Method for determining valley areas accessible by aircraft

Description

[0001] The present invention relates to a method for determining valley areas accessible by an aircraft. The present invention also relates to an associated electronic device. The present invention also relates to an aircraft comprising such an electronic device.

[0002] In the field of aeronautics, valleys are generally favored by pilots in low altitude flight in order to benefit from the optical, magnetic and acoustic masking effects naturally provided by the terrain.

[0003] However, not all valleys are passable, for two reasons. First, the flight dynamics of a fixed-wing aircraft do not allow for addressing excessively sharp radii of curvature. Second, pilots want to be able to turn around in the valley without having to climb back in altitude and therefore potentially expose themselves by leaving the natural masking, which excludes valleys that are too narrow.

[0004] Also, before entering a valley, the pilot must ensure that it meets predefined operational characteristics to guarantee its survival once entered. For example, the valley must be flyable (in the dynamic sense of flight) and allow for a U-turn without uncovering. All these constraints can be satisfied by respecting a single "envelope" constraint, which is a sufficient width of the valley.

[0005] The pilot thus makes an estimate "by eye" from a navigation map, any external visual information and his possible knowledge of the theatre of operations.

[0006] However, such an estimate is not entirely reliable and presents an increased risk of poor decision-making in flight. Indeed, according to the situational awareness model proposed by Endsley in 1988, good decision-making requires good understanding of the situation and adequate management of the urgency of the decision. However, good situational awareness is not sufficient to ensure good decision-making. For example, Endsley in 1995 identified that in 27% of aviation accidents, pilots had good situational awareness and still made a poor decision. The main reason for this is highly complex environments or cognitive resources limited by decision time or situational constraints (stressful conditions).

[0007] In particular, decision-making with experienced operators is generally not a problem when the situation is known and well-defined. However, when the situation is completely new and uncertain, decision-making, even for experienced operators, is difficult. Moreover, when survival is at stake, instinct pushes one to move away from the threat, sometimes adding new hazards with the risk of degrading survival chances.

[0008] Furthermore, the Master's thesis by Robert Nagy (University of Oslo) entitled "Automatic detection of valley forms" and published on July 3, 2015 discloses the analysis of topographic images to determine the characteristics of certain valleys, in this case the curvature, and the article "Terrain Following and Terrain Avoidance with Synthetic Vision" by E. Theunissen et al. published at the conference "DIGITAL AVIONICS SYSTEMS CONFERENCE, 2005" which took place in WASHINGTON, DC, USA, between October 30 and November 3, 2005 deals with flight simulation.

[0009] There is therefore a need for a method for improving the determination of valley areas accessible by an aircraft.

[0010] For this purpose, the present description relates to a method according to claim 1.

[0011] According to other advantageous aspects of the invention, the method comprises one or more of the features of claims 2 to 7.

[0012] The present description further relates to an electronic device according to claim 8.

[0013] The present description also relates to an aircraft according to claim 9.

[0014] The present description also relates to a computer program product comprising a readable information medium, on which is stored a computer program comprising program instructions, the computer program being loadable onto a data processing unit and adapted to cause the implementation of a determination method as previously described when the computer program is implemented on the data processing unit.

[0015] The present description also relates to a readable information medium on which a computer program product as previously described is stored.

[0016] Other features and advantages of the invention will become apparent upon reading the following description of embodiments of the invention, given by way of example only, and with reference to the drawings which are: [ Fig 1] figure 1 , a schematic representation of an example electronic device, [ Fig 2] figure 2 , a flowchart of an example of a method for determining valley areas, and [ Fig 3] figure 3 , a schematic representation of a land elevation for a central point and the eight neighbors surrounding this central point.

[0017] An example of an electronic device 10 configured to determine valley areas accessible by an aircraft is illustrated by figure 1 .

[0018] Valley areas are areas of an environment that are intended to be flown over by aircraft. A valley area is defined as a geographical depression, generally elongated in shape and shaped in a relief (for example, by a river or a glacier). In other words, a valley is materialized by a hollow in a terrain.

[0019] A valley area is considered accessible to an aircraft when the width of the valley(s) that compose it is greater than or equal to a predefined width. The valley thus meets predefined operational characteristics, for example, according to which the valley allows good flight dynamics (limited radii of curvature) and to turn around without being uncovered.

[0020] In the example illustrated by the figure 1 , the electronic device 10 comprises a calculator 11 and a computer program product 12.

[0021] The calculator 11 is preferably a computer.

