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

A transform-domain, instrumentation Global Positioning System (GPS) receiver is developed for high-fidelity signal quality monitoring (SQM), GPS anomalous event monitoring (GAEM), and GPS software-defined radio (SDR) research. Features of the receiver include: a radio frequency front-end with 24 MHz bandwidth on the GPS L1 (1575.42 MHz) and L2 (1227.6 MHz) frequencies with 14-bit sampling capability to capture and analyze high-dynamic-range signals such as in-band interference; An integrated GPS/Inertial Measurement Unit (IMU) data collection capability at 105 Mbytes/sec sustained transfer rate and 2-Terabyte capacity, with a novel, sub-microsecond resolution IMU time stamping method that significantly simplifies GPS/IMU deeply-integrated processing; a continuous-processing transform-domain engine that computes 1024-point complex parallel-code-correlation functions in less than 15 microseconds for 1-ms blocks of data; A runtime-configurable serial engine containing several hundred ‘split-sum' coarse/acquisition (C/A) code correlators operating on 14-bit input samples; A realtime transform-domain GPS receiver with full message decoding, range measurement, and position-velocity-time solution updates up to a 1 kHz rate. The receiver's graphical user interface allows runtime interaction via a set of software controls, and realtime internal-parameter graphing capabilities similar in function to a combined digital storage oscilloscope and spectrum analyzer. High-fidelity capabilities of the receiver include 55 points per C/A-chip SQM, and 10-correlator Precise-code SQM. The instrument's unique GPS/IMU interleaved data collection capability enabled a flight test where GPS carrier phase tracking was maintained for signals with carrier-to-noise ratios (CNR) at the 15 dB-Hz level. The receiver's application layer is built using a custom-developed, object-oriented applications programming interface that supports customization to suit a variety of applications. The instrument's (open full item for complete abstract)

Committee: Frank van Graas (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2012, Electrical and Computer Engineering

In the past few decades, GPS has revolutionized navigation positioning and timing with numerous civilian and military applications. Recently, there is increased interest in GPS navigation for small cylindrical platforms which can have a potentially high rotation rate (up to 350 Hz). The purpose of this work is to extend the state-of-the-art of GPS receiver and antenna technology for this specific application of small cylindrical platforms. This presents a set of design challenges for engineers, and this work will make contributions to three aspects of the problem: antenna design, satellite coverage, and receiver design. First, a novel dual-band antenna that provides right-hand circular polarization (RHCP) coverage at the GPS L1/L2 bands for reception of C/A-, P(Y)-, and M-coded GPS signals is designed. The availability of GPS measurements at two bands allows one to remove the biases due to the ionsphere and reception of P(Y) and M-coded signals improves navigation accuracy. Importantly, the antenna size is only 4cm × 4cm × 5.08mm (λ/6 × λ/6 × λ/50). Second, this antenna is specifically designed to have a robust tuning such that it can be mounted on metal cylinders of various diameters (60-160mm) and still function properly. For these cylinders, the antenna has broad RHCP coverage and good gain bandwidth performance. Third, the satellite coverage provided by the antenna is investigated. As expected, a single element cannot provide the full spherical coverage which is needed for continuous satellite tracking as the platform rotates. It is shown that the maximum gain method (i.e. choosing the element with the highest gain) is able to obtain full spherical coverage even with only two elements. However, it is a challenge to implement this method because the time-varying platform attitude is unknown. Therefore, a novel receiver tracking algorithm that implements the maximum gain method is designed by modifying the receiver itself, specifically the delay lock loop. Example (open full item for complete abstract)

Committee: Inder Gupta PhD (Advisor); Chi-Chih Chen PhD (Committee Member); Joel Johnson PhD (Committee Member); Hesham El-Gamal PhD (Committee Member) Subjects: Electrical Engineering; Electromagnetics

Doctor of Philosophy, The Ohio State University, 2007, Geodetic Science and Surveying

One of the major error sources in using Global Positioning System (GPS) measurements for modeling the ionosphere is the receiver differential code bias (DCB). Therefore, the determination of the receiver DCB is important, and to date, it has been done mostly using the single-layer ionospheric model assumption. In this dissertation, a new and efficient algorithm using the geometry conditions between the satellite and the tracking receivers is proposed to determine the receiver DCB using permanent reference stations. In this method, an assumption that ionosphere is represented by a single-layer model is not required, which makes DCB computation independent on the pre-selected ionosphere model. In addition, this method is simple, accurate and computationally efficient. The principal idea is that the magnitude of the signal delay caused by the ionosphere is, under normal conditions, highly dependent on the geometric range between the satellite and the receiver. The proposed algorithm was tested with the Ohio Continuously Operating Reference Stations (CORS) and the Transantarctic Mountains Deformation (TAMDEF) sub-network data. The results show that quality comparable to the traditional DCB estimation method is obtainable with greater computational efficiency and simple algorithmic implementation.

