DOT logo NAVCEN logo

Civil GPS Service Interface Committee
International Information Subcommittee

Regional Meeting
Prague 1999

The International Information Subcommittee (IISC) of the Civil GPS Service Interface Committee (CGSIC) convened at the Hotel Praha in Prague, The Czech Republic, on December 2-3, 1999.

The meeting minutes are below.

Meeting Minutes

Thursday, December 2, 1999

9:00-10:30 am - Session 1

9:08 Welcome and Introduction of Minister Gurlichova, Deputy Minister of Telecommunications, The Czech Republic
Frantisek Vejrazka, Czech Technical University

9:10 Opening Remarks
Deputy Minister M. Gürlichová

Deputy Minister Gurlichova welcomed the group to Prague and began to discuss the privatization of the telecommunications industry in the Czech Republic and the importance of growing private sector markets for information technologies, including GPS.

The Deputy Minister concluded her remarks by expressing her appreciation for the Czech Technical University's assistance and participation in this activity with Industry

9:15 Introduction to the CGSIC and Status of the International Information Subcommittee
Mike Saville, Chair, IISC
View presentation (PowerPoint file)

After thanking Deputy Minister Gurlichova for agreeing to open the meeting despite a very busy schedule, Mike Saville introduced himself as chair of the CGSIC International Information Subcommittee. He then introduced the US Government and Industry representatives at the meeting, including Joe Canny, CGSIC Chair and US Deputy Assistant Secretary of Transportation for Radionavigation Policy and Captain Tom Rice, CGSIC deputy Chair and Commander of the US Coast Guard Navigation Center (NavCen). He also introduced Mr. Hiroshi Nishiguichi, Japan & Far East Regional Vice Chair of the IISC and George Weber, Europe Regional Vice Chair. He then thanked the Czech Technical University for all their efforts in organizing the meeting.

Mr. Saville began his prepared remarks by briefly describing the overall mission of the CGSIC, the mission of the International Information Subcommittee (IISC) and the IISC's current activities. During the presentation he discussed the fact that the IISC's European region is in the process of identifying national points of contact for each country participating on the IISC. Several have already been identified, including Prof. Vejrazka for the Czech Republic. He also mentioned that the next IISC meeting in the IISC Japan and Far East region would be held in February 2001 in Tokyo.

Mr. Saville summarized his presentation by stating he believes that the IISC has made major achievements in providing international user feedback to the US Government. It has also established useful information services for these users. The IISC must now ensure it maintains a stable funding base, becomes even more useful, and increases its level of importance with official international governmental bodies.

9:38 GPS Policy and Planning
Joe Canny, Chair, CGSIC,USDOT
View presentation (PowerPoint file)

Mr. Canny presented a broad overview of current GPS policy and planning Joe's presentation was a broad discussion on GPS policy, planning, and management. He discussed the Interagency GPS Executive Board, GPS Modernization and the impact of the FY00 Congressional budget decisions, international consultations carried out by the US Government in an effort to ensure the compatibility of future global navigation satellite systems (GNSS), spectrum issues, and the status of the Federal Radionavigation Plan. Highlights of Mr. Canny's presentation follow.

  • The third civil signal, referred to in the US as L5, will be broadcast from the modernized GPS constellation at 6 dB higher power than current GPS signals. It will also be 20 MHz in bandwidth, making it more robust than the current L1 GPS signal. L5 will be an aeronautical radionavigation service signal that will be used for safety-of-life applications. Dual frequency use of this signal along with the L1 signal will allow aircraft avionics to correct for ionospheric error and may allow great reductions in the ground-based aviation navigation infrastructure.
  • The Executive Office of the President was not pleased that Congress failed to fund the third civil signal in Fiscal Year 2000. The DOT has been asked to find ways to mitigate the impact of this loss of funding on civil GPS modernization.
  • US principles for GNSS discussed in international consultations include: seamless, global interoperability; open signal structure; no direct user fees for basic civil and public safety services; and open market access for equipment manufacturers.
  • The US will pursue four GPS-related actions at the 2000 World Radio Conference in Istanbul: the protection of the L1 frequency band from MSS incursions; the elimination of national L1 Band footnotes for non-ARNS systems; a new space-to-space allocation for L1 and L2; and, an RNSS allocation for the third civil signal at 1176.45 (+/-12 MHz). He also mentioned the need to protect GNSS spectrum from emerging threats such as ultra-wide-band radar systems.