[0022] More generally, the computer 11 is an electronic computer capable of manipulating and / or transforming data represented as electronic or physical quantities in computer 11 registers and / or memories into other similar data corresponding to physical data in memories, registers or other types of display, transmission or storage devices.

[0023] The calculator 11 interacts with the computer program product 12.

[0024] As illustrated by the figure 1 , the computer 11 comprises a processor 14 comprising a data processing unit 16, memories 18 and an information medium reader 20. In the example illustrated by the figure 1 , the computer 11 comprises a human-machine interface 22, such as a keyboard, and a display 24.

[0025] The computer program product 12 comprises an information medium 26.

[0026] The information medium 26 is a medium readable by the computer 11, usually by the data processing unit 16. The readable information medium 26 is a medium suitable for storing electronic instructions and capable of being coupled to a bus of a computer system.

[0027] For example, the information medium 26 is a USB key, a floppy disk or a flexible disk (from the English term “ Floppy disk "), an optical disc, a CD-ROM, a magneto-optical disc, a ROM memory, a RAM memory, an EPROM memory, an EEPROM memory, a magnetic card or an optical card.

[0028] The computer program 12 comprising program instructions is stored on the information medium 26.

[0029] The computer program 12 is loadable onto the data processing unit 16 and is adapted to cause the implementation of a method for determining valley areas when the computer program 12 is implemented on the processing unit 16 of the computer 11.

[0030] In another example, the computer 11 is produced in the form of one or more programmable logic components, such as FPGAs (Field Programmable Gate Arrays), or in the form of one or more dedicated integrated circuits, such as ASICs (Application Specific Integrated Circuits). The computer 11 is in this case configured to implement a determination method as will be described in the remainder of the description.

[0031] The electronic device 10 is, for example, fully integrated into an aircraft.

[0032] Alternatively, the electronic device 10 is, for example, arranged partly in a ground unit and partly in an aircraft. In this case, the electronic device 10 comprises, for example, a first computer 11 on the ground and a second computer 11 integrated in the aircraft 14.

[0033] The operation of the electronic device 10 will now be described with reference to the figure 2 , which schematically illustrates an example of implementation of a method for determining valley areas accessible by an aircraft and at the figure 3 which illustrates in more detail an example of a step in this process.

[0034] The determination method is, for example, suitable for being implemented during a flight preparation phase of the aircraft 14 so as to define in advance trajectories for the aircraft favoring valley areas.

[0035] Alternatively or additionally, the determination method is suitable for being implemented during the flight of the aircraft 14. This allows, for example, the pilot to favor valley areas if he wishes or must modify his flight path.

[0036] The different steps of the determination method are implemented by the electronic device 10, in particular by the calculator 11, that is to say are implemented by computer.

[0037] The determination method comprises a step 100 of obtaining an initial image IM I of an environment comprising valley areas.

[0038] The initial image IM I is, for example, a digital terrain image, i.e. a digital representation of the altitudes of a terrain (real or fictitious). The initial image IM I has, for example, been obtained by means of measurements carried out by one or more sensors. For example, the initial image IM I has been acquired by one or more sensors during the flight of an aircraft carrying said sensor(s). The or at least one sensor is, for example, a stereoscopic camera or a lidar. Alternatively, the initial image IM I has been acquired by a satellite system.

[0039] The determination method comprises a step 110 of processing the initial image IM I so as to eliminate the imaged elements on the initial image IM I whose dimension is less than a predetermined dimension to obtain a first processed image IM1 T . The predetermined dimension has been chosen so as to eliminate the valleys (too narrow) with a width less than the minimum width of the valleys sought, that is to say valleys considered accessible by the aircraft. For example, the predetermined dimension has been chosen so as to eliminate the valleys with a width less than 3000 meters.

[0040] The processing step 110 notably comprises reducing the resolution of the initial image IM I so as to eliminate the imaged elements on the initial image IM I whose dimension is less than a predetermined dimension.

[0041] To do this, the sampling frequency is chosen based on the predetermined dimension. This actually amounts to applying the converse of Shannon's theorem, which states that "sampling an image with regularly spaced samples can describe a signal provided that the signal does not contain any frequency higher than half the sampling frequency, known as the Nyquist frequency."

[0042] At the end of this reduction, the details of the digital terrain model smaller than the predetermined dimension are eliminated, and thus the valleys smaller than this dimension.

[0043] Advantageously, the processing step 110 also comprises the application of a Gaussian blur filter to the reduced resolution image obtained so as to obtain the first processed image IM1 T .

