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Volume 13, No. 1 |
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ION's New 2003-2004 Officers
The new officers of the ION elected for the coming year took over at the conclusion of the ION's Annual Meeting held in Albuquerque, New Mexico, June 23-25. These officers also serve on the ION Council along with other members of the Council, chairs of ION sections and past presidents. The ION thanks the outgoing officers for their hard work and wishes the best to the incoming officers.
President: Larry Hothem, U.S. Geological Survey
Executive Vice President: Dr. Penina Axelrad, University of Colorado
Treasurer: John Clark, The Aerospace Corporation
Eastern Region Vice President: Dr. Chris Bartone, Ohio University
Western Region Vice President: Dan Crouch, 46th Test Group/XP
Immediate Past President: Dr. Rudy Kalafus, Trimble Navigation
Western Council Member-at-Large: Tom Stansell, Stansell Consulting
Eastern Council Member-at-Large: Dr. Pratap Misra, MIT Lincoln Lab.
Air Representative: Barbara Clark, Federal Aviation Administration
Land Representative: Dr. Dorota Grejner-Brzezinska, Ohio State University
Space Representative: John Nielson, Rockwell International
Marine Representative: Douglas Taggart, Overlook Systems Technologies
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From the ION President: Continuing Progress and Success for the ION
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The past year has been a good one for the ION, especially considering the flatness of the world economies. Conference attendance and paper submission has remained high, and there have been a number of developments that have resulted in the need for new studies, assessments, and research.
NTM 2003
The National Technical Meeting in January was a good meeting, and several people told me that they thought the quality of papers was particularly high. Congratulations to Jay Spalding and Todd Walter and their track and session chairs.
Priorities
This year I have concentrated primarily on three areas: ION Fellow Selection, Congressional/Executive Fellows, and the Reserve Fund.
At the January meeting the Council accepted a number of changes in the Fellow Selection Committee procedures that had been developed by the ad-hoc committee chaired by A.J. Van Dierendonck. The Fellow Selection Committee, chaired by Tom Stansell, selected nine new ION Fellows, plus an Honorary Fellow and a Posthumous Fellow. They were honored in June.
Approval of Congressional and Executive Fellows
The Council also approved the selection of both a Congressional Fellow and an Executive Fellow for this year and special thanks to Dick Greenspan and his Committee on this effort. I asked Finance Chair Mike Braasch to take a fresh look at the reserve fund, and he has come up with what I think are some good recommendations.
I have also asked the regional vice presidents to work closely with their respective council members-at-large and section chairs to generate enthusiasm and participation among the membership. One of the great things about the ION is the continuing influx of new people into the planning and execution of our meetings and in the institute itself, and we need to continue and expand this momentum.
Many Thanks
The National Office has continued to do an outstanding job in their support for the meetings, responding to the members, keeping the books straight, and keeping me, among others, on track. It's a pleasure to work with a group of people that have such a responsible, professional attitude. They haven't been content to just repeat previous processes, but are always looking for ways to improve the operation.
I want to thank all the members of the Council for performing their work well; and to those of you that I have worked with closely, thanks for your great responsiveness.
Finally, I want to thank the ION members for enabling me to serve as ION president for this past year. I have thoroughly enjoyed it, and I consider it an honor.
I'm totally confident that Larry Hothem will be an outstanding ION president for the next year. He has lots of good ideas and lots of enthusiasm. I'm sure you will give him your full support.
WAAS Achieves IOC
The Federal Aviation Administration (FAA) on July 10 declared Initial Operational Capability (IOC) for The Wide Area Augmentation System (WAAS). This program milestone for WAAS will allow instrument flight use and is the first step toward opening pilot access to more than 500 published satellite runway procedures at more than 200 U.S. airports.
Pending certification of avionics with vertical navigation capabilities and approval of individual approach procedures, pilots will be able to navigate as low as 350 feet above the runway end under instrument flight rules using WAAS to provide stable vertical guidance. Later this year, a new procedure will be published for the full capability of WAAS, resulting in approaches down to 250 feet above the runway.
"Once avionics are certified to receive the system's full capability, WAAS will allow precision instrument approaches at thousands of runways at airports and airstrips that have little or no ground-based landing capability," said FAA Administrator Marion C. Blakey. "WAAS will also provide improved en route capabilities because pilots can fly more direct and shorter routes without depending on ground-based navigation aides."
United Parcel Service Aviation Technology and Chelton Flight Systems have received certification for WAAS avionics with horizontal navigation capability.
The equipment is available for the aviation community to purchase. Later this year, these avionics systems will be further certified to receive WAAS' vertical navigation capability. Several other manufacturers are currently working towards certification for WAAS receivers.
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Executive Vice President: Dr. Penina Axelrad Treasurer: Mr. John Clark Eastern Region Vice President: Dr. Chris Bartone Western Region Vice President: Mr. Dan Crouch Satellite Division Chair: Mr. John Lavrakas Immediate Past President: Dr. Rudy Kalafus
Facsimile: 703-383-9689 Web site: http://www.ion.org E-mail: membership@ion.org
Technical Director: Carl Andren Assistant to the Technical Director: Miriam Lewis Meeting Services/Author Liaison: Connie Mayes Member Services/Registrar: Wendy Hickman Graphic Design/Editor: Paula Danko Information Manager: Rick Buongiovanni |
GLONASS, GPS and Galileo: Present and Future Aspects
By Mr. Leeke van der Poel, Hydro International
Editor's note: Mr. Leeke van der Poel, editor in chief of Hydro International, a well-known journal published by GITC bv, a Nether-lands company, posed the following questions to several professionals in the field. The responses with graphics were provided by three of the experts selected by Mr. van der Poel and were orginally published in the April 2003 issue of Hydro International. The interview as it appears here has been edited slightly for publicaion in the ION Newsletter. The ION thanks GITC bv for its permission to reprint the interview.