Immediately following Mr. Canny's presentation no questions were asked. However, later in the session several relevant questions were raised. Responding to a question about reports of problems in achieving Category I accuracy using WAAS, he stated that he was unaware of any accuracy problems. He mentioned that there have been some software delivery problems, but this will not impact the scheduled initial operating capability dates for WAAS.

Another questioner asked if the US has any alternative plans for providing new civil GPS signals if allocation problems are encountered at WRC 2000. Mr. Canny clearly stated that an extensive selection process was carried out to determine the third civil frequency and there are currently no plans to deviate from its use.

10:14 GPS Constellation and Control Segment Status
Captain Zannas Pappas, US Air Force Space Command
View presentation (PowerPoint file)

Captain Pappas gave a brief but thorough presentation on the current operational status of the GPS. He mentioned that 29 GPS satellites are currently in orbit, and 27 of these are operational. He also reported that the third Block IIR satellite to be launched, SVN 46, will be designated as operational for its navigation mission in a matter of days. The 29th satellite, SVN 28, is under going end of life testing and is no longer broadcasting a usable navigation signal.

Captain Pappas also briefly discussed the current plan for upgrading the GPS control segment and transitioning from one prime contractor to another. Lockheed Martin will complete all upgrades originally in the GPS Operational Support Contract, then Boeing will add IIF functionality.

In summary, he stated that the GPS is a healthy but aging constellation, and mentioned the following points:

A member of the audience asked Captain Pappas what GPS pseudo-random number (PRN) will be assigned to SVN 46. His answer was that he did not know. However, when navigation signals are ready for broadcast from the satellite, users will be notified and given the correct PRN.

  • the Block IIA satellites that constitute the majority of the current constellation have a life expectancy that has recently increased from 8.6 to 10.6 years;
  • Air Force satellite operators are doing extraordinarily well at maintaining the functionality of older satellites in the constellation;
  • it appears that the Block IIR satellites are exhibiting superior navigation accuracy to the older Block IIA satellites.

10:30-11.00 - Coffee break

11:00-12:30 - Session 2

11:00 Session 2 Opening Remarks
Captain Tom Rice
US Coast Guard Navigation Center

Captain Tom Rice, chair of session 2, briefly discussed the US Coast Guard operation of the Maritime DGPS service and LORAN-C before introducing Rebecca Casswell from the DOT/USCG Navigation Center (NavCen)

11:03 GPS User Support
Rebecca Casswell, US Coast Guard NavCen
View presentation (PowerPoint file)

Ms. Casswell's presentation was broadly focused on the US Department of Transportation's responsibility for civil outreach and information dissemination. She summarized the roles of the CGSIC, the Navigation Information Service (NIS), and the FAA's National Operations Control Center (NOCC). She then briefly discussed the recently established DOD User Support Center that acts as a single point of contact for military users and provides information to the NIC and the NOCC.

Ms. Casswell's concluding remarks included a statement that the DOT is currently working to reduce the amount of time it takes to respond to questions and concerns sent to the NavCen by users throughout the world.

11:15 GPS International Consultations
Julie Karner, US Department of State
View presentation (PowerPoint file)

Julie Karner began her presentation of US Government international consultations on GNSS by discussing successful recent meetings held in Washington, D.C. under the framework of the Joint US-Japan Agreement on the Use of GPS. She then focused on consultations with Europe and mentioned that the most recent meeting between the US and the EU focused on GNSS was held on November 10th, 1999. In a summary report from a November 1998 US EU meeting, the US outlined a number of principles for future civil GNSS that it plans to pursue in on going discussions:

  • Common GPS time, geodesy, and signal structure;
  • Seamless, global interoperability with GPS;
  • Protecting current radionavigation spectrum;
  • No direct user fees;
  • Open signal structures;
  • Open market-driven competition for user equipment and applications;
  • Recognition of national and international security issues.

During the discussion of a viewgraph on the larger context of on going international GPS Discussions, Ms. Karner pointed out the arduous and contentious process that took place within the US Government that led to selection of 1176.45 MHz as the center frequency for the third civil signal.

