Classifications

• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09B—EDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS
  • G09B29/00—Maps; Plans; Charts; Diagrams, e.g. route diagram
  • G09B29/10—Map spot or coordinate position indicators; Map reading aids
• • G—PHYSICS
  • G08—SIGNALLING
  • G08G—TRAFFIC CONTROL SYSTEMS
  • G08G5/00—Traffic control systems for aircraft, e.g. air-traffic control [ATC]
  • G08G5/0017—Arrangements for implementing traffic-related aircraft activities, e.g. arrangements for generating, displaying, acquiring or managing traffic information
  • G08G5/0021—Arrangements for implementing traffic-related aircraft activities, e.g. arrangements for generating, displaying, acquiring or managing traffic information located in the aircraft
• • G—PHYSICS
  • G08—SIGNALLING
  • G08G—TRAFFIC CONTROL SYSTEMS
  • G08G5/00—Traffic control systems for aircraft, e.g. air-traffic control [ATC]
  • G08G5/0047—Navigation or guidance aids for a single aircraft
  • G08G5/0052—Navigation or guidance aids for a single aircraft for cruising
• • G—PHYSICS
  • G08—SIGNALLING
  • G08G—TRAFFIC CONTROL SYSTEMS
  • G08G5/00—Traffic control systems for aircraft, e.g. air-traffic control [ATC]
  • G08G5/0073—Surveillance aids
  • G08G5/0086—Surveillance aids for monitoring terrain
• • G—PHYSICS
  • G08—SIGNALLING
  • G08G—TRAFFIC CONTROL SYSTEMS
  • G08G5/00—Traffic control systems for aircraft, e.g. air-traffic control [ATC]
  • G08G5/04—Anti-collision systems
  • G08G5/045—Navigation or guidance aids, e.g. determination of anti-collision manoeuvers

Definitions

• the invention relates to navigation aid for a mobile subject to maneuverability and course constraints such as an aircraft operating over a territory having prohibited areas of overflight below a certain floor or reliefs and obstacles to be avoided because they are close to or higher than its flight altitude.
• Various systems have been developed to warn the crew of an aircraft of a risk of collision with the ground.
• TAWS systems (acronym of the English expression: "Terrain Awareness and Warning System”), make a short-term trajectory forecast for the aircraft from flight information (position, course, orientation and amplitude of the speed vector) provided by the on-board equipment, (a place in relation to a map of the overflown region extracted from a database of terrain elevations accessible from the edge and emit alarms intended for the crew whenever the foreseeable short-term trajectory collides with the ground.
• TAWS systems supplement their alarms with rudimentary recommendations such as "Terrain Ahead, Pull up”.
• Some of them also give information on the level of risk of collision caused by the reliefs and obstacles surrounding the aircraft in the form of a map showing the reliefs or obstacles of the terrain overflown in strata of different colors depending on the level of risk involved.
• a navigation aid map representing the area of evolution of a mobile divided into regions shown in false colors and demarcated according to the possibility of the mobile to cross them and the time it would take to reach them when they are passable, for example red for insurmountable obstacles, yellow for distant regions of access and green for regions near access.
• This navigation map is produced using a distance map constructed from a database of terrain elevations and parts of the terrain assimilated to obstacles to be bypassed.
• the distance map lists the curvilinear distances separating the instantaneous position of the mobile with respect to the different points accessible from the mapped evolution zone by considering only the routes avoiding the obstacles to be circumvented. These distances are estimated by means of a distance transform by propagation.
• the known navigation aid maps indicating the impassable or prohibited parts of crossing as obstacles to be circumvented do not give information on the extent of the zones bordering the obstacles in which the mobile has freedom of maneuver. reduced in the short term due to the proximity of an obstacle to be bypassed.
• this information is interesting, especially in the case of an aircraft, because it can be used to signal moments when piloting becomes more delicate and when the crew must redouble their attention.
