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A coordinate conversion algorithm for multisensor data processing

August 5, 1986
  |
Project Report
Author:
Eric M. Shank
Published in:
MIT Lincoln Laboratory Report ATC-139
Topic:
air traffic control
R&D area:
R&D group:

Summary

Processing of aircraft surveillance data from several geographically separated radars is most easily accomplished using a common coordinate system to represent data from all sensors. The Multisensor Data Processing system currently being developed for the FAA in support of the Advanced Automation System (AAS) requires a degree of accuracy and consistency that is not available from the current NAS implementation of coordinate conversion. A study has been undertaken to design a coordinate covnersion algorithm that meets the needs of Multisensor Data Processing. The process of projection of the ellipsoidal surface of the earth onto a planar surface is examined in light of teh requirements of air traffic control systems. The effects of the non-spherical nature of the earth and of limited computational resources are considered. Several standard cartographic projection techniques are examined, and the sterographic projection is found to be the projection of choice. A specific implementation of stereographic projection that makes the needs of Multisensor Data Processing is described. This implementation makes use of several approximations to decrease the computational load. The systemic errors introduced by these approximations are removed by the addition of a correction term determined from a precomputed error surface. The performance of this conversion system is demonstrated using realistic test data.
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Summary

Processing of aircraft surveillance data from several geographically separated radars is most easily accomplished using a common coordinate system to represent data from all sensors. The Multisensor Data Processing system currently being developed for the FAA in support of the Advanced Automation System (AAS) requires a degree of accuracy and...

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A coordinate conversion algorithm for multisensor data processing

Pilot evaluation of TCAS in the Long Ranger helicopter

June 3, 1986
  |
Project Report
Author:
John W. Andrews
Published in:
MIT Lincoln Laboratory Report ATC-136
Topic:
collision avoidance
R&D area:
R&D group:

Summary

A specially modified version of the Traffic Alert and Collision Avoidance System (TCAS) was installed in a Bell Long Ranger helicopter in order to investigate the feasibility of TCAS operation in rotorcraft. This installation employed TCAS air-to-air surveillance to provide automated traffic advisories that were displayed in the cockpit on a color cathod ray tube display. As part of this study, 12 subject pilots evaluated the utility of the installation thorugh brief test flights in the vicinity of a major airport. Among the topics investigated were the rate of alarms, the computer logic for issuing advisories, the bearing accuracy, and the display symbology. Several recommendations for adapting TCAS to the rotorcraft environment resulted from the testing.
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Summary

A specially modified version of the Traffic Alert and Collision Avoidance System (TCAS) was installed in a Bell Long Ranger helicopter in order to investigate the feasibility of TCAS operation in rotorcraft. This installation employed TCAS air-to-air surveillance to provide automated traffic advisories that were displayed in the cockpit on...

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Pilot evaluation of TCAS in the Long Ranger helicopter

WX1 - an expert system for weather radar interpretation

January 1, 1986
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Conference Paper
Author:
Steven D. Campbell
…
Published in:
Coupling Symbolic and Numerical Computing in Expert Systems, Elsevier Science Publ. B. V., 1986.
Topic:
air traffic control
R&D area:
R&D group:

Summary

This paper describes work performed by M.I.T. Lincoln Laboratory for the Federal Aviation Administration to investigate the use of expert system techniques for weather radar interpretation. The design of WX1, a prototype system for recognizing low-altitude wind shear hazards from Doppler weather radar data, is presented. The WX1 system consists of a rule-based expert system coupled to an object-oriented image processing package. Initial results for recognition of two types of low-altitude wind shear are provided.
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Summary

This paper describes work performed by M.I.T. Lincoln Laboratory for the Federal Aviation Administration to investigate the use of expert system techniques for weather radar interpretation. The design of WX1, a prototype system for recognizing low-altitude wind shear hazards from Doppler weather radar data, is presented. The WX1 system consists...

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WX1 - an expert system for weather radar interpretation

Evaluation of the ASR-9 weather reflectivity product

June 21, 1985
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Conference Paper
Author:
Mark E. Weber
…
Published in:
Proc. Second Int. Conf. on the Aviation Weather System, 19-21 June 1985, pp. 196-202.
Topic:
aviation weather
R&D area:
R&D group:

Summary

The ASR-9 is a modern airport surveillance radar (ASR) under procurement by the United States Federal Aviation Agency. The radar operates at S-band, providing range-azimuth position information on aircraft targets within a 111-km radius. A fully-coherent klystron amplifier, large dynamic range and digital signal processing enable high integrity target processing and display under condition of ground clutter, weather, angel clutter, RF interference and ground vehicular traffic. To aid controllers in the identification of hazardous weather conditions, the processor will also generate two- or six-level weather reflectivity contours for display at the terminal radar control center and (potentially) remote sites. In this paper, we present an overview of the ASR-9 and its weather processor, emphasizing those features that raise issues with respect to the utility of the weather reflectivity product in an air-traffic control environment. We then describe a simulation procedure that utilizes pencil-beam Doppler weather radar data and ground clutter measurements to preview the ASR-9 product and assess the effects of the radar's configuration on the weather intensity reports. Examples of the simulated weather reports are used to illustrate" (a) partial beamfilling die to the fan-shaped surveillance antenna pattern; (b) attenuation of low velocity weather by the clutter filters' (c) the effects of the spatial filters used in weather processing.
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Summary

The ASR-9 is a modern airport surveillance radar (ASR) under procurement by the United States Federal Aviation Agency. The radar operates at S-band, providing range-azimuth position information on aircraft targets within a 111-km radius. A fully-coherent klystron amplifier, large dynamic range and digital signal processing enable high integrity target processing...

