Airborne EM footprints

As frequency-domain airborne electromagnetic (AEM) studies move towards more detailed assessments of the near-surface, the behaviour of system footprints, and hence the spatial averages involved in the measurement, becomes important. Published estimates suffer from two main limitations: first, they are based on perfectly conducting, thin sheet models and, secondly, they are system specific. The present study is a revision of footprint estimates based on (i) a finitely conducting half-space and (ii) an at-surface scale estimate that uses the spatial equivalent of the conventional electromagnetic skin depth. In order to remove the system dependence, a transmitter footprint is defined in terms of electromagnetic skin distance. Only the limiting cases of vertical and horizontal magnetic dipole sources then require analysis. Electromagnetic skin distances, two for each of the coil orientations, are defined. The revised definition makes it possible to investigate the footprint behaviour of both towed-bird and fixed-wing AEM systems over an altitude range from 20 to 100 m. The footprint/altitude ratio has a primary dependence on altitude and a secondary dependence on both resistivity and frequency. The analysis covers a frequency range from 1 to 100 kHz and results are presented for two specific resistivity values that represent conductive (10 Ωm) and resistive (1000 Ωm) environments. The revised footprint parameters display a quasi-linear behaviour with altitude, particularly for mid-range frequencies. This behaviour enables the coefficients of linear, least-squares relationships to be obtained, thus assisting with the prediction of footprint estimates for survey planning and interpretation. A comparison of the new estimates with published values suggests that existing footprint values for a vertical magnetic dipole should be revised downward

3D modelling of near-surface, environmental effects on AEM data

This study considers the three-dimensional (3D) modelling of compact, at-surface conductive bodies on frequency domain airborne electromagnetic (AEM) survey data. The context is the use of AEM data for environmental and land quality applications. The 3D structures encountered are typically conductive, of limited thickness (<20 m) and form ‘point’ source locations carrying potential environmental risk. The scale of such bodies may generate single-profile, ‘bulls-eye’ anomalies. In attempts to recover geological information, such anomalies may be considered to represent noise. In environmental AEM, the correct interpretation of such features is important. The study uses a combination of theoretical models and trial-fixed-wing survey data obtained in populated areas of the UK. Scale issues are discussed in terms of the volumetric footprints of the induced electric field generated by systems flown at both low and high elevation. One of the primary uses of AEM survey data lies in the assessment of conductivity maps. These are typically obtained using one-dimensional (1D) conductivity models at individual measurement points. In order to investigate the limitations of this approach, 3D modelling of conductive structures with dimensions less than 350×350 m and thicknesses extending to 20 m has been carried out. A 1D half space inversion of the data obtained at each frequency is then used to assess the behaviour of the spatial information. The results demonstrate that half space conductivity values obtained over compact 3D targets generally provide only apparent conductivity results. For thin, at-surface bodies, conductivity values are biased to lower values than the true conductivity except at high frequency. The spatial perturbation to both coupling ratios and 1D conductivity models can be laterally extensive. The results from 3D modelling indicate that the use of horizontal derivatives applied to the conductivity models offers enhanced edge detection. The practical application of such derivatives to both regional- and local-scale survey data is presented.. The special case of a near-surface, metallic pipeline has been modelled. The problem constitutes an inductive limit (current gathering) response in which the perturbation is largely confined to the in-phase coupling ratios. The main perturbations, in data and conductivity models, are within about 40 m of each side of the pipeline. The maximum perturbation to the conductivity model is only a factor of 1.5 above background. Detailed survey data across a former compact landfill (about 100×100 m) are used to compare the model behaviour predicted by the 3D modelling with survey results. The survey, conducted at two separate altitudes, provides a demonstration of 3D effects on 1D survey models as a function of frequency and elevation. Although the nature of the landfill materials and their location are not known precisely, the mapping information appears realistic