• the invention aims to provide a mobile with information on the extent of its lateral maneuvering freedom in the present moment and in the short and medium terms.
• It relates to a lateral maneuverability map for mobile representing, within an evolution zone, the contours of regions of complete freedom of lateral evolution for the mobile, taking into account the maneuvering capacities of the mobile and the need for the mobile to avoid regions considered arbitrarily impassable.
• the lateral maneuverability map is added, in transparency, on a map delivered by a navigation system.
• the lateral maneuverability card is added, transparently, to a card issued by a TAWS system for preventing risks of collision with the ground.
• the lateral maneuverability map is added, transparently, to a map delivered by a navigation system, the regions of complete freedom of lateral evolution emerging by a semi-transparent masking.
• the lateral maneuverability map is added, in transparency, to a map delivered by a navigation system, the regions of complete freedom of lateral evolution emerging by a masking of textures.
• the lateral maneuverability card for mobile represents, within an evolution zone, different types of regions which are distinguished from each other by the possibility or not for the mobile to cross them and, for the types of regions which can be crossed by the 'extent of lateral freedom of maneuver left to the mobile because of its maneuvering capabilities and the need to avoid impassable areas.
• the regions represented are at least of three distinct types: a first type corresponding to impassable regions, a second type corresponding to bands surrounding the impassable regions and having the width of a maneuvering space considered as necessary for a free lateral evolution of the mobile, and a third type corresponding to regions of free lateral evolution
• the different types of regions are represented in false colors.
• the different types of regions are represented by different textures.
• At least one of the second and third types of region is represented with lines of iso distance from the borders of the regions to be bypassed.
• at least one of the second and third types of region is represented with color gradations representative of the distances from the borders of the regions to be bypassed.
• the width of the bands constituting the second type of region takes into account the instantaneous performance of the aircraft.
• the width of the bands constituting the second type of region takes account of the flight envelope of the aircraft.
• the width Sd of the bands constituting the second type of region is determined by application of the relation:
• HLD_L being a configuration data defined in flight time or in distance traveled on the ground
• g being the acceleration of gravity GS being the ground speed of the aircraft and HLDJ3 the maximum value accepted for the roll angle taken in turn by the aircraft.
• the distance map used in the process for obtaining the lateral maneuverability map is obtained by means of a chamfer distance transform.
• a figure 1 represents a first step in the development of a lateral maneuverability map according to the invention consisting in marking by zero the cells of the regions considered to be inaccessible
• a figure 2 shows an example of a chamfer mask usable by a propagation distance transform used for distance estimates
• FIGS. 3a and 3b show the cells of the chamfer mask illustrated in FIG.
• a figure 4 represents a second stage of the development of a lateral maneuverability map according to the invention consisting in estimating the distances of the cells of the regions accessible by relative to the limits of inaccessible regions, - a figure 5 represents a way of estimating the width of l minimum space necessary for the free lateral movement of an aircraft,
• FIG. 1 is a diagrammatic representation of a lateral maneuverability map according to the invention consisting in estimating the distances of the cells of the regions accessible by relative to the limits of inaccessible regions, - a figure 5 represents a way of estimating the width of l minimum space necessary for the free lateral movement of an aircraft, FIG.
• FIG. 6 shows a third step in the development of a lateral maneuverability map according to the invention consisting in delimiting around inaccessible regions, by thresholding the estimated distances, bands surrounding the inaccessible regions of insufficient width for a free evolution of the mobile, the remaining portions of the card being considered as belonging to regions of free lateral evolution for the mobile, - a figure 7 represents an example of lateral maneuverability map according to the invention, and FIG. 8 represents a diagram of a navigation aid device for aircraft displaying a lateral maneuverability map according to the invention.
• the development of the lateral maneuverability map covering an evolution area is based on:
• the development of the lateral maneuverability map begins with the construction of a distance map initiated by the authoritative assignment of an estimate of zero distance to the cells of the mapped area resulting from the division adopted for the terrain elevation database, which belong to parts of the evolution area considered to be bypassed.
