Publications
Automated extraction of weather variables from camera imagery
August 18, 2005
Conference Paper
Published in:
Proc. of 2005 Mid-Continent Transportation Research Symp., 18-19 August 2005.
Summary
Thousands of traffic and safety monitoring cameras are deployed or are being deployed all across the country and throughout the world. These cameras serve a wide range of uses from monitoring building access to adjusting timing cycles of traffic lights at clogged intersections. Currently, these images are typically viewed on a wall of monitors in a traffic operations or security center where observers manually monitor potentially hazardous or congested conditions and notify the appropriate authorities. However, the proliferation of camera imagery taxes the ability of the manual observer to track and respond to all incidents. In addition, the images contain a wealth of information, including visibility, precipitation type, road conditions, camera outages, etc., that often goes unreported because these variables are not always critical or go undetected. Camera deployments continue to expand and the corresponding rapid increases in both the volume and complexity of camera imagery demand that automated algorithms be developed to condense the discernable information into a form that can be easily used operationally by users. MIT Lincoln Laboratory (MIT/LL) under funding from the Federal Highway Administration (FHWA) is investigating new techniques to extract weather and road condition parameters from standard traffic camera imagery. To date, work has focused on developing an algorithm to measure atmospheric visibility and prove the algorithm concept. The initial algorithm examines the natural edges within the image (the horizon, tree lines, roadways, permanent buildings, etc) and performs a comparison of each image with a historical composite image. This comparison enables the system to determine the visibility in the direction of the sensor by detecting which edges are visible and which are not. A primary goal of the automated camera imagery feature extraction system is to ingest digital imagery with limited specific site information such as location, height, angle, and visual extent, thereby making the system easier for users to implement. There are, of course, many challenges in providing a reliable automated estimate of the visibility under all conditions (camera blockage/movement, dirt/raindrops on lens, etc) and the system attempts to compensate for these situations. This paper details the work-to-date on the visibility algorithm and defines a path for further development of the overall system.
Summary
Thousands of traffic and safety monitoring cameras are deployed or are being deployed all across the country and throughout the world. These cameras serve a wide range of uses from monitoring building access to adjusting timing cycles of traffic lights at clogged intersections. Currently, these images are typically viewed on...
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Description of the Corridor Integrated Weather System (CIWS) weather products
August 1, 2005
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-317
Summary
Improved handling of severe en route and terminal convective weather has been identified by the FAA in both the Operational Evolution Plan (OEP) (FAA, 2002) and the Flight Plan for 2004-2008 (FAA, 2003) as a major thrust over the coming decade for the National Airspace System (NAS) modernization. Achieving such improved capabilities is particularly important in highly congested corridors where there is both a high density of over flights and major terminals. Delay increases during thunderstorm season have been the principal cause of the dramatic delay growth in the US aviation system. When major terminals also underlie the en route airspace, convective weather has even greater adverse impacts, especially if the convective weather occurs frequently. In response to the need to enhance both safety and capacity during adverse weather, the FAA is exploring the concept of a Corridor Integrated Weather System (CIWS). CIWS is designed to improve convective weather decision support for congested en route airspace (and the terminals that lie under that airspace) by automatically generating graphical depictions of the current severe weather situation and providing frequently updated forecasts of the future weather locations for forecast times from zero to two hours. An operational demonstration of the CIWS was conducted during the summer of 2003. This document provides a detailed description of each CIWS weather information product as it was demonstrated in 2003, including a general description of the product, what data sources are used by the product, how the product is generated from the input data, and what caveats in the technical performance apply. A discussion of how the products might be used to enhance safety and support decision-making for traffic management is also included. Detailed information on the operational benefits of the CIWS products demonstrated in 2003 is provided in a companion report (Robinson et al., 2004). Improvements made to the products for the 2004 and 2005 CIWS operational demonstrations are briefly discussed in the final chapter.
Summary
Improved handling of severe en route and terminal convective weather has been identified by the FAA in both the Operational Evolution Plan (OEP) (FAA, 2002) and the Flight Plan for 2004-2008 (FAA, 2003) as a major thrust over the coming decade for the National Airspace System (NAS) modernization. Achieving such...
