I Vvot
111
8 0 UhH\
stitution in a local area, i.e. through the state surveying
agency. At the University of Hannover, Institut fiir
Erdmessung, research has started in co-operation with
the „Landesvermessungsamt", to investigate this ques
tion by use of two Tl 4100 GPS receivers and the devel
opment of appropriate software packages (fig. 6). First
results will be available early in 1985 [Seeber u.a., 1984].
qPILSUM
BREMEN
H0HEN-
109 RiiNSTflRF
307
\l05
DOTEBERGO
VELBER^M/^pl N
/LINDENj
tf\SPRINGE
/20.7
N. 00ER-
\bruck
/32
ÖSPRINGE
i
BREITENBERG
Fig. 6. Differential tests with two Tl 4100 in Northern Germany July
1984. Interstation distances in km. UH University Hannover.
For photogrammetric control GPS will be of large value
especially in areas with difficult access. For future appli
cations, the inclusion of precise control points or also of
original GPS observables within an integrated photo
grammetric adjustment seems to be a feasible approach.
For inertia!surveying up to now TRANSIT control points
with a spacing of 100 km have been used successful
ly. In the future this technique will be replaced by GPS.
The high accuracy potential of GPS will possibly reduce
the application of the very expensive inertial equipment
for point positioning.
Furtheron the increasing accuracy of GPS measure
ments will lead to applications for the determination of
crustal movements in tectonically active areas. Up to
now it is not yet clear, however, whether GPS also pro
vides sufficient accuracy over longer distances for moni
toring relative plate motions.
In marine geodesy many applications can be expected.
Compared to present day techniques like Omega, Loran
C, TRANSIT and integrated navigation, GPS will pro
vide much better accuracies. This is also true during the
present limited coverage. At the University of Hannover,
much research has been done with respect to the use of
satellite methods for precise positioning at sea. Fig. 7
shows the comparison between the Tl 4100 real time po
sitioning and an integrated system (TRANSIT, Doppler
Sonar, Gyro) during a test on the German research ves
sel „Polarstern". Application fields are amongst others
sea-gravimetry, mapping of sea-bottom with „Sea-
beam", ocean exploration, ocean mining, hydrography.
For obtaining optimal results, however, differential tech
niques will have to be developed.
Within the field of Antarctic research, in recent years ice
motion determination has been performed by use of
TRANSIT techniques [Seeber, Hinze, 19841For future
years the use of GPS will lead to much shorter observa
tion periods and higher accuracy. This is an extremely
NGT GEODESIA 85
important feature for expeditions under difficult logisti
cal conditions. During the Antarctic summer 1985/1986
a first Tl 4100 experiment on the Filcher Shelf is planned
by the IFE, University of Hannover.
0 1 2 3 4 5 Km
Fig. 7. Comparison between GPS navigation and Integrated Navi
gation System on Polar Research VesselPolarstern", Arktis II,
Fram Street, Lat. 80° North, August 26, 1984. Note the update of
integrated system through TRANSIT pass at 21.26 hours.
6. Conclusion
GPS will develop to be a very powerful tool for future
geodetic activities. Already today, with the present
satellite coverage and the present receiver-equipment,
first experiences can be gained and valuable work can be
done. For the active geodesist it is a must to become
familiar with these new methods in order to be prepared
when the system begins to be operational. TRANSIT
Doppler techniques will lose most of their importance for
geodetic applications within the next years. However,
most of the experiences coming from TRANSIT and
most of the solution concepts can be transferred to
GPS. This is especially true for the datum problem and
the combination of terrestrial networks with satellite
methods. As such, scientific and practical work, which
has been done over years with TRANSIT, is an excellent
preparation for the challenges of the Global Positioning
System within the field of geodesy.
Literature
Beutler, G., D. A. Davidson, R. B. Langley, P. Vanicek, D. E.
Wells, Some theoretical and practical aspects of geodetic positio
ning using carrier phase difference observations of GPS satellites.
Technical Report no. 109, Dep. of Surv. Engineering, UNB Frede-
rictown, Canada, 1984.
Fell, P. J., Geodetic Positioning Using a Global Positioning System
of Satellites. Ohio State University, Dep. of Geodetic Science,
Rep. no. 299, 1980.
Goad, C. C., B. W. Remondi, Initial Relative Positioning Results
Using the Global Positioning System. Bulletin Géodésique, 58, no.
2, 193-210, 1984.
Hothem, L. D., L. J. Fronczek, Report on Test and Demonstration
of Macrometer Model V-1000 Interferometric Surveyor. FGCC Re
port IS83-2, 1983.
Lindstrot, W., Ergebnisse von Macrometermessungen in Nord-
rhein-Westfalen und Vergleiche mit anderen Verfahren. Forum,
477-486, 1984.
Mc Doran, P. F„ SERIES-GPS, Codeless Pseudo-Ranging Positio
ning Technology. CSTG Bulletin, no. 5, 46 ff, 1983.
Richardus, P., Project Surveying, Rotterdam 1983.
Schenke, H. W., Untersuchungen zur Genauigkeit von Doppler-
Satellitenbeobachtungen in Testnetz Westharz. Dissertation Han
nover 1984. Wiss.Arb. Fachr.Verm.Wesen Univ. Hannover, no.
129, 1984.
Seeber, G., Die Rolle des NAVSTAR Global Positioning Systems
fur die Lösung geodatischer Aufgaben. Z.f. Vermessungswesen,
109, 1-11, 1984.
Seeber, G., H. Hinze, Bestimmung von Gletschereisbewegungen
mit Doppler-Satellitenmessungen in der Antarktis. Z.f. Vermes
sungswesen, 109, 176-185, 1984.
Seeber, G., D. Egge, G. Wübbena, Erste Erfahrungen mit einem Tl
4100 GPS Empfangssystem. Z.f. Vermessungswesen 109, 435-438,
1984.
Van Dierendonck, A. J., S. S. Russell, E. R. Kopitzke, M. Birn-
baum, The GPS Navigation Message. Navigation 25, no. 2, 1978.
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