Sight Angle Research Articles

Guidance Algorithm Design: A Nonlinear Inverse Approach

The design of a missile guidance algorithm valid for any initial missile and target orientation is described. The limitations of proportional navigation- (PN-) or line-of-sight rate-based guidance for this problem are pointed out. Design heuristics are explained, and general guidelines for the synthesis of guidance algorithms are stated. It is shown thatthedesign of an algorithm valid forany initial missileand target orientation leadsto a nonlinearinverse problem. Standard geometric methods for solving nonlinear inverse problems are adapted to derive a new class of algorithms based on the relative heading error angle (RHEA). Examples of RHEA algorithms are then discussed and compared with PN guidance for different engagement scenarios. am = missile acceleration at = target acceleration Vm = missile speed Vt = target speed Xm, Ym = dimensional missile coordinates Xt, Yt = dimensional target coordinates xm, ym = nondimensional missile coordinates xt, yt = nondimensional target coordinates ®m = nondimensional missile acceleration ®t = nondimensional target acceleration µ = line of sight (LOS) angle µ 0 = LOS rate o = target to missile velocity ratio Ω = nondimensional distance to go ? = nondimensional time Âm = missile heading angle Ât = target heading angle A = relative heading error angle

Study of the Magnetic Field of the Galaxy using Correlation Functions of the Intensity of Synchrotron Background Radio Emission

The possibility to study magnetic field of the Galaxy calculating correlation or structure functions of synchrotron background radio emission have been known long ago (Kaplan and Pikel'ner (1963); Getmantsev (1958)). But this method had not been as popular as other methods of magnetic field studies. However theoretical calculations made by Chibisov and Ptuskin (1981) showed that correlation functions of intensity of synchrotron background radio emission can give a lot of valuable information about galactic magnetic fields because of the intensity of synchrotron background radio emission depends on H⊥. According to this theory correlation C(θ, φ) and structure S(θ, φ) functions of intensity, as functions of angular separation θ between two lines of sight and position angle φ on the sky between this two lines of sight, can be presented as a sum of isotropic (not dependent from angle φ) and anisotropic parts:

The angle-of-sight signature for two-dimensional shape analysis of manufactured objects

A new two-dimensional (2D) shape-encoding scheme is introduced which is based on the idea of the angle-of-sight (AOS). Using this scheme, a shape can be efficiently transformed into a one-dimensional (1D) signature by recording the AOS vs. distance of each boundary point with respect to a shape-specific chord-of-sight (COS). The COS is selected by using an extension of the notion of shape boundary, to the idea of shape-specific points and the characteristic ellipse (CE). The AOS signature has many important properties including: it is information-preserving and thus unique, it does not require boundary smoothing; it has its own selectable smoothing property; it can provide a set of multi-scale representations by means of a simple operation; it is transformation-invariant; it is defined at all points; it preserves symmetries. As well, for matching purposes, a two-level matching process is proposed using a global measure (the eccentricity of the CE of a shape) and a dissimilarity measure based on the AOS signature. The encoding and matching techniques developed have been tested with 35 manufactured objects. The results obtained show that the AOS signature and the two-level-matching technique are quite effective and reliable for the recognition of 2D shapes of typical manufactured objects.

On evidence for quasi-parallel and quasi-perpendicular acceleration in supernova remnants

An attempt is made to determine whether or not the structure of supernova remnant shells is dependent on the angle between the line of sight and the Galactic magnetic field and if this structure can be explained either by quasi-parallel or quasi-perpendicular acceleration. The method used to determine the line of sight angles to the magnetic field is described. A model for the emissivity of a supernova remnant is developed.

Maximizing the Minimum Sight Angle of a Set of Shapes

Abstract A set of shapes is located in the plane. From each point in the plane, outside all shapes, a sight angle of that shape is defined. Procedures for finding the location of a point in the plane that maximizes the minimal sight angle of all shapes are presented. Some extensions to the problem are discussed and computational results reported.

Residence time distributions in extrusion cooking. Part I: Coincidence detection of radiotracer

A method suitable for the measurement of residence time distributions in food extruders based on radiotracer techniques has been improved by the introduction of a coincidence detection system which replaces the single-detector system with its asymmetrical sight angle of detection. The major advantage of the new system is the better resolution due to minimization of the sight angle. The influence of the detector arrangement on the residence time distribution curves for a single-screw extruder was measured and is discussed with the help of a residence time distribution model. 64Cu was used as the tracer.

MU radar observations of the aspect sensitivity of backscattered VHF echo power in the troposphere and lower stratosphere

By using the fast beam steerability of the MU radar, we have studied the characteristics of the aspect sensitivity of the VHF backscattered echo power in the troposphere and lower stratosphere. The tropopause clearly divides the altitude range into regions with and without large aspect sensitivity. In the stratosphere, large aspect sensitivity occurs in the entire altitude region and is clearly correlated with the echo power received in the vertical direction. From investigation of the Doppler spectra, it is found that the aspect sensitivity of the echo power is correlated with the zenith angle dependence of the spectral width. Fairly large aspect sensitive echoes are also received from intense scattering layers in the troposphere, although their time‐height variation is large. Because of the large aspect sensitivity of the stratospheric echo power, the effective zenith angle of the antenna beam is smaller than the bore sight angle, so that the horizontal wind velocity can not be estimated correctly from the radial wind velocity measurements done at small zenith angles.

Preferred line of sight angle.

Abstract Recent experiments with 16 male and 16 female subjects indicated that they like to look down rather steeply at an average of −29° below horizontal, s.d. 11·6°, when sitting with trunk and head upright. This angle is steeper when the visual target is at 0·50 m distance (−33°±11·3°) but flatter when the target is at 1·00 m (−24° ± 10·4°). When head and trunk are reclined to 105° behind horizontal, the overall angle of the preferred line of sight is reduced to −20° ±11·7° below horizontal, with −23° (± 12·5°) at 0·5 m and −16° (±9·6°) below horizontal at 1·0 m target distance. These preferred visual angles did not depend on the visual task. The finding that people look down much more steeply than listed in most human engineering design guides has obvious implications for the layout of workplaces where the task has a strong visual component, e.g. at computer workstations.

A simple model of light penetration into row crops

A simple model of light penetration into row crops was derived by considering the projections of the foliage elements to be confined to a potentially-shaded region ( R ∗ ) of a horizontal plane subtending the canopy. Individual plants were modelled as optionally truncated ellipsoids. The extent and area of R ∗ were estimated from the extent of the ellipsoids and their distribution on the soil surface in relation to the position of the sun. Uniform spatial distributions of projected foliage elements between the sun and R ∗ , and empirical, ellipsoidal distributions were appraised. The ellipsoidal distributions were based on the structure of the plants comprising the canopies. Apart from crops with extreme gradients in vertical distribution of leaf area density, appraisal against a relatively complex numerical method showed the simple model incorporating ellipsoidal distributions of foliage over R ∗ reliably estimated profiles of light penetration into a range of theoretical crops with contrasting structures. The simple model accounts for differences in extent of individual plants in a readily envisaged manner, for distinct and overlapping plants within rows, and for differences in light penetration attributable to angle of sight. Canopy light interception may be analysed in terms of the light intercepted by the isolated plants constituting the canopy, the extent of competition for light over R ∗ , and the extent of light penetration direct to the soil surface through failure to intercept the canopy volume.

Line-of-sight reconstruction for faster homing guidance

A novel way to generate the signal required for homing guidance is to reconstruct the line of sight angle by combining seeker boresi ht error with an integrated rate gyro signal (1.2,3,1,5). The paper shows that line-of-sight (LQS) reconstruction allows reduced stabilization loop gain requirements over other guidance implementations. For a given stabilization loop gain, faster guidance system time constants can be achieved with LQS reconstruction, thus enabling the guidance system to achieve more accurate hominq than other implementations.

Transit Sagging of Conductors Using a Calculated Angle of Sight

Transit Sagging of Conductors Using a Calculated Angle of Sight

Transit Sagging of Conductors using a Calculated Angle of Sight

A method is developed to compute a transit vertical angle for the accurate sagging of long spans of aerial cables. The computation method is well suited to hand-held programmable calculators and allows the use of convenient transit locations.