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Evaluation of the ASR-9 weather reflectivity product

Collision avoidance for Naval training aircraft

March 8, 1985
  |
Project Report
Author:
John W. Andrews
…
Published in:
MIT Lincoln Laboratory Report ATC-125
Topic:
collision avoidance
R&D area:
R&D group:

Summary

Lincoln Laboratory was tasked by the FAA to assist the Naval Air Training Command in evaluating the feasibility of using the FAA's TCAS I concept as the document summarizes the results of a brief study and flight test activity conducted to that end. It begins with a review of Lincoln Laboratory's understanding of the nature of the mid-air collision problem at the Naval Air Training Center. This is followed by a brief analysis of a set of documented collisions and near-miss encounters involving aircraft of Navy Training Air Wing 5 at Whiting Naval Air Station in Florida in 1982 and 1983. Experience gained from FAA and Lincoln Laboratory flight tests of similar encounters is reviewed and applied to the Navy encounter data base. This is followed by a review of the results obtained when a Lincoln Laboratory aircraft equipped with a TCAS Experimental Unit (TEU) was flown to Whiting Field to evaluate the ability of TCAS I equipment to perform reliable surveillance in the Naval training environment. Flight test results show that the environment is quite unlike typical civil environments, but that the TCAS surveillance design would be capable of providing a significant degree of protection to Naval trainers.
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Summary

Lincoln Laboratory was tasked by the FAA to assist the Naval Air Training Command in evaluating the feasibility of using the FAA's TCAS I concept as the document summarizes the results of a brief study and flight test activity conducted to that end. It begins with a review of Lincoln...

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Collision avoidance for Naval training aircraft

Air-to-air visual acquisition performance with TCAS II

November 7, 1984
  |
Project Report
Author:
John W. Andrews
Published in:
MIT Lincoln Laboratory Report ATC-130
Topic:
collision avoidance
R&D area:
R&D group:

Summary

The ability of pilots to visually acquire aircraft approaching on collision cources is analyzed using a mathematical model of visual acquisition. The model is calibrated by reference to subject pilot flight test data resulting from testing of the Traffic Alert and Collision Avoidance System (TCAS). Techniques are presented that allow the determination of the probability of visual acquisition for a range of intruder aircraft sizes and closing rates. The effect of visual range (atmospheric visibility) upon visual acquisition performance is analyzed.
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Summary

The ability of pilots to visually acquire aircraft approaching on collision cources is analyzed using a mathematical model of visual acquisition. The model is calibrated by reference to subject pilot flight test data resulting from testing of the Traffic Alert and Collision Avoidance System (TCAS). Techniques are presented that allow...

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Air-to-air visual acquisition performance with TCAS II

Ground clutter cancellation for the NEXRAD system

October 19, 1983
  |
Project Report
Author:
James E. Evans
Published in:
MIT Lincoln Laboratory Report ATC-122
Topic:
radar
R&D area:
R&D group:

Summary

Returns from the ground and associated obstacles surroudning a NEXRAD weather radar (i.e., ground clutter) will contaminate the estimates of weather echo spectral features (e.g., reflectivity, mean velocity, and spectral width). The ground clutter returns are particularly large at low elevation angles and close range (e.g., within 40 km). Additionally, the pulse repetition frequency (PRF) values necessary to obtain the desired weather Doppler features result in ground clutter contamination at ranges that are multiples of the unambiguous range interval (e.g., 115-175 km for a typical NEXRAD). Fortunately, the groung clutter power spectrum is localized around zero velocity so that one can reduce its effect by appropriate Doppler signal processing. Automatic reduction of clutter contamination is essential if NEXRAD is to achieve the desired automatic weather product generation capability. The results of an analytical/experimental study oreinted toward development of a clutter cancellation specification and assiciated quality assurance tests for the NEXRAD system are described.
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Summary

Returns from the ground and associated obstacles surroudning a NEXRAD weather radar (i.e., ground clutter) will contaminate the estimates of weather echo spectral features (e.g., reflectivity, mean velocity, and spectral width). The ground clutter returns are particularly large at low elevation angles and close range (e.g., within 40 km). Additionally...

