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Articles 1 - 30 of 59
Full-Text Articles in Engineering
Electromagnetic Interference Estimation Via Conditional Neural Processing, Edgar E. Gomez
Electromagnetic Interference Estimation Via Conditional Neural Processing, Edgar E. Gomez
Theses and Dissertations
The goal of this thesis is to determine the efficacy of employing Machine Learning (ML) to solve Joint Urgent Operational Need (JUON) CC-0575, which aims to develop a Common Operating Picture (COP) of the Global Positioning System (GPS) Electromagnetic Interference (EMI) environment. With the growing popularity of Artificial Neural Networks (ANNs), ML solutions are quickly gaining traction in businesses, academia and government. This in turn allows for problem solutions that were previously inconceivable using the classical programming paradigm. This thesis proposes a method to develop a COP of the battlefield via ANN ingestion of multiple-source signals and sensors. We conduct …
Signal Quality Monitoring Of Gnss Signals Using A Chip Shape Deformation Metric, Nicholas C. Echeverry
Signal Quality Monitoring Of Gnss Signals Using A Chip Shape Deformation Metric, Nicholas C. Echeverry
Theses and Dissertations
The Global Navigation Satellite System continues to become deeply em-bedded within modern civilization, and is depended on for confident, accurate navigation information. High precision position and timing accuracy is typically achieved using differential processing, however these systems provide limited compensation for distortions caused by multi-path or faulty satellite hardware. Signal Quality Monitoring (SQM) aims to provide confidence in a receivers Position, Navigation, and Timing solution and to offer timely warnings in the event that signal conditions degrade to unsafe levels. The methods presented in this document focus on implementing effective SQM using low-cost Commercial Off-the-Shelf equipment, a Software Defined Radio, …
Characterization Of Quad-Copter Positioning Systems And The Effect Of Pose Uncertainties On Field Probe Measurements, James C. Dossett
Characterization Of Quad-Copter Positioning Systems And The Effect Of Pose Uncertainties On Field Probe Measurements, James C. Dossett
Theses and Dissertations
When measuring the Radar Cross Section (RCS) of a test object, many uncertainties must be accounted for, such as the non-homogeneous nature of the medium between the radar test equipment and the platform under test. There are a variety of other error sources, including clutter and Radio Frequency Interference (RFI), motivating the development of techniques to measure and model the uncertainties in RCS measurements. The following research, in unison with prior and current efforts, intends to reduce the impact of these uncertainties by utilizing a unique two-way field probe in the form of a geodesic sphere encompassing a commercial quad-copter …
Augmenting The Global Positioning System With Foreign Navigation Systems And Alternative Sensors, Christopher B. Killion
Augmenting The Global Positioning System With Foreign Navigation Systems And Alternative Sensors, Christopher B. Killion
Theses and Dissertations
The United States Global Positioning System (GPS), with its great accuracy, receives extensive use by civilians and military organizations throughout the world. However, in areas with limited or partially obstructed views of the sky, such as amongst tall buildings or imposing geographic features, a position solution can be difficult or impossible to obtain as the limited view of the sky decreases the number of visible satellites. Augmenting the GPS constellation by receiving signals from foreign satellite navigation systems as well as using measurements from inertial and barometric sensors can increase the availability of a position solution in a degraded reception …
The Effects Of Cognitive Jamming On Wireless Sensor Networks Used For Geolocation, Michael A. Huffman
The Effects Of Cognitive Jamming On Wireless Sensor Networks Used For Geolocation, Michael A. Huffman
Theses and Dissertations
The increased use of Wireless Sensor Networks (WSN) for geolocation has led to an increased reliance on this technology. Jamming, protecting jamming, and detecting jamming in a WSN are areas of study that have greatly increased in interest. This research uses simulations and data collected from hardware experiments to test the effects of jamming on a WSN. Hardware jamming was tested using a Universal Software Radio Peripheral (USRP) Version 2 to assess the effects of jamming on a cooperative network of Java Sun SPOTs. The research combines simulations and data collected from the hardware experiments to see the effects of …