Global Navigation and Hydrography is the theme of this issue. GALILEO has received a "green light", GPS has planned some important improvements and GLONASS has entered a significant development program. It is time for Hydro International to ask experts of each GNSS to give their opinion on certain topics and to address the question: "What is in it for us surveyors?" The experts we interviewed are: Dr. Vidal Ashkenazi (GALILEO), Mr. Keith McDonald (GPS) and Dr. Boris Shebshaevich (GLONASS).
The planned GALILEO-system involves some discussions with the already present GNSS elements and some of our questions have a political aspect. Dr. Ashkenazi preferred therefore to give a view on our questions that we publish under the last question.
Question: Are you concerned that the different GNSS system elements are competing in a political, technical and economic sense? If so, what consequences to quality and availability of services to the user community do you observe or foresee?
Shebshaevich: Generally speaking, competition is an inevitable aspect of any human activity. GNSS activities are not excluded. Actually, GPS and GLONASS appeared initially as elements of national security. Both were strongly stimulated by political and technical competition of the 1970's and 80's.
The economic aspect emerged later (in the 1990's) when both GNSS system elements became operational and their civil capabilities were declared available free of charge to the world community. Economic reasons provide a serious guarantee of the quality and availability of services now. Of course, there are certain negative consequences of competition but they are the same as for any other international business and will be minimised by the same juridical instruments.
McDonald: The various navigation satellite systems are in many ways competing but in my view this is not a real concern. All systems need to justify their existence to their respective backers but there are significant benefits from the competition. The systems will work together to serve the users.
The availability of several systems provides substantially improved capabilities such that there is an enhanced value for each of the systems. An example of this is shown in Table 1 that compares the capabilities of GPS and GALILEO by themselves and in combination. There are advantages evident in accuracy, integrity, availability and coverage. It is important that the system sponsors don't detract from this by attempting to establish unreasonable restrictions or monopolies on their system's use.
Also, the experience of GPS (see Fig. 1 for representative spacecraft) indicates that there is an economic stimulus associated with the navigation satellite technology and equipment area that encourages others to proceed with alternative navigation satellite systems. The navsat field is a growth industry!
Two important factors that may thwart the development of certain capabilities of these systems are first, the several billion dollar cost associated with the implementation of a navsat system; and second, the system provider's concerns (including again, cost) and their efforts to deny the use of available systems to adversaries during times of hostilities.
However, there are no plans to cease transmitting the GPS signals. Also, there is strong interest and a commitment to maintaining GPS capabilities for all users outside the area of hostilities. This implies some secure provisions (e.g., encryption) or other safeguards for all or a portion of the military signal structure. This is, in general, not a concern for hydrographic users.
Question: GPS is available as an operational system to civil users. Consequently, it emerged into a major success for the (US) industry and the user community has become addicted to GPS. As a trade-off, there is no guarantee that user access remains unrestricted in the event of (US) national security or defense concerns. This might greatly harm friend and foe economically and security wise. Do you think that a guarantee to the International civil community should be given that at least in case of severe danger to lives, a basic GNSS signal should be guaranteed, or is there a national or regional responsibility for back-up -facilities?
Shebshaevich: Juridical guaranties for all and unconditional system availability are not realistic at the present time for many reasons. The process of particular agreements is more practical.
The Russian contribution to GNSS is GLONASS. The adopted governmental plans consider international cooperation to be one of the basic principles of its development and employment.
The September 11, 2001 events initiated investigations for additional back-up facilities. Ground based long range navigation systems like LORAN-C are among potential candidates. Russia has its own system of this type - CHAYKA. Its European, Northern and Far East transmitting station networks cover East Europe, Arctic and the Far East regions of Russia.
McDonald: Guarantees have been made by both the governments of the US and the Russian Federation for access to GPS and GLONASS. These occurred in 1985 at a meeting of the International Civil Aviation Organization (ICAO), an arm of the United Nations, in which both states committed to provide free access to their civil signals for ten years and an indefinite period beyond this. Further, the US government committed to informing the international community six years prior to any planned degradation of GPS civil (aviation) service. This commitment has the strength of an international treaty, and there has never been any interest to my knowledge in modifying this -commitment.
Of course, war conditions can change the character of any arrangements. However, the US has always guaranteed unrestricted access to its GPS civil signals (now the C/A-codes on L1) and has no plans to discontinue it. In fact, these signals are required in many cases to acquire the military (P/Y) signal. Also, access to the augmentations to GPS is open and available to all properly equipped users.
As a member of the US National Academy of Science Committee on The Future of GPS that studied the access and many other issues of GPS, two things among others became clear:
- The use of Selective Availability (SA) to degrade the performance of GPS is not a sensible or viable way to deny access of GPS civil signals to adversaries. SA was reduced to zero on May 1, 2000, and there are no plans to change this.
- There is consensus that the appropriate way for the military to control GPS operations in times of hostilities is to develop techniques that first, deny the signal to adversaries in a region of operations, and second, accomplish this without adversely affecting civil uses in adjoining areas. A substantial program to provide this capability is in -progress.
So, in summary, the current GPS civil signals will be available indefinitely without degradation. Additional civil signals (unrelated to any military use) are planned for the future at L2 (1227.6 MHz) and a pair of more capable signals are to be placed at a lower L5 frequency (1176.45 MHz). Figure 2 shows the civil and military signal evolution for GPS.
Question: GNSS systems have an important function not only in navigation and positioning but also in (industrial) timing and synchronization. There is little awareness of the increasing dependency of our society to this "by-product." When GNSS timing signals are distorted or absent we might be faced with serious problems in communications, data networks (e.g. electronic financial transactions), distribution of energy, remote control, etc. Do you consider this issue subject to international, national or institutional concern?
Shebshaevich: GNSS-techniques and applications are penetrating all areas. It makes no sense to stop this process. The only sensible plan is to minimise the risks and here, all possible coordination and agreements should be involved at international, national and institutional levels.
For example, the Russian Ministry of Telecommunication decree of 1999 prescribes the use of dual system GLONASS/GPS receivers for Russian telecommunication networks synchronisation. Photo 1 illustrates the RIRT's product set for this application including a 16-channel GLONASS/GPS OEM-board and smart clocks controlled by GNSS signals. These clocks are capable of keeping time in a holdover mode when satellite visibility is limited.
The Ministry of Transport considers similar safety measures for Autonomous Identification System (AIS) transponders. One can imagine the national regulations of this kind for critical applications.
McDonald: In my view, there has been considerable international, national, and institutional concern in this area for many years. The international timing community has defined standards, techniques and practices that have generally been adopted.
Many US power grids, cell phone systems and data networks are synchronized by GPS and have been for some time. The systems whose infrastructures are linked to GPS time typically have backup mechanisms such as very stable quartz or atomic standard clocks that can provide reliable operation for an extended period following any GPS timing failure.
Question: WRC1 2003 will allocate spectrum to GNSS. Do you think that the international GNSS community has sufficient power to claim the various frequencies to provide bandwidth for the different proposed system (extensions)? Economic preference for spectrum use consistently appears to go to satellite communications and the various communication services. Is there consensus to divide the allocated spectrum over the different GNSS systems in the most efficient way?
Shebshaevich: Satellite navigation and satellite communication are of equal importance. As a result, the existing systems are continuously improved in the frames of allocated frequency bands.
The current spectrum allocation provides rather non-conflicting coexistence of satellite navigation and communication systems. By the way, to reach electromagnetic compatibility with satellite communication systems, GLONASS frequencies are being shifted.
Future satellite systems will integrate both navigation and telecommunication functions in one and it will be the most efficient solution from all points of view.
But any attempt to violate the "status quo" in the nearest future is not reasonable, to my mind.
McDonald: There is a problem in that traditionally communications services appear to take some priority over navigation services because of the relative economics involved. However, WRC 2000 held in Budapest provided substantial spectrum for both US and European systems such that additional requirements appear to me to be modest. Figure 4 illustrates the specific ITU radionavigation frequency assignments relating to GNSS services.
As far as a consensus to divide the spectrum in the most efficient way, it is seldom that international bodies select the most efficient way. They normally are quite good however, at providing an acceptable solution that is workable to the parties involved. Obtaining consensus can be difficult and at times isn't possible, mainly because of political pressures.
Question: A solution to many issues is a well-defined interoperability and ultimately merging/integration of the three global systems. Is there a political will and has the technical feasibility been examined?
Shebshaevich: It must be agreed that a universal international satellite navigation system is a perfect solution. To move in this direction many non-technical problems must be solved. The level of cooperation in this field is still not sufficient to say it is feasible just now. But nevertheless, we shall move step by step. It is much easier to integrate GPS, GLONASS and GALILEO in user equipment. And it is what we are doing now and shall continue to do.
McDonald: The technical feasibility of integrating user equipment for operation with all systems has been examined and does not appear to be a significant problem. However, the political will to provide well-defined interoperability specifications does not appear uniformly strong. Interoperability will probably first occur in the marketplace. Clever engineering will provide receivers that are interoperable and will meet the market demands of the user community.
Question: Public Private Partnership (PPP) is a means to spare the taxpayer and involve private enterprises in building the system, providing services and supporting the maintenance and upgrading processes. However, when an activity is not profitable, the continuity and quality of the system might be at stake. Do you believe that governments may be forced to take over those activities from industry which are indispensable to the public?
Shebshaevich: The GLONASS development program for the next ten years makes economic efficiency the corner stone for the employment of GLONASS. The program financing implies federal and state budget components and off budget investments too. Funding of the most critical system segments are mainly the responsibility of governmental bodies.
The responsibility for user equipment and augmentation systems development as well as service providing can be non-state responsibilities to a considerable extent. Many applications, for example natural resource exploitation, land cadastre management and vehicle tracking are attractive enough for business at the local and private level.
McDonald: Many have had concerns about the workability or viability of the PPP arrangement planned for the GALILEO development if it places a significant burden on the industry participants. It appears that a PPP can be successful and desirable if the states involved are willing to take over the lion's share of the funding, the management of the economic arrangements and monitor how the private business develops.
The private partners' involvement and success may be strongly determined by the public sector's economic and management commitment. This can be problematic. It therefore, seems to me that the governments involved will have to show leadership in providing the major part of the funding and a commitment to the success of a PPP arrangement.
Question: Inmarsat started as an Institution financially supported by -member states and a stakeholder acting on behalf of the US. Inmarsat has been transformed into a private organization which is not dependant on financial support by governments. Do you think that GNSS could go the same way?
McDonald: No, in my opinion GNSS cannot go the same way. The financial arrangements for Inmarsat have been successful partly because they involve a product that can literally be sold by the bit (or byte) to end users who are easily identified (and billed). Navigation/position determination/time services differ in that they normally involve a multi-satellite one-way transmission to unknown passive users. These costs are typically the responsibility of, and are paid for by, user organizations or states. Public service and other encryption techniques may possibly make this practical in the future.
In general, government agencies provide safety related navigation services. Augmentation services that are primarily of a communications nature (e.g., downlinks of differential data) can be and currently are provided by a number of service providers on a fee basis.
Question: Defense agencies, holders of intellectual property rights and patents might object to interoperability or merging of systems for different reasons. For the sake of safety of navigation, however, a basic service level globally should be guaranteed by the operator(s) under all circumstances. This basic civil service level should be fully operationally capable (FOC). All additional levels of service could become available on a commercial basis as long as it does not interfere with the defined public tasks to facilitate Safety of Life (SOL) Navigation and Search and Rescue (SAR) activities. WAAS, LAAS, RTK and other (additional) services could be made available by local authorities or (private) concessionaires, consistent with the GNSS operating regulations. What is your comment?
McDonald: The services could be made available to local authorities and concessionaires in some circumstances, but it does not generally appear necessary. The services indicated provide a revenue stream to the governments involved through the tax base of this growth industry. Governments are equipped and can be motivated to support GNSS technology developments much as they support other developments of benefit to their industries and citizens.