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Operational benefits of the Integrated Terminal Weather System (ITWS) at Atlanta
July 15, 2005
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-320
Summary
This report summarizes the results of an initial study to estimate the yearly delay reduction provided by the initial operational capability (IOC) Integrated Terminal Weather System (ITWS) at Hartsfield-Jackson Atlanta International Airport (ATL). Specific objectives of this initial study were to: (1) analyze convective weather operations at ATL to determine major causes of convective weather delay and how those might be modeled quantitatively. (2) provide estimates of the ATL ITWS delay reduction based on the "Decision/Modeling" method using questionnaires and interviews with Atlanta Terminal Radar Approach Control (TRACON) and Air Route Traffic Control Center (ARTCC) operational ITWS users. (3)assess the "reasonableness" of the model-based delay reduction estimates by comparing those savings with estimates of the actual weather-related arrival delays at ATL. In addition, the reasonableness of model-based delay reduction estimates was assessed by determining the average delay savings per ATL flight during times when adverse convective weather is within the coverage of the ATL ITWS. (4)conduct an exploratory study confirming the ATL ITWS delay savings by comparing Aviation System Performance Metrics (ASPM) database delays pre- and post-ITWS at ATL. (5) assess the accuracy of the "downstream" delay model employed in this study by analyzing ASPM data from a major US airline, and (6) make recommendations for follow-on studies of the ITWS delay reduction at Atlanta and other IOC ITWS facilities. [not complete]
Summary
This report summarizes the results of an initial study to estimate the yearly delay reduction provided by the initial operational capability (IOC) Integrated Terminal Weather System (ITWS) at Hartsfield-Jackson Atlanta International Airport (ATL). Specific objectives of this initial study were to: (1) analyze convective weather operations at ATL to determine...
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Quantifying convective delay reduction benefits for weather/ATM systems
June 27, 2005
Conference Paper
Published in:
USA/Europe Air Traffic Management Seminar, 27-30 June 2005.
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Summary
This paper investigates methods for quantifying convective weather delay reduction benefits for weather/ATM systems and recommends approaches for future assessments. This topic is particularly important at this time because: 1. Convective weather delays continue to be a dominant factor in the overall National Airspace System (NAS) delays, and 2. Benefits quantification and NAS performance assessment have become very important in an era of significant government and airline budget constraints for civil aviation investments. Quantifying convective weather delay benefits for ATM systems has proven to be quite difficult since the delays arise from complicated, highly variable, poorly understood interactions between convective weather and a very complex aviation system. In this paper, we consider key aspects of convective weather disruptions of the aviation system, how the weather severity can be characterized, and discuss practical experience with benefits quantification by a variety of approaches. The paper concludes with recommendations for a methodology to be used in future convective weather delay reduction quantification studies.
Summary
This paper investigates methods for quantifying convective weather delay reduction benefits for weather/ATM systems and recommends approaches for future assessments. This topic is particularly important at this time because: 1. Convective weather delays continue to be a dominant factor in the overall National Airspace System (NAS) delays, and 2. Benefits...
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Safety analysis methodology for unmanned aerial vehicle (UAV) collision avoidance systems
June 27, 2005
Conference Paper
Published in:
USA/Europe Air Traffic Management Seminar, 27-30 June 2005.
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Summary
The integration of Unmanned Aerial Vehicles (UAVs) into civil airspace requires new methods of ensuring collision avoidance. Concerns over command and control latency, vehicle performance, reliability of autonomous functions, and interoperability of sense-and-avoid systems with the Traffic Alert and Collision Avoidance System (TCAS) and Air Traffic Control must be resolved. This paper describes the safety evaluation process that the international community has deemed necessary to certify such systems. The process focuses on a statistically-valid estimate of collision avoidance performance developed through a combination of airspace encounter modeling, fast-time simulation of the collision avoidance system across millions of encounter scenarios, and system failure and event sensitivity analysis. Example simulation results are provided for an implementation of the analysis process currently being used to evaluate TCAS on the Global Hawk UAV.
