Master of Science (MS), Ohio University, 1996, Electrical Engineering & Computer Science (Engineering and Technology)

Investigating the effect of the DGNSS SCAT-I data link on VOR signal reception

Committee: Trent Skidmore (Advisor) Subjects:

Master of Science (MS), Ohio University, 1998, Electrical Engineering & Computer Science (Engineering and Technology)

Implementation and optimization of a Global Navigation Satellite System software radio

Committee: Michael Braasch (Advisor) Subjects:

Doctor of Philosophy (PhD), Ohio University, 1997, Electrical Engineering & Computer Science (Engineering and Technology)

The software radio has been described as the most significant evolution in receiver design since the development of the superheterodyne concept in 1918. The software radio design philosophy is to position an analog-to-digital converter (ADC) as close to the antenna as possible and then process the samples using a combination of software and a programmable microprocessor. There are a number of important advantages to be gained through full exploitation of the software radio concept. The most notable include: 1) The removal of analog signal processing components and their associated nonlinear, temperature-based, and age-based performance characteristics. 2) A single antenna/front-end configuration can be used to receive and demodulate a variety of radio frequency (RF) transmissions. 3) The software radio provides the ultimate simulation/testing environment. Global Navigation Satellite Systems (GNSSs) are the latest and most complex radionavigation systems in widespread use. The United States' Global Positioning System (GPS) and, to a lesser extent, the Russian Global Orbiting Navigation Satellite System (GLONASS) are being targeted for use as next generation aviation navigation systems. As a result, it is critical that a GNSS achieve the reliability and integrity necessary for use within the aerospace system. The receiver design is a key element in achieving the high standards required. This work presents the complete development of a GNSS software radio. A GNSS receiver front end has been constructed, based on the software radio design goals, and has been evaluated against the traditional design. Trade-offs associated with each implementation are presented along with experimental results. Novel bandpass sampling front end designs have been proposed, implemented and tested for the processing of multiple GNSS transmissions. Finally, every aspect of GNSS signal processing has been implemented in software from the necessary spread spectrum acquisition algorithms to those (open full item for complete abstract)

Committee: Michael Braasch (Advisor) Subjects:

Master of Science (MS), Ohio University, 2020, Electrical Engineering (Engineering and Technology)

With a growing demand for large unmanned aircraft system operations in the national airspace system, a method to safely and automatically land unmanned aircraft at a wide range of airports with varying levels of equipage is still needed. Currently no navigation system is capable of a fully coupled precision approach and landing without the use of ground based navigational aids. To enable widescale adoption and usage of unmanned aircraft systems, an aircraft based augmentation system that provides precision approach and landing service without sacrificing safety is required to land the aircraft at all runways. This thesis proposes an aircraft based GPS augmentation system using an on-board downward facing radar altimeter for precision approach and landing of unmanned aircraft systems. The proposed architecture is initially evaluated using a simulation environment designed to test multiple different GNSS, radar altimeter, and terrain elevation database configurations. Following the offline simulation, a flight test analysis is completed testing the proposed architecture using pre-recorded flight test data at the Ohio University Airport (OH) and Reno-Tahoe International Airport (NV). Furthermore, this thesis provides a sensitivity study on the systematic errors in the augmentation system to better characterize and account for the inherent errors of the architecture's subsystems. This thesis then discusses modifications to the previously developed terrain database spot algorithm to better account for the characteristics of the selected radar altimeter. Finally, an approach for future certification is proposed followed by recommendations for further research on the topic.

