Master of Science (MS), Ohio University, 2019, Electrical Engineering & Computer Science (Engineering and Technology)

From aviation and safety critical applications to personal navigation; Global Navigation Satellite System (GNSS) technology has found a place in everyday civilian life and will only become more intertwined as the technology continues to improve. One of the issues with GNSSs is that they are susceptible to interference in the forms of intentional (i.e., jamming) or unintentional sources. As this interference is a threat to civil applications, this thesis focuses on providing the framework to understand the performance degradation of GNSS receivers in the presence of interference. More specifically, this paper focuses on the high accuracy user, and how interference affects a commercially available differential GNSS (DGNSS) receiver system. A comparison was done to investigate differences between two commercially available DGNSS receivers' performances as well as analyze the different approaches manufactures take in the integration of multi-constellation GNSS signals. After testing two DGNSS receivers, two things were clear when analyzing the data. First, there is a significant benefit when using multi-constellation GNSS signals. Not only does this help improve position accuracies; it also allows for a more robust system in the presence of GNSS interference. Second, both of the receivers tested performed worse in the presence of a GPS L1 interference signal compared against a GPS L2 interference signal when in either a GPS only or all GNSS receiver configuration.

Committee: Chris Bartone Dr. (Advisor) Subjects: Electrical Engineering

Master of Science (MS), Ohio University, 2018, Electrical Engineering (Engineering and Technology)

Many mobile devices (phones, tablets, smartwatches, etc.) have incorporated embedded GNSS receivers into their designs allowing for wide-spread on-demand positioning. These receivers are typically less capable than dedicated receivers and can have an error of 8-20m. However, future application, such as UAS package delivery, will require higher accuracy positioning. Recently, the raw GPS measurements from these receivers have been made accessible to developers on select mobile devices. This allows GPS augmentation techniques usually reserved for expensive precision-grade receivers to be applied to these low cost embedded receivers. This thesis will explore the effects of various GPS augmentation techniques on these receivers.

Committee: Maarten Uijt de Haag (Advisor); Chris Bartone (Committee Member); Michael Braasch (Committee Member); Viorel Popescu (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy (PhD), Ohio University, 2010, Electrical Engineering (Engineering and Technology)

Four primary contributions are made to the treatment of noise and conspiring bias for dual frequency differential Global Satellite Navigation Systems (GNSSs). These contributions enhance accuracy and protection levels for aircraft precision approach and landing operations and similar applications.A statistical characterization is presented of Global Positioning System (GPS) user range error as an uncorrelated, normally distributed random variable with non-zero mean over the length of the aircraft precision approach operation. This leads directly to modeling GPS error in the position domain as multivariate normal with non-zero mean. Based on this model, a vertical composite protection level VPLc and a horizontal composite protection level HPLc are each implemented as univariate normal distributions with non-zero means. A method is presented by which exact values – that is, values accurate to a user-defined error tolerance and consistent with statistical assumptions – of VPLc and HPLc are obtained, and by which computationally efficient approximations may be evaluated. A statistical quadratic form under the multivariate normal distribution is then used to derive a new class of protection levels based on the probability enclosed within a radius defined in two or more dimensions. A central chi-square representation of this quadratic form is also presented, and is incorporated into a six-step computational procedure for the two-dimensional composite radial protection level RPLc. This procedure is extended to the composite spherical protection level (SPLc) and the ellipsoidal protection level (EPLc). Two additional algorithms are presented for dual-frequency differential Global Positioning System (GPS) use. Performance improvements are achieved first through the exchange of pseudorange noise and multipath for reducible biases using a modified Code Noise and Multipath (CNMP) algorithm applied both to reference station and aircraft ranging measurements. In this algorithm, (open full item for complete abstract)

Committee: Frank van Graas PhD (Advisor); Maarten Uijt de Haag PhD (Committee Member); Michael Braasch PhD (Committee Member); James Rankin PhD (Committee Member); Jacqueline Glasgow PhD (Committee Member); John Coulter Colonel USAF (Committee Member) Subjects: Electrical Engineering; Remote Sensing; Systems Design; Transportation

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:

Doctor of Philosophy (PhD), Ohio University, 1999, Electrical Engineering & Computer Science (Engineering and Technology)

Low-cost Inertial Navigation Systems (INS) technology has evolved rapidly over the last decade with the development of less-expensive and higher-accuracy inertial measurement units (IMU). The development in the field of differential GPS (DGPS) has also matured over the past decade to provide reliable centimeter level accuracy in real-time. This dissertation provides a detailed study of the feasibility of using a low-cost IMU with accurate DGPS to achieve higher-accuracy, reliability, and continuity of the position solution. Detailed INS equations are provided as well as the hardware integration of a low-cost IMU and a centimeter-level DGPS system. The integrated system was dynamically tested in a van and a DC-3 research aircraft. In the absence of DGPS updates for a period of time of 10 seconds, IMU-derived positions diverged by 5-10 meters for the van tests and by tens of meters for flight tests. Noise on the IMU-derived position between successive, one-second DGPS position updates was observed to be on the order of a few millimeters for the van tests and one centimeters for the flight tests.

Committee: Frank van Graas (Advisor) Subjects:

Master of Science (MS), Ohio University, 2001, Electrical Engineering & Computer Science (Engineering and Technology)

The next generation of advanced aircraft landing system will utilize the Global Positioning System (GPS). The availabilityof GPS is augmented by the use of pseudolites "pseudo satellites." Pseudolites transmit a GPS-like signal that can be used as a ranging source in place of or in addition to ranging sources from a satellite. The Local Area Augmentation System (LAAS) is being used to further augment GPS for precision approaches and landings by using a concept known as Differential GPS (DGPS). One major error source in DGPS is due to transmitted signal reflections (multipath) off nearby obstacles. Efficient antenna design can be used to mitigate multipath by severely attenuating signals from negative elevation angles. The research contained in this document was conducted in order to optimize the current wideband airport pseudolite (WBAPL) multipath limiting antenna (MLA) for pseudolite transmission in the LAAS. To that end, three phases of study were conducted. The first stage modeled the ground-to-air link between the WBAPL transmitting MLA and the reception antenna during approaches with an attempt to define optimal WBAPL antenna locations. The second stage was conducted to characterize the basic pattern requirements of the WBAPL transmitting MLA and sought to project a hypothetical coverage volume given a preliminary pseudolite antenna pattern. The third stage was performed to attain some level of validation for the new WBAPL MLA transmitting antenna pattern measured by an external contractor through the independent synthesis of a similar antenna radiation pattern.

Committee: Chris Bartone (Advisor) Subjects: