NASA Technical Memorandum 81278 USAAVRADCOM TR 81-A-8 Characteristics of Flight Simulator Systems (NASA-TM-81278) CHARACTERISTICS OF FLIGHT N81-21060 SIMULATOR VISUAL SYSTEflS (NASA) 89 p HC A05/HF JU>1 CSCL 01C Unclas G3/05 42058 April 1981 United States Aviation Research (\JASA and Development National Aeronautics and Command Space Administration NASA Technical Memorandum 81278 USAAVRADCOM TR 81-A-8 Characteristics of Flight Simulator Visual Systems Irving C. Statler, Editor, Aeromechanics Laboratory AVRADCOM Research and Technology Laboratories Ames Research Center, Moffett Field, California NASA National Aeronautics and United States ArmV Space Administration Aviation Research and Development Ames Research Center Command Moffett Field. California 94035 PREFACE The Flight Mechanics Panel (FMP) of the Advisory Group for Aerospace Research and Development has maintained a continuing involvement in assessing the fidelity of aircraft simulation. In keeping with this continuing interest and in recognition of the need for a common method of assessing motion system charac- teristics, the FMP, in October 1976, established Working Group 07 on "The Dynamic Characteristics of Flight _Simulator_Hotij3jiJystenis_.^_ThaOlorkjjig Group was charged with definingjand^determining metrics of the hardware-delivered performance of the various degrees of freedom of~th>Tiotioh~systenvr"its~report~(Ref:r~l') was issued in September 1979. As a follow-on activity to FMP WG-07, FMP WG-10 was established in March 1979 to consider "The Charac- teristics of Flight Simulator Visual Systems." This Working Group was charged with identifying and defining the physical parameters of the flight simulator visual display that characterize it and determine its fidel- ity. At its first meeting on 26-27 April 1979 at the British Ministry of Defense, London, the Working Group reviewed the terms of reference, defined in more detail its projected scope, and agreed upon three broad categories within which all of the parameters could be identified. At its second meeting at the Hochschule der Bundeswehr, Neubiberg, Germany, on 30-31 August 1979, the members reviewed the identification and defi- nitions of the engineering parameters, agreed upon a format for their presentations, and initiated the study of the importance of these parameters to the performance of a flight task and the degree to which this impor- tance is known. The third meeting of the Group took place on 21-23 April 1980 at the Ames Research Center, NASA, Moffett Field, California. At that meeting, the results of the study efforts of the members were dis- cussed and put into formal context as definitive characteristics. Problems of measurement were discussed and alternatives were reviewed. Tentative agreements were reached on statements regarding the relative importance of the parameters. All members were asked to consider the unknowns in this area and to recommend, prior to the next meeting, the research needed. At its final meeting on 24-26 September 1980 at AGARD Head- quarters, Paris, the draft of the Group's final report was reviewed and approved. WORKING GROUP 10 - MEMBERSHIP Chairman and Editor: Ir. C. J. Jansen (Sept 80 - Mar 81) Dr. Irving C. Statler National Aerospace Laboratory (NLR) Director, Aeromechanics Laboratory P.O. Box 90502 U.S. Army Research and Technology 1006 BM Amsterdam, Netherlands Laboratories (AVRADCOM) Ames Research Center, M/S 215-1 Ir. W. P. Koevermans (Apr 79 - Aug 80) Moffett Field, CA 94035, U.S.A. National Aerospace Laboratory (NLR) P.O. Box 90502 1006 BM Amsterdam, Netherlands Technical Secretary: Mr. John B. Sinacori Dr. Conrad L. Kraft 0. B. Sinacori Associates Boeing Aerospace Company P.O. Box 1043 P.O. Box 3999 Hollister, CA 95023, U.S.A. Org. 2-3541, M/S 8H-04 Seattle, WA 98124, U.S.A. Mr. A. G. Barnes Simulator Manager Mr. K. J. Staples British Aerospace Flight Research Division Warton Aerodrome Royal Aircraft Establishment Preston, Lanes. PR4 1AX, United Kingdom Bedford MK41 6AE, Beds., United Kingdom Mr. John C. Dusterberry Mr. D. Suveran Research Assistant to the Director Simulation Department Ames Research Center, M/S 200-10 CEV/ISTRES Moffett Field, CA 94035, U.S.A., BP, No. _19 13800 Istres, France Dr. D. Falco Combat Aircraft Group Dipl. Ing. M. Wekwerth Computer/Simulator Department Deutsche Lufthansa AG AERITALIA Department NT3 Corso Marche 41 D-6000 Frankfurt/M Airport 10146 Torino, Italy Federal Republic of Germany Mr. Don R. Gum Mr. Brian Welch Simulation Techniques Branch (ASM) CAE Electronics Ltd. Air Force Human Resources Laboratory P.O. Box 1800 Wright-Patterson AFB, OH 45433, U.S.A. Montreal, Quebec H4L 4X4, Canada Special appreciation is extended to Mr. Trevor Wilcock, Executive, FMP, AGARD NATO, Paris, France, for his excellent assistance during the entire course of the