Question: Nautical and Aeronautical Charts are published for worldwide application. It is of major importance that users can rely on globally standardized geodetic and geographical references. For GPS, the reference system is WGS84 which is continuously maintained and periodically updated. Tracking information is available and contributes to the ITRS (International Terrestrial Reference System). GLONASS and GALILEO are also using terrestrial tracking stations which are tied in to ITRS. Despite this commonality GLONASS and GALILEO use their own reference systems, which differ slightly from WGS 84. Also there is no satellite clock synchronization between the 3 systems. Standardization between the GNSS systems would make the individual system more robust and would economize on costs and efforts. Is global co-operation and standardization considered and by whom?
Shebshaevich: Systems of national standards and the certification of system developments are important activities in the GLONASS development program. Harmonisation of national and international requirements is one of the tasks. The necessity for co-operation with international co-ordination bodies is evident.
Meanwhile, modernised GLONASS space craft (S/C) will transmit messages containing GLONASS-GPS time reference discrepancy. Naturally our GLONASS/GPS user equipment operates with both geodetic reference systems. Proper transformations do not introduce noticeable errors.
McDonald: Standardization is normally desirable. However, there is some question as to whether or not inter-system standardization would make the individual systems more robust or economize on costs or efforts. It would make multiple systems easier to work with in combination, but the costs and efforts to maintain an acceptable infrastructure for accomplishing the inter-system standardization and synchronization could be significant. However, this may not be a significant concern.
The WGS-84 reference frame for GPS is now nearly identical to the ITRF (to the cm level) and the computation of WGS-84 fundamental coordinates is accomplished using a number of stations also employed in ITRF computations. ITRF/WGS-84 coordination is therefore not a concern. The Russian Federation has stated on a number of occasions that they plan to provide GLONASS coordinate transformation data or change from their PZ-90 reference to the ITRF.
The clock synchronization and related data among the three systems can be established in a straightforward manner. The inter-system biases, drifts and drift rates [e.g., between UTC(USNO) and UTC(USSR)] can be easily distributed. All systems use or plan to use stable atomic standards so the values are normally stable for periods of hours. Plans have been structured to provide this data to users so that corrections can be made to user clocks in much the same way that data message corrections are currently applied by the user to the various GPS spacecraft clocks.
Global cooperation and standardization are normally considered by international organizations in addition to the individual states' national standardization and measurement laboratories. These organizations include ICAO for aviation, the IMO (International Maritime Organization), the International Telecommunications Union (ITU), the Bureau Internationale des Poids et Mesures (BIPM) and in the US, the RTCA (formerly the Radio Technical Commission for Aeronautics), the AGU (American Geophysical Union), the Naval Observatory (USNO) Time Service, the National Institute of Standards and Technology (NIST) and others.
Question: And finally "What is in it for us surveyors?" or better phrased: "Our readers are eagerly looking forward to apply the improvements to GNSS that are underway and promised. What are the specific benefits for hydrographic surveying and offshore positioning in your vision will realistically be provided by each individual system in its own and/or by combining or integrating the systems? Can you also give a timescale to the new opportunities?"
Ashkenazi: To tackle this question, it is important to give a brief summary of the history of satellite navigation, and the reasons which led the European Union to embark on the GALILEO Project. In the 1990's, two independent satellite navigation systems were declared fully operational. They were GPS and GLONASS, both designed to meet the respective military requirements of the USA and the USSR (now Russia). In the case of GPS, the system was later declared to be a dual-use asset for both civil and military users, although all its funding still comes through the US Department of Defense.
GPS was designed to provide pre-determined levels of horizontal and vertical positioning accuracies 50% and 90% of the time, which were considered to be adequate for the requirements of military navigation on land, sea and air. Early civilian users of GPS in the 1980's included yachtsmen, fliers of light aircraft and hikers. The advent of Differential GPS or DGPS soon increased the number of civilian users of GPS. With DGPS they could achieve quasi-instantaneous positioning accuracies of the order of 1 to 3 metres, so long as they were located within several hundred kilometres of a DGPS reference station and received its broadcast of differential corrections. However, the real breakthrough for civilian users of GPS came with the development of the Carrier Phase Positioning technique, which was first proposed by two radio astronomers from MIT. This was the beginning of centimetric GPS, which led to hundreds of applications, ranging from Geodesy, Geophysics, Oceanography, land and offshore surveying, to timing, meteorology, agriculture, fisheries and space. GPS became an essential measurement tool for monitoring both the natural and the built environment.
This very wide variety of applications did not include safety-critical transportation. There were, of course, some general transport applications, such as fleet monitoring of trucks, taxis and cargo boats, but not aircraft landing or railway signalling. GPS, which was designed for military use, could not deliver on its own the tight requirements of accuracy, integrity and continuity of service, which are essential for safety critical applications. The missing ingredients were not within GPS itself, but external to it.
The breakthrough in meeting this demand for extra accuracy, integrity and continuity came with the development of the Wide Area Augmentation Systems, WAAS in the USA, EGNOS in Europe and MSAS in Japan. Wide area systems consist of one or more geostationary satellites, which provide a platform for the broadcast of differential corrections and continuous integrity messages coming from a dense network of ground based satellite tracking stations.
However, there still remains the possibility of critical failure of GPS. Some of this risk can be alleviated either by coupling GPS with other well tested back up systems, such as INS and VOR/DME for air navigation, and Loran-C for marine navigation, or by installing dense LAAS's, which include pseudolites emitting GPS like signals. However, the concern of "what happens in case of unintentional or intentional failure of GPS" still remains. How can one certify a navigation system for safety-critical civilian navigation, which is basically under the control of a single country and the requirements of its military establishment, however well intentioned these might be?
Hence, the European GALILEO System, which is being designed to be fully compatible and interoperable with GPS, but will be operated under the civilian control of the European Union. What difference will GALILEO make to hydrographic surveying and offshore positioning operations which, barring some exceptions such as ship docking, cannot be considered as strictly safety-critical transportation operations, like aircraft landing or railway signalling?
GALILEO will offer 4 types of service:
- Open Access Service (OAS) which, like the GPS Standard Positioning Service, will be freely available for mass market applications.
- Commercial Access Service (CAS), which will involve encrypted value added data in the signal, providing local augmentation services, integration with communication networks, etc.
- Safety of Life Services (SAS), which will provide additional integrity, for safety-critical applications in civil aviation, marine navigation and train signalling.