Committee: Dorota Grejner-Brzezinska (Advisor) Subjects: Geodesy

Doctor of Philosophy, The Ohio State University, 2005, Geodetic Science and Surveying

Accurate knowledge about sea level and its change is essential to humanity because a large proportion of the Earth's population lives in coastal regions. This study discusses the existing techniques for sea level measurements, including the use of different types of gauges (e.g., water level gauge or tide gauge, and bottom pressure gauge), as well as GPS and satellite altimetry. The GPS water level measurements from a buoy or a vessel are presented and utilized in this study along with other techniques to collect ellipsoidal, geocentric sea surface height measurements for various studies that help improve our knowledge about sea level and its change. An operational technique of using GPS water level measurement is proposed in this study. The limitation and an upper bound accuracy of the kinematic (epoch-by-epoch) positioning in terms of baseline length are discussed. A set of GPS data in Lake Erie, including buoy data as well as a local GPS network on land, are used to provide the numerical results. Three main applications of using the GPS water level measurements are presented in this study. They are integration of various data sources in the coastal, satellite radar calibration, and GPS hydrology. The objective of these applications is to demonstrate the potential of the GPS technique in collecting water level measurements. The use of GPS measurements is also highlighted in connection with the improvement that they may bring to various techniques such as the use of coastal water level gauge and bottom pressure gauge, and satellite altimetry. This study discusses three applications of using GPS water level measurements. They have shown the capabilities of the GPS technique on buoys or vessels to interact with other techniques for making accurate water level measurements. With the water impacts humanity, such measurements have proven to be valuable for better understanding for the coastal environment.

Committee: Che Kwan Shum (Advisor) Subjects: Geodesy

Doctor of Philosophy (PhD), Ohio University, 2009, Electrical Engineering (Engineering and Technology)

The orbit and clock errors of GPS satellites are examined culminating in error distributions and Gaussian overbounds. The Precise Orbit and Clock (POC) data are then used to produce a Precise Point Position (PPP) solution with a maximum vertical error of ±1 meter. Flight test data are processed using the Single Difference Residual (SDR) method to detect and correct cycle-slips. The corrected carrier phase measurements are then used in PPP to determine the user's position. The results are compared with truth data to characterize the PPP solution accuracy performance.POC data from the International GNSS Service (IGS), National Geospatial-intelligence Agency (NGA), and the Center for Orbit Determination in Europe (CODE), are used as the truth reference and compared to the broadcast GPS ephemerides obtained from the Scripps Orbit and Permanent Array Center (SOPAC). The error is then analyzed over the three year period from June 2005, through June 2008. Two hundred forty-seven events in which the error in orbit or clock exceed 25 m are identified. These events are classified as outliers. The outliers are compared against data from IGS station receivers to determine if the event is observable. Observable events are reclassified as anomalies. Thirteen anomalies are identified and tabularized to enable future researchers to test anomaly detection mechanisms against historical events. The table of anomalies represents an original contribution to existing research in this field. The anomalies are removed from the data. The remaining data are analyzed statistically. Seven error metrics are analyzed. Error distribution and a Gaussian overbound are provided by error metric and satellite block type. The error data are then differenced over time. Three Operational Scenarios (OSs) are analyzed. OS1 is the normal operating procedure in which each ephemeris is used as soon as it is received. OS2 uses only one ephemeris. In OS2 the ephemeris is used from the time it is received until (open full item for complete abstract)

Committee: Frank van Graas PhD (Advisor); Carl Brune PhD (Committee Member); Louis Wright PhD (Committee Member); Michael Braasch PhD (Committee Member); Michael DiBenedetto PhD (Committee Member); Maarten Uijt de Haag PhD (Committee Member) Subjects: Electrical Engineering

Master of Science (MS), Ohio University, 2021, Electrical Engineering (Engineering and Technology)

