Publications
Contributions to the American Meteorological Society's 26th International Conference on Radar Meteorology
April 1, 1993
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-199
Summary
Eleven papers contributed by the Lincoln Laboratory Weather Sensing Group to the American Meteorological Society's 26th International Conference on Radar Meteorology, to be held May 24-28, 1993 in Norman, Oklahoma, are compiled in this volume. The work reported was sponsored by several FAA programs, including Terminal Doppler Weather Radar (TDWR), Air Surveillance Radar-9 (ASR-9), Integrated Terminal Weather System (ITWS), and Terminal Area Surveillance System (TASS). The papers are based on analyses completed over the past year at Lincoln Laboratory and in collaboration with staff at the National Severe Storms Laboratory, the University of Oklahoma, Raytheon Corporation, and the FAA Technical Center in Atlantic City, NJ. The staff members of the Weather Sensing Group have documented their studies in four major areas: Operational Systems (TDWR Operational Test and Evaluation results); Radar Operations (future airport weather surveillance requirements, a "machine intelligent" gust front detection algorithm, microburst asymmetry study results, a shear-based microburst detection algorithm, and a hazard index for TDWR-detected microbursts); Signal Processing (coherent processing across multi-PRI waveforms, clutter filter design for multiple-PRT signals, and identification of anomalous propagation associated with thunderstorm outflows); and Analysis Methods (multiple-single Doppler wind analysis using NEXRAD data, and an adjoint method wind retrieval scheme).
Summary
Eleven papers contributed by the Lincoln Laboratory Weather Sensing Group to the American Meteorological Society's 26th International Conference on Radar Meteorology, to be held May 24-28, 1993 in Norman, Oklahoma, are compiled in this volume. The work reported was sponsored by several FAA programs, including Terminal Doppler Weather Radar (TDWR)...
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Two simulation studies of precision runway monitoring of independent approaches to closely spaced parallel runways
March 2, 1993
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-190
Summary
This report documents the findings of two simulation studies of air traffic controller reaction to the Precision Runway Monitor (PRM). The PRM is a new system for monitoring independent approaches, to closely spaced parallel runways. It consists of a radar which has higher accuracy and a faster update interval than the current system. The PRM radar is accompanied by a high-resolution color display which provides automated visual and vocal warnings to alert controllers of impending and actual penetration of a 'No Transgression Zone' between parallel runways. The studies, were conducted in order to determine the effects of key variables on controller reaction time and to determine controller opinion on system acceptability. Study I examined the use of the PRM when the runway separation was both 3,400 ft and 4,300 ft. Study II examined the use of the PRM when the runway separation was 3,000 ft. Real-time simulated approach blunders were presented to controllers, and measurements of their reaction times were recorded and analyzed. Independent variables studied included sensor update interval, runway separation, deviation angle, deviation range, flight path condition, approach blunder type, and controller experience level. In addition, controller opinions of the PRM were surveyed. Findings regarding the effects of each of the variables are reported. Survey results of controller opinion are reported. Recommendations for enhancing the realism of the simulation and recommendations of issues for future study are discussed.
Summary
This report documents the findings of two simulation studies of air traffic controller reaction to the Precision Runway Monitor (PRM). The PRM is a new system for monitoring independent approaches, to closely spaced parallel runways. It consists of a radar which has higher accuracy and a faster update interval than...
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Machine intelligent gust front detection
March 1, 1993
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 6, No. 1, Spring 1993, pp. 187-212.
Summary
Techniques of low-level machine intelligence, originally developed at Lincoln Laboratory to recognize military ground vehicles obscured by camouflage and foliage, are being used to detect gust fronts in Doppler weather radar imagery. This Machine Intelligent Gust Front Algorithm (MIGFA) is part of a suite of hazardous-weather-detection functions being developed under contract with the Federal Aviation Administration. Initially developed for use with the latest generation Airport Surveillance Radar equipped with a wind shear processor (ASR-9 WSP), MIGFA was deployed for operational testing in Orlando, Florida, during the summer of 1992. MIGFA has demonstrated levels of detection performance that have not only markedly exceeded the capabilities of existing gust front algorithms, but are competitive with human interpreters.
Summary
Techniques of low-level machine intelligence, originally developed at Lincoln Laboratory to recognize military ground vehicles obscured by camouflage and foliage, are being used to detect gust fronts in Doppler weather radar imagery. This Machine Intelligent Gust Front Algorithm (MIGFA) is part of a suite of hazardous-weather-detection functions being developed under...
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Receiver Autonomous Integrity Monitoring (RAIM) of GPS and GLONASS
March 1, 1993
Journal Article
Published in:
Navig. J. Inst. Navig., Vol. 40, No. 1, Spring 1993, pp. 87-104.
