Publications
The effects of compression-induced distortion of graphical weather images on pilot perception, acceptance, and performance
November 21, 1997
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-243
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Summary
The Graphical Weather Service (GWS) is a data link application that will provide near-real-time graphical weather information to pilots in flight. To assess the effect GWS, as well as to aid in the proper design, implementation and certification of the use of GWS in aircraft, two human factors studies have been conducted. The second study conducted (Phase Two) is the topic of this report. Phase Two was conducted to determine the maximum level of compression-induced distortion that would be acceptable for transmission of weather images to the cockpit. To make this determination the following data were collected and analyzed: pilot subjective ratings of the perceived amount of distortion of a compressed image, pilot subjective ratings of the acceptability of a compressed image for use in the flight task, and pilot route selections as a function of the amount of compression presented in an image. Results indicated that images of low to moderate compression levels were generally acceptable for transmission to the cockpit, while images that were highly compressed were generally unacceptable. In addition, computed measures of image quality have been identified to enable the establishment of a criteria for transmitting images to aircraft.
Summary
The Graphical Weather Service (GWS) is a data link application that will provide near-real-time graphical weather information to pilots in flight. To assess the effect GWS, as well as to aid in the proper design, implementation and certification of the use of GWS in aircraft, two human factors studies have...
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The Weather-Huffman method of data compression of weather images
October 31, 1997
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-261
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Providing an accurate picture of the weather conditions in the pilot's area of interest is a highly useful application for ground-to-air datalinks. The problem with using data links to transmit weather graphics is the large number of bits required to exactly specify the weather image. To make transmission of weather images practical, a means must be found to compress the data to a size compatible with a limited datalink capacity. The Weather-Huffman (WH) Algorithm developed in this report incorporates several subalgorithms in order to encode as faithfully as possible an input weather image within a specified datalink bit limitation. The main algorithm component is the encoding of a version of the input image via the Weather Huffman runlength code, a variant of the standard Huffman code tailored to the peculiarities of weather images. If possible, the input map itself is encoded. Generally, however, a resolution-reduced version of the map must be created prior to the encoding to meet the bit limitation. In that case, the output map will contain blocky regions, and higher weather level areas will tend to bloom in size. Two routines are included in WH to overcome these problems. The first is a Smoother Process, which corrects the blocky edges of weather regions. The second, more powerful routine, is the Extra Bit Algorithm (EBA). EBA utilizes all bits remaining in the message after the Huffman encoding to correct pixels set at too high a weather level. Both size and shape of weather regions are adjusted by this algorithim. Pictorial examples of the operation of this algorithm on several severe weather images derived from NEXRAD are presented.
Summary
Providing an accurate picture of the weather conditions in the pilot's area of interest is a highly useful application for ground-to-air datalinks. The problem with using data links to transmit weather graphics is the large number of bits required to exactly specify the weather image. To make transmission of weather...
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Performance characteristics of an algorithm used to remove anomolous propagation from the NEXRAD data
September 12, 1997
Conference Paper
Published in:
28th Conf. on Radar Meteorology, 7-12 September 1997, pp. 317-319.
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An important limitation of precipitation sensors is contamination from ground clutter targets under conditions of anomalous propagation (AP). This problem can be mitigated significantly by high-pass clutter filters such as used by the Terminal Doppler Weather Radar (TDWR) and Next Generation Weather Radar (NEXRAD) systems....MIT Lincoln Laboratory (MIT/LL) has developed and tested an algorithm that removes AP from the NEXRAD reflectivity data. In this paper, we will first provide a brief description of the algorithm. Next we will present the truthing methodology used to identify AP. Then, we will show the algorithm performance results and failure mechanisms with this initial version. Finally, we consider refinements to improve the algorithm's performance.
Summary
An important limitation of precipitation sensors is contamination from ground clutter targets under conditions of anomalous propagation (AP). This problem can be mitigated significantly by high-pass clutter filters such as used by the Terminal Doppler Weather Radar (TDWR) and Next Generation Weather Radar (NEXRAD) systems....MIT Lincoln Laboratory (MIT/LL) has developed...
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Terminal Weather Information for Pilots (TWIP) Program Annual Report for 1995
September 8, 1997
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-253
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The Federal Aviation Administration (FAA) is currently embarking on programs, such as the Terminal Doppler Weather Radar (TDWR) and Integrated Terminal Weather Systems (ITWS), that will significanlty improve the aviation weather information in the terminal area. For example, TDWR data will be available at 47 airports across the United States that have high traffic and significant risk of wind shear. The TDWRs automatically report microburst, gust front and precipitaion near the airport to air traffic control personnel on a 24-hour basis. Given the great increase in the quantity and quality of terminal weather information, it is highly desirable to provide this information directly to pilots rather than relying on voice communications. Providing terminal weather information automatically via data link will enhance pilot awareness of weather hazards and lead to more efficient utilization of aircraft. It may also decrease air traffic controller workload and reduce ratio frequency congestion. This report describes work performed in 1995 to provide direct pilot access to terminal weather information via an existing data link known as ACARS (Aircraft, Communication Addressing and Reporting System). More than 4000 aircraft operate in the United States with ACARS equipment. During 1995, five Lincoln-operated testbeds provided near real-time terminal weather information to pilots of AFCARS-equipped aircraft in both text and character graphics formats. This effort follows earlier successful demonstrations during the summers of 1993 and 1994. Section 2 of the report describes the TWIP message formats, Section 3 discusses the 1995 operational demonstration, and Section 4 presents TWIP software design. Section 5 provides case analyses from the 1995 demonstration, Section 6 discusses future work, and Section 7 is the summary.
