Straight Flight Path Research Articles

Identification of Spin Bowling Deliveries with an Advanced Smart Cricket Ball

The type of throw of a spin bowler can be analysed in the laboratory using a motion analysis system. However, there is still no method to determine the type of throw using other means and less effort. To solve this problem, we revised the traditional classification of spin bowling throws and analysed whether spin bowling throws are separate entities or continuous concepts. We used an advanced smart cricket ball with high-speed gyroscopes to record the bowling actions and mathematically transformed the spin axis from the ball coordinate system (BCS) to the global coordinate system (GCS). We developed a visualisation method to map spin bowling throws from the yaw and pitch angles of the ball’s spin axis in the GCS. We compared the data from the smart ball with the data from the motion analysis system and profiled seven spin bowlers using the new method. The results of this study have shown that spin bowling throws are continuous concepts and that all differences between the two spin axis measurement methods were within 95% limits of agreement. The Smart Ball is sufficiently accurate to measure the direction of the ball’s spin axis in the GCS and is therefore well suited for profiling spin bowlers. Hybrid deliveries between sidespin, top/backspin, and swerve maximise the deviations of the ball in flight from the straight flight path in all three planes of the GCS. Hybrid throws between sidespin, top/backspin, and spin maximise the ball’s deviation from the straight trajectory in all three planes of the GCS.

Compensating Image Distortions in a Commercial Reflectron-Type Atom Probe.

In atom probe tomography, the spatial resolution and accuracy of the data critically depend on the 3D reconstruction of the 2D detector data. Atom probes with a reflectron have an improved mass resolving power and must include a model of the imaging properties of the reflectron. However, for modern wide-angle reflectron instruments, these imaging properties are not trivial and need to be determined for the reflectron used. This is typically done by the instrument manufacturer, and due to the proprietary nature of the instrument design, the imaging properties are opaque to the user. In this paper, we provide a method to determine the imaging properties of a reflectron that can easily be carried out on commercial instrumentation. This method is used to provide the user with a transformation function from the provided detector data, which can already contain some corrections applied, to a virtual detector placed before the reflectron. From there on, 3D reconstructions can be carried out analogous to straight flight path instruments. Correction algorithms and reference data for Imago/CAMECA LEAP 3000, 4000, 5000, and 6000 series instruments are also provided.

A Modified High-Precision Imaging Algorithm Based on Imaging Plane Optimization with Minimum Entropy Applied to UAV SAR

The miniaturized and lightweight unmanned aerial vehicle synthetic aperture radar (UAV SAR) is gradually becoming a research hotspot. The motion errors of UAVs lead to a deviation from a straight flight path couple with an unknown elevation of the target area, which leads to a degradation in SAR image quality. To achieve high-precision SAR imaging results, external terrain elevation information should be utilized. However, such data are challenging to obtain and limited in accuracy. In response to this problem, a modified high-precision imaging algorithm based on imaging plane optimization with minimum entropy is proposed. The proposed algorithm makes good use of the nonlinear trajectory of the UAV, which is unfriendly to imaging. Then, the image entropy is taken into account as the evaluation metric to acquire an approximated optimization imaging plane. Finally, the BP imaging is performed on the optimization imaging plane. The proposed method does not rely on external terrain information. Instead, it makes full use of the non-linear trajectory of the UAV and autonomously generates the optimal imaging plane for different terrain areas. By doing so, it achieves high-precision imaging results. Simulations and actual measurements have validated the effectiveness and enhancement of the proposed method.

Multiple mechanisms mediate the suppression of motion vision during escape maneuvers in flying Drosophila

SummaryDuring voluntary behaviors, animals need to disable any reflexes that could interfere with the intended movements. With the optomotor response, flies stabilize a straight flight path by correcting for unintended deviations sensed as the panoramic motion of the surround. HS cells of the fly are thought to mediate optomotor responses to horizontal motion. During spontaneous flight turns, an efference copy acts on HS cells with the right sign to counteract the visual input elicited by the fly’s own behavior. Here, we investigated, whether looming-elicited turns in flying Drosophila have a similar effect on HS cells. We show that looming stimuli themselves can influence the processing of panoramic motion stimuli in HS cells and that an inhibitory efference copy suppresses excitatory motion responses during turns in both directions, but only in a subset of HS cells. Our findings support the notion that the processing of sensory information is finely tuned to behavioral context.