Predictive Features of a Cockpit Traffic Display: A Workload Assessment

Eighteen pilots flew a series of traffic avoidance maneuvers in an experiment designed to assess the support offered and workload imposed by different levels of traffic display information in a free flight simulation. Three display prototypes were compared which differed in traffic information provided. A BASELINE (BL) display provided current and (2nd order) predicted information regarding ownship and current information of an intruder aircraft, represented on lateral and vertical displays in a coplanar suite. An INTRUDER PREDICTOR (IP) display, augmented the baseline display by providing lateral and vertical prediction of the intruder aircraft. A THREAT VECTOR (TV) display added to the IP display a vector that indicates the direction from ownship to the intruder at the predicted point of closest contact (POCC). The length of the vector corresponds to the radius of the protected zone, and the distance of the intersection of the vector with ownship predictor, corresponds to the time available till POCC or loss of separation. Pilots time shared the traffic avoidance task with a secondary task requiring them to monitor the top of the display for faint targets. This task simulated the visual demands of out-of-cockpit scanning, and hence was used to estimate the head-down time required by the different display formats. The results revealed that both display augmentations improved performance (safety) as assessed by predicted and actual loss of separation (i.e., penetration of the protected zone). Both enhancements also reduced workload, as assessed by the NASA TLX scale. The intruder predictor display produced these benefits with no substantial impact on the qualitative nature of the avoidance maneuvers that were selected. The threat vector produced the safety benefits by inducing a greater degree of (effective) lateral maneuvering, thus partially offsetting the benefits of reduced workload. The three displays did not differ in terms of their effect on performance of the monitoring task, used to infer head-down time, nor in the extent of vertical or airspeed maneuvering. The results are discussed in terms of their implications for 19 cognitive engineering design features

Aspects of Synthetic Vision Display Systems and the Best Practices of the NASA's SVS Project

NASA s Synthetic Vision Systems (SVS) Project conducted research aimed at eliminating visibility-induced errors and low visibility conditions as causal factors in civil aircraft accidents while enabling the operational benefits of clear day flight operations regardless of actual outside visibility. SVS takes advantage of many enabling technologies to achieve this capability including, for example, the Global Positioning System (GPS), data links, radar, imaging sensors, geospatial databases, advanced display media and three dimensional video graphics processors. Integration of these technologies to achieve the SVS concept provides pilots with high-integrity information that improves situational awareness with respect to terrain, obstacles, traffic, and flight path. This paper attempts to emphasize the system aspects of SVS - true systems, rather than just terrain on a flight display - and to document from an historical viewpoint many of the best practices that evolved during the SVS Project from the perspective of some of the NASA researchers most heavily involved in its execution. The Integrated SVS Concepts are envisagements of what production-grade Synthetic Vision systems might, or perhaps should, be in order to provide the desired functional capabilities that eliminate low visibility as a causal factor to accidents and enable clear-day operational benefits regardless of visibility conditions

Effect of Multiple Range Rings VS. a Single Range Ring on Pilot Perception of Vertical Separation on a Cockpit Display of Traffic Information

The purpose of this study was to determine the effectiveness of both a two and four mile range ring versus a single three mile range ring on pilot\u27s perception of future vertical separation as viewed on a cockpit display of traffic information. The subjects consisted of 30 volunteer pilots from Embry-Riddle Aeronautical University and the surrounding Daytona Beach, Florida area. The simulation of a cockpit display of traffic information was generated using SuperCard® Version 1.6 software and a Macintosh IIx® personal computer. Eighty unique scenarios were monitored by the pilots in which they determined, as early as possible, what the vertical miss distance would be when a single intruder passed the subject\u27s aircraft (ownship). The pilots\u27 perceived vertical miss distance (error) and decision time were compiled for each scenario. The use of multiple range rings required significantly more time for the pilots\u27 to choose a vertical miss distance versus a single range ring. The use of multiple range rings had no significant effect on error versus the single range ring