Her presentation concluded with a statement that the U.S. is consulting with other countries to further mutual interests for the peaceful use of GPS and its augmentations. This led directly to a question from the audience asking how peaceful use of GPS is defined and by whom? Her answer was that as a general rule, the US believes that civil uses of GPS are assumed to be peaceful uses.

11:35 Federal Highway Administration Use of GPS
Jim Arnold, US Federal Highway Administration (FHWA)

Jim Arnold discussed the current and planned uses of GPS and the Nationwide DGPS (NDGPS) network within the US. Although the US has the best transportation system in the world, according to Arnold, many people are killed on US highways every year and many programs are underway to improve highway safety that require radionavigation capabilities. In fact many of these applications require accuracy on order of 1 meter, which should be achievable using NDGPS. The applications mentioned by Mr. Arnold included navigation and route guidance, automatic vehicle location (AVL), the advanced law enforcement & response technology (ALERT), and roadway maintenance and construction activities.

Mr. Arnold summarized by stating that radionavigation is viewed as an enabling technology by the FHWA, and other advances are also needed, such as more accurate maps, in order to take full advantage of DGPS. Nevertheless, he stated that someday, he hopes that the NDGPS network will provide 20-30 cm accuracy across the entire US.

11:55 Spectrum Protection: Is the Battle Won?
Michael Swiek, US GPS Industry Council

Mike began his presentation by urging new international users to ask questions and raise issues with any of the US Government and industry representatives present at this meeting. GPS has fostered not just government-to-government cooperation, but also government-to-industry participation worldwide. It is an open community that should remain open.

After telling a joke about being the last speaker before lunch, Mr. Swiek turned to spectrum issues, pointing out that if users cannot receive the signal from space provided by GPS or any other GNSS, it is of no use to users. He then summarized the current status of GPS-related spectrum issues within the process of preparing for the 2000 World Radio Conference (WRC 2000). Key points mentioned were as follows:

  • Although GNSS and mobile satellite service (MSS) applications are complementary for users and often share customers and platforms, the radio frequency characteristics of the two classes of services are very different, and GNSS and MSS simply cannot share the same band
  • The MSS sharing proposal, known as Resolution 220 is still on the agenda for WRC 2000 despite the fact that INMARSAT is no longer pursuing additional spectrum
  • The US GPS industry strongly supports the suppression of Resolution 220 and is urging the US government not to embroil GNSS spectrum protection in the horse-trading that takes place at world radio conferences
  • The US has its own domestic threats to GNSS spectrum such as ultra wide-band radar and out-of-band emissions that must be monitored and countered

Mr. Swiek concluded his remarks by reiterating the importance of protecting GNSS spectrum to allow evolving user needs to be met and stating that free GPS/GNSS add value to all forms of infrastructure.

12:30-2:00 pm - Lunch

2:00-3:30 - Session 3

2:00 Session 3 Opening remarks
Joe Canny, Chair, CGSIC, USDOT

Mr. Joe Canny, chair for session 3, introduced the first presenter of the afternoon, Mr. Kan Sandhoo, who gave one paper on behalf of Mr. Dan Hanlon, Federal Aviation Administration Wide-area Augmentation System program manager, and his own paper.

2:05 FAA Satellite Navigation Programs
Kanwaljit Sandhoo, The MITRE Corporation
View presentation (PowerPoint file)

Mr. Sandhoo's first presentation on behalf of the FAA summarized the status of the Wide-area Augmentation System (WAAS), Local-area Augmentation System (LAAS) and civil GPS modernization. He began by discussing the current air navigation deficiencies that the FAA's satellite navigation programs are trying to address.

Focusing on WAAS, Mr. Sandhoo discussed the programs perceived benefits to the aviation community, the three phase approach to implementing the program, and results of a recent satellite navigation investment analysis that considered four basic options for WAAS:

1) no WAAS; 2) WAAS with full network of ground-based navigation aids; ;3) WAAS with a 50 percent reduction in ground-based navigation aids; and, 4) WAAS with a 75 percent reduction in ground-based navigation aids. The FAA ultimately selected option 4) because it had the largest cost to benefit ratio of the four alternatives. He also briefly summarized the status of the LAAS program and GPS modernization for civil aviation.

