Electronic aircraft navigation assistance system, associated method and computer program

Abstract

Electronic system for assisting the navigation of an aircraft, associated method and computer program This system (10), includes: - an acquisition module (12) of source databases (28) of terrain data corresponding to an area of ​​a terrain, divided into a plurality of cells;each source base (28) containing, for each cell, an elevation, - a transposition module (14) of each source base (28) into a respective transposed base of terrain data corresponding to said terrain area, divided according to a reference grid into a plurality of transposed cells, each transposed base including, for each transposed cell, a transposed elevation, - an evaluation module (16) of a local consistency level, based on the comparison of the transposed elevation of said cell with the transposed elevation of the corresponding transposed cell of at least one other transposed base, and - an assistance module (18) configured to determine aircraft navigation assistance data, based on the evaluated local consistency level. Figure for the abstract: Figure 1;

Description

Title of the invention: Electronic navigation assistance system for an aircraft, associated method and computer program

[0001] The present invention relates to an electronic navigation assistance system for an aircraft.

[0002] The invention also relates to a method for assisting the navigation of an aircraft, implemented by such an electronic assistance system.

[0003] The invention also relates to a computer program comprising software instructions which, when executed by a computer, implement such an assistance method.

[0004] The invention relates to the field of terrain databases and aircraft navigation assistance systems. By terrain database is meant here a collection of data representative of physical characteristics of a terrain, before their compilation into a data set readable by a calculation processor. The aircraft navigation assistance systems are for example on board an aircraft and provide navigation assistance information to a user of the aircraft or to an aircraft control system. The navigation assistance systems are alternatively used outside of an aircraft. The navigation assistance systems then generate for example information intended to be loaded or transmitted to an aircraft, in order to assist a user, or an on-board computer, in the navigation of the aircraft.

[0005] Terrain databases generally correspond to an area of ​​terrain likely to be flown over by the aircraft. Such databases include terrain elevation data which are used in aircraft navigation assistance. Knowledge of terrain elevation is essential for aircraft navigation, particularly when the aircraft is piloted autonomously.

[0006] In order to better understand the degree of confidence that can be had in the elevations of a terrain database, it is known to characterize terrain databases by a confidence index in a consistency level. The consistency level corresponds, for example, to a difference between the elevation at a point or position of a database and the elevation at the same point or position of another database. The consistency level thus reflects a vertical precision via the comparison of the elevations of two terrain databases for the same position. The confidence index then characterizes, for example, the probability that the difference in elevation between the databases used to evaluate consistency is less than a given consistency level, i.e. a given elevation difference.

[0007] A terrain database based on the SRTM (Shuttle Radar Topography Mission) model, developed in the late 1990s, is known. More recent models are also known, such as the NASADEM (NASA Digital Elevation Model), the ASTER GDEM (Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model), the ALOS (Advanced Earth Observing Satellite) model, or the ArcticDEM (Arctic Digital Elevation Model). The value of the consistency level is generally lower for a given confidence index in recent models than in older models.

[0008] It is further known to use the confidence index and consistency level values ​​of terrain databases for aircraft navigation assistance. The RTCA DO-276 rev C and EUROCAE ED-98 rev C standards define, for example, confidence indices in a consistency level to be respected.

[0009] For example, it may be required that a 95% confidence index at a 30m consistency level be verified so that elevation data from a terrain database can be used for navigation in an airport area.

[0010] Similarly, it may be required that an 80% confidence index at a consistency level of 80m be verified so that elevation data from a terrain database can be used for navigation outside airport areas.

[0011] Current electronic aircraft navigation assistance systems, for which navigation is based on an index of confidence in a level of consistency for an entire database, are nevertheless not entirely satisfactory.

[0012] Indeed, even if such systems assist navigation via values ​​characterizing a database as a whole, these systems do not allow possible local errors of the model to be taken into account. The data passing through such systems cannot then, for example, be used to actively assist in the development of a trajectory by generating data to assist the navigation of an aircraft and can generally only be used to verify such a trajectory already developed.