Over the coming decades, as the volume of space missions continues to grow and iversify, so too does the demand for methods to achieve improved position, navigation, and timing service performance in geostationary orbit and beyond. For high-altitude spacecraft to utilize GNSS navigation techniques, it is required that they must utilize signals from GNSS space vehicles from across the limb of the Earth, which severely limits the quality and quantity of measurements that can be made. The performance potential for such a spacecraft can be improved, however, by having the ability to utilize any combination of satellites visible at a given time, across all GNSS constellations. Interoperability of this kind depends primarily on the ability to resolve the differences in each system's specific time scale. This thesis proposes and develops methods to provide high-accuracy GNSS measurements from a GNSS receiver in low Earth orbit to facilitate the estimation of GNSS inter-constellation timing offsets. The Bobcat-1 CubeSat was developed to support the collection of this data, and this thesis describes the capabilities and measurement accuracy achieved by the CubeSat as well as the post-processing performed to produce precise inter- constellation timing offsets. Furthermore, a study was conducted using a simulation that was developed to evaluate the performance impacts that GNSS system time offsets impose on a user in geostationary orbit. This study produces quality of service benchmarks that are used to provide performance targets for the accuracy of the inter-constellation time offset estimates enabled by data from Bobcat-1. This thesis compares the inter-constellation timing offset estimates achieved by these methods against the Galileo-to-GPS time offset that is produced by the Galileo Control Segment and included within the navigation messages of Galileo space vehicles.

Committee: Sabrina Ugazio (Advisor); Frank Van Graas (Committee Member); Chad Mourning (Committee Member); Nathaniel Szewczyk (Committee Member) Subjects: Aerospace Engineering; Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2019, Earth Sciences

Tide gauges record relative sea level (RSL), i.e. the vertical position of the sea surface relative to the adjacent land mass or relative to the seafloor under the gauge. A tide gauge cannot distinguish between a rise in sea level or subsidence of the land or seawall or pier that supports the gauge. Absolute sea level (ASL) refers to the level or height of the sea surface stated in some standard geodetic reference frame, e.g. ITRF2008. Since satellite altimeters make a geometrical measurement of sea level, this constitutes a determination of ASL. Satellite altimeters suffer from instrumental drift and thus need to be calibrated using tide gauges. This requires us to estimate the rate of RSL change at each tide gauge and convert this into an estimate of the rate of ASL change. This is done using a GPS station located at or near the tide gauge, since it can measure the vertical velocity of the lithosphere – often referred to as vertical land motion, VLM – which allows us to exploit the relationship ASL = RSL + VLM. This goal has motivated geodesists to build dozens of continuous GPS (or CGPS) stations near tide gauges – an agenda sometimes referred to as the CGPS@TG agenda. Unfortunately, a significant fraction of all long-lived tide gauges – especially those in the Pacific - have also recorded non-steady land motion caused by earthquakes. Rather than simply delete such datasets from the agenda, this thesis explores a new analytical method, based on the concept of a geodetic station trajectory model, that allows us to compute RSL and ASL rates even at tide gauges affected by regional earthquakes. We illustrate this method using two tide gauges (PAGO and UPOL) and three GPS stations (ASPA, SAMO and FALE) located in the Samoan islands of the Southwest Pacific. In addition to managing the impact of large regional earthquakes, we also seek new approaches to reducing noise in RSL rate estimates by suppressing the higher frequency sea level changes associated with ocean (open full item for complete abstract)

Committee: Michael Bevis (Committee Chair); C.K. Shum (Committee Member); Loren Babcock (Committee Member); Michael Barton (Committee Member) Subjects: Earth; Geological; Geophysical; Geophysics; Geotechnology; Ocean Engineering; Oceanography

Master of Science in Electrical Engineering (MSEE), Wright State University, 2018, Electrical Engineering

This thesis considers the use of synthetic aperture radar (SAR) to provide absolute platform position information in scenarios where GPS signals may be degraded, jammed, or spoofed. Two algorithms are presented, and both leverage known 3D ground structure in an area of interest, e.g. provided by LIDAR data, to provide georeferenced position information to airborne SAR platforms. The first approach is based on the wide-aperture layover properties of elevated reflectors, while the second approach is based on correlating backprojected imagery with digital elevation imagery. Both of these approaches constitute the system we have designated: SARNAV. Building on 3D backprojection, localization solutions result from non-convex optimization problems based on image sharpness or correlation measures. Results using measured GOTCHA data demonstrate localization errors of only a few meters with initial uncertainty regions as large as 16 km^2. Finally, the system is incorporated into a Kalman filter tracker, where periodic SARNAV updates could be used to correct drift from an inertial navigation system. With measured data, the system was able to track the true position along the route within a few meters of error.