[0044] The Gaussian blur filter is a digital filter that blurs a digital image by reducing sudden changes in intensity, by calculating the weighted average of the values in the neighborhood of each pixel. Pixels in the neighborhood that are close to the central pixel have a greater weight (more influence) than those that are further away. The weighting coefficients to be applied are calculated as follows: Gaussian kernel coefficients Oh, yeah = exp ( - ( i 2< +j 2< ) / 2 σ 2< ) where i is the distance from the origin along the horizontal axis, j is the distance from the origin along the vertical axis, and σ is the standard deviation of the Gaussian distribution.

[0045] By applying such a Gaussian blur filter, the "staircase effects" related to the resolution reduction are reduced on the first processed image IM1 T .

[0046] The determination method comprises a step 120 of determining the curvature of each element imaged on the first processed image IM1 T. The valley areas accessible by the aircraft are the elements imaged on the first processed image IM1 T whose curvature is strictly less than zero (negative).

[0047] The curvature determination step 120 is based, for example, on the article by Zevenbergen, LW, Thorne, CR, 1987, entitled "Quantitative analysis of land surface topography", published in Earth surface processes and landforms, volume 12, pages 47 to 56.

[0048] In particular, according to this article, the curvature of the plane at any point on the ground, called the central point, is obtained via a polynomial identification based on this central point and its eight nearest neighbors within a Cartesian grid.

[0049] More specifically, with reference to the figure 3 , we note Z 1 to Z9 the elevation of the land at each of the nine points considered (point 5 being the central point, points 1 to 4 and 6 to 9 the neighboring points).

[0050] Ten coefficients (denoted A, B, C, D, E, F, G, H, I, J) are obtained by identification with a Lagrange polynomial Z(x,y) = Ax 2< y 2< + Bx 2< y + Cxy 2< + Dx 2< + Ey 2< + Fxy, +Gx + Hy + I , assumed to approximate the height of the terrain at any point ( x, y ) located in the area of the plan delimited by the eight neighbors.

[0051] The curvature of the terrain is then obtained by deriving in the vicinity of the central point: Curvature ≡ ∂ 2< Z / ∂ 2< S = 2( Dcos 2< φ + Esin 2< φ + Fcosφsinφ ) Or f is an azimuthal direction.

[0052] In order to define a quantity characterizing the central point (and therefore not depending on the azimuthal direction f ) ,a quantity is defined combining the curvature in two complementary directions: the direction of greatest slope i = arctan(- H / - G ) and its complement ϕ ≡ θ + π 2 . The characteristic quantity thus obtained is called “ground curvature”, and is worth 2( D + E ) .

[0053] The determination method comprises a step 130 of processing the first processed image IM1 T so as to assign a zero value to the imaged elements on the first processed image IM1 T whose curvature is positive to obtain a second processed image IM2 T . This amounts to keeping only the “hollows” on the second processed image IM2 T , such hollows being the valley areas accessible by the aircraft.

[0054] Advantageously, the method comprises a step 140 of processing the second processed image IM2 T to obtain a final image IM F. The step of processing the second processed image IM2 T comprises for example: the normalization (between 0 and 1) of the histogram of the second processed image IM2 T , and / or the increase in the contrast of the second processed image IM2 T by a predetermined value (for example to the power of 100), where appropriate after normalization of the histogram, and / or the increase in the resolution of the second processed image IM2 T , where appropriate after normalization of the histogram and increase in the contrast, so that the resolution of the final image IM F is equal to the resolution of the initial image IM I .

[0055] Normalization and contrast enhancement allow to obtain a final IM F image in which the determined valley areas are highlighted on the final IM F image with a range of values corresponding to the sensitivity of the human eye. These two actions also allow to obtain images usable by a neural network.

[0056] Increasing the resolution makes it possible to obtain a final image IM F of the same size as the initial image IM I, which makes it easier to use the final image IM F , for example, by comparing it to the initial image IM I .

[0057] Optionally, the method comprises a step 150 of displaying the final image IM F on a display, such as the display 24 of the computer 11.

[0058] In one example, the final image IM F is, for example, superimposed on the initial image IM I .

[0059] Advantageously, when the display 24 is arranged in an aircraft and the aircraft is in flight, the final image IM F is preferably displayed as a function of the position of the aircraft determined in real time. This makes it possible to display the most relevant accessible valley areas determined as a function of the position of the aircraft.

[0060] Optionally, the method comprises a step 160 of using the final image IM F as a cost map in a flight trajectory determination tool for the aircraft (for example using an Eikonal type solver).