• the selection of these cells results from various considerations which will not be detailed here since they are not part of the invention.
• these may be cells corresponding to reliefs close to or greater than the altitude instruction of its flight plan or to a short or medium term forecast of the altitude of the aircraft based on its parameters. of current flight.
• the construction of the lateral maneuverability map continues with the distance estimates of the other cells of the mapped area relative to the edges of the parts to be bypass, that is to say by the estimates of the lengths of the shortest paths going from the cells concerned to the nearest part to bypass. They are advantageously made using a distance transform by propagation also known under the name of bevel distance transform. Chamfer distance transforms first appeared in image analysis to estimate distances between objects.
• a distance transform by propagation estimates the distance of a pixel called "goal" pixel with respect to a pixel called “source” pixel by building gradually, starting from the source pixel, the shortest possible path following the mesh of the pixels and ending at the goal pixel, and using the distances found for the pixels of the image already analyzed and a table called the chamfer mask listing the values of the distances between a pixel and its close neighbors.
• the object is considered to be made up of a set of source pixels and the shortest of the estimated distances between the pixels is adopted as the distance estimate. purpose and the different source pixels of the object.
• a chamfer mask is in the form of a table with an arrangement of boxes reproducing the pattern of a pixel surrounded by its close neighbors.
• a box assigned the value 0 identifies the pixel taken as the origin of the distances listed in the table.
• Around this central box are agglomerated peripheral boxes filled with non-zero proximity distance values and repeating the arrangement of the pixels in the vicinity of a pixel supposed to occupy the central box.
• the value of proximity distance appearing in a peripheral box is that of the distance separating a pixel occupying the position of the peripheral box concerned, from a pixel occupying the position of the central box. Note that the proximity distance values are distributed in concentric circles.
• a third circle of eight boxes corresponding to the eight pixels of third row, which are closest to the pixel of the central box while remaining outside the line, the column and the diagonals occupied by the pixel of the central box, are assigned a proximity distance value D3.
• the chamfer mask can cover a more or less extended neighborhood of the pixel of the central box by listing the values of the proximity distances of a more or less large number of concentric circles of pixels of the neighborhood. It can be reduced to the first two circles formed by the pixels in the vicinity of a pixel occupying the central box as in the example of distance maps in Figures 4, 6 or be extended beyond the first three circles formed by the pixels. of the vicinity of the pixel of the central box. It is usual to stop at the first three circles as for the chamfer mask shown in figure 3.
• the values of proximity distances D1, D2, D3 which correspond to Euclidean distances are expressed in a scale whose multiplicative factor allows the use of whole numbers at the cost of a certain approximation. This is how G.
• Borgefors adopts a scale corresponding to a multiplicative factor 3 or 5.
• a chamfer mask retaining the first two circles of proximity distance values, therefore of dimensions 3x3, G.
• Borgefors gives , at the first proximity distance D1, which corresponds to a step on the abscissa or on the ordinate and also to the multiplicative factor of scale, the value 3 and, at the second proximity distance, which corresponds to the root of the sum of the squares steps on the abscissa and on the ordinate -Jx 2 + y 2 , the value 5.
• the initial distance values assigned to the goal points are updated during the scanning of the image by the chamfer mask, an update consisting in replacing a distance value assigned to a goal point, by a new lower value. resulting from an estimation of distance made on the occasion of a new application of the chamfer mask at the target point considered.
• a distance estimate by applying the chamfer mask to a goal pixel consists in listing all the paths going from this goal pixel to the different source pixels and passing through a pixel in the vicinity of the goal pixel whose distance has already been estimated during the same scan, to search among the listed paths, the shortest path (s) and to adopt the length of the shortest path (s) as distance estimate.