Design of an Ecological Vertical Separation Assistance Cockpit Display

A tactical navigation support tool was designed to effectively deal with conflict situations in the vertical plane, while preserving travel freedom as much as possible. Based on Ecological Interface Design principles, the Vertical Separation Assistance Display is developed as an extension to the existing Vertical Situation Display. Functional information is presented via overlays that show pilots how their vertical maneuvering possibilities are constrained by ownship performance, and by limits imposed by surrounding traffic. A questionnaire-based evaluation shows that the ecological overlays considerably improved pilot traffic awareness in vertical conflict situations

EPIC 220204960: A Quadruple Star System Containing Two Strongly Interacting Eclipsing Binaries

We present a strongly interacting quadruple system associated with the K2 target EPIC 220204960. The K2 target itself is a Kp = 12.7 magnitude star at Teff ~ 6100 K which we designate as "B-N" (blue northerly image). The host of the quadruple system, however, is a Kp = 17 magnitude star with a composite M-star spectrum, which we designate as "R-S" (red southerly image). With a 3.2" separation and similar radial velocities and photometric distances, 'B-N' is likely physically associated with 'R-S', making this a quintuple system, but that is incidental to our main claim of a strongly interacting quadruple system in 'R-S'. The two binaries in 'R-S' have orbital periods of 13.27 d and 14.41 d, respectively, and each has an inclination angle of >89 degrees. From our analysis of radial velocity measurements, and of the photometric lightcurve, we conclude that all four stars are very similar with masses close to 0.4 Msun. Both of the binaries exhibit significant ETVs where those of the primary and secondary eclipses 'diverge' by 0.05 days over the course of the 80-day observations. Via a systematic set of numerical simulations of quadruple systems consisting of two interacting binaries, we conclude that the outer orbital period is very likely to be between 300 and 500 days. If sufficient time is devoted to RV studies of this faint target, the outer orbit should be measurable within a year.Comment: 20 pages, 18 figures, 7 tables; accepted for publication in MNRA

Evaluation of Perspective and Coplanar Cockpit Displays of Traffic Information to Support Hazard Awareness in Free Flight

We examined the cockpit display representation of traffic, to support the pilot in tactical planning and conflict avoidance. Such displays may support the "free flight" concept, but can also support greater situation awareness in a non-free flight environment. Two perspective views and a coplanar display were contrasted in scenarios in which pilots needed to navigate around conflicting traffic, either in the absence (low workload) or presence (high workload) of a second intruder aircraft. All three formats were configured with predictive aiding vectors that explicitly represented the predicted point of closest pass, and predicted penetration of an alert zone around ownship. Ten pilots were assigned to each of the display conditions, and each flew a series of 60 conflict maneuvers that varied in their workload and the complexity of the conflict geometry. Results indicated a tendency to choose vertical over lateral maneuvers, a tendency which was amplified with the coplanar display. Vertical maneuvers by the intruder produced an added source of workload. Importantly, the coplanar display supported performance in all measures that was equal to or greater than either of the perspective displays (i.e., fewer predicted and actual conflicts, less extreme maneuvers). Previous studies that have indicated perspective superiority have only contrasted these with UNIplanar displays rather than the coplanar display used here

Designing a Cockpit Functionalities Architecture for Trajectory Based Operations

Trajectory Based Operations (TBO) will require new procedures and systems to achieve a suitable automation of air traffic operations. Procedures and systems for automated operations are closely related and therefore frequently they need to be modeled in a combined way. Our group is currently employing recent agent-oriented methodological approaches to obtain conceptual models about TBO scenarios. Conceptual models define roles of air traffic entities as well as their interactions together with a detailed description of the entities’ architecture and dynamic behaviour. In this paper we present a cockpit functionality architecture built upon a methodological analysis and design of a TBO scenario as a multi-agent system. The proposed design has the advantage of mapping to an executable model for analytical simulation of TBO concepts and its modular architecture allows for a progressive integration of additional underlying models with specific functionalities