Summary
The Federal Aviation Administration (FAA) is currently embarking on programs, such as the Terminal Doppler Weather Radar (TDWR) and Integrated Terminal Weather Systems (ITWS), that will significanlty improve the aviation weather information in the terminal area. For example, TDWR data will be available at 47 airports across the United States...
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The capabilities and limitations of using the ASR-9 as a terminal area precipitation sensor
September 7, 1997
Conference Paper
Published in:
28th Conf. on Radar Meteorology, 7-12 September 1997.
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The Airport Surveillance Radar (ASR-9) weather channel is an invaluable tool to air-traffic and flight management specialists. The precipitation data from this sensor is currently displayed on air-traffic specialists' radar scopes and is incorporated into the Integrated Terminal Weather System (ITWS). The data are used to determine optimum routes for aircraft operating in and near the tenninal airspace. Data from other terminal area precipitation sensors such as the Terminal Doppler Weather Radar (TDWR) and the Next Generation Weather Radar (NEXRAD) are also used for this same purpose. The primary advantage of using the ASR-9 as a precipitation sensor is its high update rate, e.g. thirty seconds versus about five minutes for TDWR and N EX RAD. The ASR-9 is also quite reliable, with limited down time. Finally, range folding is not a significant problem with this radar. However, during ITWS prototype testing over the past three years, we have identified several limitations of using this radar as a precipitation sensor. For one, the maximum reflectivity of cells can be significantly underestimated by the ASR-9 due to partial filling of its fan-shaped elevation beam and cell-to-cell spatial averaging. Also, the occurrence of underestimation seems to increase when the radar operates in circular polarization mode. In addition, we have analyzed cases where significant precipitation-induced attenuation has occurred. Finally, because most ASR-9s are located on the airport, rain cores developing aloft, above the airport, maybe underestimated or missed entirely. This paper focuses on the problems identified through the ITWS prototype testing.
Summary
The Airport Surveillance Radar (ASR-9) weather channel is an invaluable tool to air-traffic and flight management specialists. The precipitation data from this sensor is currently displayed on air-traffic specialists' radar scopes and is incorporated into the Integrated Terminal Weather System (ITWS). The data are used to determine optimum routes for...
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A description of the interfaces between the Weather Systems Processor (WSP) and the Airport Surveillance Radar (ASR-9)
June 16, 1997
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-259
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The Weather Systems Processor (WSP) is an enhancement for the Federal Aviation Administration's (FAA) current generation Airport Surveillance Radars (ASR-9) that provides fully automated detection of microburst and gust front wind shear phenomena, estimates of storm cell movement and extrapolated future postion, and 10- and 20-minute predictions of the future postion of gust fronts. The WSP also generates six-level weather reflectivity free of anomalous propagation induced ground clutter breakthrough. Alphanumeric and graphical displays provide WSP-generated weather information to air traffic controllers and their supervisors. This report describes the hardware, interfaces, timing and digital signal extraction from the ASR-9 necessary to support the WSP. The digital interface circuitry between the WSP and the ASR-9, the control functions associated with the WSP, and the strategies for performing system test functions are described
Summary
The Weather Systems Processor (WSP) is an enhancement for the Federal Aviation Administration's (FAA) current generation Airport Surveillance Radars (ASR-9) that provides fully automated detection of microburst and gust front wind shear phenomena, estimates of storm cell movement and extrapolated future postion, and 10- and 20-minute predictions of the future...
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Initial comparison of lightning mapping with operational time-of-arrival and interferometric systems
May 27, 1997
Journal Article
Published in:
J. Geophys. Res., Vol. 102, No. D10, 27 May 1997, pp. 11,071-11,085.
Summary
The mapping of lightning radiation sources produced by the operational Time-of-Arrival National Aeronautics and Space Administration/Lightning Detection and Ranging (NASA/LDAR) system is compared with that of the Interferometric French Office National D'Etudes et de Recherches Aerospatiales (ONERA-3D) system. The comparison comprises lightning activity in three Florida storms and also individual flashes in one of these storms. Although limited in scope, the comparison analysis show a significant difference in the representation of lightning radiation by each mapping system. During the duration of a flash, the LDAR data show a continuity in time and a three-dimensional structure of radiation sources. The ONERA-3D radiation source data are more intermittent in time and have a more two-dimensional structure. The distinction between the radiation sources mapped by the two systems is also reflected in the difference between their propagation speeds, 10^4-10^5 m s^-1, estimated by the LDAR system, and 10^7-10^8 m s^-1, estimated by the ONERA-3D system. We infer that this difference occurs because most of the radiation sources mapped with LDAR are associated with virgin breakdown processes typical of slowly propagating negative leaders. On the other hand, most of the radiation sources mapped with ONERA3D are produced by fast intermittent negative breakdown processes typical of dart leaders and K changes as they traverse the previously ionized channels. Thus each operational system may emphasize different stages of the lightning flash, but neither appears to map the entire flash.