• the order in which the image pixels are scanned influences the reliability of the distance estimates and their updates because the paths taken into account depend on it.
• the lexicographic orders include reverse lexicographic (scanning pixels of the image line by line from bottom to top and, within a line, from right to left), transposed lexicographic (scanning pixels of the image column by column of left to right and, within a column, from top to bottom), the reverse transposed lexicographic (pixel scanning by columns from right to left and within a column from bottom to top) satisfy this regularity condition and more generally all scans in which rows and columns are scanned from right to left or left to right.
• Borgefors recommends double scanning the pixels of the image, once in lexicographic order and once in reverse lexicographic order.
• FIG. 3a shows, in the case of a scanning pass in lexicographic order going from the upper left corner to the lower right corner of the image, the boxes of the chamfer mask of FIG. 1 used to list the paths going from d 'a target pixel placed on the central box (box indexed by 0) at the source pixel passing through a neighboring pixel whose distance has already been estimated during the same scan. There are eight of these boxes, located in the upper left of the chamfer mask. There are therefore eight paths listed for the search for the shortest whose length is taken to estimate the distance.
• FIG. 3b shows, in the case of a scanning pass in reverse lexicographic order going from the lower right corner to the upper left corner of the image, the boxes of the chamfer mask of FIG.
• FIG. 4 illustrates the distance map obtained in the second stage of the development of the lateral maneuverability map, after application in FIG. 1, of the chamfer distance transform using the chamfer mask of dimension 5 ⁇ 5 of FIG. 3 During the next step, illustrated in FIG.
• the distance estimates contained in the cells of the mapped area corresponding to the division adopted for the elevation database of the terrain are used to delimit the different regions represented.
• the cells affected by an estimate of zero distance, which correspond, hypothetically to parts of the evolution zone considered to be bypassed, are represented in a specific way, for example of a red color or, as on the Figure 5, with a texture with tight hatching, signifying that they constitute areas prohibited from access.
• the cells affected with non-zero distance estimates but below a certain threshold below which it is considered that the proximity of a region prohibited from access limits, in the short or medium term, the freedom of lateral evolution of the mobile , threshold which is taken here at 17 in the adopted scale, are represented, for example of yellow color or, as on figure 5, with a texture with grid or hatching less tight than the hatches covering the affected cells of estimates of zero distance. They form bands of a certain width surrounding the prohibited access regions in which it is considered that the mobile has its freedom of lateral evolution in the short term limited by the proximity of one or more prohibited access regions.
• the other cells affected with estimates of distance greater than the threshold considered are represented, for example by a green color signifying that they constitute regions in which the mobile retains all its freedom of lateral evolution in the short term or, as on the figure 5 without any color or texture.
• the representation of the region formed by the cells affected by distance estimates below the threshold like that of the region formed by the cells affected by distance estimates greater than the threshold can be further searched for example with color gradations corresponding to the evolution of the distance estimate or with iso distance lines.
• the distance threshold taken into account to signal a short or medium term restriction of the freedom of lateral movement of a mobile depends on the maneuverability of the mobile.
• an aircraft In the case of an aircraft, it can be defined on the basis of: aeronautical procedures, required safety margins, current flight parameters of the aircraft, - flight conditions defined by the flight envelope of the aircraft.
• aeronautical procedures required safety margins
• current flight parameters of the aircraft - flight conditions defined by the flight envelope of the aircraft.
• a certain tolerance threshold expressed by a limit roll angle.
• the distance threshold to be respected is the radius of the circle circumscribed to the two possible trajectories for the waiting racetrack increased by a safety margin. As shown in FIG.
• the two possible trajectories 40, 41 for the holding racetrack form two lobes tangent to the current trajectory 42 of the aircraft.
• Each of them has two lengths HLD_L joined by two half-turns of radius HLD_T.
• the value of the lengths HLD_L is a configuration datum defined in flight time or in distance traveled on the ground.