Mr. Sandhoo summarized his presentation by stating that the FAA is committed to Satellite Navigation and the WAAS and LAAS baselines have been approve by the FAA Administrator. Responding to a question related to the lack of adequate LAAS coverage in Alaska, He explained that the US has no current plans to augment WAAS with the LORAN-C based Eurofix system that is being considered for use in Europe. LAAS is currently the leading candidate for filling gaps in Alaskan WAAS coverage.

2:25 FAA's Plan for the future use of GPS
Kan Sandhoo, The MITRE Corporation
View presentation (PowerPoint file)

The second presentation by Kan Sandhoo focused on the FAA's planned use of the third civil GPS frequency. He began the briefing by pointing out that 1176.45 MHz was selected for the third civil signal, known as L5, because interference from other systems at this frequency is actually better than in other potentially available areas of the L-band spectrum. Since one of the FAA's main objectives for the third civil frequency is enhanced resistance to radio frequency interference as compared to the use of the L1 frequency alone, L5 will be a wide-band signal that will be broadcast at a higher power than the L1 signal. Mr. Sandhoo also explained that the existence of L5 will allow the FAA to evolve from a single frequency architecture for both WAAS and LAAS to a dual frequency architecture. This will allow global ionospheric corrections to be made by users of these systems without the need for complex ionospheric modeling

Mr. Sandhoo addressed several questions related to the US Government plans for dealing with the possibility that the L5 spectrum allocation will not be approved at WRC 2000. He explained to the audience that the US plans to use L5 within its own borders even if it does not get a formal allocation at this conference. Other nations are also free to use L5 because it will be globally broadcast from the future GPS constellation. However, it will be up to each government to decide if they will protect the use of L5 within their own jurisdictions. Since the broadcast of L5 will not cause interference with any other existing system using the same bandwidth, the US government believes that this is a reasonable plan of action.

2:55 Latest Political and Legal Developments of the European Generation of Satellite Navigation Services: Galileo
Ingrid Lagarrigue, Independent Legal Counsel for the EU
View presentation (PowerPoint file)

On behalf of Luc Tytgat, Administrator at the Directorate-General for Transport (DG-VII) Ms. Lagarrigue discussed recent political and legal developments related to the proposed European Global Navigation Satellite System known as Galileo.

Complete text of the presentation

At the conclusion of her prepared remarks, Ms. Lagarrigue was asked if there is currently funding for any phase of the Galileo program beyond the definition phase. Her answer was that currently there is not. She also fielded a number of questions related to the public-private partnership (PPP) concept, possible user costs for Galileo, liability, and the overall estimated costs for Galileo. In each case, she referred the questioner to the prepared comments already presented on these subjects.

3:15-4:00 Coffee break

4:00-5:30 - Session 4

4:00 Session 4 Opening Remarks
Neil Ackroyd, Trimble Navigation, Europe

Mr. Neil Ackroyd, chair of session 3, opened the session with a few very brief comments related to the growth of GPS technology usage around the world and then introduced Hiroshi Nishiguchi, representative of the Japan GPS Council.

4:05 GPS Augmentation Services in Japan
H. Nishiguchi, Japan GPS Council
View presentation (PowerPoint file)

Mr. Nishiguchi presented a brief update on the status of GPS augmentation services in Japan and the size of the largest GPS market in Japan; car navigation systems. The Maritime Safety Agency in Japan operates a beacon DGPS network for maritime applications that complies with RTCM standards. It became fully operational in April 1999. A DGPS network that provides corrections using FM-subcarrier has also been in full service since 1997 and provides services free of direct user charges.

The Multi-functional Transport Satellite (MTSAT) -based Satellite Augmentation System. (MSAS) is being designed to fulfill three missions, voice and data communications, weather and geodetic applications, and GNSS augmentation. The MSAS GNSS objective is the same as the FAA's WAAS; to provide accuracy and integrity for Category 1 precision approach. Unfortunately, the original timeline for implementing MSAS has slipped due to the loss of the first satellite in a recent launch failure.

After receiving no questions from the audience, Mr. Ackroyd thanked Mr. Nichiguchi for his presentation and made a point of mentioning the geophysical deformation network established in Japan as another example of the interesting GPS applications that are being pursued within the country.

3:15 Status and Development of Satellite Positioning and Navigation Systems in Central and East European Countries
Frantisek Vejrazka, Czech Technical University

On behalf of himself, Professor Oszczak of Olsztyn University, Poland, and Professor Manzóni of the University of Trieste, Italy, Professor Vejrazka discussed the current usage of DGPS networks in Central and Eastern Europe.

