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Ann. Geophys., 14, 1429-1436, 1996
www.ann-geophys.net/14/1429/1996/
© European Geosciences Union 1996
Relationships between GPS-signal propagation errors and EISCAT observations
N. Jakowski, E. Sardon, E. Engler, A. Jungstand, and D. Klähn
DLR e.V., Fernerkundungsstation Neustrelitz, Kalkhorstweg 53, Germany
Abstract. When travelling through the ionosphere the
signals of space-based radio navigation systems such as the Global Positioning
System (GPS) are subject to modifications in amplitude, phase and polarization.
In particular, phase changes due to refraction lead to propagation errors of up
to 50 m for single-frequency GPS users. If both the L1 and the L2 frequencies
transmitted by the GPS satellites are measured, first-order range error
contributions of the ionosphere can be determined and removed by difference
methods. The ionospheric contribution is proportional to the total electron
content (TEC) along the ray path between satellite and receiver. Using about ten
European GPS receiving stations of the International GPS Service for Geodynamics
(IGS), the TEC over Europe is estimated within the geographic ranges -20°≤ λ ≤40°E
and 32.5°≤ Φ ≤70°N in longitude and latitude, respectively. The
derived TEC maps over Europe contribute to the study of horizontal coupling and
transport proces- ses during significant ionospheric events. Due to their
comprehensive information about the high-latitude ionosphere, EISCAT
observations may help to study the influence of ionospheric phenomena upon
propagation errors in GPS navigation systems. Since there are still some
accuracy limiting problems to be solved in TEC determination using GPS, data
comparison of TEC with vertical electron density profiles derived from EISCAT
observations is valuable to enhance the accuracy of propagation-error
estimations. This is evident both for absolute TEC calibration as well as for
the conversion of ray-path-related observations to vertical TEC. The combination
of EISCAT data and GPS-derived TEC data enables a better understanding of
large-scale ionospheric processes.
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