阅读说明：本技术 显示屏上三维合成视图的显示方法、相关计算机程序产品和显示系统 (Method for displaying a three-dimensional composite view on a display screen, associated computer program product and display system ) 是由 埃马纽埃尔·蒙瓦森 皮埃尔·马里亚尼 让-马克·拉科斯特 于 2021-06-04 设计创作，主要内容包括：本发明涉及一种显示屏上三维合成视图的显示方法、相关计算机程序产品和显示系统。该显示方法为在飞行器的控制站中的显示屏上的显示方法,该控制站包括数据库,这些数据各自包括以相应分辨率代表地形的元素的制图数据。该方法包括以下步骤：获取地形的最大海拔和飞行器的海拔；根据最大海拔和飞行器的海拔之间的高度计算可视距离(D)和目标分辨率；测试目标数据库的适用性；如果目标数据库适用,则基于目标数据库的制图数据确定三维合成视图；以及在显示屏上显示地形的区域的三维合成视图。(The invention relates to a method for displaying a three-dimensional composite view on a display screen, a related computer program product and a display system. The display method is a display method on a display screen in a control station of an aircraft, the control station comprising a database, each of these data comprising cartographic data representing elements of the terrain at a respective resolution. The method comprises the following steps: acquiring the maximum altitude of the terrain and the altitude of the aircraft; calculating a visible distance (D) and a target resolution from the altitude between the maximum altitude and the altitude of the aircraft; testing the applicability of the target database; if the target database is applicable, determining a three-dimensional synthetic view based on the drawing data of the target database; and displaying a three-dimensional composite view of the area of terrain on the display screen.)

1. A display method of displaying on a display screen (26) a three-dimensional synthetic view of an area of terrain (12) that can be flown over by an aircraft (10), a real-time display screen (26) being adapted to be embedded in a control station (16) of the aircraft (10), the control station (16) further comprising a plurality of databases (20), the plurality of databases (20) each comprising cartographic data representing elements of the terrain (12) at a respective resolution, the display method comprising the steps of:

-acquiring (110) a maximum altitude (Zt) of the terrain (12) and an altitude (Za) of the aircraft (10) in the area of the terrain (12);

-calculating (120) a visible distance (D) and a target resolution of resolutions of the plurality of databases (20), the target resolution and the visible distance (D) each being calculated at least as a function of a height (H) between the maximum altitude (Zt) of the terrain (12) in the area of the terrain (12) and the altitude (Za) of the aircraft (10);

-testing (130) the suitability of the target database (20A) associated with the target resolution by verifying, for each element of the terrain (12) that is included in the area of the terrain (12) and that is located at a distance from the aircraft (10) that is less than the visibility distance (D), whether the target database (20) includes cartographic data representative of the element of the terrain (12);

-if said target database (20A) applies, determining a three-dimensional synthetic view of said area of said terrain (12) based on said cartographic data of said elements of said terrain (12) of which a representation of said target database (20A) is included in said area of said terrain (12) and which are located at a distance from said aircraft (10) which is less than said visible distance (D); and

-displaying (140, 160) a three-dimensional composite view of the area of the terrain (12) on the display screen (26).

2. The display method according to claim 1, further comprising, before the displaying step (140, 160), the steps of:

-if the target database (20A) is not applicable, testing (150) the applicability of an alternative database (20B) of the database (20) having a resolution lower than the target resolution;

-if the substitute database (20B) applies, determining the three-dimensional synthetic view of the area of the terrain (12) based on cartographic data of elements of the substitute database (20B) representative of the terrain (12) comprised in the area (12) of the terrain (12) and located at a distance (D) from the aircraft (10) smaller than the visible distance (D).

3. The display method according to claim 2, further comprising, before the displaying step (140, 160), a disabling step (170) of disabling the determining of the three-dimensional composite view and displaying the three-dimensional composite view on the display screen (26) when any database (20) is not applicable in the database (20) at a resolution lower than the target resolution.

