Test of SISNeT-enabled EGNOS receivers. In this case, the presence of SISNeT can be simulated offline, saving communication costs (e.g. GSM or GPRS fees).EMS constitutes and enhancement of the possibilities offered by the ESA SISNeT project: while SISNeT allows accessing the EGNOS messages in real-time, EMS permits an offline access to a huge archive of already broadcast messages.
25 EGNOS Data Access Service Overall, the ultimate objectives of this activity are:Developing an operational EGNOS Data Access System (EDAS), including an EGNOSData Server and an EDAS/Service Provider Interface Software component, compliant with the technical requirements exposed in Annex 2 of this SOW.Perform some demonstrations of Service Providers exploiting the EGNOS Data Access System, and demonstrating the potential behind this concept.Having the EGNOS Data Access System ready to be integrated into the EGNOS V2 operational context.The following options are being considered for the development phase:SISNET Data ServerBroadcast of EGNOS in RTCM (Radio Technical Commission for Maritime Services) formatDevelopment of an EGNOS message and RIMS Data serverDissemination of EGNOS data in RDS formatProvision of Wide Area RTK solutionsEGNOS Broadcast through Digital Audio Broadcast (DAB)
26 EGNOS - Extensions Initial MRD developed in 1998 New Developments in the GNSS IndustryGalileoGPS ModernisationNew SignalsLaunch of WAASEGNOS V2 Concept DevelopedEGNOS - EXTENSIONSEGNOS is based on a MRD (Mission Requirements Document) Document developed in This allows EGNOS V1 service provision in 2004 with excellent performances. Since then, the GNSS environment has changedsignificantly:1. Galileo programme2. GPS Modernisation program (IIR-M, III)3. New L1/L5 GEOs4. Export opportunities for SBAS technology5. GPS/SBAS L5 standardisation work6. WAAS FOC program launchedTherefore an EGNOS V2 concept has been developed.EGNOS Evolution PlansIn June 2003 the Council of the European Union stated EGNOS is an integral part of the SatNav policy (EGNOS integration in Galileo)EGNOS should:become operational as soon as possibleallow for service availability in the long termbe used as a precursor to Galileoenable Galileo to penetrate rapidly the marketmeet the obligations of the international standardsbe extended determinedly to other parts of the world
27 EGNOS Evolution Plans Three EGNOS Versions conceived in 2005-2008 Step 1Step 2EGNOS v2.1End 2006EGNOS products over non-GEO data links (INSPIRE)Extension to MEDA and East of EuropeMessage Type 02 ExtensionEGNOS v2.2End 2007EGNOS MT 28Extension in AfricaModernised RIMS receiversSAR return linkEGNOS v2.3End 2008L5 standards and L5 GEO broadcastL1/L5/Galileo enhanced RIMS receiversEGNOS Evolution PlansStep 1 of the modernisation ( ) has been approved. This includes the release of EGNOS v2.1 early 2006 with 2 main new missions:Service Expansion to the south and eastNon GEO service multi-modal provision – EGNOS Data Access SystemMessage Type 02 ExtensionStep 2 is to be confirmed in 2005 and includes the EGNOS extension in Africa and the inclusion of SBAS L1/L5 services
28 EGNOS & GalileoFirst steps for Europe in the field of satellite navigationPrecursor to GalileoAllows early application developmentTesting of prototype business models and conceptsEGNOS & GalileoEGNOS makes it possible to offer now services similar to those that will be offered in the future by GALILEO, in particular through the transmission of an integrity message. EGNOS is the first phase of the European Union's policy on a global navigation satellite system, the second phase being the Galileo programme and the launch of a new constellation of radionavigation satellites. EGNOS, is also Europe's contribution to the international satellite radionavigation system devised by the International Civil Aviation Organisation (ICAO). EGNOS also contributes significantly to the success of GALILEO by acting as a precursor. It will facilitate GALILEO's entry into service by greatly increasing satellite navigation applications and contributing to the completion of the necessary certification and approval procedures. In addition to the development of a European satellite navigation technology resulting from the EGNOS programme, the study carried out by PricewaterhouseCoopers confirms the significant savings on the operating costs of the future GALILEO system. Lastly, EGNOS is the European vector for penetrating European markets, at a time when the equivalent American system (WAAS) is already present on several markets. On the institutional level, integrating the management of the EGNOS and GALILEO programmes into a single entity will be the best solution to ensure optimum compatibility. The Commission therefore proposes placing the EGNOS programme under the supervision of the GALILEO Joint Undertaking and to give this undertaking the task of supervising the operation of EGNOS after the Operational Readiness Review is completed in June 2004 as well as launching, as soon as possible, calls for tenders in order to conclude a concession agreement with an economic operator to operate EGNOS from June 2004.