Three-Dimensional Atomically Resolved Analytical Imaging with a Field Ion Microscope

Abstract Atom probe tomography (APT) helps elucidate the link between the nanoscale chemical variations and physical properties, but it has a limited structural resolution. Field ion microscopy (FIM), a predecessor technique to APT, is capable of attaining atomic resolution along certain sets of crystallographic planes albeit at the expense of elemental identification. We demonstrate how two commercially available atom probe instruments, one with a straight flight path and one fitted with a reflectron lens, can be used to acquire time-of-flight mass spectrometry data concomitant with a FIM experiment. We outline various experimental protocols making the use of temporal and spatial correlations to best discriminate field-evaporated signals from the large field-ionized background signal, demonstrating an unsophisticated yet efficient data mining strategy to provide this discrimination. We discuss the remaining experimental challenges that need to be addressed, notably concerned with accurate detection and identification of individual field-evaporated ions contained within the high field-ionized flux that contributes to a FIM image. Our hybrid experimental approach can, in principle, exhibit true atomic resolution with elemental discrimination capabilities, neither of which atom probe nor FIM can individually fully deliver—thereby making this new approach, here broadly termed analytical field ion microscopy (aFIM), unique.

Model Predictive Trajectory Tracking for a Ground Vehicle in a Heterogeneous Rendezvous with a Fixed-Wing Aircraft

Abstract The maneuver of landing a fixed-wing unmanned aerial vehicle (UAV) autonomously on a moving ground platform requires precise spatial synchronization of both agents. Depending on the desired control strategy for the maneuver, the unmanned ground vehicle (UGV) must be capable to track the UAV’s trajectory robustly with respect to the ground plane even in the presence of disturbances such as wind gusts. In this paper, a linear model predictive trajectory tracking controller for a UGV based on a kinematic bicycle model is presented, assuming that the UAV aims at following a straight flight path with a given velocity. The vehicle model is discretized and linearized in each sampling step, resulting in a quadratic optimization problem which yields the optimal steering angle and motor current demand of the UGV. In the optimization problem, actuator constraints as well as hardware-related dead-times are taken into account. By constraining the yaw rate of the UGV, sideslip of the UGV is prevented, preserving the consistency of the kinematic model. Main requirements for the controller are the ability to allow sufficiently precise trajectory tracking with a longitudinal and lateral deviation of less than 0.5 m, i.e., within the dimensions of the landing platform in the given hardware setup, and real-time capability. Hardware-in-the-loop simulations and experimental results with a model-scale ground vehicle are presented that indicate the validity of the proposed control scheme.

Microlocal analysis of Doppler synthetic aperture radar

We study the existence and suppression of artifacts for a Doppler-based Synthetic Aperture Radar (DSAR) system. The idealized air- or space-borne system transmits a continuous wave at a fixed frequency and a co-located receiver measures the resulting scattered waves; a windowed Fourier transform then converts the raw data into a function of two variables: slow time and frequency. Under simplifying assumptions, we analyze the linearized forward scattering map and the feasibility of inverting it via filtered backprojection, using techniques of microlocal analysis which robustly describe how sharp features in the target appear in the data. For DSAR with a straight flight path, there is, as with conventional SAR, a left-right ambiguity artifact in the DSAR image, which can be avoided via beam forming to the left or right. For a circular flight path, the artifact has a more complicated structure, but filtering out echoes coming from straight ahead or behind the transceiver, as well as those outside a critical range, allows one to obtain an artifact-free image. Initially derived under a start-stop approximation widely used in range-based SAR, we show that some of these results are robust and hold under a more realistic approximation.