Summary
The integration of Unmanned Aerial Vehicles (UAVs) into civil airspace requires new methods of ensuring collision avoidance. Concerns over command and control latency, vehicle performance, reliability of autonomous functions, and interoperability of sense-and-avoid systems with the Traffic Alert and Collision Avoidance System (TCAS) and Air Traffic Control must be resolved...
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Safety analysis for advanced separation concepts
June 27, 2005
Conference Paper
Published in:
USA/Europe Air Traffic Management Seminar, 27-30 June 2005.
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Summary
Aviation planners have called for increasing the capacity of the air transportation system by factors of two or three over the next 20 years. The inherent spatial capacity of en route airspace appears able to accommodate such traffic densities. But controller workload presents a formidable obstacle to achieving such goals. New approaches to providing separation assurance are being investigated to overcome workload limitations and allow airspace capacity to be fully utilized. One approach is to employ computer automation as the basis for separation-assurance task. This would permit traffic densities that exceed the level at which human cognition and decision-making can assure separation. One of the challenges that must be faced involves the ability of such highly automated systems to maintain safety in the presence of inevitable subsystem faults, including the complete failure of the supporting computer system. Traffic density and flow complexity will make it impossible for human service providers to safely reinitiate manual control in the event of computer failure, so the automated system must have inherent fail-soft features. This paper presents a preliminary analysis of the ability of a highly automated separation assurance system to tolerate general types of faults such as nonconformance and computer outages. Safety-related design features are defined using the Advanced Airspace Concept (AAC) as the base architecture. Special attention is given to the impact of a severe failure in which all computer support is terminated within a defined region. The growth and decay of risk during an outage is evaluated using fault tree methods that integrate risk over time. It is shown that when a conflict free plan covers the region of the outage, this plan can be used to safely transition aircraft to regions where service can still be provided.
Summary
Aviation planners have called for increasing the capacity of the air transportation system by factors of two or three over the next 20 years. The inherent spatial capacity of en route airspace appears able to accommodate such traffic densities. But controller workload presents a formidable obstacle to achieving such goals...
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Multi-PRI signal processing for the terminal Doppler weather radar, part I: clutter filtering
May 1, 2005
Journal Article
Published in:
J. Atmos. Ocean. Technol., Vol. 22, May 2005, pp. 575-582.
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Summary
Multiple pulse repetition interval (multi-PRI) transmission is part of an adaptive signal transmission and processing algorithm being developed to aggressively combat range-velocity ambiguity in weather radars. In the past, operational use of multi-PRI pulse trains has been hampered due to the difficulty in clutter filtering. This paper presents finite impulse response clutter filter designs for multi-PRI signals with excellent magnitude and phase responses. These filters provide strong suppression for use on low-elevation scans and yield low biases of velocity estimates so that accurate velocity dealiasing is possible. Specifically, the filters are designed for use in the Terminal Doppler Weather Radar (TDWR) and are shown to meet base data bias requirements equivalent to the Federal Aviation Administration's specifications for the current TDWR clutter filters. Also an adaptive filter selection algorithm is proposed that bases its decision on clutter power estimated during an initial long-PRI surveillance scan. Simulations show that this adaptive algorithm yields satisfactory biases for reflectivity, velocity, and spectral width. Implementation of such a scheme would enable automatic elimination of anomalous propagation signals and constant adjustment to evolving ground clutter conditions, an improvement over the current TDWR clutter filtering system.
Summary
Multiple pulse repetition interval (multi-PRI) transmission is part of an adaptive signal transmission and processing algorithm being developed to aggressively combat range-velocity ambiguity in weather radars. In the past, operational use of multi-PRI pulse trains has been hampered due to the difficulty in clutter filtering. This paper presents finite impulse...