30 Differential GNSS Differential GNSS DGNSS can provide higher accuracies of 2.5 metres in moving applications and even better in stationary situations, by cancelling out most of the natural and man-made errors arising from normal GNSS measurements. DGNSS works by having a fixed receiver at a known ground-based reference station (e.g. marine radio beacon stations) which continuously monitors the GNSS errors and transmits corrections to the measurements taken by mobile receivers operated by users of the system. The DGNSS service is intended to offer accuracies for general navigation of better than 5 metres for vessel position-fixing in areas where the freedom to manoeuvre is restrictedDGNSS is provided from radio beacons by modulating the carrier with the correction data and other information on the system:The modulation is Minimum Shift Keying (MSK), a special form of Frequency Shift Keying (FSK)The modulation rate is usually 100 or 200 bits per secondThe International Telecommunications Union (ITU) Recommendation M.823 incorporates the RTCM SC-104 protocol and the International Association of Lighthouse Authorities has adopted these standards for use with maritime radio beacons to transmit DGPS corrections.The radio beacon system uses the LF/MF band kHz in Europe ( kHz in other parts of the world). The Radio Regulations governing the use of this band allow for supplementary information to be transmitted - such as DGPS signals. A full description of the technical characteristics of the system can be found in ITU-R Recommendation M.823 (1996).
31 IALA DGNSS Performance The figure shows the significant enhancement to horizontal accuracy that using Differential GNSS can bring. The areas of blue signify an accuracy of less than 2m. The map shows that the DGNSS beacons around Europe are predominantly around the coasts. The darkest blue are areas of the highest accuracy and are closest to the DGNSS transmitters.
32 RTK GNSS RTK (Real-Time Kinematic) RTK is a process where GNSS signal corrections are transmitted in real time from a reference receiver at a known location to one or more remote rover receivers. The use of an RTK capable GNSS system can compensate for atmospheric delay, orbital errors and other variables in GNSS geometry, increasing positioning accuracy up to within a centimetre. Used by engineers, topographers, surveyors and other professionals, RTK is a technique employed in applications where precision is paramount. RTK is used, not only as a precision positioning instrument, but also as a core for navigation systems or automatic machine guidance, in applications such as civil engineering and dredging. It provides advantages over other traditional positioning and tracking methods, increasing productivity and accuracy.Using the code phase of GNSS signals, as well as the carrier phase, which delivers the most accurate GNSS information, RTK provides differential corrections to produce the most precise GNSS positioning.The RTK process begins with a preliminary ambiguity resolution. This is a crucial aspect of any kinematic system, particularly in real-time where the velocity of a rover receiver should not degrade either the achievable performance or the system's overall reliability.Conventional ambiguity resolution follows this procedure:Define a search area based on an approached solution and its uncertainty.Test all potential solutions within the area statistically.Select the most likely solution among the possible solutions, according to a minimal variance criterion.Validate the chosen solution according to statistical criteria or by comparison with the second best candidate.
33 Assisted GNSS Assisted GNSS The system known as Assisted GNSS (A-GNSS) uses the mobile phone network to assist the GNSS receiver in the mobile phone to overcome the problems associated with TTFF (Time to First Fix) and the low signal levels that are encountered under some situations.The network provides the Ephemeris data to the cell phone GNSS receiver and this improves the TTFF. This can be achieved by incorporating a GNSS receiver into the base station itself, and as this is sufficiently close in position to the mobile the data received by the base station is sufficiently accurate to be transmitted on to the mobiles. The base station receiver is obviously on all the time, and will be located in a position where it can "see" the satellites.The information provided can be either the Ephemeris data for visible satellites or, more helpfully the code phase and Doppler ranges over which the mobile has to search, i.e. 'acquisition data'. These ranges can be estimated as the position of the mobile is bounded because it must be within the cell served by the particular base station. This technique is able to improve the TTFF by many orders of magnitude.Assisted GNSS is also used to improve the performance within buildings where the GNSS signals are by 20 dB or possibly more. Again by providing information to the GNSS receiver in the mobile it is able to better correlate the signal being received from the satellite when the signal is low in strength. Using this technique it is possible to gain considerable increases in sensitivity and some manufacturers have claimed it is possible to receive signals down to power levels of around -159dBm. The base station supplies the receiver with navigation message bits - 'sensitivity data'.