Computer simulation of spatial filtering of modes by vertical array steering and double symmetrical angles of sight in shallow water propagation

A method is proposed for angular filtering for a selected normal mode by means of a steered array. Examples are given for spatial filtering by a single angle of sight and by association of the symmetrical angle of sight. Calculations were made for the particular case corresponding to previous experiments. Identity between the spatial filtering by amplitude shading with functions of one of the normal modes and by electronic steering with phase-shifters is demonstrated. Possibilities for modal spectroscopy and adaptive filtering are investigated.

Simplified computation of synthetic spectra in the far-infrared

A simplified computation method is suggested for determining the spectral luminance from the stratosphere, observed in the far-infrared. The spectral range concerned lies between 10 and 200 cm −1. Observations are conducted from balloon and satellite altitudes and are aimed at the terrestrial limb. The calculations are carried out for the same height and sight angle conditions as in recent experiments. The synthetic spectra and measured spectra are compared. The computation parameters are optimized and the computation times are discussed.

Interaction of Single Tobacco Plants With Direct-Beam Light

The interaction of single plants of tobacco with direct-beam light was investigated using coordinate data describing the three-dimensional display of foliage. The projection of unit leaf area of single plants showed little variation with either plant size or azimuth angle of sight but showed a major dependence on the zenith angle. In contrast, the beam-lit area of foliage varied with each of these factors. Zenith angle also had the largest effects on the distribution of beam-lit foliage area with respect to the leaf-beam angle. These variables were also estimated with a model which took account of the basic structural features of the plants. The assumption of a uniform distribution of the leaf projections on the plane normal to the beam led to systematic errors in estimates of the proportion of beam-lit foliage. These deviations were used for estimates of an empirical index of the dispersion of the projections of the elements of foliage. The index varied with plant size and zenith angle of sight. Satisfactory estimates of the projections of unit leaf area and of distributions of the beam-lit foliage with respect to the leaf-beam angle were obtained from the model orientation distributions and assuming that foliage intercepts light in proportion to its frequency in the orientation distributions. Results are discussed in terms of changes in the structure of the plant associated with growth and development.

Observations of coastal water surface currents using an airborne inertial sighting system

This paper describes the use of an inertial sighting system for measuring the positions of surface water features from an aircraft. Sight angle and navigation data for any target sighted by the system operator during flight are recorded and can later be used to compute the target's position to an accuracy of about 10 m. The system makes use of a standard inertial navigation unit. The drift errors inherent in these units are corrected by making periodic sightings of reference targets. The system also has the capability of recording data from a variety of other airborne sensors. This paper describes the accuracy and limitations of the system and discusses examples of measurements of position and movement of surface water features and drogues.

Earth radiation model for infrared horizon sensor applications

The concept of equivalent atmospheric path length as viewed from an orbiting satellite is developed from a basic consideration of the slant path line of sight to the region near the horizon. The concept is shown to be pertinent to the selection of a suitable infrared wavelength band for horizon detection as applied to attitude control of an orbiting satellite. A method of determining the radiation envelope as a function of line of sight angle, θ, and spectral wavelength band is described. Some conclusions are drawn that indicate the radiance levels to be expected and the wavelength bands that should yield the most discrete earth-sky interface to be sensed.

Utilization of Desirable Seating Areas in Relation to Screen Shapes and Sizes and Theater Floor Inclinations<!--<xref ref-type="fn" rid="fn110.5594_J05557">*</xref>-->

The aim of this paper is to establish a relation between the bodily posture of the viewer, the size and shape of the picture, and the architectural form of the theater in all its details. The present type of theater floor is compared with the reversed type described in a previous paper in order to show how the latter type of floor permits placing a greater number of seats within the desirable seating areas than the present type. An analysis is made also of the effect of reversing the floor on the ability of the viewer to assume a comfortable bodily posture. Definite angles of sight specified by the various tilts of chair backs found necessary for comfortable posture are shown. Several forms of theaters of various seating capacities and screen sizes are described in order to show the broad application of the theories involved in reversing the pitch of the orchestra floor.