- Public Regulated Service (PRS), which will carry encrypted signals under EU government control, providing greater continuity of service for public service applications, such as police, fire, customs etc. To fulfil this requirements, the signal will be designed to offer better resistance to interference and jamming.
From the offshore positioning community's point of view, GALILEO will offer some distinct advantages. To begin with, it will double the number of available satellites, which will automatically increase accuracy and integrity, and provide better coverage and therefore better protection against masking in difficult offshore environments. To achieve this, the GALILEO signal will have to be both fully compatible with GPS (ie non-interfering operations for the benefit of end users), and offer an acceptable level of inter-operability also with GPS (eg a fully compatible geodetic coordinate datum and timing system).
Another issue of importance to the offshore community is the type and nature of the value-added data in the GALILEO CAS signal. Will CAS be offered by the GALILEO Operator or be sub-contracted to private companies, which would provide the interface with the different user communities? GALILEO also proposes to offer a certain level of service guarantees, an attribute which would distinguish it from GPS which offers a completely free service, with no guarantees.
The commissioning of GALILEO in 2008 or soon afterwards will open a new chapter in satellite positioning and navigation, with new opportunities for commercial exploitation and increased competition, and a favourable environment for generating new ways of using these multiple sources of satellite data for better solutions and an even wider range of applications.
Shebshaevich: To my mind, two development trends will give the main new opportunities for GNSS applications, for hydrographic applications in particular:
- Progress in GNSS functional quality;
- Progress in GNSS application techniques.
The first one will make the GNSS function more accurate, available and reliable for mass application. The second one will result in the GNSS function penetration to all human activities where accurate positioning and timing are attributes of event description.
The GLONASS functional improvements are based on its space segment, ground segment (including augmentation systems) and user segment modernisation and development. Starting with the year 2003, modernised GLONASS spacecraft (S/C) will be launched with an increased 7-year active life cycle, providing two civil signals available.
The GLONASS Development Program implies reconstructing the orbiting of an 18 S/C constellation in 3-4 years. After that, the space segment will be restored by the next generation of GLONASS S/C that are now under design. These have a 10-12 year life cycle, reduced mass so that six S/C can be launched into orbit at one time and three civil signals that will be available to the users. (see Figure 5).
The orbital constellation improvements along with ground control segment improvements shall provide the availability of several meters accuracy level on the global and continuous basis.
During the next 10 years the coastal regions will be successively covered by about 30 GLONASS/GPS differential reference stations based on medium frequency marine beacons. About 25 differential stations will operate on the main rivers and lakes at the same time. The main ports shall be equipped by autonomous identification system (AIS) ground stations. The long range navigation system CHAYKA will be modernised to provide for a differential correction transmission capability. These measures will result in about one meter accuracy together with integrity monitoring and user notification of safety of navigation concerns and provide reliable offshore positioning.
The user equipment segment is being modernised and has rapid growth. The ship`s models of GLONASS/GPS user equipment designed and mass produced by the Russian Institute of Radionavigation and Time are presented in Figure 6. These include GLONASS/GPS OEM-products of business card size for integrating in cartographic systems and AIS as well as completed devices for autonomous usage and for coupling with cartographic systems.
All equipments are 16-channel universal GLONASS/GPS receivers with code and phase measurement capability for receiving and processing WAAS, EGNOS and MSAS signals and data. Completed devices integrate marine beacon signals and differential data receiving functions. The next generation models will also integrate LORAN-C/CHAYKA extension. GALILEO integration is planned beginning in 2007.
The next generation of GLONASS/GPS user equipment, available in two years, incorporates the "system on a chip" (SOC) design approach. As a result, power consumption and costs will go down significantly and become reasonable for new mass applications that were not feasible before. For example, monitoring of the geographic environment including: ocean and sea, ice cover and iceberg dynamics, ocean-atmosphere interaction processes, tsunami and earthquake forerunners, etc.
Global positioning and telecommunications capabilities will be combined in thousands of cheap compact autonomous monitoring platforms: fixed, maneuverable or drifting. These can be the basis for global and continuous process monitoring in a few years.
McDonald: Although the timescale for the new opportunities has been configured, it is sensitive to the vagaries of annual funding and changing priorities. The schedule for GPS is reasonably clear at any given time but it frequently changes over time. Recent delays have surfaced because of US (and other states) plans to combat international terrorism as well as large expenditures for the second Gulf War. These circumstances give priority to operations (receivers, installations, personnel) as opposed to system improvements, e.g. system modernization and GPS III (the next generation GPS spacecraft). The schedule for GPS III slipped by 2-3 years this past January but some of this delay may be revised. Other setbacks will likely follow.
This delay in GPS modernization (the main elements of which are shown for the GPS Block IIF spacecraft in Figure 7) may be good news for GALILEO in that the delay may significantly widen Galileo's window of opportunity. This window is the time interval during which GALILEO will have significantly better performance capabilities than GPS. It relates primarily to the time span between the start of Galileo operational capabilities and the establishment for GPS of modernized civil operational capabilities.
The GPS new civil L2 signals may be available by about 2012 but the L5 civil signals (I5 and Q5 at 10 Mbps) will likely be delayed until 2016 or later. This provides GALILEO with a window of about 5-7 years or more, depending upon when GALILEO becomes operational (see Figure 8).
A summary of the GPS capabilities planned for users in the future is given in Table 2. Many of these constitute navigation, positioning, time determination and related enhancements of great benefit to users. Similar improved capabilities will be available in the Galileo and GLONASS systems. This confluence will markedly improve the accuracy, speed, timeliness and coverage available for survey, equipment positioning and other diverse activities of hydrographic professionals and other users.
NOTES: 1. WRC. World Radio Conference (ITU International Telecommunications Union)
BIOGRAPHIES
Mr. V. Ashkenazi is Chief Executive of Nottingham Scientific Limited, an emeritus Professor of the University of Nottingham, and a Fellow of the Royal Academy of Engineering. Professor Ashkenazi has supervised about 40 doctorate students, and has acted as a Consultant to a large number of commercial and government organisations in Europe, North America and elsewhere. In 1996, Professor Ashkenazi was awarded the James Alfred Ewing Medal by the Royal Society and the Institution of Civil Engineers, in recognition of his Significant Contribution to the Exploitation of GPS in a Wide Range of Scientific and Commercial Applications.