35 Shortfalls & Limitations InterferenceJammingAccuracyIntegrityAvailabilityMultipathPowerShortfalls & LimitationsDue to the satellite signals from space being inherently week by the time they arrive at the Earths surface, they are subject to several limitations:InterferenceDue to the low strength of the radio signals it is possible that they can easily be swamped by other radio signals from stations on the ground.JammingThe weak signals and sensitive nature of the GPS receivers, means that a relatively low power device transmitting static on the GPS frequencies can completely wipe out the signals.Further limitations to the current satellite navigation systems (i.e. GPS):AccuracyAt present stand alone accuracy using GPS is approximately 8m, however this accuracy is under the control of the US government. They are able to reduce the accuracy for security purposes to ensure their own system can not be used against them.IntegrityA measure of the equality of the navigation system. Integrity is a measure of confidence in the information provided by the whole system. It includes the capacity of a system to be prevented to a user in sufficient time so that the system cannot be used for the desired operation.AvailabilityAvailability is the measure of the suitability of the navigation system for a particular operation. In relation to satellite navigation this can often be affected by the surrounding environment and the satellite constellation design.MultipathMultipath is the corruption of the direct GPS signal by one or more signals reflected from the local surroundings. These reflections affect both code and carrier based measurements in a GPS receiver. If multipath signals are used in the position determination process it can vastly affect the accuracy of the users location.PowerThe transmission power of the satellites is very low and the GPS satellites currently transmit at approximately 50 watts. This means that by the time the signal reaches the earths surface, the signal is very weak and below the noise floor.
36 Technical Issues Geometry Current Systems Galileo Good Geometry For a reasonable calculation of the user position, a reasonable geometry of satellites is required. Good geometry is where the satellites are distributed evenly/well across the visible sky. Poor geometry is where satellites are grouped in certain areas, this means that the radio signals are coming from similar directions, which degrades the accuracy of the position calculations. The geometry of satellites is measured using a figure known as Dilution of Position or DOP. DOP is an indicator of the quality of a GPS position which takes account of each satellite’s location relative to the other satellites in the constellation and their geometry in relation to the GPS receiver. A low DOP value indicates a higher probability of accuracy. Standard DOP terms are:PDOP – Position Dilution of Precision. A unit-less figure of merit expressing the relationship between the error in user position and the error in satellite position. Geometrically, PDOP is proportional to 1 divided by the volume of the pyramid formed by lines running from the receiver to four satellites observed. Values considered good for positioning are small.(such as 3) Value greater than 7 are considered poor.RDOP – Relative Dilution of Precision. It is usually in units of meters/cycle. Multiplying RDOP by the uncertainty of a double-difference measurement yields the spherical relative-position error. RDOP is used as a guide to the adequacy of receiver observation during real-time surveying measurements in static mode.HDOP – Horizontal Dilution of Precision.VDOP – Vertical Dilution of Precision.TDOP – Time Dilution of Precision.GDOP – Geometric Dilution of Precision. The relationship between errors in user position and time and in satellite rangeWith the advent of Galileo and the improvement of the GLONASS constellation, the geometry will improve for users of combined receivers. Currently the GPS system is optimised for use over the USA and can be altered to suit US military activities. Galileo upon launch will be optimised for use over the whole of Europe.Good GeometryBad Geometry
37 Operational Issues Availability Continuity Blocked Signals Urban Areas TreesUndergroundContinuityOperational IssuesAvailabilityThe availability of satellite navigation depends greatly on the users location and surrounding environment. For example users in urban environments may have difficulty receiving satellites due to them being blocked by the surrounding buildings, this has an immediate impact on the geometry of the position fix and hence the accuracy. This is also the case in urban areas. The satellite navigation signals also do not work underground, therefore making it impractical to use in tunnels.ContinuityContinuity is the ability of a system to function within specified performance limits without interruption during a specified period. This is particularly critical to operations where safety is paramount. If performing complex manoeuvres in a harbour the pilots relying on the satellite navigation system will be conscious that they will require precise measurement for the period of the manoeuvres.