Analysis of Anemotactic Flight Tendencies of the Spotted Lanternfly (Lycorma delicatula) during the 2017 Mass Dispersal Flights in Pennsylvania

Video-recordings were made of adult spotted lanternflies, Lycorma delicatula, taking flight from apple trees in an orchard in northeast Pennsylvania in September, 2017 during a mass dispersal flight event involving thousands of adults. The trajectories of adults flying upwind in straight and level or gradually descending flight allowed them to traverse only up to ca. 40 m in a single flight-bout. Many did not make it to trees or bushes that were at even shorter distances than this and they landed in the grass. Flight tracks of 162 adults launching themselves into the wind from the upper branches of apple trees were video-recorded in plan view from below by a camera placed on the ground aimed straight up at the sky. The tracks were then digitized and analyzed using a triangle of velocities technique to determine the degree to which the adults were progressing in a directly upwind flight track, with the wind vector experienced by each adult calculated from the adults’ flight track itself. Average airspeeds of upwind-flying L. delicatula had been previously measured in another group of adults and shown to not vary with wind speed. The headings (direction of thrust) of adults in the video frames were determined by matching the image of the adult in each video frame with a template image of a pinned adult of a known distance from the camera and heading. Matching the body axis in this way works for this species because the adults flying in these elongated fairly straight flight paths did so with forewings spread out flat to the ground with little discernable roll. Having determined airspeed and heading plus ground speed and track for each set of images allowed the third side of the triangle of velocities — the wind velocity vector — to be calculated for each flying adult at whatever altitude or lateral location in the camera’s field of view it was flying. Adult L. delicatula were found to head upwind in flight at 10.7° off the wind line to produce resulting track angles of progression over the ground averaging 30.9° off the wind line due to this discrepancy between their headings and the wind velocities into which they were flying. The wind velocity vectors provided by a ground-based anemometer during the periods each adult was flying through the video frames deviated from the wind velocity vectors calculated using the triangle of velocities technique by nearly 22° and were 50% lower in wind speed than the calculated vectors taken at the higher altitudes and locations each adult was flying. The triangle of velocities technique might provide a new way of using certain species of insects as free-flying anemometers to take wind velocity readings at different heights and spatial locations that are not attainable through the use of ground-based anemometers.

Three Dimensional Intruder Closest Point of Approach Estimation Based-on Monocular Image Parameters in Aircraft Sense and Avoid

The paper deals with monocular image-based sense and avoid assuming constant aircraft velocities and straight flight paths. From very limited two dimensional image information it finally characterizes the whole three dimensional collision situation by estimating the time to closest point of approach, the horizontal relative distance and its direction and the vertical relative distance also. The distances are relative to the intruder aircraft horizontal and vertical sizes. The overall estimated relative distance is the closest between the two aircraft in three dimension. So finally, every important information can be extracted to be used in a collision decision. The applicability of the developed method is presented in software-in-the-loop simulation test runs. Several intruder size and speed values are considered together with trajectories covering the whole three dimensional space. The horizontal intruder flight directions relative to the own aircraft cover 360∘ and the intruder can come from below ar above also. Detailed evaluation and discussion of the results is also included. Finally, the missed detection rate results to be superior (below 3% in every test scenario) though the false alarm rate results a bit high between 7–14%.

How bumblebees use lateral and ventral optic flow cues for position control in environments of different proximity

Flying insects frequently navigate through environments of different complexity. In this study, buff-tailed bumblebees (Bombus terrestris L.) were trained to fly along tunnels of different widths, from 60 to 240 cm. In tunnel widths of 60 and 120 cm, bumblebees control their lateral position by balancing the magnitude of translational optic flow experienced in the lateral visual field of each eye. In wider tunnels, bumblebees use translational optic flow cues in the ventral visual field to control their lateral position and to steer along straight tracks. Our results also suggest that bumblebees prefer to fly over surfaces that provide strong ventral optic flow cues, rather than over featureless ones. Together, these strategies allow bumblebees to minimize the risk of collision and to maintain relatively straight flight paths in a broad range of environments.

Experimental aeromagnetic survey using an unmanned air system

Currently, Stratus Aeronautics is developing an unmanned aircraft system (UAS), called the Venturer, for aeromagnetic surveying. On 2 October 2013, in southern Alberta, Canada, an experimental survey of the UAS was conducted. Approximately 13 km of preprogrammed survey lines, along with calibration maneuvers, were flown, providing 45 minutes worth of data collection. The UAS was stable in flight and only required operator intervention for takeoff and landing. There was a + 2 m offset from the nominal altitude of 150 m, with variations of approximately ± 1.4 m. Deviations from a straight flight path were approximately ± 0.9 m along traverse lines and ± 25 m along tie-lines, the latter being affected mainly by crosswind. The noise envelope for the magnetic data acquired during the survey was approximately ± 0.05 nT, allowing a high-quality total-magnetic-intensity map to be created.

A new generic processing scheme for large baseline spaceborne bistatic SAR data imaging

Standard synthetic aperture radar (SAR) processors use analytically derived transfer functions that rely on the assumption of hyperbolic range histories of monostatic SARs with straight flight paths. The range histories for bistatic SARs are no longer hyperbolic and simple analytic transforms do not exist. In this article, a bistatic subsection hyperbolic range history (BS-HRH) model is proposed and based on it; a generic processing scheme for bistatic SAR imaging is given with which simple analytic transforms for standard monostatic SARs can still be applied. One-dimensional and two-dimensional signal-level simulations are done using the orbit parameters of Envisat and a classic pendulum-like bistatic configuration under different baselines. It is found that the proposed BS-HRH algorithm performs well for spaceborne bistatic SARs even with extreme bistatic configurations and/or very high azimuth resolution. Compared with the existing analytical ‘method of series reversion (MSR)’ and the numerical ‘NuSAR’ algorithm, easy implementation, high efficiency and accuracy, and mathematical simplicity are among the advantages of the proposed algorithm. The approach of BS-HRH has the potential to solve the general HRH-deviation problem for other new SARs with more complex imaging geometry.

Factors influencing ice formation and growth in simulations of a mixed‐phase wave cloud

In this paper, numerical simulations of an orographically induced wave cloud sampled in‐situ during the ICE‐L (Ice in Clouds Experiment ‐ Layer clouds) field campaign are performed and compared directly against the available observations along various straight and level flight paths. The simulations are based on a detailed mixed‐phase bin microphysics model embedded within a 1‐D column framework with the latest parameterizations for heterogeneous ice nucleation and an adaptive treatment of ice crystal growth based on the evolution of crystal habit. The study focuses on the second of two clouds sampled on 16th November 2007, the in‐situ data from which exhibits some interesting and more complex microphysics than other flights from the campaign. The model is used to demonstrate the importance of both heterogeneous and homogeneous nucleation in explaining the in‐situ observations of ice crystal concentration and habit, and how the ability to isolate the influence of both nucleation mechanisms helps when quantifying active IN concentrations. The aspect ratio and density of the simulated ice crystals is shown to evolve in a manner consistent with the in‐situ observations along the flight track, particularly during the transition from the mixed‐phase region of the cloud to the ice tail dominated by homogeneous nucleation. Some additional model runs are also performed to explore how changes in IN concentration and the value of the deposition coefficient for ice affect the competition between heterogeneous and homogeneous ice formation in the wave cloud, where the Factorial Method is used to isolate and quantify the effect of such non‐linear interactions. The findings from this analysis show that the effect on homogeneous freezing rates is small, suggesting that any competition between the microphysical variables is largely overshadowed by the strong dynamical forcing of the cloud in the early stages of ice formation.

