Michael S. Braasch
Ohio University
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Featured researches published by Michael S. Braasch.
Proceedings of the IEEE | 1999
Michael S. Braasch; A. J. Van Dierendonck
Although originally developed for the military, the Global Positioning System (GPS) has proven invaluable for a multitude of civilian applications. Each application demands specific performance from the GPS receiver and the associated requirements often vary widely. This paper describes the architectures and functions of civilian GPS receivers and then focuses on performance considerations. The fundamental receiver measurements are described and the quality of these measurements are related to the aforementioned receiver architectures.
ieee aerospace conference | 2001
Michael S. Braasch
As the Global Positioning System (GPS) has matured over the last decade, expectations regarding system performance have grown steadily. This has placed pressure on receiver manufacturers and system providers to be ever more creative in their efforts to mitigate error sources. Historically, multipath has been the dominant error source in differential GPS (DGPS). However, with the recent decision to deactivate Selective Availability, multipath has become a significant error source for all GPS users. In 1991, the narrow correlator was introduced to the market and was shown to reduce multipath errors by as much as 90% over conventional receivers. Over the past several years, a number of multipath-mitigation techniques have been developed and promoted. This paper explores the theory behind each technique and provides a performance comparison. The inherent assumptions and limitations of each technique are discussed as well.
ieee aerospace conference | 2003
D.P. Burch; Michael S. Braasch
Systems and methods for providing an enhanced head up display to an aircraft pilot are disclosed. According to a first aspect of the present invention, a system for increasing pilot situational awareness is disclosed. The system includes a navigational component that determines one or more of an aircraft location and attitude. The system also includes a scene generator that produces one or more virtual images of the space into which the aircraft is flying based, at least in part, on the aircraft location and/or attitude. The system further includes one or more head up displays that display the one or more virtual images to facilitate increasing pilot situational awareness. Other systems and methods for providing an enhanced head up display are also disclosed.
ieee/ion position, location and navigation symposium | 1996
Michael S. Braasch
Multipath represents the dominant error source in satellite-based precision guidance systems. Since multipath errors are not common to the reference station and remote receivers, they are not eliminated through differential corrections and they do not cancel out in a differential carrier-phase tracking system. For precision approach applications, multipath is the most significant obstacle to overcome in the quest for CAT III accuracy and integrity using code-DGPS. Although a multitude of GPS articles discuss the effects of multipath, few derive the basic relationships between the composite signal at the antenna and the resulting measurement error. Furthermore, no validation of the aforementioned theory has been performed to date. This paper presents a comprehensive treatment of the problem. The traditional theoretical multipath error relationships are presented along with validation results obtained from bench-testing using a multichannel satellite simulator. Results are presented for standard and narrow-correlator C/A-code architectures as well as standard P-code. One result of particular interest to the aviation community is validation of the theoretical results which indicate that airframe-based multipath error cannot be reduced with narrow-correlator or P-code technology.
IEEE Transactions on Aerospace and Electronic Systems | 1997
Michael S. Braasch
The effects of autocorrelation sidelobes on multipath errors in pseudorandom noise (PRN) ranging systems are investigated. It is shown that both medium-delay (i.e., on the order of 1 PRN chip) as well as long-delay multipath errors are affected. Results are applied to the case of the Global Positioning System (GPS).
IEEE Transactions on Aerospace and Electronic Systems | 2001
Michael S. Braasch; Michael F. DiBenedetto
Spread-spectrum ranging multipath model validation results are presented. Previously published theoretical results are compared with data obtained from bench-testing using a multichannel satellite simulator. Results are presented for standard or wide-correlator (i.e., 1 chip early-to-late correlator spacing) and narrow-correlator (i.e., 0.1 chip) GPS C/A-code architectures as well as standard P-code. The close agreement of the bench data and theoretical results confirm the validity of the theoretical model.
IEEE Transactions on Aerospace and Electronic Systems | 2006
Sai K. Kalyanaraman; Michael S. Braasch; Joseph M. Kelly
It is well known that carrier-phase multipath is one of the limiting error sources in high-precision differential GPS (Global Positioning System) applications. A thorough understanding of carrier-phase multipath is the first step in the course of mitigating its impact in high precision applications. Complete characterization of carrier-phase multipath error requires a fundamental theoretical description and mathematical modeling. However, the theory and models must be validated with real data. This paper documents the results of a study of the influence of GPS receiver code tracking architecture (coherent and noncoherent) on the carrier-phase multipath error, and provides a thorough validation of carrier-phase multipath theory. Validation is carried out for wide and narrow correlator spacing within coherent and noncoherent code tracking architectures by comparing bench test data to theoretical predictions. Prior to this effort, scant attention had been given to validating carrier-phase multipath theory against GPS data (Townsend et al., 1995). In addition, data collected for non-zero multipath phase rates is presented. The impact of GPS receiver architecture on the mitigation of phase-rate multipath was discussed.
IEEE Aerospace and Electronic Systems Magazine | 2010
Ryan J. Kephart; Michael S. Braasch
See-and-avoid is the current FAA approved method for pilots to avoid objects and other aircraft while flying in visual meteorological conditions (VMC). Although fully autonomous “sense-and-avoid” or “detect-and-avoid” systems are in development, none are currently certified. Thus existing unmanned aerial vehicle (UAV) operations are limited to case-by-case restricted airspace or require escort by manned aircraft. Many UAVs are equipped with at least a forward-looking camera. In the transition between current technology and future fully autonomous, certified sense-and-avoid systems, it seems reasonable to require a ground-based operator to perform the see-and-avoid function. This discusses the flight-testing performed to establish air traffic detection ranges for low-time pilots, and for a low-cost UAV camera system. The system was evaluated to determine if it could provide the equivalent see-and-avoid performance as the tested pilots.
ieee aerospace conference | 2001
Joseph M. Kelly; Michael S. Braasch
Although GPS multipath error envelopes have been well-explored both mathematically and in hardware environments, the range biases caused by Doppler-shifted multipath pulling on the GPS receiver tracking loops have long remained the target of purely analytical discussion. This paper examines the effect of so-called fast-fading multipath on GPS code phase tracking performance and proposes a test method for isolating system range biases in an off-the-shelf receiver. The biases, which may be on the order of several meters, are based on the use of a noncoherent delay-lock loop (NCDLL) in the receivers code tracking structure. In addition, existing models show a complete elimination of these bias errors in the presence of fast-fading multipath if a coherent delay-lock loop (CDLL) architecture is employed in the receiver. Bench data shows the existing theoretical model to be incomplete and a revised model is presented in order to explain the observed results.
ieee/aiaa digital avionics systems conference | 2008
Ryan J. Kephart; Michael S. Braasch
See-and-avoid is the current FAA approved method for pilots to avoid objects and other aircraft while flying in visual meteorological conditions (VMC). Although fully autonomous dasiasense-and-avoidpsila or dasiadetect-and-avoidpsila systems are in development, none are currently certified. Thus existing unmanned aerial vehicle (UAV) operations are limited to case-by-case restricted airspace or require escort by manned aircraft. Many UAVs are equipped with at least a forward-looking camera. In the transition between current technology and future fully autonomous, certified sense-and-avoid systems, it seems reasonable to require a ground-based operator to perform the see-and-avoid function. This paper discusses the flight-testing performed to establish air traffic detection ranges for low-time pilots, and for a low-cost UAV camera system. The system was evaluated to determine if it could provide the equivalent see-and-avoid performance as the tested pilots.