38 Safety Issues Receiver Autonomous Integrity Monitoring (RAIM) Ground Integrity Channel (GIC)Backup SystemsCommon ModeSafety IssuesRAIMReceiver Autonomous Integrity Monitoring or RAIM is a method of determining if the satellite signals have been corrupted. RAIM was devised by the aviation community, and is implemented within the GNSS receiver. It requires no additional architecture, however it does require one additional satellite visible to work. Therefore instead of requiring a minimum of 4 satellites, 5 are required to provide a position and a RAIM statistic.GIC - ConceptWorld-wide coverage disseminated through MEO (Medium Earth Orbit) broadcastGalileo and GPS/(GLONASS) satellite integrityChannels available for non-European States/Regions wishing to generate their own integrity information (up to 8)Common ModeThe use of one single navigation system, introduces a singular common mode of failure. In the case of GPS, if the system fails or is turned off for security reasons, this could have a global impact on navigation, safety and business.Backup SystemsFor safety applications a backup system is preferable to GNSS. A back up system would allow continuous navigation if GNSS fails. A complimentary system such as an Inertial Navigation System has
39 Regulatory Issues Applied for GNSS use in safety applications MUSSST StudyMethods to authorise for operational useSpecification of validation proceduresSafety case approachRegulatory IssuesThe main objective of MUSSST was to help the different user communities that are considering the use of GNSS for their safety-critical applications, to authorise its operational use. As a consequence, the MUSSST study objectives were to identify the methodology forthe validation of the use of GNSS for safety-critical applications in the different modes of transport, to apply this methodology to GNSS-1 and GNSS-2, to identify the missing elements and the obstacles, and to formulate recommendations of actions for the validation ofGNSS.The MUSSST methodology specifies a formal validation procedure for the entire GNSS from signal generation to signal processing including the use of the resulting information in navigation and control of mobiles. This means that a GNSS architecture is established, theGNSS elements meet their performance requirements, and the system as a whole achieves its performance target and is protected against all credible hazardous operations. The MUSSST methodology is based on the safety case methodology which is a risk-based approach applied to the system lifecycle, to the engineering process allowing to divide the validation task into four parts, SIS verification, sensor qualification, mobile certification and operational approval.The safety case approach is proposed as the basis for formal approval requiring formal demonstration of safety and functionality of GNSS, a systematic identification of hazards with an assessment of associated risks, the derivation of the target level of safety (TLS), and safety requirements. The safety case approach requires a system development, the validation and assessment process to run in parallel, each milestone is assessed and endorsed by an appropriate authority. SIS verification, application identification, sensor qualification, mobilecertification, operational approval are the steps proposed in the MUSSST methodology, the application identification being an additional element mandatory to proceed in the validation process.
40 Legal Issues Privacy Concerns Data Protection Evidence Time Stamping With the increase in tracking capabilities and telematic applications, there is increased concern that a users location will no longer be private. The data collected must be protected to ensure an identified users location can not be used illegally. There are definate issues which may concern users of location based services in terms or location targeted promotions and advertisements.Data ProtectionIf a users location is to be recorded it is paramount that the security is assured. This will add further burden on the already existing data protection laws.EvidenceIt has already been seen that the use of tracking/location data can be used as evidence in a court of law. Therefore it is expected that this type of evidence will become more commonplace in the future.Time StampingSatellite navigation provides precise timing and can be used to time stamp such things as stock exchange transactions.
42 Other Positioning Methods & Enhancements Other methods of positioning that can be combined with GNSS are as follows:PseudolitesTerrestrial Radio NavigationMobile Telecommunication PositioningOther SensorsOther Positioning Methods & EnhancementsOther methods of positioning that can be combined with GNSS are as follows:PseudolitesTerrestrial Radio Navigation e.g. eLORANMobile Telecommunication PositioningOther Sensors e.g. inertial, maps, radar
43 Pseudolites Ground Based “Satellites” GPS-like signals Provide additional ranges to enhance positioning in difficult operating environmentsPseudolitesPseudolites (PLs) are ground-based satellite-like transmitters that can generate and transmit GPS-like ranging signals to improve outdoor GPS availability or even entirely replace the GPS constellation for indoor applications. PLs transmit GPS-like signals on the L1 ( MHz) and possibly on L2 ( MHz) frequencies, using either the C/A-code or both C/A- and P-code. Normally, standard GPS receivers with minor firmware modifications can track PL signals. Introducing PL arrays can significantly improve satellite geometry. Consequently, positioning accuracy and reliability (both internal and external) can improve, especially in the vertical component and mainly as the result of the low elevation angle of PLs (normally less than 15 degrees).PL signals may also support integer ambiguity resolution. The geometric configuration of PLs is very important, however, and becomes crucial for indoor applications. Even though PLs generally improve positioning accuracy, users should be aware of their negative aspects. For example, a much shorter distance exists between a PL and the user receiver than with a GPS satellite, so any errors in PL location will have a significant effect on the determined receiver antenna coordinates. The degree of influence depends on the geometry between the PLs and the receiver (weak geometry may even cause a singularity in the solution).Another problem arises when a PL signal has a strong multipath signature, which may come not only from reflecting objects in the vicinity of a GPS receiver's antenna but also from the transmitter itself. In addition, the mixed differential technique (i.e., GPS and PL combined) compared with regular differential GPS (DGPS) might eliminate fewer error sources because of totally different geometry. As well, the PL signal could interfere with the satellite signals because the PL transmitter is very close to the receiving antenna, in contrast to the GPS satellites' position (the so-called near–far problem). Thus, the power level of the PL should be carefully controlled.Typical applications of PLs are indoor/outdoor local positioning systems, personnel tracking systems, mobile object tracking and control systems in large factories, aircraft precision landing systems such as the Local Area Augmentation System, precision harbor entry, precision farming, heavy industry control in dangerous areas, military and special applications, and DGPS data links.