Orbital Tori Construction Using Trajectory Following Spectral Methods, Ralph E. Bordner Iii
Orbital Tori Construction Using Trajectory Following Spectral Methods, Ralph E. Bordner Iii
Theses and Dissertations
By assuming the motion of a satellite about the earth’s geopotential mimics the known Kolmogorov-Arnold-Moser (KAM) solution of a lightly perturbed integrable Hamiltonian system, this research focused on applying trajectory following spectral methods to estimate orbital tori from sampled orbital data. From an estimated basis frequency set, orbital data was decomposed into multi-periodic Fourier series, essentially compressing ephemerides for long-term use. Real-world Global Positioning System (GPS) orbital tracks were decomposed and reconstructed with error from as low as few kilometers per coordinate axis over a 10-week span to tens of kilometers per coordinate axis over the same time period, depending …
Aiding Gps With Additional Satellite Navigation Services, Yasin A. Mutlu
Aiding Gps With Additional Satellite Navigation Services, Yasin A. Mutlu
Theses and Dissertations
In modern warfare navigation services are very important. GPS is currently providing service for accurate navigation, except in some areas, especially urban areas, where GPS signals cannot always be tracked by users. In these cases some additional navigation support could be provided by other global navigation satellite systems. If GPS is combined with other navigation systems than the navigation gap will be minor. In this thesis, the effect of combining GPS with other satellite navigation systems, specifically GLONASS, Galileo and Compass, is evaluated in terms of availability and position dilution of precision (PDOP) values. First, satellite constellations are simulated in …
Global Navigation Satellite System Software Defined Radio, Jason M. Mcginthy
Global Navigation Satellite System Software Defined Radio, Jason M. Mcginthy
Theses and Dissertations
The GNSS world is quickly growing. The United States’ GPS, the European Union’s Galileo, China’s Compass, and Russia’s GLONASS systems are all developing or modernizing their signals, and there will soon be more navigation satellites in space than ever before. The goal of this research was to develop an initial capability for an AFIT GNSS software receiver. This software receiver is intended to be used for research purposes at the Advanced Navigation Technology (ANT) Center. First a GPS-only software receiver was built. It successfully acquired, tracked, and provided reasonable position estimates. Next, the receiver was successfully modified to acquire and …
Failure Detection Of A Pseudolite-Based Reference System Using Residual Monitoring, Michael A. Ciampa
Failure Detection Of A Pseudolite-Based Reference System Using Residual Monitoring, Michael A. Ciampa
Theses and Dissertations
The 746th TS uses a flight reference system referred to as the Central Inertial and GPS Test Facility (CIGTF) Reference System (CRS). Currently the CRS is the modern standard flight reference system for navigation testing, but high accuracy is dependent on the availability of GPS. A pseudolite system is currently being developed to augment the CRS and supply the capability to maintain high accuracy navigation under normal and jamming conditions. Pseudolite measurements typically contain cycle slips and other errors (such as multipath, tropospheric error, measurement noise) that can affect reliability. Past work relied on the receiver-reported signal-to-noise (SNR) value to …
A Feasibility Study Of A Persistent Monitoring System For The Flight Deck Of U.S. Navy Aircraft Carriers, Jeffrey S. Johnston
A Feasibility Study Of A Persistent Monitoring System For The Flight Deck Of U.S. Navy Aircraft Carriers, Jeffrey S. Johnston
Theses and Dissertations
This research analyzes the use of modern Real Time Locating Systems (RTLS), such as the Global Positioning System (GPS), to improve the safety of aircraft, equipment, and personnel onboard a United States Navy (USN) aircraft carrier. The results of a detailed analysis of USN safety records since 1980 show that mishaps which could potentially be prevented by a persistent monitoring system result in the death of a sailor nearly every other year and account for at least $92,486,469, or 5.55% of the total cost of all flight deck and hangar bay related mishaps. A system to continually monitor flight deck …
