Heft 20-2/1985

des Instituts für Geodäsie

Heft 20-2/1985

WELSCH, Walter M. /
LAPINE, Lewis A.

Internationale Federation of Surveyors  - FIG -

Proceedings Inertial, Doppler and GPS Measurements for National and Engineering Surveys

Joint Meeting of Study Groups 5B and 5C, July 1-3, 1985

S. 311-630

Auflage:  900

ISSN:  0173-1009


Closing Remarks



Table of Contents Volume 1 311
Table of Contents Volume 2 313
Gerlach, Bodo E.
     Positioning with a GPS Pseudorange Receiver
     - Functional Model Test Results -

Gervaise, Jean / Mayoud, Michel / Beutler, Gerhard /
Gurtner, Werner

     Test of GPS on the CERN-LEP Control Network

Grafarend, Erik W. / Lindlohr, Wolfgang / Stomma, Anna
     Improved Second Order Design of the Global Positioning System
     - Ephemerides, Clocks and Atmospheric Influences -

Gründig, Lothar / Neureither, Matthias / Bahndorf, Joachim
     Including Macrometer-Type Observables into a Standard
     3D Adjustment Program

Hartl, Philipp / Schöller, Wolfgang / Thiel, Karl-Heinz
     GPS Related Activities of the INS

Hein, Günter W.
     From the Phase Observables of the Global Positioning
     System to 3D-Baseline Components

Henson, Dennis J. / Collier, E. Ann / Schneider, Kevin R.
     Geodetic Applications of the Texas Instruments TI 4100
     GPS Navigator

Hofmann-Wellenhof, Bernhard
     GPS in Practice  -  From Measurements to Results

Hofmann-Wellenhof, Bernhard / Remondi, Benjamin W.
     Determination of the Trajectory of a Moving Platform
     Using GPS Carrier Phase

Landau, Herbert
     GPS Baseline Vectors in an Integrated Threedimensional

Le Cocq, Cathérine / Boucher, Claude
     Geodetic Applications of the SERCEL TR5S GPS Receiver

Papo, Haim B. / Perelmuter Avraham
     Should Our Concept of Geodetic Datum Change with the
     Introduction of GPS?

Seeber, Günter / Wübbena, Gerhard
     Geodetic Measurements with TI 4100 GPS Receivers

Stansell, Thomas A. jr. / Chamberlain, Steven M. / Brunner, Fritz K.
     The First Wild-Magnavox GPS Satellite Surveying
     Equipment: WM101

Stiller, Albert
     Development of Civilian GPS Receivers in the Federal
     Republic of Germany for Different Applications

Strauss, Robert
     On the Variation of the Transformation Parameters
     between GPS and the German Horizontal Network

Wübbena, Gerhard
     Model- and Program Developments for cm-Positions
     with GPS


The Modern Techniques for Developing Countries

Wassef, Attallah M.
     - Review Paper -
     Modern Techniques for Developing Countries

Jonsson, Bo
     Doppler Observations in Zambia

Seeber, Günter
     Some Examples of Doppler Measurements for Control
     Surveys in Latin America

Hirsch, Otto
     Vote of Thanks

Welsch, Walter M.
     Closing Remarks

Richardus, Peter
     After Dinner Speech

List of Participants 617

Closing Remarks

The final words to the symposium on "Inertial, Doppler and GPS Measurements for National and Engineering Surveys" have to answer the same questions which can be asks at the end of any conference: Has the event met the expectations of both the organizers and the participants? Has the goal been reached? What are the results of the symposium? And what can be recommended for the future?

The first question can be answered by the organizers by a clear YES. More than 170 students, practitioners and scientists coming from 21 countries have listened to some 35 lectures. Many old friends have met and new colleagues have become acquainted to the community. The organizers are happy to have been the hosts and to have been able to show on an academic event their guests the University of the Bundeswehr.

The two study groups of FIG have updated what has been under development the past years according to the recommendations given to them by the last FIG congress in Sofia. Thus they are ina position to report to the next congress in Toronto.

The organizers have to thank the chairmen for their work, the speakers for their presentations which were good, clear, on a high level, and presented topics, experiences and results on new high technology systems the first time in Europe on the occasion of an international symposium of this kind. For all this the organizers thank the participants very warmly.

The second question whether or not the event has met the participant's expectations has to be answered by themselves. It may be that some, especially those not being busy with inertial, Doppler and GPS techniques every day, have expected some more basic information. However, it is possible that some others have expected somme deeper insights. If one takes in this case, as geodesists often do, the mean - doesn't the mean result in what was presented?

What are the results of the symposium?
As mentioned in the preface: satellite and inertial survey systems are basically different systems. But they do not really complete, they rather complete each other.

The currently operating inertial survey systems are still in the state of being geodetically applied to large unmapped areas, if one refrains from purely navigational applications. They are not stand-alone instruments but have to be supported either by terrestrial ground control or by being updated by Doppler or GPS fixes. More sophisticated software applied during the mission or in postprocessing may lead to accuracies satisfactory for geodetic applications even in geodetically well developed areas or in regions of rough terrain. Comparative investigations are still ongoing.

The general impression of the papers on Doppler results was retrospective, was that something that happened in the past was reported on. Even if "interferometric fringe count" processing enables TRANSIT technqiues to provide 12 cm-accuracy in 4 hours with only two receivers, even if the thought of spending several days on each site with TRANSIT receivers could become only a memory, and even if the TRANSIT system is updated by launching additional satellites rather than switching off the system - the number of papers, the general interest, the general impression is, that the times of TRANSIT Doppler measurements are over, sooner or later.

In contrast to this experience the general view on GPS has been prospective. The symposium has been a forum crammed with information on GPS. The intense interest has left no doubt that GPS is viewed as the bright star of promise for the next generation of survey and positioning applications. Many experiments, optimistically and enthusiastically researching and experimenting with the really promising properties of GPS were reported on. It is appropriate and necessary that designers and users accentuate the positive side of GPS. However, user's investment decisions must also consider the potential negative aspects. Some of them are that

  • the exact effect on differential positioning of the military's accuracy aerial techniques will not fully be known until those techniques are implemented in orbiting satellites,
  • the L 2 and the P-code frequency are not expected to be available to standard code GPS users (SDS). There are indications that precise GPS code data-gathering for the highest level of dynamic positioning accuracy must be accomplished, or controlled, by the government rather than just the processing. This is unlike the TRANSIT policy. It is likely that in the longer term the commercial survey community will develop means of obtaining adequate precision from SDS service without the inconvenience and cost of government PPS assistance. But this is not the case for the time being,
  • scheduled launch of operational satellites is dependent on the developments of the Shuttle program and on the budget allocations of the U.S. Congress,
  • the first GPS operational satellites will require a period of performance verification as they are not identical to the present provisional Block I satellites,
  • GPS will not provide geodetic accuracies in independent point positioning.

A footnote of the WM-101 brochure describes the current GPS situation very simply by "The GPS satellites currently in operation are experimental in nature".

Thus, one may not throw away or sell TRANSIT Doppler equipment too early.

Can on the occasion of this meeting something be recommended for the future? In the field which has been covered by the meeting, it cannot. There was no resolution committee established, because things are too much in a state of flux, their progress does - at least for the time being - not depend on the resolutions this meeting could be able to pass.

What can be done is to watch carefully and thoroughly what is going on, is to gather knowledge and to be prepared for the thing to come. This meeting was meant to contribute in this sense a little bit.

W. M. Welsch


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