44 eLoran (Terrestrial System) Alternative Positioning method to GPSeLoran incorporates the latest:ReceiverAntennaTransmission TechnologyEnhanced systems can now provide accuracies of 8-20meLoranBecause GPS is vulnerable to intentional, unintentional, and natural interference, the US government is placing increased emphasis on technologies that can lessen the overdependence on GPS. While GPS technology is satellite-based and very high frequency, Loran uses ground-based transmitters and is low frequency. Loran signals are very high-powered, so they penetrate cities, buildings and densely foliaged areas where low level GPS signals are often blocked. From a practical perspective, Loran is virtually unnameable because of its high power. Enhanced Loran or eLoran is a Loran system that incorporates the latest receiver, antenna, and transmission system technology to enable Loran to serve as a back-up to, and complement global navigation satellite systems (GNSS) for navigation and timing. This new technology provides substantially enhanced performance beyond what was possible with Loran-C, eLoran’s predecessor.For example, it is now possible to obtain absolute accuracies of 8-20 meters using eLoran for harbour entrance and approach. Similarly, eLoran can function as an independent, highly accurate source of Universal Time Coordinated (UTC). eLoran transmission infrastructure is now being installed (2004) in the US, and a variation of eLoran is now operational in northwest Europe. It is expected that there will be a global evolution towards eLoran, and users can anticipate integrated eLoran/GNSS receivers in the near future for a variety of applications.Technical and Cost/Benefit Evaluations of eLoranA report on the US Loran technical evaluation was completed in March 2004 and states: "The evaluation shows that the modernized Loran system could satisfy the current NPA, HEA, and timing/frequency requirements in the United States and could be used to mitigate the operational effects of a disruption in GPS services, thereby allowing the users to retain the benefits they derive from their use of GPS." Clearly, eLoran has met US performance requirements.In February 2004, another DOT (Department of Transport) report stated: "If enhanced Loran meets the aviation NPA and maritime HEA performance criteria, and is cost effective across multiple modes, the Federal Government should operate Loran as an element of the long-term US radio navigation system mix."In order to address this economic criterion, the DOT’s Volpe Centre conducted a Loran cost/benefit analysis, which was also completed in March Although the results have not yet been made public, modernization towards eLoran is well underway in the US. To date, approximately $120 million has been spent on eLoran, and after the modernization is complete, the US eLoran system will have annual operations costs of about $15 million. This is a remarkably low figure, particularly because eLoran will provide the US with benefits in aviation, marine, terrestrial, and timing applications, benefits that single modal systems could never provide. Of course, nations with smaller eLoran systems can expect proportionately smaller modernization and operational costs.Implications for eLoran’s FutureThe last several years have brought a tremendous interest in eLoran’s potential, and the realization of this potential will have major implications in two areas. First, there will be an expansion of eLoran systems internationally. More areas of the world will be covered by eLoran, and eLoran will be used for more applications in those areas (e.g. the use of precise timing signals from the new UK transmitter). Second, there will be an intense period of integrated eLoran/GNSS user equipment development, as evidenced by GPS/Loran integration work already underway for aviation, marine, and timing applications.