Summary
A receiver autonomous integrity monitoring (RAIM) algorithm is proposed, and used to analyze the integrity monitoring capabilities of potential sole-means (or stand-alone) systems based on integrated use of GPS and GLONASS, GPS supplemented with a geostationary overlay, and enhanced GPS constellations. As in the other RAIM algorithms, the idea is to take advantage of the redundant measurements. Our focus, however, is on the quality of the position estimate, rather than on diagnosing whether the system is working as intended. The proposed approach uses the redundant measurements to generate a position estimate and a measure of its quality. The latter, called integrity level, is defined as an upper bound on the position error. The estimation of the integrity level is the main innovation in the proposed scheme. The RAIM algorithm is tailored to an abundant redundancy of the measurements, and addresses the following issue: Given a snapshot of the pseudo range measurements, one of which may be in error, can we compute a position estimate that can be shown with high confidence to meet the user's accuracy requirement?
Summary
A receiver autonomous integrity monitoring (RAIM) algorithm is proposed, and used to analyze the integrity monitoring capabilities of potential sole-means (or stand-alone) systems based on integrated use of GPS and GLONASS, GPS supplemented with a geostationary overlay, and enhanced GPS constellations. As in the other RAIM algorithms, the idea is...
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Setting values for TDWR/LLWAS 3 integration parameters
February 5, 1993
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-195
Summary
In 1993 the FAA will begin deploying the Terminal Doppler Weather Radar (TDWR) at selected airports in the United States. Forty-five TDWRs will be collocated with LLWAS 3 systems, and the FAA has decided that all TDWRs collocated with LLWAS 3 systems must be integrated with LLWAS 3 prior to commissioning. The algorithm chosen to perform this integration must be supplied with a set of site-specific parameters. This report gives guidance on how to set the values of theme integration parameters.
Summary
In 1993 the FAA will begin deploying the Terminal Doppler Weather Radar (TDWR) at selected airports in the United States. Forty-five TDWRs will be collocated with LLWAS 3 systems, and the FAA has decided that all TDWRs collocated with LLWAS 3 systems must be integrated with LLWAS 3 prior to...
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Impact of weather event uncertainty upon an optimum ground-holding strategy
January 1, 1993
Journal Article
Published in:
Air Traffic Control Q., Vol. 1, No. 1, January 1993, pp. 59-84.
Summary
When weather events are expected to produce significant delays at destination airports, the traffic flow management system in the United States holds departing aircraft on the ground in an attempt to reduce delay costs to the operator and to alleviate airborne congestion. Selecting the correct amount of ground holding is made difficult because of uncertainty in predicting weather events that produce congestion. In general, decision-makers must strike a balance between the amount of predicted delay absorbed on the ground and the amount absorbed in the air. This paper first addresses the question of how uncertainty in the required delay should influence the amount of ground holding. It then establishes the relationship between delay uncertainty and uncertainties in predicting the onset and duration of weather events. Delay costs are minimized under an assumption that there is a fixed ratio between the cost of a unit of ground delay and a unit of airborne delay and that the landing sequence employed at the destination terminal is based upon the originally scheduled landing order. The analysis indicates that uncertainty in the delay prediction must be considered in selecting the optimum amount of ground holding for an individual flight. In predicting delays, it is desirable to keep the ratio of the standard error to the mean delay (σ / μ) well below 1.0 in order to avoid loss of benefits. A corresponding figure of merit for weather systems is shown to be the ratio of the uncertainty in onset/termination times to the duration of the weather event. Weather prediction systems must keep this ratio well below one-third to avoid significant loss of ground-holding benefits. The analysis indicates that reductions in the delay uncertainty through improved weather forecasting and traffic management systems can result in better decision-making and significant cost savings.
Summary
When weather events are expected to produce significant delays at destination airports, the traffic flow management system in the United States holds departing aircraft on the ground in an attempt to reduce delay costs to the operator and to alleviate airborne congestion. Selecting the correct amount of ground holding is...
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Results of simulation studies of precision runway monitoring of independent approaches to closely-spaced parallel runways
January 1, 1993
Journal Article
Published in:
J. ATC, January-March 1993, pp. 18-24.
Summary
Increased air travel in recent years has resulted in a steady increase in the number and duration of flight delays. In an attempt to increase airport capacity, MIT Lincoln Laboratory, under the sponsorship of the Federal Aviation Administration (FAA), has supported the development of a Precision Runway Monitor (PRM). The PRM is an advanced radar monitoring system designed to increase utilization of closely-spaced, multiple, parallel runways during adverse weather conditions. The PRM consists of radar which has higher accuracy and a faster update interval than the current system, and a high resolution, color display that informs the Monitor Controller of the occurrence of hazardous flight path deviations by means of automated visual and vocal warning alerts. Studies of air traffic controller reaction to the PRM were conducted at Memphis Airport and Raleigh-Durham Airport in order to evaluate system effectiveness and to assess the effects of key variables on controller reaction time. This paper documents the results of the controller studies conducted at Memphis by MIT Lincoln Laboratory. The testing consisted of the presentation of real-time simulations, and measurement of air traffic controllers were surveyed regarding the acceptability of the PRM.