Mr. B.V. Shebshaevich graduated from Leningrad Electrical Engineering Institute in 1975. From 1975 up until the present time he has been a member of the Russian Institute of Radio navigation and Time (RIRT) team as engineer, head of the department, deputy director and now as first deputy director. In 1984 he attained his PhD degree in radiolocation and radio navigation.
Since l985 he has been involved in the GLONASS programme. He is and has been project manager on more than twenty R&D projects in GNSS positioning, timing and system integration.
Mr. K.D. McDonald is the Technical Director and Chairman of Navtech Seminars, Inc. and president of Navtech Consulting in Alexandria, Va. McDonald was scientific director of the U.S. Department of Defense Navigation Satellite Program and executive director of the Four Service Group that initiated the Navstar GPS program in the early 1970s. He served as the director of Federal Aviation Administration satellite development activities from 1974 to 1990. McDonald was a member of the National Academy of Sciences /National Research Council Committee on the Future of GPS during 1994-1995. He served as president of the U.S. Institute of Navigation in 1990-1991 and president of the International Association of Institutes of Navigation from 1997-2000.
ABBREVIATIONS USED
GNSS Global Navigation Satellite System
ITRS International Terrestrial Reference System
LAAS Local Area Augmentation System
LBS Location Based Services
PPP Public Private Partnership
RIRT Russian Institute of Radionavigation and Time
RTK Real Time Kinematic
WAAS Wide Area Augmentation System
WRC World Radio Conference
ITU International Telecommunications Union
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Portney's Corner: Space Alien Visit
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A space alien visits the Earth and reveals that on his Earth-sized planet major cities are connected by a series of straight evacuated tunnels that are always 22.5 minutes away. Choose the only correct interpretation of this revelation from the following:
A. Diamonds will plunge in value.
B. Plutonium will become more abundant.
C. The planet is 45 light years away.
D. Shades of Sutter's Mill.
Note: The average density of the Earth is 5.5 gm/cu cm.
And the Answer is D
Sutter's Mill was the location of the famous gold discovery in California in 1848. For all destinations to be reached in an invariant time in travel, the transportation system must be based on gravitational assisted free fall utilizing frictionless evacuated tunnels. The round trip would be the period solved by the following equation:
This period T (which is twice the duration of a one-way trip) is the same as the period of an orbital satellite at the surface of the planet. For the Earth, it is 84 minutes. For the space alien's planet, it is 45 minutes (2 x 22.5). It can be shown that the densities of planets are inversely proportional to the square of the ratio of their periods.
Therefore, we can determine the density of the aliens' planet:
Where p is the planet's density and p(e) is the Earth's density (5.5 gm/cu cm). Thus, solving the equation we find:
This answer is the approximate density of gold. Thus, the alien's planet is composed of gold.
| We're Sorry: Jack and the Rope Stalk Revisited |
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The answer to Joe Portney's "Jack and the Rope Stalk" that appeared in the last issue of the ION Newsletter was incorrect. We are reprinting the correct answer here in its entirety. Our sincere apologies to Mr. Portney and our readers.
The rope remains in geosynchronous orbit since it is in an equatorial plane (Quito is on the equator) and its centripetal acceleration is balanced by its gravitational acceleration. The equation for this condition is depicted below, where R is the radius of the Earth, e is the length of the rope, r is the radial distance from the center of the Earth, _ is the density of the rope, G is the gravitational constant, M is the mass of the Earth, and r_2 is the cen-tripetal acceleration of the "satellite." The "satellite" remains in orbit provided that its centripetal acceleration is matched by its gravitational acceleration as expressed by:  The integration proceeds as follows:   Using the general solution of the quadratic equation results as: The solution is simplified as we remember that GM/R2 = g (9.8 m/sec2). The radius of the Earth used is R = 6.4 x 106 m and the Earth's rotation is __= 2¹ rad/24 hrs = 7.3 x10-5 rad/sec. We find that the length of the rope is 1.5 x108 m or 80,994 nmi (93,206 statute miles). |
You can find more of Portney's Ponderables at www.navworld.com.
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From the ION Historian: Matthew Fontaine Maury And The Mapping of the Oceans |
By the mid 19th century, America was a burgeoning maritime nation yearning for respect from the established European colonial powers. Interconnection by maritime commerce was critically important not just to America, but to all nations. Yet long sailing voyages in the early 1800s were always unpredictable and often hazardous. Crude navigation techniques, coupled with the lack of knowledge of prevailing winds and currents, made route planning and guidance a hit-or-miss affair. There were no "highways" on the seas, and hundreds of shipwrecks occurred each year resulting in an enormous loss of property and life.
Tracks in the Sea
Chester G. Hearn's biography of Matthew Fontaine Maury entitled "Tracks in the Sea," captures a rich chapter in the history of seafaring: the systematic mapping of the earth's physical oceanography parameters. Position fixing in the open oceans, still only recently expedited by the invention and dissemination of chronometers, provided only an instantaneous piece of information. If a sailing ship were to make a fast and comfortable voyage, it must also know the direction and speed of ocean currents, the direction and seasonal variations of the winds, and how to forecast changes in weather, for the mariner is always at risk of squalls, gales and hurricanes, foul tides and contrary currents.
By Word of Mouth And the Skin of Your Teeth
Historically, navigators shared their knowledge of winds and currents with other seafarers, passing down through generations a combination of wisdom and anecdotes. But it remained for Matthew Fontaine Maury, a self-educated lieutenant of the nineteenth-century U.S. Navy, to apply any sort of scientific discipline to the collection and analysis of meteorologic and oceanographic data. In eighteen years of sustained and inspired labor, drawing on the logbooks of sailing ships from many nations, Maury transformed the oceans from trackless hazards into a network of highways marked by predictable winds and currents. His research led to publication of wind and current tables for the Atlantic, Pacific, and Indian Oceans and later, in 1855, to the first textbook of oceanography, his Physical Geography of the Sea. In the centuries preceding Maury, the success or failure of an ocean voyage often owed as much to luck as to seamanship and navigational skill.