Committee: Joshua Ash Ph.D. (Advisor); Michael Saville Ph.D., P.E. (Committee Member); Arnab Shaw Ph.D. (Committee Member) Subjects: Electrical Engineering

Master of Science, University of Toledo, 2015, Engineering (Computer Science)

Unmanned systems or remotely piloted vehicles can easily accomplish tasks where human lives would be at risk. These systems are being deployed in areas which would be time-consuming, expensive and inconclusive if done by human intervention. Air, ground and underwater vehicles are three major classes of unmanned systems based on their operational environment. Clearly, in terms of causing damage, unmanned aerial vehicles (UAVs) are most efficient and have been known to change the course of several recent wars. If security of these systems is compromised, it will pose a serious threat to human lives as well as the nation. Therefore, it is important to analyze various possible attacks that can be attempted on these systems. Federal Aviation Administration (FAA) has limited the use of UAVs to 400 feet or below in the US National Airspace (NAS), primarily, due to the threat to the general population. This makes real world testing difficult in an academic setup. The best solution to this problem is to have a simulation based environment where different operational scenarios, related cyber-attacks, and their impacts on UAVs can be easily studied. Software based simulators are very economical to test different features of a UAV in terms of various defense mechanisms against cyber-attacks. In this thesis, we enhance UAVSim, a simulation test-bed for UAV Network cyber-security analysis, to include the Global Navigation Satellite System (GNSS), or more specifically, the Global Positioning System (GPS). The testbed allows users to perform security experiments by adjusting different parameters of the satellites and UAVs. It also allows implementation of different attacks in attack hosts. In addition, each UAV host works on well-defined mobility framework, radio propagation models, etc., resembling real-world operational scenarios.

Committee: Weiqing Sun Dr. (Advisor); Mansoor Alam Dr. (Committee Co-Chair); Hong Wang Dr. (Committee Member) Subjects: Computer Engineering

Master of Science (MS), Ohio University, 2011, Electrical Engineering (Engineering and Technology)

The objective of this thesis is to determine the feasibility of using 3D weather radar data for troposphere propagation delay modeling as well as to improve the understanding of GPS signal propagation through the troposphere during severe weather conditions. Equations are summarized to calculate the atmospheric index of refraction along the signal propagation path, including the effects of severe weather conditions. A ray tracing algorithm is developed and implemented to incorporate 3-Dimensional (3D) weather radar reflectivity data to calculate the troposphere propagation delay due to the index of refraction and ray bending. Ray tracing differences using 3D weather reflectivity data between two locations separated by 5 km are compared with differences obtained from GPS measurements at the two locations. It is found that the propagation differences between the two locations are dominated by the temperature and relative humidity along the signal propagation path. It is also found that the 3D radar reflectivity data is insufficient to extract the temperature and relative humidity profiles. The 3D radar reflectivity data is a good source to calculate the effects due to rain rate and suspended water droplets; however, the impact of these on troposphere delay differences was found to be less significant. Applications of improved understanding of troposphere propagation delays include not only aircraft precision approach operations, but also precision agriculture, construction, atmospheric sciences and surveying.

Committee: Frank van Graas (Advisor); Trent Skidmore (Committee Member); Zhen Zhu (Committee Member); Maarten Uijt de Haag (Committee Member) Subjects: Aerospace Engineering; Atmosphere; Electrical Engineering; 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, 1989, Electrical Engineering & Computer Science (Engineering and Technology)

GPS effective data rate optimization with applications to integrated GPS/INS attitude and heading determination

Committee: Robert Lilley (Advisor) Subjects:

Master of Science, The Ohio State University, 2013, Civil Engineering

The Height Modernization Program, which has been designed and is being implemented by the National Geodetic Survey (NGS), is an ongoing operation focused on forming accurate, reliable heights using the Global Navigation Satellite System (GNSS) technology. The determination of GPS-derived ellipsoidal heights is one of the most critical components in the Height Modernization Program and subject to potentially significant error sources in GPS. The GPS error sources may reduce the accuracy of GPS-derived coordinates and ellipsoidal heights. The height component is primarily affected by inherent geometric weakness and by un-modeled part of the neutral atmosphere (troposphere). Some recent studies have shown that tropospheric delay is one of the most challenging and essential error sources in space-based geodetic applications; especially, in the determination of ellipsoidal height, if it is not sufficiently accounted for. This thesis focuses on possible improvements in the accuracy of the GPS-derived ellipsoidal height, and addresses the effects of tropospheric delay, pertinent to the NGS web-based GPS processing engine, OPUS-Projects, based on the national Continuously Operating Reference Station (CORS) network. This thesis validates that the effect of tropospheric delay, through the combination of the national and global permanent GNSS networks (CORS and International GNSS Service (IGS)), can be reduced, resulting in the improved accuracy of GPS-derived ellipsoidal heights. Specific experiments have been designed and performed to illustrate the improvements. The experiments presented in this study were conducted in the State of Ohio and used the Ohio CORS stations to generate case studies with variable GPS data spans, baseline lengths, and network designs. In addition to CORS stations, IGS stations are included to improve the accuracy of the estimated tropospheric corrections. The experimental results show that the reliability of tropospheric corrections is highly corr (open full item for complete abstract)

Committee: Dorota A. Grejner-Brzezinska Prof. (Advisor); Charles Toth Dr. (Committee Member); Alper Yilmaz Prof. (Committee Member) Subjects: Atmosphere; Civil Engineering; Engineering; Geotechnology

Master of Science, The Ohio State University, 2007, Graduate School

Committee: Not Provided (Other) Subjects:

MS, University of Cincinnati, 2024, Engineering and Applied Science: Mechanical Engineering

Unmanned Aerial Vehicles (UAVs) have seen a rise in applications to various fields. With plenty of algorithms to support automation in UAV flights, Global Positioning System (GPS) is still the major source of position estimation. This has limited the application of UAVs to areas where GPS signal is available and strong. Thus, some other method of position estimation for the UAV is required to expand the UAV application to GPS-denied areas. Moreover, when an operator is piloting a UAV from a remote location, the operator is solely relying on the camera feed coming from the UAV to move the UAV. This camera feed gives a limited field of view of the environment, and the human operator may accidentally run the UAV into an obstacle. In this research, a method of using Hector SLAM for performing position estimation of the UAV in a GPS-denied indoor environment is presented. The Hector SLAM uses a 2D LiDAR mounted on top of the quadcopter to scan the unknown environment. Furthermore, to empower the UAV to autonomously avoid obstacles, an algorithm using Artificial Potential Field method is developed in this thesis which maneuvers the UAV away from obstacles while being piloted by a human operator. The system is developed using Robot Operating System (ROS) and PX4 autopilot. Two different ways, setpoints and attitude commands, of operating the UAV using a keyboard are implemented and compared. The algorithm has been tested in Gazebo Classic simulator and its performance is evaluated.

Committee: Manish Kumar Ph.D. (Committee Chair); David Thompson Ph.D. (Committee Member); Janet Jiaxiang Dong Ph.D. (Committee Member) Subjects: Mechanical Engineering

Master of Science (MS), Ohio University, 2024, Mechanical Engineering (Engineering and Technology)

Aerial Vehicle (UAS) remote and autonomous operation is a growing industry with applications in defense and the commercial space. UAS's can use the Global Positioning System (GPS) to determine their position when signals are available. Operational environments like urban canyons, forested areas, and indoors can block the UAS from receiving GPS signals and prevent the receiver from determining a position, which can hinder the vehicle's ability to successfully complete the mission. Unreliable positioning from GPS data requires UAS's to have an alternative means of localization, which can be accomplished by utilizing ultra-wideband ranging to landmarks and other aerial systems. Machine learning can be used to train models to utilize raw data from intervehicle distance sensors on the agent and anchors to determine the location of the agent without access to GPS data. This work will explore using machine learning as an adaptable localization system using neural networks and gradient descent methods. Fully trained neural networks will be capable of learning specific noise models and performing cooperative localization using unfiltered intervehicle ranges and anchor positions.