45 Mobile Phone Positioning For use in the provision of Location Based ServicesNetwork Based SolutionsPDEAngle of ArrivalTime of ArrivalHandset Based TechniquesSIME-OTDMobile Phone PositioningThe terms mobile positioning and mobile location are sometimes used interchangeably in conversation, but they are really two different things. Mobile positioning refers to determining the position of the mobile device. Mobile location refers to the location estimate derived from the mobile positioning operation. There are various means of mobile positioning, which can be divided into two major categories - network based and handset based positioning. The purpose of positioning the mobile is to provide location-based services (LBS), including wireless emergency services.Network-based Mobile Positioning TechnologyThis category is referred to as "network based" because the mobile network, in conjunction with network-based position determination equipment (PDE) is used to position the mobile device.Network based PDECOO is not always available (for example: via SS7 with non-GSM WAP based services) nor does it always meet the QOS requirements of the LBS application. Therefore, network-based (or handset based) PDE must be employed.Angle of Arrival MethodThis method involves analysis of the angle of arrival (AOA) of a signal between the mobile phone and the cellular antenna. AOA PDE is used to capture AOA information to make calculations to determine an estimate of the mobile device position.Time of Arrival MethodThis method uses the time of arrival (TOA) of signals between the mobile phone and the cellular antenna. TOA PDE is used to capture time difference of arrival (TDOA) information to make calculations to determine an estimate of the mobile device position.Handset-based Mobile Positioning TechnologyThis category is referred to as "handset based" because the handset itself is the primary means of positioning the user, although the network can be used to provide assistance in acquiring the mobile device and/or making position estimate determinations based on measurement data and handset based position determination algorithms.SIM ToolkitThe SIM Toolkit (STK), as an API between the Subscriber Identity Module (SIM) of a GSM mobile phone and an application, provides the means of positioning a mobile unit. Positioning information may be as approximate as COO or more precise through additional means such as use of the mobile network operation called timing advance (TA) or a procedure called network measurement report (NMR). In all cases, the STK allows for communication between the SIM (which may contain additional algorithms for positioning) and a location server application (which may contain additional algorithms to assist in mobile positioning). STK is a good technique to obtain position information while the mobile device is in the idle state.Enhanced Observed Time Difference (E-OTD)This is what is also referred to as reversed TOA or handset based TOA. The basic method is employed as with TOA, only the handset is much more actively involved in the positioning process. Specially equipped handsets are required.
46 Other Systems Gyrocompass Inertial Measurement Units Magnetometers Digital MapDigital Elevation ModelRadar etc.Onboard SystemsGyrocompassOne of the main low cost heading sensors on the market today is a Gyrocompass. A gyrocompass is a compass which finds North by using an (electrically powered) fast spinning wheel and friction forces in order to exploit the rotation of the Earth. Gyrocompasses are widely used on ships. They have two main advantages over magnetic compasses:they find true North, i.e. the direction of Earth's rotational axis, as opposed to magnetic North,they are not affected by metal in a ship's hull.Inertial Measurement Units (IMU)A full inertial navigation system (INS) consists of three mutually orthogonal accelerometers and three single-degree-of-freedom (or two twin-degree-of-freedom) gyroscopes. By sensing the forces acting on a body, acceleration can be extracted. A vehicle's velocity can then be determined by integrating this acceleration with respect to time, and distance can be derived from a further integration. The gyroscopes measure angular velocity with respect to inertial space. Attitude can then be determined by integrating with respect to time again. An INS can therefore determine three-dimensional position and orientation in an entirely self-contained manner, i.e. with no external aiding. This operational independence means inertial systems are not subject to the availability problems that can limit the use of GPS.Inertial systems essentially measure relative positions, which can only be converted into an absolute reference frame by calibrating the system at a known point, or by using aiding data from an external source. In periods when the INS is used as the sole means of navigation, the computed position will tend to drift as a function of time. The cost of an INS is related to the size of this drift, with more expensive systems having a significantly lower drift rate (e.g. 0.3 to 0.5m per minute, rather than 30 to 50m/minute).MagnetometersA magnetometer is an instrument for measuring the intensity and/or direction of a magnetic field. This is a way of determining where magnetic north is, which aids the navigation process.Digital Map & Elevation ModelThe use of digital map and elevation data can aid the navigation process by constraining the solution. Map or model matching can be used to ‘snap’ a users location to a particular feature e.g. a road, depending on the data from the other navigation sensors.RadarElectromagnetic sensor characterized by RAdio Detection And Ranging, from which the acronym RADAR is derived. Predicted in the early part of the 20th century, the first important system was built in England in Basic building blocks of a radar are the transmitter, the antenna (normally used for both transmission and for reception), the receiver, and the data handling equipment. Using this equipment users can determine the bearing and range of obstacles.