Modeling Gps Satellite Orbits Using Kam Tori, Rachel M. Derbis
Modeling Gps Satellite Orbits Using Kam Tori, Rachel M. Derbis
Theses and Dissertations
Global Positioning System (GPS) satellite orbits are modeled using Kolmogorov, Arnold, Moser (KAM) tori. Precise Global Positioning System satellite locations are analyzed using Fourier transforms to identify the three basis frequencies in an Earth Centered, Earth Fixed (ECEF) rotating reference frame. The three fundamental frequencies are 1) the anomalistic frequency, 2) a combination of earth’s rotational frequency and the nodal regression rate, and 3) the apsidial regression rate. A KAM tori model fit to the satellite data could be used to predict future satellite locations. This model would allow rapid determination with fewer computational requirements than the typical method of …
Real-Time Gps-Alternative Navigation Using Commodity Hardware, Jordon L. Fletcher
Real-Time Gps-Alternative Navigation Using Commodity Hardware, Jordon L. Fletcher
Theses and Dissertations
Modern navigation systems can use the Global Positioning System (GPS) to accurately determine position with precision in some cases bordering on millimeters. Unfortunately, GPS technology is susceptible to jamming, interception, and unavailability indoors or underground. There are several navigation techniques that can be used to navigate during times of GPS unavailability, but there are very few that result in GPS-level precision. One method of achieving high precision navigation without GPS is to fuse data obtained from multiple sensors. This thesis explores the fusion of imaging and inertial sensors and implements them in a real-time system that mimics human navigation. In …
Use Of Two-Way Time Transfer Measurements To Improve Geostationary Satellite Navigation, Benjamin G. Dainty
Use Of Two-Way Time Transfer Measurements To Improve Geostationary Satellite Navigation, Benjamin G. Dainty
Theses and Dissertations
An emerging use of GPS is to provide accurate navigation information for satellites in orbit. The GPS satellites are designed to provide service to terrestrial users, so the antenna array points directly towards the Earth and uses a narrow primary beamwidth. Because GEO altitudes are well above the GPS constellation, the Earth occludes most of the GPS signals to the satellite. Decreased satellite visibility is debilitating, as GPS navigation requires at least four visible satellites to determine position. To assist with the visibility problem, the receiver can look at the GPS satellite transmit antenna side lobes, but this does not …
Development And Testing Of A High-Speed Real-Time Kinematic Precise Dgps Positioning System Between Two Aircraft, Christopher J. Spinelli
Development And Testing Of A High-Speed Real-Time Kinematic Precise Dgps Positioning System Between Two Aircraft, Christopher J. Spinelli
Theses and Dissertations
This research involves the design, implementation, and testing of a high-speed, real-time kinematic, precise differential GPS positioning system for use in airborne applications such as automated aerial-refueling and close formation flying. Although many of the current ambiguity resolution techniques use the residuals from the least squares position estimation to determine the true ambiguity set, this thesis presents a novel approach to the ambiguity resolution problem, called the minimum indicator. Instead of assuming the ambiguity set with the lowest residuals is the true set, other special characteristics of the residuals are examined. This increases the confidence that the algorithm has selected …
Development Of A Low-Latency, High Data Rate, Differential Gps Relative Positioning System For Uav Formation Flight Control, Stephen J. Comstock
Development Of A Low-Latency, High Data Rate, Differential Gps Relative Positioning System For Uav Formation Flight Control, Stephen J. Comstock
Theses and Dissertations
In order for Unmanned Aerial Vehicles (UAVs) to be able to fly missions currently performed by manned aircraft, they must be able to conduct in-flight refueling. Additionally, significant fuel savings can be realized if multiple UAV's are able to fly in precise formation and align wingtip vortices. In either case, the precise relative position between the aircraft must be known to an accuracy of only a few centimeters. Previous research at the Air Force Institute of Technology culminated in the development of a relative positioning system for manned aircraft. This thesis presents the development of the next-generation system designed for …