Although it was recognized that winds, currents and weather patterns were interrelated and largely predictable, Maury was the first to combine empirical and theoretical data over large ocean expanses, and subsequently to document and distribute his findings to an international maritime community.
A Man of Accomplishments
Maury was a prolific writer and his book, Navigation, became the standard textbook for midshipmen at the Naval Academy. His scientific accomplishments and organizational abilities helped secure his appointment, in 1844, as the first superintendent of the U.S. Naval Observatory. Maury served in this capacity for seventeen years during which his books and maps on physical oceanography gained international recognition while also establishing the Observatory as a major astronomical center.
In 1861, at the outbreak of the Civil war, he remorsefully sent his resignation to President Abraham Lincoln, two days after submitting for publication his monograph, The Southeast Trade Winds of the Atlantic, which he called "one of the most valuable contributions that I have ever made to navigation." He served for the Confederacy where ironically the efforts of this man dedicated to maritime safety were used to raid Union commerce.
With the decline of the great Clipper ships and the emergence of the steamship age in the late nineteenth century, Maury's writings became less utilized. But Maury introduced more than a science to sailing; he imposed a discipline of carefully documented empirical observations that continues in oceanography, hydrography, and navigation. In tracing Maury's intellectual odyssey and the dramatic conflicts of his life and career, Chester Hearn recounts a fascinating era in seafaring as well as in the history of a young America.
Tributes to Maury's accomplishments include paintings and busts at the Naval Observatory, a Naval Oceanographic survey ship and a maritime library at the National Space Technology Laboratory in Bay St. Louis, Mississippi.
Marvin B. May teaches navigation courses for Pennsylvania State University.
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GNSS AROUND THE GLOBE
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Section News
NEW ENGLAND SECTION
The New England met May 7 at the campus center of Worcester Polytechnic Institute (WPI). After an enjoyable dinner, three presentations followed.
Dr. William Michalson, an associate professor at WPI presented "The Role of Navigation in Wireless Healthcare." Dr. Michalson discussed the technology being developed in the Center for Untethered Healthcare for the U.S. Army Medical Research and Materiel Command. The project objective is to investigate the development of key components of a system which includes low-level, wearable, vital sign sensors; human-machine interfaces and diagnostic algorithms to enhance field operation of an imaging system; and a low maintenance, field deployable computer, communications and positioning network.
Dr. David Cyganski's talk, "A Multi-Carrier Technique for Precision Geolocation for Indoor/Multipath Environ-ment" concentrated on a novel means for precise and multi-path compatible geolocation and is contrasted with currently proposed Impulse based UWB systems. By applying super-resolution radar inspired range recovery algorithms, location solutions can be obtained for one or more signal sources in spite of immediately adjacent reflectors. The technique allows location of true sources and the multi-path reflectors without resorting to impulsive, wideband signals and is well suited for deployment as a system for precision relative location of ad hoc transceivers with respect to one another. Dr. Cyganski is a Weston Hadden Professor at WPI.
The final presentation was given by Mr. Jim Dunn on "ATP/FASTec 'Breakthru' FUEL CELL Powered Electric Airplane Project." Dunn is the CEO and chief technical officer of the Center for Technology Commercialization in Westborough, Mass., and the director of NASA's New England Region Technology Trans-fer Center. Dunn outlined his innovative research and educational projects that focus on designing, building, and testing a safe, practical two-seat general aviation airplane, powered by DC electricity from fuel cells and advanced rechargeable batteries. The airplane can take off at impressive climb rates, fly over 250 miles on a single charge, and land safely. An existing light-weight, low-drag, aircraft is being converted to electric propulsion, replacing the current gasoline powered engine with a high efficiency electric drive system, and advanced controls and instruments. The electricity to power the aircraft will be generated by a bank of advanced high energy Lithium-Ion batteries, to be eventually augmented by a hydrogen powered fuel cell, to extend the range.
This project is aimed at providing a unique mechanism to attract and involve students of all ages, to further develop their interest in pursuing science and technology careers.
ROCKY MOUNTAIN SECTION
The Rocky Mountain Section and the University of Colorado-Boulder co-hosted a the May 27 meeting at the Boulder campus. The meeting featured three outstanding presentations on GPS time transfer. Approximately 20 members and students took part in the session.
Dr. Marc Weiss, a mathematician at the National Institute of Standards and Technology (NIST) Time and Frequency Division, presented "Time and Time Transfer with GPS and WAAS." Dr. Weiss has worked with GPS since 1980, as a user of common-view time transfer and a consultant for GPS development. He covered a range of topics, including comparisons between one-way, two-way, and common-view time transfer, and a brief tutorial on the differences between stability and accuracy.
The second presentation was entitled "USNO Precise Timekeeping," delivered by Dr. Lara Schmidt. Dr. Schmidt is a mathematician at the U.S. Naval Observatory Alternate Master Clock in Colorado Springs. She works both in GPS and atomic timescales, and specializes in the statistical technique of long-memory modeling.
She presented a history of timekeeping, uses of precise time, an overview of several timescales, and some statistical analysis of GPS time transfer from 2002.
Dr. Kristine Larson presented the final topic, "High Precision GPS Carrier Phase Time Transfer." Dr. Larson is an associate professor in the Department of Aerospace Engineering Sciences at CU-Boulder. She specializes in geophysical applications and technique development of the GPS for measurements of plate tectonics, plate boundary deformation, volcano monitoring, ice flow and loading, and time transfer. Her presentation summarized some of the on-going dissertation work of John Plumb, a Ph.D. candidate at CU. She presented some of their results which compare carrier phase time transfer performance to common-view and two-way time transfer.
The presentations are posted at www.rms-ion.org. The section would like to extend its gratitude to Dr. Penny Axelrad, an active ION member and associate professor in the Department of Engineering Sciences at CU-Boulder, for her assistance in coordinating this event.
