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Title: Observation-domain sidereal filtering for high-rate GPS precise point positioning
Author: Atkins, C. L. E.
ISNI:       0000 0004 7659 4917
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2016
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Accurate and timely determination of coseismic displacement (the quasi-permanent displacement of the ground caused by an earthquake) is crucial for tsunami warning and situational awareness systems. Seismometers measure acceleration or velocity very precisely. However, the process of integrating such data to yield displacement data is difficult and error-prone. In contrast, The Global Positioning System (GPS) can measure displacement directly, but is also subject to errors, one of which is multipath. Multipath errors can lead to errors in the measurement of small displacements or obscure the displacement entirely. Errors due to multipath are highly dependent on the geometry of GPS satellite orbits and surrounding reflectors relative to the receiving antenna itself. Each satellite has a ground track repeat period of approximately one sidereal day. Hence, this relative satellite-reflector geometry will repeat with the same period. Using this fact, it is possible to identify and remove the error signature induced by multipath by analysing data from adjacent days, yielding an improved time series of displacements and hence a more discernible coseismic offset. This process is commonly known as 'sidereal filtering'. This thesis describes a sidereal filter algorithm that attempts to remove the multipath error signature from the GPS measurements themselves before processing them rather than from the resulting position time-series. It is shown to generally produce a more stable position time series over periods from a few tens to a few hundred seconds, remove high-frequency multipath error more effectively, yield better stability during satellite outages and measure small centimetre-level displacements more accurately than a position-domain sidereal filter. However, results are inconclusive when applying the algorithm to the measurement of the coseismic displacements of a real earthquake, but it is demonstrated that an observation-domain sidereal filter is better at enabling one to distinguish certain types of seismic wave from a position time series.
Supervisor: Ziebart, M. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available