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Ground clutter cancellation for the NEXRAD system

A traffic alert and collision avoidance system for general aviation

October 1, 1983
  |
Conference Paper
Author:
Vincent A. Orlando
…
Published in:
IEEE/AIAA 5th Digital Avionics Systems Conf., Seattle, WA, 31 October - 3 November 1983, pp. 20.
Topic:
air traffic control
R&D area:
R&D group:

Summary

One component of the Federal Aviation Administration approach to independent aircraft separation assurance is known as the Traffic Alert and Collision Avoidance System I (TCAS I), which employs passive or active techniques for the detection of nearby transponder-equipped aircraft. This paper gives the results of a study conducted by Lincoln Laboratory of simple techniques for the passive and active detection of transponders. Filter criteria that may be used to restrict passive detections to potentially threatening aircraft are described and evaluated. These techniques and criteria were used in a candidate passive detector whose performance was evaluated in flight against targets of opportunity. A candidate low-power active interrogator was also evaluated through link calculations and airborne measurements. The results indicate that a low-power active interrogator can provide more reliable detection of nearby aircraft and a lower false alert rate than any of the simple passive techniques considered. The active technique generates insignificant levels of interference and, unlike a passive system, also provides protection in regions where there are no ground interrogators.
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Summary

One component of the Federal Aviation Administration approach to independent aircraft separation assurance is known as the Traffic Alert and Collision Avoidance System I (TCAS I), which employs passive or active techniques for the detection of nearby transponder-equipped aircraft. This paper gives the results of a study conducted by Lincoln...

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A traffic alert and collision avoidance system for general aviation

Short-term prediction of high reflectivity contours for aviation safety

June 9, 1983
  |
Conference Paper
Author:
John C. Brasunas
…
Published in:
Proc. Ninth Conf. Aerospace and Aeronautical Meteorology, 6-9 June 1983, pp. 118-122.
Topic:
aviation weather
R&D area:
R&D group:

Summary

Airspace utilization and safety could benefit significantly from accurate, real-time, short-term predictions of hazardous weather regions (e.g., 5-30 minutes). For some hazards, such as heavy turbulence, the detection process itself is in an immature stage. No universally accepted algorithm exists for indicating the regions of current turbulence - let alone predicting it. For other hazards, such as hail and more particularly for heavy rain, the detection process is in a more mature state. In fact heavy rain may be unambiguously associated with high dBZ (reflectivity), if no ice phases are present. Hail is also associated with high reflectivities. We have therefore chosen to place our initial emphasis on the prediction of reflectivity contours in the context of ATC (air traffic control) operations. For all or our prediction techniques, we begin by collecting fixed dBZ-level contours on a fixed-elevation scan by fixed-elevation scan basis, and then combining these elevation cell slices into volume cells as is done in the algorithm of Bjerkaas and Forsyth (1980). To these volume cells we attach translations vectors to make the desired prediction: at this time no provision is made for the growth or decay of reflectivity cells. We generate our translation vectors using each of several algorithms which have already been described elsewhere. Firstly, we use the centroid-tracking approach of Bjerkaas and Forsyth (1980). This is the current tracker of choice in the NEXRAD (Next Generation Weather Radar) program. Secondly, we use tracking vectors of clusters of volume cells, as described ny Crane (1979): much of this work was performed under the sponsorship of the Federal Aviation Administration (FAA). Thirdly, we generate translation vectors by cross-correlating low-altitude (0-4 cm) CAPPIs (constant-altitude plan position indicators): this correlation is done either for the entire storm, or for 30 km by 30 km segments of the storm. This approach has been motivated by the work of Rinehart and Garvey (1978), although we generally use a CAPPI of liquid water content. Fourthly, we use as a prediction the current, composite reflectivity map - our so-called status-quo prediction.
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Summary

Airspace utilization and safety could benefit significantly from accurate, real-time, short-term predictions of hazardous weather regions (e.g., 5-30 minutes). For some hazards, such as heavy turbulence, the detection process itself is in an immature stage. No universally accepted algorithm exists for indicating the regions of current turbulence - let alone...

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Short-term prediction of high reflectivity contours for aviation safety

Traffic Alert and Collision Avoidance System (TCAS): a functional overview of minimum TCAS II

April 8, 1983
  |
Project Report
Author:
Jerry D. Welch
…
Published in:
MIT Lincoln Laboratory Report ATC-119
Topic:
collision avoidance
R&D area:
R&D group:

Summary

The Traffic Alert and Collision Avoidance System (TCAS) is a beanon-based airborne collision avoidance system that is able to operate in all airspace without reliance on ground equipment. The TCAS concept encompasses a range of capabilities that include TCAS I, a low-cost, limited-perofrmance version, and TCAS II, which is intended to provide a comprehensive level of separation assurance in all current and predicted airspace environments through the end of this century. This document provides a functional overview of the TCAS II including operating features, a description of the avionics package, and examples of surveillance data obtained with experimental TCAS equipment.
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Summary

The Traffic Alert and Collision Avoidance System (TCAS) is a beanon-based airborne collision avoidance system that is able to operate in all airspace without reliance on ground equipment. The TCAS concept encompasses a range of capabilities that include TCAS I, a low-cost, limited-perofrmance version, and TCAS II, which is intended...

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Traffic Alert and Collision Avoidance System (TCAS): a functional overview of minimum TCAS II
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