  • A DGPS network with 6 stations exists in Austria. The corrections are broadcast by an private sector Austrian company
  • Slovenia has a dense reference network, but DGPS corrections are not widely available by broadcast
  • Hungary has initiated a NDGPS network, with the first broadcast to begin in February 2000. Two companies will broadcast RTCM-based corrections on FM frequencies with approximately 3 meter accuracy
  • Poland operates DGPS maritime-type beacons with better than 10 meter accuracy. 12 channel receivers are available that can utilize RTCM-type DGPS broadcasts. The reliability of Poland's system has been very good. Poland also has a three station dual frequency RTK network that will be used in the Gdansk/Sopot/Guynia area to provide navigation capability to many users
  • The Czech Republic utilizes a DGPS network that is based on work performed by the Czech Technical University. A reference site at the university sends correction to a Prague TV tower which then sends out RDS broadcasts to provide corrections to users in RTCM format. Accuracy of 0.9 meter (95%) horizontal and 1.6 meter (95%) vertical accuracy is reportedly achievable

Although no questions were asked, one member of the audience did point out that Poland now has GSM-based DGPS transmissions that provide coverage to all of Poland.

3:30 Application of GPS Positioning Systems in Geodetic and Geodynamic Programmes of 16 CEI (Central European Initiative) Countries
Janusz Sledzinski, Warsaw University of Technology, Poland

Professor Sledzinski made his presentation on behalf of 16 countries that are part of the Central European Initiative (CEI), which was established in 1989 to initiate scientific, cultural, and economic cooperation in central Europe. Several of the CEI's working groups, including the science and technology working group and the education standards working group cover issues related to the use of GPS for geodesy and geophysical applications.

After discussing a number of projects conducted under the CEI, Professor Sledzinski discussed the CERGOP-2 project, which is waiting for funding from the European Union's 5th Framework Program. 14 countries will participate in the project -- which will expand the Central European GPS Reference Network (CERN) with additional permanent and temporary reference sites. Currently, this network, which has 8 data processing centers, has been used to study geophysical phenomena in central Europe. The results of these studies are available in a number of published monographs.

4:55 Hungary - National Radionavigation and Satellite Positioning Service
Gyula Graczka, TU, Budapest
View presentation (PowerPoint file)

The final presentation of the day, made by Professor Graczka focused mainly on general differential techniques and technology rather than specifically on Hungary's DGPS network. The accuracy of the GPS atomic clocks, user range error (URE) with and without selective availability (SA) and anti-spoofing, and techniques for correcting for SA were all discussed. He also covered his view of the relative benefits of space-based differential augmentations versus ground-based augmentations.

Professor Graczka concluded his presentation by briefly summarizing the status of the FM broadcasting sites that currently exist in Hungary to transmit differential corrections to users.

5:20 Day 1 Closing Remarks
Mike Saville, Chair, IISC

Mr. Saville concluded the day's sessions by making several announcements. First, he announced that the next European meeting of the CGSIC IISC will be held on 30 Nov-1 Dec, 2000 in Monaco. He then mentioned that the Czech Technical University will have this meetings presentations available and the US Coast Guard will also prepare a comprehensive file of the meetings minutes and presentations that will be available on the NavCen web site. He also suggested that it would also be useful to provide links to other web sites with information related to international GPS activities on the IISC portion of the NavCen website.

Mr. Saville then thanked all of the days participants and the organizers of the conference from the Czech Technical University.

Friday, December 3, 1999

8:30-10:00 am - Session 5

8:30 Three-carrier ambiguity resolution in Galileo
Borje Forssell, NTNU, Norway

Borje Forssell gave a paper co-authored by himself and M. Martin-Ncira of ESA-ESTEC that focused on the resolution of carrier ambiguity for three possible Galileo signals. He began by presenting the basic equations that govern the resolution of ambiguity for the two-carrier GPS case. He used the term "wavelength gap bridging" to explain the advantage of ambiguity resolution using three frequencies, often referred to as "trilaning" in the context of the GPS L1, L2, and L5 signals.

