Analysis of GNSS time series obtained from Turkish national permanent GNSS stations network-active system using Hilbert-Huang transform /

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2014
Özdemir, Soner
In this thesis, time series of position estimates are generated from the data collected at Turkish National Permanent GNSS Stations Network-Active (TNPGN-Active) stations with high-precision GNSS analysis methods, and obtained time series are analysed using Hilbert Huang Transform (HHT) whereby associated problems of this transformation are investigated. The accuracy of the positional correction parameters sent to the end users on the field from TNPGN-Active system is important when it is considered these coordinates are used in the new cadastral applications. After the generation of time series, problematic sites are detected which can impose adverse effects on coordinate accuracies. GNSS time series show non-linear and/or non-stationary behaviours due to the underlying physical processes. Adaptive nature of HHT makes it possible to address each time series seperately and sheds light upon the individual characteristics of the time series. With Empirical Mode Decomposition (EMD) method, original GNSS signals are transformed into amplitude/frequency modulated Intrinsic Mode Functions (IMFs) in this study. Together with the Hilbert Spectrum, a more detailed representation of the physical processes is supplied. Problematic areas in HHT, such as interpolation technique between extrema, end effects, stopping criteria for sifting process, mode mixing, and some coproducts of EMD, such as detrending and denoising are also evaluated. With this study, HHT is applied to TNPGN-Active time series for the first time. Great efforts are awaiting for physical interpretation of the results obtained in this study.

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Citation Formats
S. Özdemir, “Analysis of GNSS time series obtained from Turkish national permanent GNSS stations network-active system using Hilbert-Huang transform /,” M.S. - Master of Science, Middle East Technical University, 2014.