[0013] One of the aims of the invention is then to propose a system making it possible to generate data to assist the navigation of the aircraft taking into account possible local elevation errors in a terrain database.

[0014] To this end, the invention relates to an electronic navigation assistance system for an aircraft, comprising:

[0015] - an acquisition module configured to acquire a plurality of source bases of terrain data, each source base corresponding to an area of ​​terrain likely to be flown over by the aircraft, divided according to a mesh into a plurality of cells, each corresponding to a sector of the terrain area; each source base containing, for each cell, an elevation,

[0016] - a transposition module configured to transpose each source base into a respective transposed base of terrain data, each transposed base corresponding to said area of ​​the terrain, divided according to a reference mesh into a plurality of transposed cells, the reference mesh being common to all the transposed bases, each transposed base including, for each transposed cell, a transposed elevation,

[0017] - an evaluation module configured to evaluate a local consistency level for at least one transposed cell of a respective transposed base, based on comparing the transposed elevation of said cell with the transposed elevation of the corresponding transposed cell of at least one other transposed base, and

[0018] - an assistance module configured to determine assistance data at the na aircraft monitoring, depending on the local coherence level evaluated for said at least one transposed cell.

[0019] Such an electronic system in which the navigation assistance data is calculated as a function of the local coherence level evaluated for at least one transposed cell makes it possible to obtain navigation data taking into account possible local errors in the source bases used to generate the assistance data.

[0020] Such an electronic system then makes it possible to better meet the requirements specific to the terrain databases used in the aeronautics field and in particular the requirements of the DPAL 1 assurance level (from the English "Data Process Assurance Level 1") defined in the RTCA DO-200B / EUROCAE ED-76A standard (standard entitled in English "Standards for Processing Aeronautical Data") as well as the requirements of the FAA AC20-153 standard (standard entitled in English "Acceptance of Aeronautical Data Processes and Associated Databases").

[0021] According to other advantageous aspects of the invention, the electronic navigation assistance system of an aircraft comprises one or more of the following characteristics, taken individually or in all technically possible combinations:

[0022] - the evaluation module is configured to evaluate the local consistency level in function of the smallest elevation difference between the transposed elevation of said cell and the transposed elevation of the corresponding transposed cell of each other transposed base;

[0023] - the local consistency level is chosen from a high consistency level, a medium consistency level and a low consistency level the local consistency level evaluated being: - a high level of consistency if the smallest elevation difference is less than or equal to 15m; - an average level of consistency if the smallest elevation difference is greater than 15m and less than or equal to 30m; - a low level of consistency if the smallest elevation difference is greater than 30m and less than or equal to 100m;

[0024] - each source base also contains, for each cell, an associated metadata at elevation, each transposed base including, for each transposed cell, a transposed metadata, the evaluation module then being configured to evaluate the local consistency level for each transposed cell of a respective transposed base, based on the transposed metadata of said cell and the transposed metadata of the corresponding cell of each other transposed base;

[0025] - the metadata is indicative of a measured elevation or a predefined elevation, the evaluation module then being configured to evaluate the local consistency level based solely on the comparison of transposed cell elevations whose metadata is indicative of a measured elevation;

[0026] - the system comprises:

[0027] - a segmentation module configured to segment the area of ​​the terrain cor corresponding to at least one of the transposed bases in a plurality of areas of interest, each area of ​​interest comprising a plurality of adjacent transposed cells;

[0028] the assistance module being configured to determine, for the area of ​​interest, a confidence index in a given level of coherence, the confidence index forming the assistance data and being determined as a function of the local level of coherence of each transposed cell of the area of ​​interest;

[0029] - the confidence index in a given level of consistency is determined as a function of the proportion, in the area of ​​interest, of transposed cells whose local coherence level is greater than or equal to said given coherence level;

[0030] - the system comprises:

[0031] - a user interface configured to receive, from a user, a target consistency level and a confidence limit index in said target consistency level; and

