Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    ASSESSING FAULT SLIP HAZARD IN TAIWAN USING SPACE GEODESY
    (2022) Robbins, Kathryn Rose; Huang, Mong-Han; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Taiwan is a geologically complex region due to the continuous collision of the Eurasian Plate and the Philippine Sea Plate. This study aimed to quantify the interseismic crustal deformation of Taiwan and detail the island’s seismic hazard potential using space geodesy. Data were collected between 2016 and 2021 through C-band Copernicus Sentinel-1 synthetic aperture radar imagery and continuous GNSS data from Academia Sinica, Taiwan. I excluded major earthquake events within this time period and generated a dataset consisting of interferometric synthetic aperture radar ground motion velocities with GNSS corrections and interpolated GNSS ground motion velocities. Then, utilizing this dataset, I performed a deformation rate analysis and error analysis. Next, I explored block modeling and used a total variation regularization approach to determine the reference block model that best reduced velocity residuals and minimized the number of independently rotating blocks. Results suggested that the Taipei Basin, Ilan Basin, Western Foothills, and Longitudinal Valley were experiencing increased total strain rate accumulation and, therefore, posed increased seismic hazard.
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    Gravity Gradiometer Aided Inertial Navigation Within Non-GNSS Environments
    (2008-01-25) Richeson, Justin Arthur; Pines, Darryll J; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Gravity gradiometer aiding of a strapdown inertial navigation system (INS) in the event of Global Navigation Satellite System (GNSS) signal loss, or as a complement to an INS/GNSS system, is proposed. Gravity gradiometry is ideal for covert military applications where a self contained, passive, spoof-free aid is desirable, and for space navigation near planetary bodies and moons where GNSS is unavailable. This dissertation provides the first comprehensive discussion on gravity gradiometry fundamentals, map modeling, and regional and altitude effects on the gravitational gradient signal for use as a navigation aid. A thorough methodology to implement strapdown and stabilized gravity gradiometer instruments (GGIs) into an autonomous extended Kalman filter is also presented in the open literature for the first time. Lastly, a brief discussion on extraterrestrial navigation using gravity gradiometry is given. To quantify the potential performance for future gravity gradiometer instruments as an INS aid, extensive Monte Carlo simulations of a hypersonic scramjet cruise missile were performed. The results for the 1000 km range mission indicate that GGI updates significantly improve the navigation accuracy of the autonomous INS. The sensitivities of the system to variations in inertial measurement unit (IMU) quality, gravity field variation, GGI noise, update rate, and type are also investigated along with a baseline INS/Global Positioning System (GPS). Given emerging technologies that have the potential to drastically decrease gradiometer noise levels, a hypothetical future grade gravity gradiometer aided INS is shown to bound root-mean-square (RMS) position errors at 0.336 m, velocity errors at 0.0069 m/s, and attitude errors at 0.00977 degrees, which is comparable to the nominal INS/GPS system with 10 sec updates. The performance of two subsonic cases is also investigated and produced impressive passive navigation accuracy. A commercial aircraft simulation using a future grade GGI provided RMS errors of 0.288 m in position, 0.0050 m/s in velocity, and 0.0135 degrees in attitude. A low altitude and velocity gravity gradiometer based survey simulation similarly showed sub-meter RMS position errors of 0.539 m, velocity errors of 0.0094 m/s, and attitude errors of 0.0198 degrees.