Display for a traffic alert and collision avoidance system

Abstract: A traffic situation awareness display (60) in a craft has the craft represented by a center symbol (22), has other traffic entities represented by position symbols (23,62,72,74) that indicate by shape the horizontal heading of a craft, having the shape of the represented vehicle and varying size to represent level of traffic threat or closeness in altitude differential. Symbols (14, 20, 70) that indicate altitude and trend of altitude change and the same or other symbols (30, 34, 78) in shape and color redundantly indicate the level of traffic threat.

Description: The present invention pertains to air traffic displays and particularly to display formats for an air traffic alert and collision avoidance system (TCAS). More particularly, the invention pertains to TCAS displays having three-dimensional perspective color graphics. Display formats of this type comprising the features of the preamble of Claim 1 are described in earlier EP-A-0 405 430 published 02.01.1991 and EP-A-0 411 309 published 06.02.1991. Background of the Invention The function of a TCAS display is to present air traffic information, declare threats, and provide advisories on potential air traffic conflicts before the closest point of approach. The TCAS display of the related art uses two-dimensional graphics to convey traffic information in the own aircraft's protected volume of airspace. However, since two-dimensional graphics can only depict information on two (X- and Y-axes) of the three dimensions required to complete represent spacial traffic relationships for TCAS (X-, Y- and Z-axes), numerics are used to portray relative altitude on the Z-axis. This two-dimensional plan view display of TCAS traffic information (supplemented with numeric data tags for the third-dimension, altitude) does not provide a direct visual display of dynamic spacial relationships existing between air traffic in the natural three-dimensional space. Interpretation of such a display requires considerable time and mental effort, in that it requires pilots to mentally construct a three-dimensional image of the traffic situation by combining graphically displayed azimuth and range information with numerically-presented altitude information. The related art TCAS display, therefore, is limited to function as an aid to direct visual acquisition of target aircraft, rather than as a correct, veridical, and easily interpretable complete "picture" of the current traffic situation. Pilots simply use the presented information as a cue for visual search to locate potential threats by direct visualization of aircraft outside the cockpit. Furthermore, since the traffic information is dynamic and continuously updated, direct visualization will require pilots to continuously alternate their attention from reading the numerics on the head-down TCAS display to the head-up search for aircraft outside the cockpit. Thus, using the related art TCAS display, pilots often find it time-consuming and confusing to visually acquire and process dynamic changes in the air traffic situation under moderate or high cockpit work load situations. Attempts of the related art to solve the problems of indirect visualization of conventional displays have focused on basic symbology refinement for the two-dimensional TCAS display format. Efforts have been made to reduce confusion and misinterpretation by modifying the symbols. For example, all the numeric codes were intially displayed above the aircraft symbol with a "plus" or "minus" sign to indicate relative elevation. The most current baseline TCAS display presents the numerics either above or below the symbol for conceptual compatibility. No effort has been made to explore other innovative approaches or to empirically validate current design concepts. However, research on display formats for other applications reveals potential benefits of an innovative three-dimensional perspective format. Ground-based perspective traffic display formats have been studied in the related art to demonstrate the advantages of utilizing respective graphics for portraying complex spacial situations. Conditionally, respective displays for naval battle field management systems have been previously studied to examine the feasibility and the advantages of three-dimensional graphic presentations. Such studies have shown significant advantages of three-dimensional formats over two-dimensional formats. Summary of the Invention The present invention as characterized in the claims displays data of an airborne environment to assist the pilot in being more cognizant of the conditions in his/her airspace, thereby enhancing his/her situational awareness. This format is specifically designed for the TCAS, in which aircraft information in a protected three-dimensional volume of air space surrounding an aircraft is presented with respect to that aircraft. The present invention implements three-dimensional perspective graphics in color to display easily and directly interpretable dynamic spacial relationships for the TCAS system. This format is equally applicable to military situation awareness formats where the pilot needs to quickly and accurately recognize what traffic and targets are in the surrounding airspace. The invention in the preferred embodiment uses three-dimensional perspective graphics rather than a two-dimensional format supplemented with numeric data tags. The advantages of the present invention are: the realistic and intuitive portrayal of traffic information in three-dimensional perspective that results in the correct perception of the three-dimensional air space; appropriate use of color, shape and size coding that is compatible with the pilot's expectations; and the integration of displayed situational information to facilitate rapid interpretation by the pilot. The primary objectives of this new display format are: to enhance the speed and accuracy of the pilot's understanding of the egocentric traffic situation; to minimize complex cognitive processing and pilot mental workload; and to allow the pilot to review and plan evasive maneuvers earlier and more effectively in order to avoid potential air traffic conflicts. Therefore, the function of the TCAS display is greatly extended and is no longer limited to providing cues for visual acquisition of traffic outside the aircraft. Brief Description of the Drawings Figure 1 reveals the TCAS format of the present invention, wherein the threat level is indicated by the size of the traffic alert symbol. Figure 2 reveals a TCAS format of the present invention, wherein the altitude differential is indicated by the size of the traffic alert symbol. Figure 3 is a 2.5 dimensional perspective format of the invention wherein the traffic symbols are of uniform size. Description of Preferred Embodiments The present invention is a view presentation for a TCAS system which integrates color coding and symbols which rotate to provide horizontal trend and threat levels to the pilot. This view can be observed from various perspective viewpoints which can vary from direct overhead normal plan view (look-down view) to a direct forward view, or to a viewpoint about halfway between the two. The present display format enhances the pilot's understanding and monitoring of dynamic spatial relationships between his or her own aircraft and other aircraft within the proximal airspace and to improve his or her ability to detect and avoid potential traffic and collisions. The function of the TCAS display is to present traffic information, declare threats, and provide resolution advisories before the closest point of approach. Figure 1 depicts the present invention which is a direct look-down view of the TCAS plan view presentation with horizontal trend data. The TCAS plan view of Figure 1 utilizes an aircraft symbol 12, for instance, which resembles a passenger jet aircraft and indicates the aircraft directional trend. A numerical readout 14 indicates relative altitude and directional arrow 16 indicates the vertical trend of the aircraft resembled by symbol 12. On symbol 12 there is a traffic alert symbol 18 which is a yellow medium circle superimposed on symbol 12. Symbol 20 associated with altitude symbol 14 indicates that the aircraft represented by symbol 12 is at an altitude above the own aircraft which is represented by symbol 22 at the center of format 10. When symbol 20 is a "-", that means that the associated symbol 12 represents an aircraft which is at an altitude below own aircraft 22. Since aircraft symbol 12 may rotate the position of the altitude tags, 14, 16 and 20 are situated such that the tag centroid is directly behind the right wing tip of symbol 12. The centroid of the altitude tags 14, 16 and 20 thus rotates with aircraft symbol 12 although the numerics and associated symbols remain upright for easy reading. This approach allows the pilot to more easily correlate the aircraft observed and its corresponding symbol 12 with its associated altitude tags 14, 16 and 20. The particular format of Figure 1 has aircraft symbols that enlarge as the threat level of the represented aircraft increases. Normal traffic is presented at a 0.75 size, the traffic having a traffic advisory is drawn at a 1.0 size, and the traffic having a resolution advisory is drawn at a 1.25 size, relative to a norm of a 1.0 dimension. Hence, the most prominent threat is clearly larger than the normal traffic. Threat status is also indicated by overlaying TCAS threat symbols on the traffic or airplane symbol 12. These items provide the pilot a triple redundant coding of threat, that is, color, size and overlaid threat symbol. A traffic symbol 24 having no threat symbol superimposed upon it, represents an aircraft that is above a certain altitude and is not a threat to own aircraft 22. Not having extra symbols, which would represent the absence of threat, superimposed on traffic symbols such as symbol 24, helps declutter display 10. Symbol 26, not having altitude tags, represents an aircraft whose altitude is unknown to the pilot of own aircraft 22. Typically, an aircraft represented by symbol 26 has no altitude transponders to provide own aircraft with altitude or vertical directional data. Symbol 28 is a symbol of 1.25 size indicating a resolution advisory of the aircraft that it represents. Superimposed on symbol 28 is symbol 30 which is a square which means a resolution advisory and has a color red which also indicates a resolution advisory of the aircraft represented by symbol 28. A normal proximate traffic symbol 24 represents an aircraft or traffic that is more than 1200 feet in altitude differential. Aircraft symbol 32 is at size 0.75 but has a normal proximate traffic symbol superimposed on it which represents that the aircraft is within 1200 feet of the present altitude of own aircraft 22. Symbol 34 is a diamond-shape representing normal proximate traffic at less than 1200 feet altitude differential and has a color of cyan also designating normal traffic of less than 1200 feet altitude differential from own aircraft 22. The twelve asterics symbols 36 represent azimuth about own aircraft symbol 22 and constitute a two nautical mile range indicator from own aircraft 22. Figure 2 depicts a format wherein the size of aircraft symbol 42, 44 or 50 has a size related to altitude differential from own aircraft represented by symbol 22 rather than having a size related to a threat level as in Figure 1. The changing size of aircraft symbols 42, 44, 48 and 50 provide relative motion cues to the pilot as the planes move away from or approach own aircraft 22. Such enhancement is useful to the pilot of own aircraft where direct visual contact is limited due to bad weather, for instance, or instrument flying is necessary. Symbol 46 is a relatively large symbol that represents proximate traffic of unknown altitude. A relatively small