After explaining the basic equations and their application to the three-frequency case, Mr. Forssell explained that the limitation of the technique is the need to have ideal frequency separation. This is not easy to achieve, given the current demand for spectrum. However, he proposed two methods for improving ambiguity resolution with less than optimal frequency spacing. The first uses state vector methodology to determine all unknowns. The second is a linear combination of measurements method that resolves ambiguity by solving the noise component of the equations for two frequency comparisons and then uses the least noise solution when moving to the next set of carrier comparisons.

Responding to a supposition that three frequencies do not seem to improve ambiguity resolution much when compared to two, Mr. Forssell stated that this is true for the wavelength gap bridging method. However, improvements will result using three frequencies when simultaneous solution methods such as the least squares method are utilized.

9:00 Evaluation of GNSS System Requirements for Long Range Ambiguity Resolution
Peter J. G. Teunissen, Delft University of Technology

Peter Teunissen presented an evaluation of long baseline ambiguity resolution with three frequencies conducted by himself and two Delft University colleagues, P. Joosten, and N.F. Jonkman. Even with three frequencies, instantaneous ambiguity resolution cannot be achieved for a long baseline, although the addition of a third frequency does improve the success rate of ambiguity resolution. To achieve a 99% success rate, Mr. Teunissen explained that three frequencies will require much fewer epochs than two frequencies (two to five times fewer). He also pointed out that a fully modernized GPS with the L1, L2, and L5 frequencies will require fewer epochs than three frequency Galileo ambiguity resolution based on currently proposed Galileo frequencies.

9:30 Some experiences from centimeter positioning using dual frequency GPS/GLONASS
Bo Jonsson, National Land Survey of Sweden

Bo Jonsson's presentation, co-authored by Ch. Ottoson and J. Boman, focused on the National Land Survey of Sweden's experience with combined GPS and GLONASS real-time kinematic (RTK) positioning and navigation. He made several comparisons between RTK using just GPS and RTK using GPS and GLONASS. The major advantage of using both systems is the improvement in a users dilution of precision (DOP). In addition, the vertical component of pseudorange accuracy is also improved.

Mr. Jonsson also discussed the Swedish network of permanent differential reference stations. All of the sites for this network collect GPS data, and some also collect GLONASS data. Post processed data derived from the network is made available to users on the world-wide-web, and real time differential data is broadcast by a private company using FM RDS datalinks. He then explained that a new program has begun in Sweden to combine the differential network with RTK techniques to form a centimeter level real-time positioning service. More information on this project and others under the auspices of the National Land Survey of Sweden can found on the world wide web at

After the completion of his presentation, the audience had several questions for Mr. Jonsson. Responding to a question regarding who the potential users of a centimeter-level real-time positioning service are expected to be, he stated that the farming and construction industries are considered to be potential users. When asked why they compared the dual use of GPS and GLONASS with GPS only, but not GLONASS only, he explained that there simply not enough GLONASS satellites currently operating for stand-alone GLONASS RTK positioning.

10:00-10:30 Coffee break

10:30-12:00 pm - Session 6

1030 A higher DGPS accuracy by means of a new correction -- The azimuth-distance-correction ADCo
Johannes Dittrich, Federal Agency for Cartography and Geodesy, Federal Republic of Germany

Mr. Dittrich presented material prepared by himself and colleague E. Kühmstcdt that was focused on the ALF DGPS network in Germany and recent improvements in the systems accuracy. In the past, the ALF provides real-time RTCM-type corrections to users using RDS technology based on a data collected by a single reference station in Mainflingen, Germany. Available accuracy was reported to be as good as 1-2 meters. The development of ALF began in 1992 and in 1996 it became operational 24 hours a day, 365 days a year. Since 1996, efforts have been under way to make ALF a more reliable service with higher accuracy.

Mr. Dittrich explained that with the help of the Czech Technical University, data from their reference station in Prague was incorporated into the ALF network. It is used to develop a proprietary algorithm, known as ADCo, that improves a users accuracy to between 0.5 to 1.8 meters by providing additional azimuth and distance corrections.

At the conclusion of the presentation, a questioner asked Mr. Dittrich how the ADCo correction is transmitted to users. He explained that it is not part of the RTCM correction, instead, it relies on separate receiver hardware that must be purchased.