48 GPS III Enhance the overall GPS system Continuing development in response to military and civilian needsEnhanced Anti-Jam CapabilitiesImproved security, accuracy and reliabilityGPS IIIGPS III will address the military transformational and civil needs across the globe, including advanced anti-jam capabilities, improved system security and accuracy, and reliability.The GPS III program objective is to preserve and build on the successes of the Navstar Global Positioning System (GPS) by creating a new architecture (based on the operational requirements of the AFSPC/ACC I/II/III GPS ORD, dated 18 Feb 2000) for the assured delivery of enhanced position, velocity, and timing (PVT) signals, and related services to meet the needs of the next generation of GPS users.The GPS III program includes an integrated space segment (SS) and control segment (CS) system that incorporates the Nuclear Detonation Detection System (NUDET) and defines the Signal-in-Space (SIS) to User Equipment (UE) interface. The system should provide a best value solution with the flexibility to anticipate and respond to future military and civilian needs. The GPS III security infrastructure should provide user access to and protection of the entire system. The GPS III system should facilitate the incorporation of additional mission capabilities (i.e. Blue Force Tracking (BFT), Search and Rescue (SAR) missions, etc.).Lockheed Martin is leading a team to develop the next generation GPS satellites. The team which includes Raytheon ITT Industries and General Dynamics is currently under contract for GPS III concept definition and plans to compete for the future development.
49 Future GLONASS GLONASS K Modernisation of Russian Geodetic Network IntegritySearch and RescueModernisation of Russian Geodetic NetworkIndia may become a partner in the future of the GLONASS programmeFuture GLONASSGLONASS-K will be the future generation GLONASS satellite and will have a third civil signal. It will also weigh much less than the GLONASS-M (800 kg versus 1,400 kg). GLONASS-K will transmit integrity information and will support search and rescue operations.Russia is modernizing its national geodetic network to be compatible with the ITRF (IERS Terrestrial Reference Frame). It has updated the coordinates of the fundamental geodetic control network throughout Russia and in addition has defined a high precision geodetic network tied to the ITRF.Russia has recently signed an agreement with India, which includes potential cooperative efforts regarding GLONASS.The Russian Aerospace Agency is now generating precise orbits for the GLONASS satellites from Russian tracking data and from the IGS's network data. It is considering contributing these precise orbits to the IGS. Furthermore, the Agency is considering co-locating GPS-GLONASS receivers at IGS stations.India is to help Russia replenish its constellation of GLONASS navigation satellites, including launching some satellites on Indian vehicles. Under an agreement signed by Russian president Vladimir Putin, the two countries will work together to bring the GLONASS system up to a minimum effective size of 18 operational satellites by 2007.
50 QZSSQZSS will bring“Value added services for mobile users by combining communications, broadcasting, and positioning. Nationwide coverage is available since the QZSS is directly overhead.“QZSSOver the past several years, leading public and private organizations in Japan have been investigating proposals for developing an advanced space-based augmentation system for GPS. Last year, the Japanese government authorized continued work on a concept for a Quasi-Zenith Satellite System (QZSS), or Jun-Ten-Cho in Japanese, developed by the Advanced Space Business Corporation (ASBC) team, including Mitsubishi Electric Corp., Hitachi Ltd., and GNSS Technologies Inc. If all proceeds as planned, by 2008 the QZSS would provide a new integrated service for mobile applications in Japan based on communications - video, audio, and data broadcasts and positioning. QZSS's positioning capabilities would, in effect, represent a new-generation GPS space augmentation system, with limited navigation capabilities. In other words, although the QZSS is seen primarily as an augmentation to GPS, without requirements or plans for it to work in standalone mode, QZSS can provide limited accuracy positioning on its own. The service also can be augmented with geostationary satellites in Japan's MTSAT Satellite-based Augmentation System (MSAS) currently under development.SystemThe QZSS constellation will consist of three satellites moving in periodical highly elliptical orbits (HEOs) over the Asia region. The QZSS satellites will be launched with Japan's H-IIA launch vehicle or a similar type of launcher. Satellites will have L-, S-, and Ku-band capabilities (S-band for broadcasts and low-speed communications, Ku-band for high-speed communications and TT&C).Five types of constellations, which are being considered for QZSS, were registered with the International Telecommunications Union in November A symmetrical 8-shape orbit has been dropped from consideration due to the frequent satellite manoeuvres that would be required to avoid collisions as a satellite passes through the highly populated geostationary belt. Also this constellation would provide less favourable visibility over the northern hemisphere in comparison with HEO.Due to the highly elliptical shape of the QZSS orbit, a satellite will linger in the part of the orbit with high altitude, as