Fusion Of Imaging And Inertial Sensors For Navigation, Michael J. Veth
Fusion Of Imaging And Inertial Sensors For Navigation, Michael J. Veth
Theses and Dissertations
The motivation of this research is to address the limitations of satellite-based navigation by fusing imaging and inertial systems. The research begins by rigorously describing the imaging and navigation problem and developing practical models of the sensors, then presenting a transformation technique to detect features within an image. Given a set of features, a statistical feature projection technique is developed which utilizes inertial measurements to predict vectors in the feature space between images. This coupling of the imaging and inertial sensors at a deep level is then used to aid the statistical feature matching function. The feature matches and inertial …
Optimal Geometric Deployment Of A Ground Based Pseudolite Navigation System To Track A Landing Aircraft, Matthew P. Crawford
Optimal Geometric Deployment Of A Ground Based Pseudolite Navigation System To Track A Landing Aircraft, Matthew P. Crawford
Theses and Dissertations
With much of the military and civilian communities becoming dependent on GPS technology to navigate it has become imperative that the navigation systems be tested in situations in which GPS does not work. This testing is especially necessary for precise tasks such as landing an aircraft. Currently, research is being conducted into using a pseudolite-based reference system to use as a truth model for the GPS jamming test. Pseudolite systems have been proven to provide sub-centimeter level accuracy in the horizontal plane; however in the vertical plane the position error is still in the decimeter to meter level range. This …
Methods For Aiding Height Determination In Pseudolite-Based Reference Systems Using Batch Least-Squares Estimation, John H. R. Amt
Methods For Aiding Height Determination In Pseudolite-Based Reference Systems Using Batch Least-Squares Estimation, John H. R. Amt
Theses and Dissertations
There are many situations in which GPS is either unable to provide the desired level of accuracy or is unavailable. Use of a pseudolite-based reference system for navigation can be a means for positioning during these times. While there are advantages in using a pseudolite-based reference system, there are still implementation issues and deficiencies that must be addressed. In many cases, a pseudolite system with ground-based transmitters has difficulty determining the height of the receiver accurately. This is due to the poor vertical observability inherent in the geometry of the system. A common approach in naval applications for solving the …
A Climatological Study Of Equatorial Gps Data And The Effects On Ionospheric Scintillation, Katharine A. Wicker
A Climatological Study Of Equatorial Gps Data And The Effects On Ionospheric Scintillation, Katharine A. Wicker
Theses and Dissertations
Ionospheric scintillation is detrimental to radio signals, especially those from the global positioning system. Such scintillation is caused when a signal permeates the ionosphere through plasma bubbles. The signal’s phase and amplitude can be altered, and a receiver on the ground can lose lock on the GPS signal. Measured using a zero to one index known as S4, scintillation severity is based upon season, solar cycle, time of day, location and frequency. The most severe scintillation occurs at the equatorial anomaly, or fifteen degrees north and south of the equator. Seven years of data from fifteen different locations around the …
Characterizing The Impact Of Precision Time And Range Measurements From Two-Way Time Transfer Systems On Network Differential Gps Position Solutions, Kendra L. B. Cook
Characterizing The Impact Of Precision Time And Range Measurements From Two-Way Time Transfer Systems On Network Differential Gps Position Solutions, Kendra L. B. Cook
Theses and Dissertations