symbol 48 represents normal proximate traffic more than 1200 feet of relative altitude from own aircraft 22. The size of symbol 44 represents the relative altitude of the aircraft from own aircraft 22; however, the advisory of this aircraft is indicated by symbol 30 superimposed on symbol 44 wherein symbol 30 is a square signifying a resolution advisory and further has the color red likewise signifying a resolution advisory. Symbol 50 is of a relatively large size on format 40 in that it represents an aircraft at a low altitude difference (e.g., zero feet) from own aircraft 22. Symbol 34 superimposed on symbol 50 indicates normal proximate traffic at less than 1200 feet. Symbol 34 is a diamond which represents normal proximate traffic and is of the color cyan that also represents normal proximate traffic at less than 1200 feet relative altitude from own aircraft 22. Aircraft symbol 42 represents an aircraft that is about 1000 feet in relative altitude from own aircraft 22 which altitude is represented not only by symbol 14 but also by the size of symbol 42. Superimposed on symbol 42 is symbol 18 which is a medium circle that indicates a traffic alert and has the color yellow that likewise indicates a traffic alert. Figure 3 is a 2.5-dimension perspective view of the TCAS plan format 60. Format 60 is similar to plan view format 10 except that the observer of format 60 is looking at the scene from a point behind the scene at a particular elevation above the horizon rather than from directly above the scene. This is a preferred implementation. However, the pilot can switch perspectives for better perception of the horizontal or vertical positions of the traffic, respectively. In format 60, an aircraft symbol 62 sits on top an elevation post 64 which is proportional to the represented aircraft's relative altitude with respect to own aircraft represented by symbol 22. Elevation post 64 alternates between dashed and solid lines on a 500-foot basis, that is, a series of dashes represents 500 feet and a solid line represents 500 feet, and so on. The TCAS warning symbols, that is, filled-in square 30, filled-in circle 78, filled-in diamond 34 and open diamond 68, are located in reference plane 66 to indicate locations of represented aircraft, threat levels of aircraft, and threat azimuths of aircraft. The spoked reference plane 66 of figure 3 replaces the twelve symbols 36 in figures 1 and 2, to enhance the perspective view and to increase the pilot's cognizance of his or her own altitude reference plane. The color codings, red, yellow and cyan, respectively, of filled-in square 30, filled-in circle and filled-in diamond, are like that of the standard TCAS format and present TCAS formats 10 and 40. Open diamond 68 represents no threat. Digital readout 14 indicates the relative altitude of the aircraft represented by symbol 62, with respect to own aircraft represented by symbol 22, in Figure 3. Digital readout symbol 14 is placed just behind the right wing tip of symbol 62 representing the aircraft. Altitude vertical trend data of the aircraft is represented by the direction that filled triangles 70 are pointing, on the end of each of wing tip of symbol 62. In this case triangles 70 point upwards indicating that difference between the altitude of the own aircraft indicated by symbol 22 and the other aircraft indicated by symbol 62 tends to increase and therewith the threat decreases. No triangles on wing tips of aircraft symbol 72 indicate no vertical trend in altitude of the represented aircraft. Format 60 may be decluttered by removing digital readout symbols 14 and 20 wherein the pilot relies wholly on the analog elevation post 64 height to determine relative altitude of the represented aircraft. Aircraft symbols 62 and 72 rotate to indicate horizontal trend in the same manner as aircraft symbols in the two-dimensional formats of Figures 1 and 2. A large aircraft symbol 74 (1.25 size) is red, extends from symbol 30 which is likewise red and represents resolution advisory traffic. A medium aircraft symbol 76 is yellow and extends from a solid yellow circle 78 thereby representing a traffic alert with respect to the represented aircraft. Symbols 76 point upwards indicating a trend to decrease the difference between the altitude of the associated aircraft and the flight plane of the own aircraft. A small aircraft symbol 23 would be cyan and extend from a cyan solid diamond thereby representing normal proximate traffic within 1200 feet of altitude to own aircraft 22. The sizes of aircraft symbols 23, 62, 72 and 76, including other undesignated aircraft symbols, may indicate the level of threat of the respective represented aircraft on format 60 may be changed, like those aircraft symbols of Figure 1. Another version is that sizes of the aircraft symbols represent closeness of the represented aircraft in terms of relative altitude, i.e., the closer the aircraft in altitude, the larger the symbol. The other version of aircraft symbols in format 60 is implemented, as illustrated in figure 3, wherein all aircraft symbols are of the same size and represent neither a level of threat discrimination nor nearness to own aircraft in terms of relative altitude. Various sorts of processing devices may be utilized for generating the TCAS formats disclosed herein. In this particular embodiment, a Series 10000 personal supercomputer, from Apollo Computer Inc., of Chelmsford, MA 01824, is utilized with the ensuing programs listed in Attachment A. The Apollo personal supercomputer may be used in actual operational use or as simulator for testing, or operational training. The TCAS format imagery from the computer may be displayed on a conventional CRT, color active matrix liquid crystal display or another kind of display device. The inputs of traffic information to the TCAS system may come from ground stations, own aircraft detection electronics, and/or other aircraft as is known in the field of TCAS.