10:55 The Real time Implementation of GPS Carrier Phase Measurements for Distant Frequency Standard Comparisons
Piotr Fraczyk, NAVI

This paper presented by Mr. Fraczyk and co-authored by A.Tyranowska, of the Polish Space Research Center, was focused on the use of GPS carrier phase to compare frequency standards (time difference) computed at geographically separated time and frequency standard institutes.

Using the Allen deviation as a point of comparison, he explained that carrier phase measurements are more accurate than either C/A-code or P-code based measurements. Mr. Fraczyk acknowledged that carrier phase measurements are already used for frequency determination at the US Naval Observatory, and BIPM (Bureau International des Poids et Mesures) but use of this technique by non-high precision timing laboratories would be beneficial. For example, if phase measurements could be used by the telecom industry, the necessary frequency measurement accuracy of 10 -12 could be achieved in 100 seconds rather than thousands of seconds. However, he explained that to make the use of carrier phase measurements for time transfer possible, near real time data exchange between two time standard sites is necessary.

11:15 Proposed Alternative Modernization Approaches to Achieve at a Minimum NATO/ICAO Interoperability with a Category-I Precision Approach Capability prior to April 2000 and Full Compliance by the Year 2010
Andrzej Fellner, Henrik Jafernik, The Air Force Academy, Poland

Noting that it was almost lunch time, Mr. Andrzej Fellner stated that he would speak briefly although his co-prepared presentation was rather long. He began by mentioning an initiative proposed by the Clinton Administration in 1994 to offer assistance to Central European countries for the purpose of coordinating the management of their national airspaces and air traffic control systems. Existing navigation aids and avionics used in Poland are primarily of Soviet design. However, in the future, interoperability with NATO countries will be necessary for all phases of aviation operations.

The Polish government is in the process of making decision regarding how to properly transition from their old aviation infrastructure to a new infrastructure that complies with NATO and ICAO interoperability requirements. Mr. Fellner stated that it is their intent to equip with navigation and landing systems based on GNSS (initially GPS and then perhaps Galileo), but due to a lack of time, he was unable to fully discuss proposed approaches to accomplish this task that are currently under study.

11:30 Civil GPS Service Interface Committee Web Site Demonstration
Mike Saville, Chair, IISC
Rebecca Casswell, US Coast Guard NavCen

With the help of several students from the Czech Technical University, Mr. Saville and Ms. Casswell were able to briefly demonstrate the capabilities and information available on the US Coast Guard NavCen web site to the meeting's attendees.

1:20-3:00 Session 7

1:20 Impact of Trail Network on Landscape in Western Krkonose Mts. National Park, Czeck Republic - GPS mapping and evaluation in GIS
Ondrej Vitek, Charles University, Prague
View presentation (PowerPoint file)

Mr. Vitek, a PhD student at Charles University, presented his work and that of his colleagues, M. Vitková, M. Brani, on analyzing the impacts of road and trail erosion on the environment of the Krkonose Mountains National Park in the Czech Republic using GPS as a tool. The goals of the research are to determine the extent of non-natural vegetation growth and natural vegetation loss in order to determine appropriate environmental protection strategies. GPS provides the positioning information necessary for the geographic information system (GIS) database that also contains information related to trail width, trail stabilization material, and trail edge vegetation.

Trails, roads, chalets, and tourists are all having a negative influence on the natural environment of the Krkonose National Park, which was formally established in 1963. The man-made features of the park are causing some plant/vegetation to disappear, while at the same time allowing non-indigenous species to invade. Fortunately, however, some vegetation does remain stable.

One of the challenges encountered using GPS was the need to have 40 cm accuracy, which was only achievable when PDOP (precision dilution of precision) was less than 6. Many times the PDOP rises above 6, which means measurements must be halted for periods of time. Additional accuracy issues include the instability of a backpack or shaft mounted antenna used while walking. This can create errors up to 1.0 meters depending on the walking style of the user.

The GIS database developed revealed that 1% of the park's total land area is comprised of trails, 71% of this trail network has been built with a stabilizing material. Trail edge vegetation comprises approximately 3% of the park's square area.