Precise positioning plays an important role for both military and civilian users, from cell phones and OnStar to precision munitions and swarms of UAVs. Many applications require precise relative positioning of a network of vehicles (such as aircraft, tanks, troops, etc). Currently, the primary means for performing precise positioning is by using the Global Positioning System (GPS), and although GPS has become commonplace in today’s society, there are still limitations affecting the system. Recent advances in dynamic Two-Way Time Transfer (TWTT) have potentially provided a means to improve precise relative positioning accuracy over differential GPS (DGPS)-only approaches. TWTT is a …
Characterization Of Binary Offset Carrier (Boc) Systems Coexisting With Other Wideband Signals, John M. Hedenberg
Characterization Of Binary Offset Carrier (Boc) Systems Coexisting With Other Wideband Signals, John M. Hedenberg
Theses and Dissertations
Results for modeling, simulation, and analysis of interference effects that modern interfering signals have on the system performance of the Binary Offset Carrier (BOC) signals, such as the Global Positioning System (GPS) Military System (M-Code signal) are addressed in this work. Three signals are addressed as potential interferers. These include the current GPS clear/acquisition code (C/A-Code) signal, the current GPS precision code (P-Code) signal, and an Orthogonal Frequency Division Multiplexed (OFDM) signal. All of these potential interferers are modeled as coexisting within the same bandwidth as the M-Code signal. Interference effects are characterized by comparing the bit error performance of …
Head Tracking For 3d Audio Using A Gps-Aided Mems Imu, Jacque M. Joffrion
Head Tracking For 3d Audio Using A Gps-Aided Mems Imu, Jacque M. Joffrion
Theses and Dissertations
Audio systems have been developed which use stereo headphones to project sound in three dimensions. When using these 3D audio systems, audio cues sound like they are originating from a particular direction. There is a desire to apply 3D audio to general aviation applications, such as projecting control tower transmissions in the direction of the tower or providing an audio orientation cue for VFR pilots who find themselves in emergency zero-visibility conditions. 3D audio systems, however, require real-time knowledge of the pilot's head orientation in order to be effective. This research describes the development and testing of a low-cost head …
Geolocation Of A Node On A Local Area Network, John R. Clarson
Geolocation Of A Node On A Local Area Network, John R. Clarson
Theses and Dissertations
Geolocation is the process of identifying a node using only its Internet Protocol (IP) address. Locating a node on a LAN poses particular challenges due to the small scale of the problem and the increased significance of queuing delay. This study builds upon existing research in the area of geolocation and develops a heuristic tailored to the difficulties inherent in LANs called the LAN Time to Location Heuristic (LTTLH). LTTLH uses several polling nodes to measure latencies to end nodes, known locations within the LAN. The Euclidean distance algorithm is used to compare the results with the latency of a …
The Use Of X-Ray Pulsars For Aiding Gps Satellite Orbit Determination, Dennis W. Woodfork Ii
The Use Of X-Ray Pulsars For Aiding Gps Satellite Orbit Determination, Dennis W. Woodfork Ii
Theses and Dissertations
This research proposes the use of an existing "signal of opportunity" - namely x-ray pulsars - to improve the accuracy and robustness of the GPS satellite and clock estimation algorithm. Improvement in satellite and clock accuracy results in a direct benefit to the user. A simulation has been developed to determine the effects of using x-ray pulsar measurements on the GPS Operational Control Segment. The epoch-specific position, velocity, and clock errors of all GPS satellites in the constellation were estimated using both pseudoranges and time-difference-of-arrival (TDOA) measurements from pulsars. The primary measure of accuracy is a constellation Signal-In-Space Range Error …
Ultra Wide Band Signal Modeling For Radar Receiver Characterization, Robert J. Backscheider
Ultra Wide Band Signal Modeling For Radar Receiver Characterization, Robert J. Backscheider
Theses and Dissertations