4. Display method according to claim 1, wherein said target resolution is a decreasing function of said height (H).

5. Display method according to claim 4, wherein each resolution is associated with a range of values of said height (H).

6. Display method according to claim 5, wherein during the step of calculating the target resolution a hysteresis function is implemented when transitioning between two ranges of values of the height (H).

7. Display method according to claim 1, wherein said visible distance (D) is an increasing function of said height (H).

8. Display method according to claim 1, wherein the variation of the visible distance (D) over time is limited to a predetermined maximum variation.

9. A display method according to claim 1, wherein said elements of said terrain (12) associated with one of said databases (20) extend over an area which is smaller than the area over which the elements of the terrain (12) associated with the one of said databases (20) having a lower resolution than the resolution of said database (20) extend.

10. A computer readable medium comprising a computer program product comprising software instructions which, when executed by an information device, perform the display method according to claim 1.

11. A display system (28) on a display screen (26) displaying a three-dimensional composite view of an area of terrain (12) capable of being flown over by an aircraft (10), the display system (28) and the display screen (26) being adapted to be embedded in a control station (16) of the aircraft (10), the control station (16) further comprising a plurality of databases (20) each comprising cartographic data representing elements of the terrain (12) at a respective resolution, the display system (28) comprising:

-an acquisition module (34) configured to acquire a maximum altitude (Zt) of the terrain (12) and an altitude (Za) of the aircraft (10) within the area of the terrain (12);

-a calculation module (36) configured to calculate a target resolution of a resolution of the plurality of databases (20) and a visible distance (D), the target resolution and the visible distance (D) each being calculated at least as a function of a height (H) between the maximum altitude (Zt) of the terrain (12) in the area of the terrain (12) and the altitude (Za) of the aircraft (10);

-a testing module (38) configured to test (130) the suitability of the target database (20A) associated with the target resolution by verifying, for each element of the terrain (12) comprised in the area of the terrain (12) and located at a distance from the aircraft (10) which is less than the visible distance (D), whether the target database (20) comprises cartographic data representative of the element of the terrain (12);

-a determination module (40) configured to determine, if the target database (20A) applies, a three-dimensional synthetic view of the area of the terrain (12) based on the cartographic data of the elements of the terrain (12) of which the representation of the target database (20A) is comprised in the area of the terrain (12) and which are located at a distance from the aircraft (10) which is smaller than the visible distance (D); and

-a display module (42) configured to display the three-dimensional composite view of the area where the terrain (12) is present on the display screen (26).

Technical Field

The invention relates to a display method for displaying on a display screen a three-dimensional composite view of a terrain area that can be flown over by an aircraft.

The invention also relates to a computer-readable medium comprising a computer program product comprising software instructions which, when implemented by a computing device, implement such a display method.

The invention also relates to a display system for displaying on a display screen a three-dimensional composite view of a terrain area that can be flown over by an aircraft.

Background

The invention relates more particularly to an aircraft, while being applicable to any type of aircraft, such as helicopters or drones.

Such aircraft include, in a known manner, a system known as an SVS from the english "synthetic vision system" (or the french "synthetic vision system"). The system allows the pilot to display a composite view of the external landscape, which typically includes information about driving or navigation. The composite view is typically displayed on a display screen located in front of the instrument panel of the aircraft cockpit.

The composite view is an at least partially conformal three-dimensional view of a terrain area that can be flown over by the aircraft, particularly an area that is forward of the aircraft in a direction of travel of the aircraft.

Conformal representations refer to graphical and symbolic representations that are exactly superimposed on the terrain actually seen by the pilot.

Document FR 3053818 a1 also discloses a method of displaying a composite view which displays only a distance from the aircraft, called the visibility distance. The visibility distance is calculated according to different parameters such as the altitude of the aircraft and allows to limit the calculation time for implementing the composite view.

However, there is a need to further improve such display of composite views, and in particular the resolution of such displays in regions of interest such as airports, without affecting the display performance of the SVS system.