• the value of the radius HLD_T of the assumed U-turns made flat, at ground speed GS and at constant rolling angle HLD_B, corresponds to the relation: the ground speed GS being a datum supplied by the equipment of the aircraft, HLD_B a configuration datum calculated as a function of the theoretical performances of the aircraft and g the acceleration of gravity.
• the value of the radius HLD_R of the circle 43 circumscribed to the two possible trajectories 40, 41 for the waiting racetrack corresponds to the relationship:
• the distance threshold Sd adopted for the width of the bands surrounding the obstacles to be circumvented takes the value: HLD_M being an additional safety margin compared to the radius HLD_R of the circle circumscribed to the two possible trajectories of the waiting racetrack.
• Figure 7 shows how the evolution zone ultimately appears in the lateral maneuverability map.
• Each access prohibited region 50 is isolated from the regions of free lateral movement 51 by a separation strip 52 of width Sd depending on the performance and the ground speed of the aircraft as well as on the cornering constraints.
• the forbidden regions are represented in a way, for example by means of a red color, the separation bands in another way, for example by means of a yellow color and the regions of free lateral evolution d 'another way for example by means of a green color so that they are easily distinguished from each other.
• the lateral maneuverability map can be more detailed and include iso-distance lines with respect to the borders of the forbidden regions. It may also include color gradations always representative of the distances from the forbidden regions.
• the lateral maneuverability map is reduced to its simplest expression, that is to say the census of regions of free lateral evolution, and put in transparency over an existing map of the same area, traced by a navigation system or by a TAWS system for protection against risks of ground collision. Its process of obtaining is then simplified since one extracts then from the map of distances that the contours of the regions of complete freedom of lateral evolution by distinguishing the connected points from the passable regions whose distances are greater than the threshold arbitrarily considered as necessary for a free lateral evolution of the mobile.
• the information on the contours of the regions of free lateral evolution provided by the lateral maneuverability map is added to the existing map by giving specific areas of free development a pigmentation highlighting these regions without hiding the information already present, for example by means of a semi-transparent mask of white color.
• the lateral maneuverability card which has just been proposed, has the advantage of allowing a lateral safety margin to be taken into account with respect to the edges of the regions considered to be prohibited, regardless of the determination process. prohibited areas. In the case of an aircraft, this makes it possible to add a lateral safety margin around the reliefs considered to be dangerous by existing terrain collision avoidance systems.
• FIG. 8 shows a navigation aid device for an aircraft, displaying a lateral maneuverability map.
• This essentially consists of a computer 60 associated with a database of terrain elevations and prohibited overflight areas 61, the navigation equipment 62 of the aircraft and a visual display device 63. database of elevations of the terrain and of prohibited zones 61 can be embarked on board the aircraft as shown, or placed on the ground and accessible from the aircraft by radio transmission.
• the calculator 60 can be a specific calculator for the development and display of a navigation map possibly listing the risks of ground collision caused by overflown terrain and obstacles or a calculator shared with other tasks such as flight management or autopilot. It receives navigation equipment 62 from the aircraft, the main flight parameters including the position of the aircraft in latitude, longitude, and altitude, and the direction and amplitude of its speed vector which enable it to determine at each instant the position on the surface of the terrestrial globe, the orientation and the dimensions of an evolution zone to display. In possession of the orientation and dimensions of the evolution zone to be displayed, he extracts from the database of elevations of the terrain and prohibited overflight zones 61, a location grid mapping the selected evolution zone and place the contours of the zones on this grid prohibited from overflight.

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• General Physics & Mathematics (AREA)
• Radar, Positioning & Navigation (AREA)
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• Theoretical Computer Science (AREA)
• Mathematical Physics (AREA)
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• 2003
  • 2003-12-19 FR FR0315020A patent/FR2864312B1/fr not_active Expired - Lifetime
• 2004
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  • 2004-11-30 US US10/583,144 patent/US7668625B2/en active Active
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