Results for modeling, simulation, and analysis of interference effects that modern wideband signals have on existing narrowband radar system performance are presented. In particular, radar detection performance is characterized using a basic radar receiver model and operational parameters consistent with those of the ARSR-4 air route surveillance radar. Two modern wideband signals (interferers) are addressed in this work, including the GPS military signal (M-Code signal) and a direct sequence ultra wideband (DS-UWB) waveform meeting outdoor emission restrictions imposed by the Federal Communications Commission (FCC). Interference effects are characterized for an unmodulated sinusoidal pulse as well as linear frequency modulated (LFM) …
A Tightly-Coupled Ins/Gps Integration Using A Mems Imu, Jonathan M. Neu
A Tightly-Coupled Ins/Gps Integration Using A Mems Imu, Jonathan M. Neu
Theses and Dissertations
Micro-Electro-Mechanical Systems (MEMS) technology holds great promise for future navigation systems because of the reduced size and cost of MEMS inertial sensors relative to conventional devices. Current MEMS devices are much less accurate than standard inertial sensors, but they can still be useful. In this thesis, data was recorded from an inexpensive MEMS inertial measurement unit and integrated with GPS measurements using a tightly-coupled Kalman filter. The overall goal of this research is to investigate the usefulness of MEMS sensors for a small, real-time, low-cost INS/GPS integration. A golf cart was used to collect dynamic data, along with a commercial …
Geolocation Of An Audio Source In A Multipath Environment Using Time-Of-Arrival, Jeffrey A. Boggs
Geolocation Of An Audio Source In A Multipath Environment Using Time-Of-Arrival, Jeffrey A. Boggs
Theses and Dissertations
The Air Force and the Department of Defense (DoD) are continually searching for ways to protect U.S. forces, both stateside and abroad. One continuing threat, especially in the current world environment, is gunfire from an unseen sniper. Designated areas, such as a forward deployed base or motorcade route, need to be continuously monitored for sniper fire. Once detected, these gunmen need to be located in real time. One possible method for accomplishing this task is to geolocate the audio signals generated using time-of-arrival (TOA) algorithms. These algorithms rely on direct-path measurements for accuracy. Multipath environments therefore pose a problem when …
Tightly-Coupled Image-Aided Inertial Navigation System Via A Kalman Filter, Michael G. Giebner
Tightly-Coupled Image-Aided Inertial Navigation System Via A Kalman Filter, Michael G. Giebner
Theses and Dissertations
Inertial navigation systems and GPS systems have revolutionized the world of navigation. Inertial systems are incapable of being jammed and are the backbone of most navigation systems. GPS is highly accurate over long periods of time, and it is an excellent aid to inertial navigation systems. However, as a military force we must be prepared to deal with the denial of the GPS signal. This thesis seeks to determine it, via simulation, it is viable to aid an INS with visual measurements.
Development And Simulation Of A Pseudolite-Based Flight Reference System, Terry J. Bouska
Development And Simulation Of A Pseudolite-Based Flight Reference System, Terry J. Bouska
Theses and Dissertations
Current flight reference systems are vulnerable to GPS jamming and also lack the accuracy required to test new systems. Pseudolites can augment flight reference systems by improving accuracy, especially in the presence of GPS jamming. This thesis evaluates a pseudolite-based flight reference system which applies and adapts carrier-phase differential GPS techniques. The algorithm developed in this thesis utilizes an extended Kalman filter along with carrier-phase ambiguity resolution techniques. A simulation of the pseudolite-based positioning system realistically models measurement noise, multipath, pseudolite position errors, and tropospheric delay. A comparative evaluation of the algorithms performance for single and widelane frequency measurements is …
The Effects Of Gps M-Code On Radar Detection, Jae K. Yang
The Effects Of Gps M-Code On Radar Detection, Jae K. Yang
Theses and Dissertations
The GPS system is undergoing a modernization effort which will add several new signals to be placed at the L1, L2, and L5 frequency bands. One of the signals to be placed on L2 is a new military code (M-code) which may be transmitted at a higher power level than current GPS signals. Other users of the L2 frequency band are concerned with the potential interference that may be caused by the increase in power of the GPS signal. One particular use of the 1215-1400 MHz frequency band is Air Traffic Control (ATC) radar applications.