Disclosure of Invention

It is therefore an object of the present invention to propose a method for displaying a three-dimensional synthetic view, allowing a better resolution display in the pilot's area of interest, while limiting the computation time for displaying the three-dimensional synthetic view in real time.

To this end, the invention relates to a display method for displaying a three-dimensional composite view of an area of terrain that can be flown over by an aircraft on a display screen adapted to be embedded in a control station of the aircraft, the control station further comprising a plurality of databases each comprising cartographic data representing elements of the terrain at a respective resolution, the display method comprising the steps of:

-obtaining a maximum altitude of the terrain in the terrain area and an altitude of the aircraft;

-calculating a target resolution of the visible distance and the resolutions of the plurality of databases, the target resolution and the visible distance each being calculated at least as a function of the height between the maximum altitude of the terrain and the altitude of the aircraft in the area of said terrain;

-testing the suitability of the target database associated with the target resolution by verifying, for each element of terrain comprised in said region of terrain and located at a distance from the aircraft that is less than the visibility distance, whether the target database comprises cartographic data representative of said element of terrain;

-if the target database applies, determining a three-dimensional synthetic view of a region of the terrain based on cartographic data of the target database, these cartographic data representing elements of the terrain included in said region of the terrain and located at a distance from the aircraft smaller than the visibility distance; and

-displaying a three-dimensional composite view of the area of the terrain on the display screen.

The display method according to the invention thus allows the target resolution to be calculated as a function of the height between the maximum altitude of the terrain in said region of the terrain and the altitude of the aircraft. For example, when the altitude is low, typically corresponding to a takeoff or landing phase of the aircraft, the calculated target resolution is high so that the pilot has a good sense of his environment. Conversely, when the altitude is high, which generally corresponds to the cruising phase of the aircraft, the calculated target resolution is low, since the pilot does not need very precise information about the terrain over which it flies from altitude.

Furthermore, the display method according to the invention allows to calculate the viewing distance associated with this target resolution, for example to limit the data to be processed for determining the synthetic view and thus to limit the calculation time required to process these data.

The target database suitability test allows the database including high resolution mapping data to be used only for pilot areas of interest, such as airports, rather than for the entire terrain being flown over. The invention therefore also allows the size of these databases to be greatly reduced, so that they can be stored in the available, usually limited memory of the aircraft.

According to other advantageous aspects of the invention, the display method comprises one or more of the following features, taken alone or in any technically possible combination:

the method further comprises, before the step of displaying, the steps of:

if the target database is not applicable, testing the applicability of the substitute database with the resolution lower than the target resolution in the database;

+ if the alternative database applies, determining a three-dimensional synthetic view of the area of terrain based on cartographic data of the alternative database, the cartographic data representing elements of terrain contained in said area of terrain and located at a distance from the aircraft that is less than the visibility distance;

-the method further comprises, prior to the step of displaying, deactivating the determining of the three-dimensional synthetic view and the displaying of the three-dimensional synthetic view on the display screen when any of the databases having a resolution lower than the target resolution is not applicable;

-the target resolution is a decreasing function of the height;

-each resolution is associated with a range of values of said altitude, preferably implementing a hysteresis function when transitioning between two ranges of values of said altitude during the step of calculating the target resolution;

-the visible distance is an increasing function of the height;

the variation of the visible distance over time is limited to a predetermined maximum variation, and

-the elements of the terrain associated with one of the databases extend over an area smaller than an area over which the elements of the terrain associated with the one of the databases having a lower resolution than the resolution of said database extend.

The invention also relates to a computer-readable medium comprising a computer program comprising software instructions which, when executed by an information device, implement the display method as defined above.

The invention also relates to a display system for displaying on a display screen a three-dimensional composite view of a terrain area that can be flown over by an aircraft, the display system and the display screen being adapted to be embedded in a control station of the aircraft, the control station further comprising a plurality of databases each comprising cartographic data representing elements of the terrain at a respective resolution, the display system comprising:

-an acquisition module configured to acquire a maximum altitude of the terrain in the area of the terrain and an altitude of the aircraft;

-a calculation module configured to calculate a target resolution of the visible distance and the resolutions of the plurality of databases, the target resolution and the visible distance each being calculated at least as a function of the height between the maximum altitude of the terrain and the altitude of the aircraft in said area of the terrain;

-a testing module configured to test the suitability of the target database associated with the target resolution by verifying, for each element of terrain comprised in said region of terrain and located at a distance from the aircraft that is less than the visible distance, whether the target database comprises cartographic data representative of said element of terrain;

-a determination module configured to determine, if the target database applies, a three-dimensional synthetic view of a region of the terrain based on cartographic data of the target database, these cartographic data representing elements of the terrain included in said region of the terrain and located at a distance from the aircraft smaller than the visibility distance; and

a display module configured to display a three-dimensional composite view of an area of the terrain on a display screen.

Drawings

These characteristics and advantages of the invention will emerge more clearly from a reading of the following description, given purely by way of non-limiting example and with reference to the accompanying drawings, in which:

figure 1 is a schematic side view of a cockpit of an aircraft;

FIG. 2 is a schematic side view of the aircraft of FIG. 1 flying over terrain;

FIG. 3 is a top view similar to the schematic diagram of FIG. 2; and

figure 4 is a schematic view of a display system according to the invention; and

fig. 5 is a flow chart of a display method according to the invention for displaying on a display screen a three-dimensional composite view of a terrain area that can be flown over by an aircraft, the method being implemented by the display system of fig. 4.

Detailed Description

In the following, the term "vertical" is generally understood with respect to the direction of gravity. The term "horizontal" is generally understood to mean perpendicular to the vertical direction.

The aircraft 10 is, for example, an airplane, helicopter or even a drone flying over terrain 12. In other words, the aircraft 10 is a flying apparatus that can be manoeuvred by the pilot 14 via a control station 16, which control station 16 is arranged inside the aircraft 10 or at a distance from the aircraft, in particular in the case of unmanned aerial vehicles.

As seen in fig. 1 and 3, the aircraft 10 extends mainly in a longitudinal direction X-X'. The longitudinal direction X-X' is also commonly referred to as the roll axis of the aircraft 10.

The aircraft 10 is capable of flying in a longitudinal direction X-X' in the direction of travel of the aircraft 10 over an area of terrain 12 in front of it.

The control station 16 is here a cockpit of the aircraft 10. As shown in fig. 1, the control station 16 includes at least one seat 18 for the pilot 14, a plurality of databases 20, an orientation sensor 22, a windshield 24 that is at least partially transparent and separates the interior of the cockpit from the environment external to the aircraft 10, and a display assembly including a display screen 26 and a display system 28.

The display screen 26 is, for example, a head-up display screen. The heads-up display screen is at least partially transparent. Advantageously, the heads-up display is a shutter 29 integrated into a helmet 30 adapted to be worn by the pilot 14, as shown in fig. 1. As a variation, the heads-up display is a transparent surface that is fixed in the cockpit and placed in front of the pilot 14.

Alternatively or additionally, the display 26 is a heads-down display. The heads-down display screen is a surface configured to display at least one image. Advantageously, the heads-down display screen is configured to display information related to the aircraft 10, such as speed, altitude relative to the terrain 12, orientation of the aircraft 10, and/or information related to the environment external to the aircraft 10, such as air traffic information and weather conditions in the vicinity of the aircraft 10.

As a variant not shown, the aircraft 10 is a drone that can be remotely manoeuvred by means of a control station 16, for example a ground control station, on the basis of which the manoeuvre of the drone is carried out. The control station 16 here comprises at least the seat 18 of the pilot 12, a display screen 26 and at least one ambient display screen, not shown. The environment display screen is configured to display an external environment of the aircraft 10 captured by at least one camera embedded in the drone.

The directional sensor 22 is adapted to determine the aiming axis a-a' of the gaze of the pilot 14. As shown in FIG. 1, the aiming axis A-A' associated with the predetermined solid angle defines a field of view 32 of the pilot 14. The heads-up display screen is intended to be at least partially disposed in the field of view 32 of the pilot 14.

The orientation sensor 22 is, for example, an accelerometer provided in a helmet 30 of the pilot 14 and is adapted to determine the posture of the head of the pilot 14 based on the measured acceleration of the helmet 30. Thus, the orientation sensor 22 is adapted to determine the aiming axis a-a' based on the pose of the head of the pilot 14 and the orientation of the aircraft 10 received at least by the sensor embedded in the aircraft 10.

As a variant, the orientation sensor 22 is an electromagnetic sensor adapted to determine the attitude of the head of the pilot 14 based on magnetic field disturbances due to movements of the head of the pilot 14.

The control station 16 advantageously comprises between two and ten different databases 20, in particular three databases 20.

Each database 20 includes mapping data representing elements of terrain 12 at a respective resolution.

For each respective resolution, the mapping data typically includes geographic coordinates, such as latitude, longitude, and altitude in a geodetic system, and information about elements of the terrain 12, such as properties of the terrain 12. For example, for each respective resolution, the mapping data is composed of said geographic coordinates and said information about the elements of the terrain 12.

Elements of the terrain 12 are, for example, mountains, existing buildings, landing areas, etc.

Resolution represents the amount of mapping data available per unit area of terrain 12. Thus, the higher the resolution, the more mapping data representative of an area of a given terrain 12 that is included in the correlation database 20, and the more accurate the pilot 14 will have a representation of the area of the terrain 12.

For example, the resolution is expressed as an angular difference between two topographical elements on the ground surface, each represented by cartographic data. Each database 20 then has a resolution in particular between 1 and 24 arcseconds.

The elements of terrain 12 associated with one of the databases 20 extend, for example, over an area that is less than an area over which the elements of terrain 12 associated with one of the databases 20 having a resolution lower than the resolution of the database 20 extend.

Thus, database 20, having the lowest resolution, includes cartographic data representing elements of terrain 12 that are over the largest area of terrain 12. In contrast, database 20 with the highest resolution includes cartographic data representing elements of terrain 12 extending over a minimum area of terrain 12. In particular, the database 20 with the highest resolution comprises only cartographic data of the elements of interest to the pilot 14, that is to say of a given point of interest, also known as POI (in english as "point of interest"), for example an airport.

Thus, the storage size of the database 20 associated with the high resolution is still limited compared to the database 20 associated with the lower resolution. In the case where the drawing data covers the same area, the high-resolution database 20 has a much larger storage size than the low-resolution database 20. This is particularly problematic in the aerospace field, since the database 20 is embedded in the aircraft 10 with reduced available memory, wherein the pass band allows the cartographic data to be loaded from the memory which is also reduced. Thus, by limiting the area associated with the high resolution databases 20, the storage size of these databases 20 is limited, e.g., smaller than the storage size of the low resolution databases 20. All databases 20 are suitable for embedding in the aircraft 10.

The elements of terrain 12 associated with one of the databases 20 extend, for example, over an area included in the area over which the elements of terrain 12 associated with one of the databases 20 having a resolution lower than the resolution of said database 20 extend.

As seen in FIG. 4, display system 28 includes an acquisition module 34, a calculation module 36, a test module 38, a determination module 40, a display module 42, and an optional disabling module 44.

The acquisition module 34 is configured to acquire a maximum elevation Zt of the terrain 12 in the area of the terrain 12, as shown in fig. 2.

In the example of fig. 3, the area of terrain 12 is constituted by a cone of axis X-X', the apex of which is the aircraft 10 and the maximum distance Dmax relative to the aircraft 10. The distance Dmax corresponds to the eye line of the pilot 14, for example. The maximum distance Dmax is typically between 10 and 160 nautical miles (hereinafter NM, from english nautical miles).

The acquisition module 34 is for example adapted to calculate the maximum elevation Zt of the terrain 12 based on cartographic data comprised in the database 20.

The acquisition module 34 is also configured to acquire the altitude Za of the aircraft 10, as shown in FIG. 2. The acquisition module 34 is, for example, adapted to acquire the altitude Za of the aircraft 10 based on measurements of an altimeter embedded in the aircraft 10.

The calculation module 36 is configured to calculate a target resolution among the resolutions of the different databases 20.

The database 20 associated with the target resolution is referred to as the target database 20A.

As shown in fig. 2, the target resolution is calculated based at least on the height H between the maximum altitude Zt of the terrain 12 in the area of the terrain 12 and the altitude Za of the aircraft 10.

The target resolution is for example a decreasing function of said height H. Thus, when the altitude H is low and the aircraft 10 is near the maximum prominence of the area of the terrain 12, typically upon landing, the target resolution is high so that the pilot 14 obtains an accurate representation of its vicinity. Conversely, when the altitude H is high, which generally corresponds to a cruising phase of the aircraft 10 over the terrain 12, the calculated target resolution is low, since the pilot 14 does not need very precise information about the terrain 12 over which it flies high.

Furthermore, each resolution is associated with a range of values of the height H. Thus, the acquisition module 34 associates one of the resolutions of the database 20 with each value range of the height H. For example, when the height H is less than 3000m, the target resolution is equal to the maximum resolution among the resolutions of the database 20. In contrast, when the height H is greater than 9000m, the target resolution is equal to the minimum resolution among the resolutions of the database 20.

In addition, a hysteresis function is implemented at the transition between the two ranges of values of the height H. The hysteresis function allows to avoid excessive transitions when the height H approaches a transition. Thus, if the resolution increases when changing from the height H to a certain transition value, the resolution can only return to its previous value if the height H decreases to a value below the transition value, and vice versa.

The calculation module 36 is also configured to calculate a visible distance D, as shown in fig. 3, which represents the maximum distance displayed by the composite view of the aircraft 10, as will be explained later. Thus, when the visibility distance D is high, the composite view displays a large range of terrain 12 originating from the aircraft 10. Conversely, when the visibility distance D is low, the composite view only displays a small range near the aircraft 10.

The visible distance D is calculated based at least on the height H between the maximum elevation Zt of the terrain 12 in the area of the terrain 12 and the elevation Za of the aircraft 10.

The visible distance D is for example an increasing function of the height H. Advantageously, the visible distance D is calculated based on a piecewise linear function.

Further, the visible distance D includes a minimum threshold value and a maximum threshold value. For example, when the height H is less than 3000m, the visible distance D remains equal to 40NM, and when the height H is greater than 9000m, the visible distance D remains equal to 160 NM.

Thus, when the altitude H is low and the aircraft 10 is approaching the maximum convexity of the area of the terrain 12, typically upon landing, the visible distance D is small and the composite view only shows the approaching area 12 of interest to the pilot 14 of the aircraft 10.

Conversely, when the altitude H is high, generally corresponding to a cruise phase of the aircraft 10, the visibility distance D is high because the pilot 14 needs to have a long-range view of the terrain 12 over which it flies.

Thus, the visible distance D is a decreasing function of the target resolution. The more the target resolution increases, the more the visible distance D decreases. Conversely, the larger the increase in the visible distance D, the more the target resolution is reduced.

Furthermore, the change of the viewing distance D over time is limited to a predetermined maximum change to avoid abrupt transitions of the viewing distance D. For example, the variation of the visible distance D is limited to 0.5NM per second.

Test module 38 is configured to test the suitability of target database 20A associated with a target resolution by verifying, for each element of terrain 12 that is included in the region of terrain 12 and that is located at a distance from aircraft 10 that is less than visible distance D, whether target database 20A includes cartographic data representative of the element of terrain 12.

In other words, test module 38 is configured to test the suitability of database 20 by verifying whether mapping data associated with elements of terrain 12 that are included in the region of terrain 12 and that are located at a distance from aircraft 10 that is less than visible distance D is available.

Test module 38 is also configured to test the suitability of a so-called replacement database 20B in database 20 having a resolution lower than the target resolution if target database 20A is not suitable, i.e., not suitable.

Test module 38 is then configured to verify, for each element of terrain 12 that is included in the region of terrain 12 and that is located at a distance from aircraft 10 that is less than visible distance D, whether replacement database 20B includes cartographic data representative of the element of terrain 12.

Thus, as seen in fig. 1, the databases 20 include a target database 20A, an optional replacement database 20B, and one or more other databases 20C.

Determination module 40 is configured to determine a three-dimensional composite view of the area of terrain 12 based on cartographic data of target database 20A representative of elements of terrain 12 contained in the area of terrain 12 and located at a distance from aircraft 10 that is less than visible distance D, if target database 20A applies.

The composite view is determined by computing and synthesizing a representation of an area of terrain 12 based on the associated cartographic data.

The computation time to obtain the composite view is substantially proportional to the amount of map data processed. Thus, the fact that the calculation module 36 is adapted to reduce the visible distance D when the target resolution increases makes it possible to limit the calculation time and thus to allow a real-time use of the display system 28 to be obtained.

The determination module 40 is further configured to determine a three-dimensional synthetic view of the area of the terrain 12 based on cartographic data of the replacement database 20B representative of elements of the terrain 12 contained in the area of the terrain 12 and located at a distance from the aircraft 10 that is less than the visible distance D, if the replacement database 20B is applicable.

Display module 42 is configured to display a three-dimensional composite view of the area of terrain 12 on display screen 26.

Display module 42 is configured to display, in particular, a composite view determined based on cartographic data of elements of terrain 12 located up to a visible distance D at the target resolution or the alternative resolution.

The display module 42 is configured to display the composite view on the heads-up display screen and/or heads-down display screen.

The disabling module 44 is configured to disable the determining module 40 and the display module 42 to disable, in other words, disable or prevent, the determination of the three-dimensional synthesized view and the display of the three-dimensional synthesized view on the display screen 26 when any database 20 of the database 20 having a resolution lower than the target resolution is not applicable.

In the event that none of the alternative databases 20B include cartographic data required for determining a composite view, the deactivation of the determination module 40 and the display module 42 allows to avoid malfunction of the determination module 40 and the display module 42.

In the example of fig. 3, the display system 28 includes an information processing unit 50, which is formed, for example, by a memory 52 and a processor 54 associated with the memory 52. Acquisition module 34, calculation module 36, test module 38, determination module 40, display module 42, and optional disabling module 44 are all implemented in software or software blocks executable by processor 54. The memory 52 of the display system 28 can then store the acquisition software, the calculation software, the test software, the determination software, and optionally the disabling software. The processor 54 is then able to execute each of these software.

In a variant not shown, acquisition module 34, calculation module 36, test module 38, determination module 40, display module 42 and optionally deactivation module 44 are all implemented in the form of programmable logic components (for example FPGAs (field programmable gate array in english)) or in the form of application-specific integrated circuits (for example ASICs (application-specific integrated circuits in english)).

When the display system 28 is implemented in the form of one or more software, i.e., in the form of a computer program, the display system can also be recorded on a computer-readable medium (not shown). The computer readable medium is, for example, a medium capable of storing electronic instructions and coupled to a bus of a computing system. By way of example, the readable medium can be an optical disk, a magneto-optical disk, ROM memory, RAM memory, any type of non-volatile memory (e.g., EPROM, EEPROM, FLASH, NVRAM), a magnetic or optical card. A computer program comprising software instructions is then stored on the readable medium.

The operation of the display system 28 according to the invention will now be explained by means of fig. 5, fig. 5 showing a flow chart of a method of displaying a composite view on the display screen 26 according to the invention, which method is implemented by the display system 28.

Initially, the aircraft 10 flies over the terrain 12. The aircraft 10 flies toward the region of the terrain 12 that it faces.

At initial step 110, the acquisition module 34 acquires a maximum altitude Zt of the terrain 12 and an altitude Za of the aircraft 10 in the area of the terrain 12, visible in fig. 2.