Mr. Vitek provided an e-mail address to contact him regarding questions or information that may be useful to his research and also referred the audience to two web sites as listed below. - personal e-mail address for Mr. Vitek - The Charles University (Prague) GIS Laboratory - The Krkonoše Mountains National Park Administration

1:55 Experience of Flight Inspection of Radionavigation Aids in Czech Republic using GPS as a reference
Karel Kucera, Marek Dobrozemsky, Flight Inspection Division, Civil Aviation Authority, Czech Republic

The primary task of the Czech Civil Aviation Authorities Flight Inspection Division, as explained by Mr. Kucera, is the testing of radio navigation aids for proper operation within specifications. A GPS-based Automatic Positioning Reference System (APRS) for use in their flight test aircraft was first installed in 1992. APRS was tested and then used operationally beginning in 1994-95. The system provides the aircraft with a specified post-processed accuracy of 14 centimeters.

The International Civil Aviation, Authority (ICAO) requires that flight test equipment must be able to measure positioning accuracy 3 times better than the actual accuracy of the system being inspected. Therefore, better than 1 meter accuracy is required to test a Category (CAT) III Instrument Landing System (ILS) with an accuracy of 3 meters. Testing confirmed that the on-board GPS-based RTK system used on the flight test aircraft met this requirement, as long as a DGPS reference station was within range. Thus, the flight test of navigation aids and landing systems as accurate as a CAT III ILS using APRS was approved.

Mr. Saville asked the presenters if the Flight Standards Division has considered the possibility of using Galileo in the future and has factored this into their budgetary planning. The answer was that Galileo is now only a thought, while GPS is an operational system. Therefore, very little thought has been put into this question. However, they stated that the division has tested many systems for possible use, so at some point they would probably test Galileo-based positioning systems as well.

2:25 RTK Positioning of the River Surveying Vessel VALENTÝNA II
Jiri Psenicka, Ales Rucky, GEOVAP, a.s., Czech Republic
View presentation (PowerPoint file)

Mr. Psenicka gave a spirited presentation of the use of GPS RTK for inland waterway vessel positioning. The Vltavy River was charted using airborne photogrammetry prior to the verification of RTK accuracy. Verification was accomplished using traditional LOS survey techniques with an optical prism placed right next to the ship-borne GPS antenna and total station survey equipment. Five control points were used in the verification process.

The river provided many challenges to the use of GPS due to terrain surrounding some parts of the river that create poor satellite visibility conditions.

When asked what the objective was for developing a GPS RTK positioning capability, Mr. Psenicka stated that the survey ship is used to determine river depth in order to maintain the navigability of the Vltavy River. He was also asked if the conversion from WGS-84 to the Czech National Geodetic System utilized accurate enough transformations. His answer was that the surveying techniques used allowed for the development of very accurate transformations.

2:50 Final Remarks
Mike Saville, Chair, IISC
Frantisek Vejrazka, Czech Technical University
Joe Canny, Chair, CGSIC,USDOT

Mr. Saville began his closing remarks by complementing the ability of all the presenters for their ability to communicate their briefings at the meeting in English, which is not the native tongue of most participants. He then thanked the US and the nations of Europe for continuing to support the activities of the International Information Subcommittee, and he thanked the IISC's officers present; especially Mr. Nishigushi, who was able to make the costly journey to the meeting from Japan. He then thanked the students and staff of the Czech technical University for their efforts in supporting the event and wished them success in their studies and future careers. He stated that some effort will need to be considered to bring them to the GNSS 2000 meeting to be held in the Spring in Edinburgh.

Professor Vraszka's remarks referred to the "memory chart" that was handed out to all meeting participants along with other meeting material at the time of registration. The chart illustrated the city of Prague and a number of landmarks of significance to the conduct of the meeting with latitudes and longitudes included and a profile view of a typical survey grade GPS antenna. He thanked all for attending and wished everyone a Merry Christmas.

Joe Canny made the final speech of the meeting and echoed all the thanks given by Mr. Saville and Professor Vraszka. The technical presentations made over the two days were impressive, especially as they pointed to extensive international cooperation in the use of GPS for many applications. He stated that he has a new appreciation for the cost issues that some potential users face when considering the use of GPS. Mr. Canny then expressed his hope that the US presentations were useful to the international attendees and will help them with their own plans for GPS usage. He wished everyone happy holidays, best wishes, and good luck passing through the upcoming Y2K milestone.

Some links on this page lead to content in Microsoft PowerPoint (PPT) format and may require you to install PowerPoint reader software. Get software

Take Action: