Michael F. DiBenedetto

Spread-spectrum ranging multipath model validation

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.

The Local Area Augmentation System: an airport surface guidance application supporting the NASA runway incursion prevention system demonstration at the Dallas/Fort Worth International Airport

The Runway Incursion Prevention System (RIPS) program is an ongoing National Aeronautics and Space Administration (NASA) research effort intended to reduce the number of runway incursions at airports throughout the National Airspace System (NAS). The RIPS program flight tests and demonstration of technologies activities at the Dallas/Fort Worth (DFW) International Airport were completed in October 2000. The demonstration involved the application of both airborne and ground based technologies, as well as the integration of these technologies to form a complete runway incursion prevention system. This paper presents information on the research activities conducted at DFW related to the Ohio University Avionics Engineering Center (AEC) installed Global Positioning System (GPS) Local Area Augmentation System (LAAS) ground facility (LGF), its use, the preliminary results obtained, and observations or conclusions when appropriate. A description of the RTCA DO-247 Surveillance and Guidance Sensor requirements is provided. Details of the DFW LAAS upgrade for NASA RIPS testing, AEC GPS LAAS test van equipage, and the Rockwell Collins Multimode LAAS receiver integration activities are presented. Data analysis activities have just been initiated.

A dynamic gps multipath model for differential reference station site evaluation

An advanced model for predicting GPS range measurement errors due to multipath is presented, with special emphasis on development of a siting tool for the GPS local area augmentation system (LAAS). The core innovation in this work is a causal, feedback-based receiver channel model that considers the influence of relative dynamics among a line-of-sight GPS signal and any number of scattered signals. An electromagnetic environment built on the uniform geometric theory of diffraction (UTD) is used to calculate characteristics of firstand second-order rays representing energy scattered by a long wedge-shaped object of specified height, composition, and distance from the reception antenna. Three cases of object placement are considered in this study: Long-delay reflection, short-delay diffraction, and blockage of the direct signal. Various receiver technologies and filtering/aiding techniques can be emulated, and select implementations are discussed. The potential of the model in determining clearance and critical areas about the receive antenna is also addressed. focus of the development effort was to provide a model of Local Area Augmentation System (LAAS) reference receiver (RR) stations. An analysis of a potential reference site will include using the model to evaluate the local electromagnetic environment and determine how scattered energy will distort pseudorange corrections for various receiver tracking architectures. While many antenna designs are available that claim to reject ground-bounce multipath to the extent that it can be bounded to a sufficiently low level, there is always some residual energy from such signals entering the receiver. Further, scattered energy from above-horizon objects is attenuated very little even with the most advanced antenna designs and can, in some cases, be of greater strength than the direct line-ofsight signal. Multipath is generally recognized as the largest source of error in DGPS schemes, as is discussed in the next section. In order to evaluate properly the threat to system performance, a model that is capable of handling a myriad of potential scattering scenarios must be developed. TABLE OF CONTENTS 2. MULTIPATH PROBLEM IN DGPS

The local area augmentation system: an airport surveillance application supporting the FAA Runway Incursion Reduction Program demonstration at the Dallas/Fort Worth International Airport

The Federal Aviation Administration (FAA) created the Runway Incursion Reduction Program (RIRP) to reduce runway incursions throughout the National Airspace System (NAS) by increasing situational awareness, incursion monitoring, and information alerting for Air Traffic Controllers (ATC), pilots, and surface vehicle operators. A recent RIRP activity involved undertaking a technical evaluation and demonstration of a prototype system at the Dallas/Fort Worth International Airport (DFW). A Local Area Augmentation System (LAAS) was one of the major sensor subsystems included in this system. As part of the RIRP team, the Ohio University Avionics Engineering Center (AEC) installed, operated, and tested the LAAS ground facility (LGF) at DFW. LAAS is a differential GPS-based precision approach and landing system that can be used to support surface operations. This paper will provide an overview of the RIRP system architecture and an introduction to LAAS. Also included are a discussion of the LGF site selection, detailed description of LGF, the test equipment used for performing accuracy and coverage assessments, and the data collection activities performed.

Microwave landing system (MLS)

An all-weather aircraft landing-guidance system that operates at microwave frequencies and provides …