The method then comprises a calculation step 120 performed by the calculation module 36, which calculates, on the one hand, the target resolution among the resolutions of the plurality of databases 20 and, on the other hand, the visible distance D.

The target resolution and the visibility distance D are each calculated at least as a function of the height H between the maximum altitude Zt of the terrain 12 in the region of the terrain 12 and the altitude Za of the aircraft 10.

Then, at step 130, test module 38 tests the suitability of target database 20A associated with the target resolution by verifying, for each element of terrain 12 that is included in the region of terrain 12 and that is located at a distance from aircraft 10 that is less than visible distance D, whether target database 20A includes cartographic data representative of the element of terrain 12.

If target database 20A applies, determination module 40 determines a three-dimensional composite view of the area of terrain 12 based on cartographic data of target database 20A representing elements of terrain 12 contained in the area of terrain 12 and located at a distance from aircraft 10 that is less than visible distance D.

Then, at step 14, the display module 42 displays a three-dimensional composite view of the area of the terrain 12 on the display screen 26 at the target resolution up to the viewable distance D.

If target database 20A is not applicable at test step 130, the method includes a second test step 150 performed by test module 38 that tests the suitability of a replacement database 20B in database 20 having a resolution lower than the target resolution.

If replacement database 20B applies, determination module 40 determines a three-dimensional composite view of the area of terrain 12 based on cartographic data of replacement database 20B representative of elements of terrain 12 contained in the area of terrain 12 and located at a distance from aircraft 10 that is less than visible distance D.

Then, at step 160, the display module 42 displays a three-dimensional composite view of the area of the terrain 12 on the display screen 26 at the alternative resolution up to the viewable distance D.

If replacement database 20B is not applicable, the display method includes a deactivation step 170 performed by deactivation module 44 that deactivates the determination of the three-dimensional composite view and displays the three-dimensional composite view on display screen 26.

The method then includes new step iterations starting at step 110.

The method is particularly implemented with a minimum frequency of 15 Hz.

A display method according to the present invention having a target resolution and a single alternative resolution is described herein.

The skilled person will thus understand that as a variant, multiple alternative resolutions are possible. According to this variant, the display method includes a plurality of suitability tests 150 that test each suitability of the respective replacement databases 20B having respective replacement resolutions. Thus, if the first replacement database 20B does not apply, the method includes a new applicability test step 150 of testing the applicability of the second replacement database 20B at a resolution less than that of the first replacement database 20B, and so on until the corresponding replacement database 20B applies.

However, when any database 20 of the database 20 with a resolution lower than the target resolution is not applicable, the method comprises a deactivation step 170 performed by the deactivation module 44, which deactivates the determination of the three-dimensional synthetic view and the display of the three-dimensional synthetic view on the display screen 26.

Thus, it can be seen that the present invention has a number of advantages.

In fact, the display method according to the invention allows to calculate the target resolution from the height H between the maximum altitude Zt of the terrain 12 and the altitude Za of the aircraft 10. When the altitude H is low, the target resolution is typically high so that the pilot 14 has a good sense of his environment.

Calculating the visible distance D also from this height H allows adjusting the visible distance D to the calculated target resolution and thus limiting the data to be processed for determining the composite view.

The computation time to obtain the composite view is substantially proportional to the amount of charting data processed, and as the target resolution increases, the decrease in the visible distance D allows for limiting the computation time and thus providing real-time use of the display system 28 according to the present invention.

Finally, the suitability testing of the target database 20A and the possible use of the alternative database 20B allow for the inclusion of high resolution mapping data, i.e., the database 20 with the target resolution is used only for areas of interest of the pilot 14, such as airports, and not for all or all of the terrain 12 that may be flown over by the aircraft 10.

The invention therefore also allows to significantly reduce the size of these databases 20, so that they can be stored in the generally limited available memory of the aircraft 10, as well as to significantly reduce the amount of relevant data to be processed by the display method according to the invention and the associated display system 18.