[0061] The use step 160 comprises, for example, the definition of a cost criterion aimed at favoring valley areas as a function of the final image IM F , and the determination of flight trajectories for the aircraft satisfying the defined cost criterion.

[0062] More generally, those skilled in the art will understand that the final image IM F obtained is suitable for being provided as input to any system using the information from this image, such an image, in particular in the field of artificial intelligence, as input to a convolutional neural network for image analysis.

[0063] Advantageously, the determination method comprises a step 170 of determining a flight trajectory for the aircraft as a function of the determined accessible valley areas. The determination step 170 is, for example, implemented just after the processing step 140, or just after the determination step 120. To facilitate decision-making, the modification step 170 is, advantageously, carried out following the display step 150.

[0064] When the aircraft flies over said environment, the determination step 170 advantageously comprises modifying the trajectory of the aircraft as a function of the areas of accessible valleys determined. The modification of the trajectory is thus carried out by favoring the valleys which have been determined to be accessible by the aircraft.

[0065] Thus, this method helps pilots in their decision-making regarding their navigation by determining the valley areas accessible to the aircraft. This method provides the pilot with better situational awareness.

[0066] The present method makes it possible in particular to identify compatible valleys from a digital terrain model and to superimpose, for example, the result obtained on a digital map in order to visually highlight the good valleys. Advantageously, the result obtained can be mathematically used as a cost map or partial cost map to be aggregated, seen from an eikonal-type solver in order to encourage the solver to find a path from point A to point B passing through the valleys identified by the method.

[0067] Thus, the present method makes it possible to improve the determination of valley areas accessible by an aircraft, and thus to improve the decision-making of a pilot faced with unforeseen situations.

[0068] Those skilled in the art will understand that the embodiments described above are capable of being combined with each other when such a combination is covered by the claims.

Claims

1. A method for determining valley areas accessible by an aircraft, a valley zone being considered accessible by an aircraft when the width of the valley or valleys that form the valley zone is greater than or equal to a predefined width, the method being implemented by an electronic device, the method comprising the following steps: a. obtaining an initial image (IMI) of an environment comprising valley areas, b. processing of the initial image (IMI) so as to eliminate the imaged elements on the initial image (IMI), the dimension of which is smaller than a predetermined dimension, to obtain a first processed image (IM1T), the predetermined dimension being chosen so as to remove valleys with a width less than the predefined width, and c. determining the curvature of each imaged element in the first processed image (IM1T), the valley areas accessible by the aircraft being the imaged elements, in the first processed image (IM1T), the curvature of which is strictly less than zero, and d. determining a flight path for the aircraft, depending on the determined accessible valley areas.

2. The method according to claim 1, wherein the method comprises a step of processing the first processed image (IM1T) so as to assign a zero value to the imaged elements on the first processed image (IM1T) the curvature of which is positive, so as to obtain a second processed image (IM2T).

3. The method according to claim 2, wherein the method comprises a step of processing the second processed image (IM2T) so as to obtain a final image (IMF), the step of processing the second processed image (IM2T) comprising: a. the normalization of the histogram of the second processed image (IM2T), and / or b. the increase of the contrast of the second processed image (IM2T) by a predetermined value, where appropriate after normalizing the histogram, and / or c. the increase of the resolution of the second processed image (IM2T), where appropriate after normalizing the histogram and increasing the contrast, so that the resolution of the final image (IMF) is equal to the resolution of the initial image (IMI).

4. The method according to claim 3, wherein the method comprises a step of displaying the final image (IMF) on a display (24), the display (24) being advantageously installed in an aircraft and the final image (IMF) preferentially being displayed according to the position of the aircraft, determined in real time.

5. The method according to claims 3 or 4, wherein the method further comprises: a. a step of defining a cost criterion aimed at favoring the valley areas according to the final image (IMF), and b. a step of determining flight paths for the aircraft meeting the defined cost.

6. The method according to any one of claims 1 to 5, wherein the step of processing the initial image (IMI) comprises: a. reducing the resolution of the initial image (IMI) so as to remove the imaged elements on the initial image (IMI) the dimension of which is less than the predetermined dimension, and b. applying a Gaussian blur filter to the resulting reduced resolution image so as to obtain the first processed image (IM1T).

7. The method according to any one of claims 1 to 6, wherein in the obtaining step, the initial image (IMI) of the environment is obtained by means of measurements made by a sensor, such as a camera or a satellite.

8. An electronic device (10) configured for implementing a method according to any one of claims 1 to 7.

9. An aircraft comprising an electronic device (10) according to claim 8.