Processing of Bistatic SAR Data From Quasi-Stationary Configurations

Standard synthetic aperture radar (SAR) processing algorithms use analytically derived transfer functions in the 2D frequency and range/Doppler domains. These rely on the assumption of hyperbolic range histories of monostatic SARs with straight flight paths. For bistatic SARs, the range histories are no longer hyperbolic, and simple analytic transforms do not exist. This paper offers two solutions for bistatic SAR data processing under the restriction of quasi-stationarity, i.e., sufficiently equal vectors of transmitter and receiver. 1) Moderately bistatic configurations can be handled satisfactorily by using hyperbolic range functions with a modified parameter, which is a solution already well known for the accommodation of curved orbits in the monostatic case. This velocity approach is shown to be of surprising range of validity even for pronounced bistatic situations. It is not to be confused with the monostatic flight path approximation, which is shown to be inapplicable for any practical case. 2) With increasing separation of transmitter and receiver, the equivalent approximation deteriorates. To cope with extreme bistatic configurations, a general approach named NuSAR is proposed, where the involved transfer functions are replaced by numerically computed ones. This paper describes how the transfer functions are computed from the given orbits and the shape of the Earth surface. In any of these two cases, the bistatic SAR data can be processed by standard SAR processors; only the conventional transfer functions need to be replaced. Neither are there time-domain prefocusing or post focusing steps required nor complicated mathematical expansions involved. The presented algorithms are also applicable to very high resolution wide-swath (or squinted) SARs on curved orbits.

Free-flight odor tracking in Drosophila is consistent with an optimal intermittent scale-free search.

During their trajectories in still air, fruit flies (Drosophila melanogaster) explore their landscape using a series of straight flight paths punctuated by rapid 90° body-saccades [1]. Some saccades are triggered by visual expansion associated with collision avoidance. Yet many saccades are not triggered by visual cues, but rather appear spontaneously. Our analysis reveals that the control of these visually independent saccades and the flight intervals between them constitute an optimal scale-free active searching strategy. Two characteristics of mathematical optimality that are apparent during free-flight in Drosophila are inter-saccade interval lengths distributed according to an inverse square law, which does not vary across landscape scale, and 90° saccade angles, which increase the likelihood that territory will be revisited and thereby reduce the likelihood that near-by targets will be missed. We also show that searching is intermittent, such that active searching phases randomly alternate with relocation phases. Behaviorally, this intermittency is reflected in frequently occurring short, slow speed inter-saccade intervals randomly alternating with rarer, longer, faster inter-saccade intervals. Searching patterns that scale similarly across orders of magnitude of length (i.e., scale-free) have been revealed in animals as diverse as microzooplankton, bumblebees, albatrosses, and spider monkeys, but these do not appear to be optimised with respect to turning angle, whereas Drosophila free-flight search does. Also, intermittent searching patterns, such as those reported here for Drosophila, have been observed in foragers such as planktivorous fish and ground foraging birds. Our results with freely flying Drosophila may constitute the first reported example of searching behaviour that is both scale-free and intermittent.

On the Probability of Collision Between Climbing and Descending Aircraft

The probability of coincidence (which is a upper bound for the probability of collision) is calculated for aircraft on arbitrary straight flight paths with constant speed: either aircraft may be climbing, descending, or in level flight and they may cross at any angle. Gaussian statistics with equal or distinct rms deviations for the two aircraft are used to calculate the probability of coincidence as a function of time in the first instance, with a correction factors for 1) the more accurate generalized error distribution; 2) asymmetry in vertical position errors. The time and distance of closest approach are used to calculate the position for maximum probability of coincidence. The cumulative probability of coincidence over all time is calculated, and expressed as a probability of coincidence per unit distance and per unit time: the latter is compared with the International Civil Aviation Organization target level of safety. Examples are given of the effect on coincidence probabilities of the seven parameters of the problem: velocities and glide slopes of each aircraft, crossing angle in horizontal projection, vertical separation, and rms position error.