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An analysis of wake vortex lidar measurements at LaGuardia Airport
November 30, 2004
Project Report
Published in:
Project Report ATC-318, MIT Lincoln Laboratory
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Summary
The majority of research into the wake vortex hazard has concentrated on the in-trail encounter scenario for arrivals. At LaGuardia Airport, wake vortex spacings are applied to arrivals on runway 22 following a heavy departure on the intersecting runway 31, resulting in delay and increased workload for controllers. Previous analysis of this problem led to a recommendation for a measurement campaign to collect data on the behavior of wake vortices generated by departing heavy aircraft. In April of 2004, MIT Lincoln Laboratory deployed its wake vortex lidar system to measure such wakes at LaGuardia. Additionally, wind speed and turbulence data were collected with the hope of correlating wake behavior with the local atmospheric conditions. Analysis of the lidar data indicates that the system was able to acquire and track vortices from departures, a task not proven prior to this deployment. Further, vortices were seen to transport toward the threshold of runway 22, verifying an assumption based on analysis of the winds that wake transport is not a solution in this case. The quantity and type of data collected were insufficient to formulate a clear relationship between atmospheric turbulence and vortex decay. However, it may be possible to develop such a model by exploiting the data gathered during previous lidar deployments.
Summary
The majority of research into the wake vortex hazard has concentrated on the in-trail encounter scenario for arrivals. At LaGuardia Airport, wake vortex spacings are applied to arrivals on runway 22 following a heavy departure on the intersecting runway 31, resulting in delay and increased workload for controllers. Previous analysis...
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Remotely piloted vehicles in civil airspace: requirements and analysis methods for the traffic alert and collision avoidance system (TCAS) and see-and-avoid systems
October 24, 2004
Conference Paper
Published in:
Proc. of the 23rd Digital Avionics Systems Conf., DASC, Vol. 2, 24-28 October 2004, pp. 12.D.1-1 - 12.D.1.14.
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Summary
The integration of Remotely Piloted Vehicles (RF'Vs) into civil airspace will require new methods of ensuring aircraft separation. This paper discusses issues affecting requirements for RPV traffic avoidance systems and for performing the safety evaluations that will be necessary to certify such systems. The paper outlines current ways in which traffic avoidance is assured depending on the type of airspace and type of traffic that is encountered. Alternative methods for RPVs to perform traffic avoidance are discussed, including the potential use of new see-and-avoid sensors or the Traffic Alert and Collision Avoidance System (TCAS). Finally, the paper outlines an established safety evaluation process that can be adapted to assure regulatory authorities that RPVs meet level of safety requirements.
Summary
The integration of Remotely Piloted Vehicles (RF'Vs) into civil airspace will require new methods of ensuring aircraft separation. This paper discusses issues affecting requirements for RPV traffic avoidance systems and for performing the safety evaluations that will be necessary to certify such systems. The paper outlines current ways in which...
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Improved range-velocity ambiguity mitigation for the Terminal Doppler Weather Radar
October 4, 2004
Conference Paper
Published in:
11th Conf. on Aviation, Range and Aerospace Meteorology, 4-8 October 2004.
Summary
The Terminal Doppler Weather Radar (TDWR) radar data acquisition (RDA) subsystem is being replaced as part of a broader FAA program to improve the supportability of the system. An engineering prototype RDA has been developed with a scalable, open-systems hardware platform. With the dramatically increased computing power and more flexible transmitter control, modern signal processing algorithms can be implemented to improve the quality of the base data. Nation-wide, the most serious data quality challenge is range-velocity (RV) ambiguity. In a previous study (Cho et al., 2003) we showed that multiple pulse repetition interval (PRI) and constant-PRI phase-code processing have complementary strengths with respect to range-fold protection, and pro-posed an adaptive waveform and processing selection scheme on a radial-by-radial basis. Here we describe the scheme and give more details about the clutter filtering and velocity dealiasing algorithms to be used on the two types of signals.
Summary
The Terminal Doppler Weather Radar (TDWR) radar data acquisition (RDA) subsystem is being replaced as part of a broader FAA program to improve the supportability of the system. An engineering prototype RDA has been developed with a scalable, open-systems hardware platform. With the dramatically increased computing power and more flexible...
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