Working Group's activities. iii PRECEDING PAQC BLANK NOT RUMEO TABLE OF CONTENTS Page PREFACE i i i WORKING GROUP 10 MEMBERSHIP ill -trIST OF-SYMBOLS ~ vii 1. INTRODUCTION 1 2. SPATIAL PROPERTIES 3 2.1 Introduction 3 2.2 Field of View 3 2.3 Viewing Region 6 2.4 Depth Considerations 7 2.5 Mapping Factors 10 2.6 Scene Content 11 3. ENERGY PROPERTIES 15 3.1 Introduction 15 3.2 Luminance 15 3.3 Contrast 20 3.4 Resolution 25 3.5 Color 32 3.6 Noise 37 3.7 Visual Simulation System Characteristics at the Component Level 39 4. TEMPORAL PROPERTIES 43 4.1 Introduction 43 4.2 Scene Generation 44 4.2.1 Excursion limits 44 4.2.2 Time lags 45 4.2.3 Noise 46 4.2.4 Linearity 48 4.2.5 Hysteresis 48 4.2.6 Threshold 49 4.2.7 Further remarks on CGI systems 49 4.3 Video Link 50 4.4 Suggested Methods of Measurement of the Complete Visual System 52 4.5 Interactions for the Complete Visual Simulation System 53 5. THE IMPORTANCE OF THE VISUAL SCENE 57 6. FUTURE HARDWARE TRENDS 61 7. RECOMMENDATIONS FOR RESEARCH 66 8. CONCLUDING REMARKS 69 REFERENCES . 71 APPENDIX A FIELD-OF-VIEW PLOTS 74 APPENDIX B PHOTOMETRIC CONVERSION FACTORS . 77 APPENDIX C GENERATION OF SINUSOIDAL INPUT SIGNALS AND ANALYSIS OF THE OUTPUT SIGNALS 78 SUMMARY 82 PRECEDING PAQE BLANK NOT FILMED LIST OF SYMBOLS AND ABBREVIATIONS aj output velocity amplitude = J2 Of^t Ap peak value of noise 2 B _.photometric_luminance.5_Lv, xd/m . _ _ — C number of luminance transitions CIE Commission Internationale d'Eclairage CGI computer-generated imagery B. - B2 C,,, modulation contrast = n—+ „ CRT cathode-ray tube d diameter of aperture, m D luminance transition density, deg"2 DFT discrete Fourier transform E illuminance = luminous flux incident per unit area, lm/m2 (or lux) f relative aperture of the optical system F focal length, m Hfkj) describing function = %°/^r for a sinusoidal input signal I intensity of the source, cd kf ith frequency, sec"1 L|j background luminance, cd/m2 LCLV liquid-crystal light valve 2 Lt target luminance, cd/n 2 Lv photopic luminance for 2° field, cd/m Ly scopotic'luminance, cd/m2 HTF modulation transfer function MTFA modulation transfer function area £n Tow-frequency nonlinearity ratio = -&• (see Sec. 4.2.3) rn noise ratio = — r peak ratio = p f2 a^ T transmission efficiency v spatial frequency, m"1 V.A. visual acuity V(x) spectral luminosity coefficient for photopic vision (for a 2° field) V'(x) spectral luminosity coefficient for scotopic vision x,y,z standardized primary colors in the CIE system X,Y,Z tristimulus values in the CIE system X0(k.j) DFT coefficients for the ith frequency of the output signal Xj(k.j) DFT coefficients for the ith frequency of the input signal vii PRECEDIW PAGE BUNK NOT FILMED YIO(A) spectral luminosity coefficient for photopic vision {for a 10° field) Y system gamma; Bout = K 6,-p Aw differential angular velocity threshold, sec"1 6 angle subtended by radius of a circular field shape 0t 2 angles equivalent to the north and south bounding latitudes, respectively, of the field of view X wavelength of light, m 2 Of rms of the fundamental signal output = a (k£) m o_ rms of the acceleration noise = £ a2(k^) - <jf2 (see Sec. 4.2.3) i=i * angle between the bounding meridians of the field of view u angular speed, sec"1 u.j fundamental frequency of input signal, sec"1 1 ut differential angular velocity threshold for monocular parallax, sec" vm 1. INTRODUCTION The importance and usefulness of out-of-the-window visual simulation displays can be judged best by the recent large increase in the use of this equipment in air-carrier trainer simulators. The military has followed suit in that the visual systems for flight simulators have become a major portion of the large simulator budget of the U.S. Air Force, especially since the feasibility and flexibility of computer- generated image systems have been demonstrated. -Equipment_for_out-of-_therW.indow visual simulation_was_largely_developed--in the-1960's-by-aipcraft manufacturers who used the simulators for engineering and test purposes. By the end of that decade, the equipment had proved sufficiently useful and dependable that it was being adopted for training. At the end of the 1970's, over 300 visual simulation systems were in use by the world's air carriers. The relatively late addition of these visual cues to training simulators, compared with inside-the-cockpit visual cues and with motion cues, may be ascribed to several factors. One of these factors is the recent rapid development in the techniques and hardware of computers and television which have greatly increased the quality and reliability and have decreased the cost of the visual simulation equipment. Another is the success of early users of visual simulation equipment in decreasing the cost of pilot training by substituting simulator time for training time in aircraft.