[0032] - a validation module configured to:

[0033] + validate an area of ​​interest if the confidence index determined in the level of target consistency is greater than or equal to the confidence limit index;

[0034] + reject an area of ​​interest if the confidence index determined in the level of target consistency is less than the confidence limit; and

[0035] - a control module, configured to:

[0036] + order a display of a validated state if the area of ​​interest is validated by the validation module, or a rejected state if the area of ​​interest is rejected by the validation module (22); and / or

[0037] + command the generation of an aircraft trajectory outside the zone(s) of interest rejected; and

[0038] - the assistance module is configured to determine a target database terrain, corresponding to the area of ​​the terrain, divided according to the reference mesh into a plurality of target cells; the target base including, for each target cell, a target elevation forming the assistance data, the assistance module then being configured to determine the target elevation of the target cell as a function of the transposed elevation of at least two corresponding transposed cells, the local coherence level of which is higher than the local coherence level of the other corresponding transposed cells.

[0039] The invention further relates to a method for assisting the navigation of an aircraft, implemented by an electronic system for assisting the navigation of an aircraft, the method comprising the following steps:

[0040] - acquisition of a plurality of field data source bases, each source base corresponding to an area of ​​land likely to be flown over by the aircraft, divided according to a mesh into a plurality of cells, each corresponding to a sector of the area of ​​land; each source base containing, for each cell, an elevation,

[0041] - transposition of each source base into a respective transposed data base terrain, each transposed base corresponding to said area of ​​the terrain, divided according to a reference mesh into a plurality of transposed cells, the reference mesh being common to all the transposed bases, each transposed base including, for each transposed cell, a transposed elevation,

[0042] - evaluation of a local coherence level for at least one transposed cell of a respective transposed base, based on comparing the transposed elevation of said cell with the transposed elevation of the corresponding transposed cell of at least one other transposed base, and

[0043] - determination of aircraft navigation assistance data, depending on of the evaluated local coherence level of at least one transposed cell of one of the transposed bases.

[0044] The invention also relates to a computer program comprising software instructions which, when executed by a computer, implement a method for assisting the navigation of an aircraft, as defined above.

[0045] These characteristics and advantages of the invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the appended drawings, in which:

[0046] [Fig-1] [Fig.l] is a schematic representation of an electronic system assistance to the navigation of an aircraft according to a first embodiment of the invention;

[0047] [Fig.2] [Fig.2] is seen similar to that of [Fig.l] according to a second embodiment of the invention;

[0048] [Fig.3] [Fig.3] is a flowchart of a method for assisting the navigation of an aircraft implemented by the electronic system of FIG. 1 or that of [Fig.2];

[0049] [Fig.4] [Fig.4] is a schematic representation of two meshes cutting out a corresponding area of ​​a terrain, before and after a transposition implemented by one of the systems of figures 1 and 2;

[0050] [Fig.5] [Fig.5] is a representation of a display controlled by the system of [Fig.l]; and

[0051] [Fig.6] [Fig.6] is a schematic representation of the reference mesh cutting out a corresponding area of ​​a terrain, for a plurality of source bases, and a representation of the reference mesh cutting out the corresponding area of ​​the terrain for a target base determined by the system of [Fig.2].

[0052] In the remainder of the description, the expression “substantially equal to” defines a relationship of equality at + / - 10%, preferably at + / - 5%.

[0053] In Figures 1 and 2, a system 10 for assisting navigation of an aircraft comprises an acquisition module 12, a transposition module 14, an evaluation module 16 and an assistance module 18.

[0054] In the embodiment of [Fig.l], the assistance system 10 further comprises a segmentation module 20, a validation module 22, a control module 24 and a user interface 26.

[0055] The assistance system 10 is for example on board the aircraft whose navigation is assisted by the system 10. Alternatively, the assistance system 10 is installed outside the aircraft whose navigation is assisted by the system 10. Alternatively, and as will be explained below, a part of the system 10, for example the user interface 26, the validation module 22 and the control module 24, is on board the aircraft, the rest of the system 10 being installed outside the aircraft.