Claims: A traffic information display apparatus for displaying traffic in a volume about an own craft, comprising: a) a display (10, 40, 60) having a border enclosing an area of said display, wherein this area represents an amount of space about said own craft; b) an own craft symbol (22), situated at an approximate center of the area of said display (10, 40, 60), representing said own craft; c) at least one traffic symbol (12, 24, 26, 28, 32; 42, 44, 46, 48, 50; 23, 62, 74), situated in the area of said display, representing a traffic entity other than the own craft; d) computer processing means for controlling said display; characterized in that said computer processing means are adapted to control said traffic symbols such that e) said traffic symbol has a shape that resembles the type of the traffic entity represented by said traffic symbol, and f) the orientation of said traffic symbol on said display is such that said orientation indicates the flight direction of said traffic entity. The display apparatus of claim 1, characterized in that said traffic symbol has a variable size that indicates a level of threat of the traffic entity to said own craft, according to the traffic symbol size. The display apparatus of claim 2, characterized in that traffic symbol has a variable size that indicates an altitude difference between the altitudes of the traffic entity and said own craft. The display apparatus according to one of the preceding claims, characterized in that the location of said traffic symbol on the area of said display indicates the position of the represented traffic entity relative to said own craft. The display apparatus according to one of the preceding claims, characterized by a plurality of azimuth and range symbols (36), in a plane (66) representing altitude of said own craft, for indicating approximate azimuth and range of a traffic entity in relation to said own craft (Fig. 2). The display apparatus of one of the preceding claims, characterized in that at least some of said traffic symbols further comprises symbols (14, 20, 16, 70, 76) that indicate altitude and/or direction of altitude change of the traffic entity relative to the altitude of said own craft. The display apparatus according to one of the preceding claims, characterized in that said traffic symbol comprises a threat symbol (18, 30, 34, 78) that indicates a level of threat of the traffic entity to said own craft, according to shape and color of said threat symbol (18, 30, 34, 78). The display apparatus according to one of the preceding claims, characterized in that the plane (66) representing the altitude of said own craft, said own craft symbol (22), said at least one traffic symbol, the location of said traffic symbol relative to said own craft symbol and said plurality of azimuth and range symbols (36) are situated on said display (10, 40, 60) as to appear to an observer at a point of view from a 90 degree angle relative to the plane representing the altitude of said own craft. The display apparatus according to one of the claims 1 to 7, wherein the plane (66) representing the altitude of said own craft, said own craft symbol (22), said at least one traffic symbol, the location of said traffic symbol relative to said own craft symbol (22), and said plurality of azimuth and range symbols (36) are situated on said display (10, 40, 60) as to appear to an observer at a point of view at an angle between zero and ninety degrees relative to the plane representing the altitude of said own craft (Fig. 3). The display apparatus according to one of the preceding claims, characterized by : a) a location symbol (34, 68, 78), associated with said traffic symbol, situated in a plane (66) representing an altitude of said own craft, and representing a position of the traffic entity relative to said plane; and b) an elevation line symbol (64) having a direction normal to the plane representing the altitude of said own craft, connected between said location symbol (34, 68, 18) and said traffic symbol (23, 62), and having a length magnitude representing a difference in altitude between the traffic entity and said own craft (Fig. 3). The display apparatus of claim 10, characterized in that a) said elevation line symbol (64) has alternate increments of solid and dashed line; and b) each increment represents a particular magnitude of distance. The display of one of the preceding claims, characterized by comprising information processing and symbol generating means, connected to said display, for receiving and processing traffic information, and generating a format and said symbols on said display (10, 40, 60). The display apparatus of one of the preceding claims, characterized in that the color of said traffic and/or said location symbols indicates a level of threat of the traffic entity to said own craft.

Inventors: HANCOCK WILLIAM R, HANCOCK, WILLIAM R.
Applicants: HONEYWELL INC, HONEYWELL INC.
Application year: 1991
Main classification: G01S7
IPC codes: G01S7, B64D45, G01S13, G08G5