| Summary: | 碩士 === 國防大學中正理工學院 === 軍事工程研究所 === 89 === ABSTRACT
GPS positioning is achieved by using basic observables transmitted with low power signal from the satellites. The GPS signal is, therefore, to be easily interfered under the near-frequency and natural environment. It would be also possible to intercept the receiving of GPS signal, or degrade the accuracy of GPS positioning. With the extensive applications of GPS to many military and civil fields, it is important to investigate the security of GPS signal affected by the interference and jamming effects.
This research is aimed at analyzing the GPS data sets collected by the field experiments for the evaluation of GPS interference effects. The interference environment studied includes the test areas nearby a near-frequency radar station and the high-voltage electricity fields, and the observation condition with anomalous ionospheric effect caused by the strong solar activity.
The results tested show that GPS signal is significantly interfered by the radar signal transmitted with near GPS frequency. However, the effects of terrain occultation and satellite azimuth can be found to reduce the interference. The results also show that the degradation of GPS accuracy is not serious under the high-voltage electricity fields, although the GPS signal quality might be damaged to those satellites with lower elevation angles. It final results tested for the ionospheric effect related to the strong solar activity reveal that the security of GPS navigation still can be ensured, but its accuracy could be lowed down to a certain level. For GPS relative positioning, the Lc linear combination of GPS observation is the one that is reliable to be used by the GPS data processing for those data collected during the period of high sunspot activity.
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