EFFECTS OF ATTRACTION RADIUS AND FLIGHT PATHS ON CATCH OF SCOLYTID BEETLES DISPERSING OUTWARD THROUGH RINGS OF PHEROMONE TRAPS

Results were analyzed from six previous studies in which marked bark and ambrosia beetles, Ips typographus, I. paraconfusus, and Trypodendron lineatum (Coleoptera: Scolytidae), were released at the center of concentric rings of pheromone traps. Assuming nearly straight flight paths, a “filtering” equation model predicts recapture percentages on several trap rings of specified radii, trap numbers, and effective attraction radius (EAR) of a pheromone trap. Equations were used to calculate recapture percentages on concentric trap rings as a function of increasing EAR and gave polynomial relationships for each ring with terms equal to the number of inner rings plus one. Results were confirmed by computer simulations. Filtering equations were iterated with increasing EAR values to find one that gave a recapture percentage for the innermost trap ring that matched the field results. The estimated EAR for a synthetic pheromone bait of I. typographus was similar in five tests (range 1.39–1.78 m), but in two other tests was larger (3.27 and 15.9 m). The EAR for pheromone of 75 male I. paraconfusus in ponderosa pine logs ranged from 0.35 to 34.5 m (mean of 4.7 m) and was generally larger for previously pheromone-responding beetles than for freshly emerged ones. For T. lineatum, the EAR of lineatin-baited traps at 100-m radius was 2.43 m. Recaptures of I. typographus were reasonably predicted by the estimated EARs in the filtering model. To obtain perfect fits, another model assumed the EAR could vary with ring radius (dispersal distance) and found that the EAR for I. typographus decreased with dispersal distance in four experiments, but increased or was variable in two others. However, in I. paraconfusus and T. lineatum, the EAR increased with dispersal distance. Simulations that varied combinations of the EAR and random angles of maximum turning (AMT) of beetles stepwise showed that a nearly straight flight path for I. typographus explained observed catches on trap rings best, while a higher AMT of 36° was better to explain catches of T. lineatum. Simulations show that catch per trap ring in relation to radial distance can be influenced by the beetle's AMT (still unobserved in the field). A conceptual model of dispersal and host selection in “aggressive” bark beetles with regard to pioneer and joiner colonization strategies is presented.

Three-Dimensional Air Circulation in a Squall Line from Airborne Dual-Beam Doppler Radar Data: A Test of Coplane Methodology Software

The detailed structure of a tropical squall line observed in central Florida was investigated from an airborne dual-beam Doppler radar, pointing respectively fore and aft. This allowed dual-Doppler observations from a straight flight path in a way similar to the coplane sampling technique proposed for two ground-based Doppler radars and for which the authors had developed an elaborate method in order to obtain a reliable wind estimation. The application of this analysis method to the airborne dual-beam radar observations is discussed, along with the basic requirements due to the specific airborne data sampling. The retrieved three-dimensional airflow structures within the convective part of the squall line are found to be quite consistent with those previously documented from ground-based radars, such as the convective-scale downdrafts sustaining a well-marked rear-to-front flow or the convective updrafts associated with the front-to-rear flow at mid-to-upper levels and that detrain into the rear part of the squall-line system. Moreover, it is found that the coplane analysis provides a more regular description of the airflow than the conventional Cartesian analysis. The suitability of the coplane approach is also examined by quantifying the uncertainty due to geometric errors that affect the accuracy of the beam pointing.

Visibility with a moving point of view

We investigate three-dimensional visibility problems in which the viewing position moves along a straight flightpath. Specifically we focus on two problems: determining the points along the flightpath at which the topology of the viewed scene changes, and answering ray-shooting queries for rays with origin on the flightpath. Three progressively more specialized problems are considered: general scenes, terrains, and terrains with vertical flightpaths.

Optimisation of the Flight Speed of the Little, Common and Sandwich Tern

Optimisation of the Flight Speed of the Little, Common and Sandwich Tern