SAN DIEGO SECTION
The San Diego Section's May 13, meeting was hosted by the DCS Corporation. Professor Gérard Lachapelle, ION’s Western Vice President, spoke on GPS signal availability Indoors and in urban canyons using a high sensitivity receiver.
Approximately 20 members attended.
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RTCA Corner
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The 61st meeting of Special Committee-159 was held on May 19 at RTCA. Items approved by the committee and the reports of select work groups follow.
Next Meeting: September 15-19, 2003
Chair: Larry Chesto, Consultant
Vice Chair: George Ligler, PMEI
Secretary: Young Lee, The MITRE Corporation
Program Director: Harold Moses, RTCA, Inc.
The sixty-first meeting of SC-159 was held on May 19 at the RTCA. No new documents were presented for approval. Capt. Perz, USAF-GPS JPO, provided a briefing on the GPS constellation currently consisting of 28 operating satellites. GPS Block IIR and Block IIF satellites will modernize signals. Eight Block IIR satellites are in orbit and the next launch is scheduled for July 29. The first GPS III satellite launch is planned for the end of the decade although the schedule could be more aggressive and is under review. GPS III requirements include increased accuracy, precision timing, integrity enhancements and enhanced signal levels.
WG-1, 3rd Civil Frequency, discussed L5 acquisition issues and signal performance. The update to DO-261, L5 Signal Specification, will await solidification of ICD-GPS-705 and may include New and Improved Ephemeris (NICE) information. In joint session with WG-2, plans for a draft WAAS LI/L5 ICD/ Signal Specification by September 2003 were set. WG- I will develop the signal specification and WG-2 will complete the data messages and message scheduling.
WG-2, GPS/WAAS, reviewed the current status of the WAAS program. IOC commissioning is scheduled for July 10, 2003. The IOC will service 95 percent of the United States and portions of Alaska with minimums down to 350 feet. FOC, expected in 2006, will service the full continental U.S and most of Alaska with minimums down to 250 feet. Over 700 LNAV/ VNAV procedures are expected to be available at WAAS commissioning.
WG-2C, GPS/Inertial, continued ionosphere modeling analysis of the International Reference Ionosphere model and the Parametrized Ionosphere Model and planned for a Ionospheric Storm Model development. A proposal was considered to develop a TSO based on DO-229C-Appendix R. The WG agreed to continue integrity coasting work and performance documentation before developing a TSO.
WG-4, GPS/LAAS, reported that the FAA awarded Phase 1 of the LAAS contract for the hardware and software design of the LAAS Cat. I system. IOC is projected for September 2006. If Phase 2 is exercised, initial systems would be installed in Chicago, Houston, Juneau, Memphis, Phoenix and Seattle.
To support a decision point for the LAAS Cat. II/III program, WG-4 is aggressively working to update the LAAS MASPS and ICD by June 2004. Terminal Approach Path (TAP) work is underway to add system requirements to support segmented and curved GLS procedures to the LAAS MASPS and ICD.
WG-5, Airport Surface Navigation and Surveillance, completed a draft report entitled Evaluation of Category I LAAS to Support Airport Surface Operation. The assessment concluded that Cat. I LAAS is capable of supporting defined airport surface operations down to visibility condition 3.
WG-6, GPS/Interference, continued work on the L5 RFI Assessment Report. Drafts of most chapters are complete. The basis is GPS L5 receiver (no WAAS) plus E5a (based on EUROCAE inputs) in a combined receiver. Environmental sources of interference and values are being finalized.
RTCA, Inc. is a private, not-for-profit corporation that develops consensus-based recommendations regarding communications, navigation, surveillance and air traffic management (CNS/ATM) system issues. RTCA functions as a federal advisory committee. Its recommendations are used by the Federal Aviation Administration (FAA) as the basis for policy, program and regulatory decisions, and by the private sector as the basis for development, investment and other business decisions.
| IN MEMORIAM | |
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Dr. John Diesel died suddenly on May 12, 2003. Dr. Diesel's vision and intellect, his intellectual gen-erosity and his immense contribution to the science, as well as the art, of navigation are an irreplaceable loss, not only to his friends and colleagues but to the entire aerospace community. Dr. Diesel began his 42-year association with Litton in 1961 by developing a modular six-degree-of-freedom computer simulation program for analyzing missile dynamics and guidance systems. Later, he managed the Simulation and Analysis Department of the Litton Guidance and Control Division and the Simulation and Software Department of Litton Aero Products. He then became a consultant to Interstate Electronics on GPS/INS, and to Litton Aero Products on strap-down software mechanizations. He rejoined Litton Aero Products in 1987 as a chief scientist and continued there after Litton Industries was acquired by Northrop Grumman Corporation in 2001. Dr. Diesel held 12 patents in the fields of control engineering, inertial and GPS navigation, and published numerous seminal papers on these topics. Among his innovations are GPS/Inertial integration techniques, which will continue to contribute to aviation safety for many years. In 1996, Dr. Diesel received the prestigious Airline Avionics Institute Pioneer Award in recognition of his long-standing dedication to the art of air navigation. He received his Ph.D. in electrical engineering at Washington University in St. Louis in 1959. |
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Corporate Profile
OmniSTAR, Inc.
OmniSTAR is a high-accuracy differential correction service that can be accessed over very wide areas without reliance on ground-based transmitters and a single reference site. In different areas of the world, the data from networks of very accurately surveyed reference sites are broadcast over entire continents from geostationary satellites. These data, together with sophisticated atmospheric modeling algorithms, are processed in the user's receiver to generate a differential correction specifically for the user's location. With a good-quality single frequency L1 DGPS receiver, consistent real-time accuracy of better than one meter horizontal is normally achievable in most areas. OmniSTAR's latest development-OmniSTAR HP (high performance)-is a unique wide-area correction service capable of providing levels of accuracy five times higher than that of standard DGPS. This new service fills the gap that has existed between submeter DGPS and centimeter-level RTK.
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CALENDAR OF EVENTS
September 2003
October 2003
November 2003
January 2004
March 2004 |
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