Committee: Jay Wilhelm (Advisor); Sergio Ulloa (Committee Member); Dusan Sormaz (Committee Member); Chris Bartone (Committee Member) Subjects: Aerospace Engineering; Computer Science

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

MS, University of Cincinnati, 2023, Engineering and Applied Science: Aerospace Engineering

One major challenge to the widespread adoption and progress of autonomous vehicles relies on answering the simple question — where am I? Vehicles operating in an urban canyon, such as a city, must be able to trust their sensors, especially for localization in the dense urban environment. The use of LiDAR and high definition maps requires effort in advance to develop the high definition map. Also, the high definition map may not be able to account for the seasonal changes in the environment like changing foliage or accumulated snow. Other localization methods require additional fixed infrastructure such as base stations in the case of Real-Time Kinematic solutions. GPS is one common sensor used for localization that suffers from noise and inaccuracies in the urban canyon, due to increased horizontal dilution of precision, multipathing, and non-line-of-sight signals. This research serves to identify when the sensor is unreliable and how much error is in the measurement. This is accomplished using a fuzzy inference system and metadata about the GPS measurement and the measurement itself. The use of two GPS sensors allows for the measured relative position of the sensors to be compared to the known relative position of the sensors for one input. Then, the reported horizontal position error for each sensor are the other inputs. The membership functions and rulebase were generated using heuristic knowledge of the GPS sensors' measurements in the urban canyon. Testing this system required the operation of an uncrewed ground vehicle in an urban canyon and a motion capture camera system to measure ground truth. After this was tested successfully, the fuzzy inference system was applied to estimate the position of the uncrewed vehicle in an urban canyon. The position was estimated using a fuzzy adaptive Kalman filter, as the fuzzy inference system estimated the measurement noise covariance matrix.

Committee: Kelly Cohen Ph.D. (Committee Chair); Ou Ma Ph.D. (Committee Member); Donghoon Kim Ph.D. (Committee Member); Sameh Eisa Ph.D. (Committee Member) Subjects: Aerospace Materials

Master of Science (MS), Ohio University, 2022, Electrical Engineering (Engineering and Technology)

Satnav Software Defined Radios (SDRs) have several advantages over legacy radio architectures, which include flexibility and configurability. An entire satnav SDR system can be described in simple configuration files. While SDRs serve as excellent research and educational tools, oftentimes SDR implementations that run on general purpose processors suffer from performance limitations and slow runtimes. Specifically, satellite timing and navigation (satnav) receivers that process multiple high sample rate data streams can result in such a decreased performance that runtimes become unreasonable. In a satnav SDR, sample decoding, carrier replica generation, carrier wipeoff, and correlation represent the most computationally intensive modules. These modules that benefit from a performance increase can be swapped out for accelerated versions making use of low level programming while leaving the other modules intact. This thesis describes the acceleration of these modules using bitwise parallel processing, SIMD instructions, and multithreading. The significant performance gains obtained through these accelerations strategies (as compared to a naive C++ implementation) captured through extensive benchmarking are presented.

Committee: Michael Braasch (Advisor); Jay Wilhelm (Committee Member); Chad Mourning (Committee Member); Sabrina Ugazio (Committee Member) Subjects: Computer Engineering; Computer Science; Electrical Engineering; Engineering

Master of Science (MS), Ohio University, 2022, Electrical Engineering (Engineering and Technology)

This thesis demonstrates an antenna manifold calibration method for a dual polarized antenna array and RF front-end for use in GNSS applications. The process described in this thesis uses a two-step process to characterize the RF receiver front-end and the antenna array. A GNSS signal simulator is used to generate a reference signal for calibration of a multi-channel RF front-end. An anechoic chamber is used to characterize the phase and gain biases of the dual-polarized phased antenna array. The results are then verified in a live-sky known environment. These combined results can then be used to characterize and compensate for the biases of the RF receiving system in a live-sky operational environment for beamforming and direction of arrival GNSS applications to mitigate interference from multipath. The antenna array and front-end, along with the calibration parameters, are then used in a live multipath environment to show polarization and spatial observability of multipath. The multipath environment consists of positive elevation angle multipath, reflected from a conductive surface. Polarization observability is shown by tracking a received signal coherently using both a RHCP and LHCP receiver channel. Spatial observability is shown by implementing a deterministic beamformer receiver channel. The results presented show that the polarization and spatial domains can be used simultaneously to mitigate multipath.

Committee: Chris Bartone (Advisor); Sabrina Ugazio (Committee Member); Frank van Graas (Committee Member); Sanjeev Gunawardena (Committee Member) Subjects: Electrical Engineering