Committee: Maarten Uijt de Haag Ph.D. (Advisor); Frank van Graas Ph.D. (Committee Member); Sabrina Ugazio Ph.D. (Committee Member); Justin Frantz Ph.D. (Committee Member) Subjects: Electrical Engineering; Engineering

Master of Science (MS), Ohio University, 1994, Electrical Engineering & Computer Science (Engineering and Technology)

A shipboard global positioning system carrier phase interferometric aircraft flight reference system

Committee: Frank van Graas (Advisor) Subjects:

Doctor of Philosophy (PhD), Ohio University, 1998, Electrical Engineering & Computer Science (Engineering and Technology)

This dissertation addresses the signal-in-space integrity monitoring of the Local Area Augmentation System. The theoretical basis and the system architecture of the integrity monitoring are described. The performance of the baseline protection level algorithms defined in the "Minimum Aviation System Performance Standards for The Local Area Augmentation System" is verified by both theoretical analysis and computer simulation. It is shown that the underlying assumptions used in calculating the protection levels do not take into account the effect of the ground processing function. A modification to the baseline algorithms is presented. Procedures in verifying the algorithms along with other ground processing functions and/or with any number of reference receivers are demonstrated. Finally, improvements to the algorithms are discussed.

Committee: Michael Braasch (Advisor) Subjects:

Doctor of Philosophy (PhD), Ohio University, 1994, Electrical Engineering & Computer Science (Engineering and Technology)

An Interferometric Global Positioning System Flight Reference System (IGPS FRS) is implemented and flight tested on a transport category aircraft. This dissertation discusses the IGPS FRS theory and principles of operation, its architecture and integration with the aircraft, and the initial static calibration and flight-test performance results. The validity of the results is established by referencing them to a known ground test point and/or a laser tracking system. The principles underlying the operation of the IGPS FRS are similar to those used for kinematic surveying, and are also referred to as differential carrier-phase tracking with integer ambiguities resolved. Flight Reference System objectives include: 0.1 m accuracy rms (each axis); one or more updates per second; UTC (Universal Time, Coordinated) synchronization better than 0.1 ms; real-time, all-weather operation; and, repeatable flight paths. The latter requirement calls for full integration with the aircraft flight control system and coupled flight.

Committee: Frank van Graas (Advisor) Subjects:

Master of Science, The Ohio State University, 2023, Geodetic Science

This thesis presents the methods to explore a large dataset of Precise Point Positioning (PPP)-derived positions to investigate the correlation between spatial and temporal variables from short-duration observations and the achieved positional accuracy of the results. This study aims to enhance decision-making in the logistical aspects of collecting high-accuracy Global Navigation Satellite System (GNSS) observations, such as establishing geodetic survey control points, where time is the main limiting factor. In the conducted experiment, daily observation files were systematically obtained and subsequently segmented into smaller time windows at varying hour lengths. The GNSS data processing package, Parallel.GAMIT, specifically employing its PPP module which is a python wrapper for the Canadian Geodetic Survey's GSPACE software, was utilized to process these segmented data sets. To establish a baseline for comparison, the obtained solutions were pitted against a "true value" derived from a daily modeled coordinate. As a noteworthy contribution to the field, the preliminary findings from the analysis introduce fresh perspectives into the correlations among observational factors and the accuracy of PPP solutions. The implications of these findings extend to the prospect of developing predictive methods for estimating the accuracy of PPP solutions in scenarios involving short-duration observation sessions.

Committee: Demián Gómez (Committee Member); Michael Bevis (Advisor); W. Ashley Griffith (Committee Member) Subjects: Civil Engineering; Earth

Master of Science (MS), Bowling Green State University, 2023, Geology

Lake Mead – the most prominent U.S. reservoir by volume – has been facing the effects of a devastating prolonged drought since 1999, which caused the lake water levels to plummet. The crust around Lake Mead has been uplifting due to an unloading effect of the current drought in the western USA. This research analyzed the crustal deformation due to elastic loading and unloading caused by climate-related water mass variation in Lake Mead over the last decade. The Global Navigation Satellite System (GNSS) measures elastic loading deformation responses to hydrological mass variations near or on the Earth's surfaces. GNSS has been used as an independent measurement to distinguish between hydrological models. This research systematically studied the Correlation between water level changes and crustal deformation around Lake Mead using data from the space geodetic technique GNSS. Other loading impacts, such as atmosphere and non-tidal ocean loading effects, were modeled and removed to study the lake-water-induced loading displacement. My result showed that the modeled elastic loading deformation is generally consistent with GNSS observations in the vertical component but usually smaller than GNSS observations in the horizontal directions, indicating the potential missing hydrological water components in the Model. This study further investigated the impacts of variations of other water loads, such as regional soil moisture and local groundwater. To compare the modeled loading deformation with GNSS observations, I calculated the correlation coefficients (r). Among all the six sites, the comparison for the sites P006 and NVLM indicated a strong correlation between observed surface deformation and modeled surface deformation from soil moisture and lake loading. After subtracting the modeled loading deformation from the corrected GNSS observations, I also discussed the Correlation between the residual series and the local groundwater level change around Lake Mead. I primarily (open full item for complete abstract)