Summary
The mapping of lightning radiation sources produced by the operational Time-of-Arrival National Aeronautics and Space Administration/Lightning Detection and Ranging (NASA/LDAR) system is compared with that of the Interferometric French Office National D'Etudes et de Recherches Aerospatiales (ONERA-3D) system. The comparison comprises lightning activity in three Florida storms and also individual...
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Analysis of downstream impacts of air traffic delay
March 3, 1997
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-257
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Reduction of air carrier flight delay in the U.S. National Airspace System (NAS) has been a major objective of the Federal Aviation Administration (FAA) for many years. Much of the current delay arises from weather-induced delays at airports. When a plane is delayed on one of the day's flights, there can be a carryover delay that affects later flights by that aircraft. In this report, we develop statistical models to predict: 1. The "downstream" delays that occur when a flight experiences an initial delay, and 2. The likelihood of flight cancellation as a function of the initial delay. Using historical airline-reported delays for December 1993, we conclude that the mean "downstream" delay is approximately 80 percent of the initial delay, i.e., the net delay for an aircraft due to an initial flight delay is approximately 1.8 x the initial delay.
Summary
Reduction of air carrier flight delay in the U.S. National Airspace System (NAS) has been a major objective of the Federal Aviation Administration (FAA) for many years. Much of the current delay arises from weather-induced delays at airports. When a plane is delayed on one of the day's flights, there...
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Convective weather forecasting for FAA applications
February 2, 1997
Conference Paper
Published in:
7th Conf. on Aviation, Range, and Aerospace Meteorology, ARAM, 2-7 February 1997.
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The Convective Weather Product Development Team (PDT) was formed in 1996 as part of the reorganization of the FAA Aviation Weather Research Program, to provide an effective way to conduct critical applied research in a collaborative and rational fashion. Detecting and predicting convective weather is extremely important to aviation, since approximately half of the national airspace delay in the warm season is caused by thunderstorms. Reliable 0--6 hr storm predictions are essential for aviation users to achieve safe and efficient use of the airspace, as well as for future air traffic control automation systems. Our goal on this PDT is to direct our research and development activities toward operationally useful convective weather detection and forecast products, and delivery of those products, so that users can receive benefits on an immediate and continual basis. Given that we have many more initiatives than funding, we have chosen to prioritize our activities according to near-term achievable benefits to users. Our hope is that the success of initial planned demonstrations will help the FAA identify a consistent level of long-term R&D funding, so that we can make real progress towards achieving our full set of goals. In this paper, we present our statement of the FAA Convective Weather Forecasting problem, evidence of the need for forecasts in the National Airspace System (NAS), and an illustration of the air traffic delay caused by convective weather. We then discuss our research plan and rationale, and outline our main initiatives for the upcoming year.
Summary
The Convective Weather Product Development Team (PDT) was formed in 1996 as part of the reorganization of the FAA Aviation Weather Research Program, to provide an effective way to conduct critical applied research in a collaborative and rational fashion. Detecting and predicting convective weather is extremely important to aviation, since...
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The impact of thunderstorm growth and decay on air traffic management in class B airspace
February 2, 1997
Conference Paper
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7th Conf. on Aviation, Range, and Aerospace Meteorology, ARAM, 2-7 February 1997.
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Air traffic management is a challenging task, especially if the airspace involved is impacted by inclement weather. The high volume of air traffic which inundates the nation's major airports compounds the difficulties with which Air Traffic Control (ATC) specialists have to cope. When you add the unpredictability of thunderstorm growth and decay to the controllers workload, air traffic management becomes even more of a challenge. ATC specialists would benefit from reliable forecasts of thunderstorm growth and decay. To determine how they would use a Growth and Decay product, ATC specialists from the Memphis Air Route Traffic Control Center (ARTCC), Traffic Management Unit (TMU), and TRACON supervisors were interviewed while viewing five movie loops of Memphis weather cases. The movies consisted of the ASR-9 six-level reflectivity data, aircraft beacons, and storm motion vectors.
Summary
Air traffic management is a challenging task, especially if the airspace involved is impacted by inclement weather. The high volume of air traffic which inundates the nation's major airports compounds the difficulties with which Air Traffic Control (ATC) specialists have to cope. When you add the unpredictability of thunderstorm growth...
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