its velocity decreases when it goes far from Earth. This will allow the QZSS satellites to spend most of their time over the desirable region. A QZSS satellite will typically operate more than 12 hours a day with an elevation above 70 degrees, a performance characteristic from which the term "quasi-zenith" derives.At the moment the asymmetrical 8-shape orbit appears to be a more probable candidate. This orbit goes about 400 kilometres below the geostationary satellites belt and therefore requires less frequent collision avoidance manoeuvres in comparison with a symmetrical 8-shape orbit. However, satellites should be monitored for a collision risk at orbit intersections, which is not the case for tear-drop shape orbits. The asymmetrical 8-shape orbit also gives better characteristics for positioning service due to superior geometry. It also has better performance for purposes of ambiguity resolution due to improved satellite visibility, geometry, and azimuth-elevation dynamics, that is, quicker satellite movement relative to a user.Differential ServiceIn terms of ranging service, QZSS will provide better geometry and more frequencies (than the MSAS system), which will allow direct estimation of ionospheric errors. Moreover, QZSS plans to follow GPS signal modernization, in which case civil codes with higher chip rates than the L1 C/A-code will be available on L2 and L5 in the near future. Apart from this, QZSS will have its own system time and therefore provide potentially better service. Differences also exist between QZSS and MSAS in the way corrections are generated. The QZSS will have dissimilar content and format in the corrections messages. Ionospheric grids for QZSS will be generated differently, partly because many more reference points will be available in Japan. MSAS ionospheric corrections are based on global modelling, which demands less density of reference stations.As with ionospheric corrections, QZSS will use a dense local grid for the tropospheric correction, rather than the global model used by MSAS. QZSS will use Japan's GeoNet network and generate more accurate atmospheric corrections by giving more weight to actual observations instead of modelling. These corrections are on satellite-by-satellite and epoch-by-epoch basis. QZSS will use the same grid data for all frequencies and for code and carrier phase corrections. In the Asian region outside Japan, however, QZSS will use global ionospheric modelling.On the other hand, QZSS will not need the same high integrity level as MSAS, which has design requirements for safety-of-life applications. In any case, achieving this integrity level with QZSS would be difficult, taking into account the different infrastructure, onboard satellite clocks, constellation dynamics relative to monitoring network, and so on. Therefore, QZSS cannot substitute MSAS for safety-critical missions, but instead can provide more high-accuracy and diverse services.
51 Future WAAS Next phase planned for 2008 Increase coverage, continuity and availabilityAdditional geostationary satellites to be secured to ensure availabilityFuture WAASThe WAAS, as with any new technology, is being developed incrementally. The next phase for WAAS planned for 2008, will support more LPV approaches over a greater area of the continental U.S. and Alaska. In this phase, the FAA plans to upgrade WAAS in the areas of coverage, continuity, and availability. To increase the coverage, additional WAAS reference stations will be installed in Alaska, Canada, and Mexico. System component additions will serve to expand WAAS service to northeastern Maine, southwestern California and southwestern Texas. These additional stations will also greatly increase WAAS coverage in Alaska as well as provide service to Canada and Mexico. The FAA also plans to upgrade software and hardware making the system more efficient and yielding increased operational performance. The current INMARSAT 2-satellite constellation results in a potential single thread failure for all of WAAS in the eastern 4/5ths of the continental United States. As a result, to improve availability, the FAA has awarded a contract to Lockheed Martin to secure additional geostationary satellites from Telesat and PanAmSat.Achieving the next phase for WAAS will serve as a springboard on the path to achieving the International Civil Aviation Organization’s standards for a Global Navigation Satellite System landing system, which will allow pilots to safely descend to a 200 ft. decision height. Achieving this capability is expected in 2013, concurrent with the addition of L5 frequency on a new GPS constellation.WAAS Program BaselineOn May 3, 2004, the FAA’s joint resource council approved a revised acquisition program baseline (APB). Prior to this, the most recent approved APB for WAAS was developed in Much of the information in the 1999 document was out of date and needed to be revised to accurately reflect the current program direction. Also, the Office of Management and Budget (OMB) raised questions about the program’s cost, schedule, and performance goals in the 1999 baseline and alerted FAA that program funding was in jeopardy of losing OMB support if it was not rebaselined. This new baseline covers development of WAAS to full GNSS Landing System (GLS) capability, providing 200 foot minimums and three-quarter mile visibility through the use of dual GPS frequencies. Implementation of GLS will be concurrent with GPS modernization and is expected to occur in the 2013 timeframe.