Summary
Increased air travel in recent years has resulted in a steady increase in the number and duration of flight delays. In an attempt to increase airport capacity, MIT Lincoln Laboratory, under the sponsorship of the Federal Aviation Administration (FAA), has supported the development of a Precision Runway Monitor (PRM). The...
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Time-scale modification with temporal envelope invariance
January 1, 1993
Conference Paper
Published in:
Proc. IEEE Workshop on Applications of Signal Processing to Audio and Acoustics, 17-20 October 1993, pp. 127-130.
Topic:
R&D area:
Summary
A new approach is introduced for time-scale modification of short-duration complex acoustic signals to improve their audibility. The method preserves the time-scaled temporal envelope of a signal and for enhancement capitalizes on the perceptual importance of a signal's temporal structure. The basis for the approach is a sub-band representation whose channel phases are controlled to shape the temporal envelope of the time-scaled signal. The phase control is derived from locations of events which occur within filterbank outputs. A frame-based generalization of the method imposes phase consistency across consecutive synthesis frames. The approach is applied to synthetic and actual short-duration acoustic signals consisting of closely-spaced and overlapping sequential time components.
Summary
A new approach is introduced for time-scale modification of short-duration complex acoustic signals to improve their audibility. The method preserves the time-scaled temporal envelope of a signal and for enhancement capitalizes on the perceptual importance of a signal's temporal structure. The basis for the approach is a sub-band representation whose...
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The Terminal Doppler Weather Radar (TDWR) Moving Target Simulator (MTS) at Orlando, Florida
August 20, 1992
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-188
Summary
Monitoring the performance of Doppler weather radars presents special problems since target returns cannot be verified by reference to other systems (e,g ., as ASR-9 aircraft reports can be compared with beacon replies). The Terminal Doppler Weather Radar (TDWR) system includes a Moving Target Simulator (MTS) which provides a point target equivalent to a 50 dBZ reflectivity weather return with an apparent radial velocity of 5 m/s. This report describes the installation results for a prototype MTS using the TDWR testbed radar in Orlando, FL. Procedures were developed for improved aiming of the MTS, using aiming of the MTS, using azimuth and elevation adjustments, which are recommended to be incorporated in the production MTS installation procedure. Initial data analyses indicate that the MTS returns from a typical radio tower would be useful for integrity monitoring in fair weather using typical TDWR filters. The use of the MTS when high -reflectivity weather or anomalous propagation (AP) is present needs further study.
Summary
Monitoring the performance of Doppler weather radars presents special problems since target returns cannot be verified by reference to other systems (e,g ., as ASR-9 aircraft reports can be compared with beacon replies). The Terminal Doppler Weather Radar (TDWR) system includes a Moving Target Simulator (MTS) which provides a point...
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Storm tracking for TDWR: a correlation algorithm design and evaluation
July 14, 1992
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-182
Summary
Storm Movement Prediction (SMP) is a proposed (future) product for Terminal Doppler Weather Radar (TDWR), aiding controllers by tracking storms approaching and passing through the terminal environment. Because the scan strategy (data acquisition) of TDWR has been critically designed to meet the needs of its primary function, which is the detection of hazardous low-altitude wind shear, there is the question of whether reliable storm tracking can be obtained from the TDWR data set. The objectives of storm tracking involve a scope (spatial range) much larger than that required for the wind-shear algorithms where volume coverage is confined (in off-airport sited radars) to a sector covering the important approach and departure corridors and the only 360-degree scans are near-surface scans for gust-front detection. This report examines the application of a correlation based method of detecting storm motion, testing the notion that reliable storm motion can be inferred from existing TDWR data. In particular, storm motion derived from an analysis of the TDWR Precipitation product (PCP) is studied. A summary description of the algorithm is presented along with an analysis of its performance using data from MIT Lincoln Laboratory's TDWR testbed operations in Denver (1988) and Kansas City (1989). The primary focus of the present analysis is on the reliability of tracking, since the algorithm is expected to operate in an autonomous environment. Some attention is given to the idea of prediction, in the form of storm extrapolation, considering 15, 30, and 60 minute predictions. Specific areas for improvement are identified, and application of hte algorithm track vectors for long-term prediction (30-60 minutes) is discussed with reference to example PCP images.
Summary
Storm Movement Prediction (SMP) is a proposed (future) product for Terminal Doppler Weather Radar (TDWR), aiding controllers by tracking storms approaching and passing through the terminal environment. Because the scan strategy (data acquisition) of TDWR has been critically designed to meet the needs of its primary function, which is the...
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