Committee: Yuning Fu Ph.D. (Committee Chair); Ganming Liu Ph.D. (Committee Member); Anita Milas Ph.D. (Committee Member) Subjects: Geology; Geophysics

Doctor of Philosophy, The Ohio State University, 2003, Geodetic Science and Surveying

By the middle of this decade, measurements from the CHAMP (CHAllenging of Minisatellite Payload) and GRACE (Gravity Recovery And Climate Experiment) gravity mapping satellite missions are expected to provide a significant improvement in our knowledge of the Earth's mean gravity field and its temporal variation. For this research, new observation equations and efficient inversion method were developed and implemented for determination of the Earth's global gravity field using satellite measurements. On the basis of the energy conservation principle, in situ (on-orbit) disturbing potential and potential difference observations were computed using data from accelerometer- and GPS receiver-equipped satellites, such as CHAMP and GRACE. The efficient iterative inversion method provided the exact estimates as well as an approximate, but very accurate error variance-covariance matrix of the least squares system for both satellite missions. The global disturbing potential observable computed using 16-days of CHAMP data was used to determine a gravity field solution (OSU02A), is commensurate in geoid accuracy to other gravity models and yields improvement in the polar region at wavelengths longer than 800 km. The annual variation of Earth's gravitational field was estimated and compared with other solutions from satellite laser ranging analysis. The annual geoid change of 1 mm would be expected mostly due to atmosphere, continental surface water, and ocean mass redistribution. The correlation between CHAMP and SLR solutions was 0.6~0.8 with 0.7 mm of RMS difference. Based on the monthly GRACE simulation, the geoid was obtained with an accuracy of a few cm and with a resolution (half wavelength) of 160 km. However, the geoid accuracy can become worse by a factor of 7 because of spatial aliasing. The approximate error covariance was found to be a very good accuracy measure of the estimated coefficients, geoid, and gravity anomaly. The resulting recovered temporal gravity fields (open full item for complete abstract)

Committee: Christopher Jekeli (Advisor) Subjects: Geodesy

Master of Science (MS), Ohio University, 2008, Electrical Engineering (Engineering and Technology)

Satellite laser communication systems provide measurements that can be further processed to provide relative attitude estimates of each satellite in the constellation. This suggests a dual-use potential yielding benefits such as the use of lower-cost inertial measurement units, achieving improved fault-tolerance, and facilitating the implementation of orbital control systems. This thesis presents a static attitude determination scheme that provides relative attitude estimates using azimuth and elevation angles provided by the laser communication system. These measurements are corrupted by noise and error sources, several of which are characterized herein, and so this thesis also presents a sensitivity analysis intended to characterize the impact that these errors have on the attitude solution. This analysis reveals a high degree of sensitivity which indicates that a dynamic attitude estimation scheme may be required that incorporates the static estimation scheme in a nonlinear filtering architecture.

Committee: Douglas A. Lawrence PhD (Committee Chair); Maarten Uijt de Haag PhD (Committee Member); Sergiu Aizicovici PhD (Committee Member); Robert Williams II PhD (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy (PhD), Ohio University, 2007, Electrical Engineering & Computer Science (Engineering and Technology)

A novel Differential Global Navigation Satellite System (DGNSS) Carrier Phase (CP) batch processor is developed in this dissertation. The batch processor estimates both the differential position solution and the ambiguities of the differential CP measurements. The design of the batch processor uses geometry change information over time to minimize the effects of time-varying measurement errors, for instance, ionospheric and/or tropospheric spatial and temporal decorrelation errors. Tropospheric errors that affect the CP batch processor are studied in detail using measurements from two GPS data collection sites. Three novel techniques are implemented in the CP batch processor: 1) A geometry correction that is applied to the single difference (SD) CP measurements and not to the geometry matrix; 2) Error bounding based on both covariance and deterministic error analyses; and 3) RAIM-based integrity analyses over time. The combination of the three techniques ensures the accuracy and integrity of the final position solution and ambiguity estimations. This dissertation provides batch processor results for simulations over a 10-km static GPS baseline as well as results for live DGPS measurements over a 5-km baseline. To make up for the reduced observability due to the use of CP measurements only and still obtain deci-meter level accuracy, the batch processor requires at least seven satellites for convergence times on the order of tens of minutes. Significantly faster convergence times, on the order of a few minutes, are obtained with multiple constellations, such as a combined GPS/Galileo constellation, which results in a practical carrier phase-only batch processor. Integrity analysis is performed for the batch processor through the injection of different types of constant and slowly varying errors into the differential CP measurements. Results show that GPS alone provides a limited failure detection/exclusion capability. However, the combined GPS/Galileo constellation pr (open full item for complete abstract)

Committee: Frank Van Graas (Advisor) Subjects:

Master of Science (MS), Ohio University, 1985, Electrical Engineering & Computer Science (Engineering and Technology)

Investigation through simulation techniques of the application of differential GPS to civil aviation

Committee: Richard McFarland (Advisor) Subjects:

Master of Science (MS), Ohio University, 1998, Electrical Engineering & Computer Science (Engineering and Technology)

Calculations for positioning with the Global Navigation Satellite System

Committee: Frank van Graas (Advisor) Subjects:

Master of Science (MS), Ohio University, 1999, Electrical Engineering & Computer Science (Engineering and Technology)

A comparative study of advanced multipath mitigating global positioning system receiver architectures

Committee: Michael Braasch (Advisor) Subjects:

Doctor of Philosophy (PhD), Ohio University, 1992, Electrical Engineering & Computer Science (Engineering and Technology)

This paper addresses the characterization of multipath errors in satellite- based precision approach and landing systems. Satellite-based navigation systems such as the NAVSTAR Global Positioning System (GPS) are currently being considered for use as precision approach aids. However, before these systems can reach full maturity the issue of multipath must be addressed. Multipath represents the dominant error source for the precision approach application. The work presented in this dissertation provides insight into the range and behavior of multipath errors in satellite-based precision approach and landing systems. Multipath error has been shown to be a function of multipath strength, delay, phase and phase rate-of-change relative to the direct signal. These parameters have been characterized for the precision approach environment and have been shown to be capable of producing severe multipath error. In the absence of pathological multipath-producing obstacles, collected data reveals the Earth's surface to be the major multipath source.

Committee: Frank van Graas (Advisor) Subjects:

MARCH, University of Cincinnati, 2013, Design, Architecture, Art and Planning: Architecture

The urbanization of major American cities has significantly increased densities and demand, often pushing land values out of the reach of the cultural, arts, and non-profit organizations that are vital contributors to the diversity and desirability of those same cities. This situation on Manhattan Island (NYC) is particularly acute. This thesis proposes several key design strategies for one such New York institution (the School of Visual Arts). First, at the urban site scale, it proposes satellite campus components to be located on dispersed, small or narrow "left-over" parcels, and the architectural identification of those small, dispersed components through visual connections that create a new kind of "urban quadrangle" experience. Second, at the scale of a specific narrow site, the design of a gallery building showcases architectural solutions that optimize the use of these tiny fragments of urban space, to enhance the viewing of art of various sizes, and to enable views of the city. The design of two opposite spaces connected by two narrow sites, one `full' and the other `void' offers different spatial experiences for people to promenade between art, space, and their city.

Committee: Michael McInturf M.Arch (Committee Chair); Aarati Kanekar Ph.D. (Committee Member) Subjects: Architecture