[0056] The aircraft is for example an airplane. Alternatively, the aircraft is a helicopter, or a drone that can be piloted remotely by a pilot or an autonomous drone.

[0057] The acquisition module 12 is configured to acquire a plurality of source bases 28 of terrain data, hereinafter called source bases 28. The acquisition module 12 is in other words configured to acquire the data contained in the plurality of source bases 28.

[0058] As visible in [Fig.4], each source base 28 corresponds to a zone 30 of a terrain likely to be overflown by the aircraft, divided according to a mesh into a plurality of cells 32, each corresponding to a sector of the zone 30 of the terrain.

[0059] The cells 32 are for example square. A resolution of each database corresponds for example to the length of one side of a cell. The resolution is for example between 90m and 15m.

[0060] Each source base 28 is for example a terrain database of the same area 30 of the terrain, the source bases 28 then being distinct from one another while corresponding to the same area 30 of the terrain. For example, a first source base is a NASADEM base, a second source base is an ASTER GDEM base and a third source base is an ALOS base.

[0061] The resolution of each of the first, second and third bases is for example substantially equal to 30m if zone 30 of the terrain is located at the equator.

[0062] For a source base 28 of the ALOS type, the terrain is cut according to a mesh such that a zone 30 of terrain extending on the Earth's surface over a region of 1° of longitude by 1° of latitude is cut into 3600 cells by 3600 cells.

[0063] For a source base 28 of the ASTER GDEM type, the terrain is cut according to a mesh such that a zone 30 of terrain extending on the Earth's surface over a region of 1° of longitude by 1° of latitude is cut into 3601 cells by 3601 cells.

[0064] For a source base 28 of the NASADEM type, the terrain is cut according to a mesh such that a zone 30 of terrain extending on the Earth's surface over a region of 1° of longitude by 1° of latitude is cut into 3601 cells by 3601 cells.

[0065] Each source base 28 contains, for each cell 32, an ELV elevation. Each source base 28 further preferably comprises, for each cell, an MD metadata associated with the ELV elevation.

[0066] The ELV elevation for a cell 32 corresponds to a height of the terrain inside the cell 32. The ELV elevation corresponds for example to a reference value of a height of the terrain relative to a reference altitude, typically the mean sea level, also noted MSL (from the English Mean Sea Level). Each source base therefore comprises for example an ELV elevation per cell 32.

[0067] The MD metadata corresponding to the ELV elevation reflects an origin of the ELV elevation in the source base 28. The MD metadata is in particular indicative of a measured elevation or a predefined elevation.

[0068] An MD metadata indicative of a measured elevation is a metadata associated with an ELV elevation having been measured during the development of the source base 28. In other words, an MD metadata indicative of a measured elevation indicates that the ELV elevation to which the MD metadata corresponds is an elevation that can be described as “authentic” for the source base 28, this ELV elevation coming from measurements specific to the source base 28. Thus, for a given source base 28, an MD metadata indicative of a measured elevation indicates that the ELV elevation to which the MD metadata corresponds is an elevation independent of the elevation of other source bases 28, that is to say that such an elevation does not does not come from another source base 28. The MD metadata thus characterizes, when it is indicative of a measured elevation, a local independence of the source base 28 with respect to other source bases 28.

[0069] In contrast, an MD metadata indicative of a predefined elevation is a metadata associated with an ELV elevation that was not measured during the development of the source base 28. In other words, an MD metadata indicative of a predefined elevation indicates that the ELV elevation to which the MD metadata corresponds is an ELV elevation that can be described as “non-authentic” for the source base 28, this ELV elevation coming from measurements that are not specific to the source base 28. Thus, for a given source base 28, an MD metadata indicative of a predefined elevation indicates that the ELV elevation to which the MD metadata corresponds is an elevation dependent on the elevation of another source base 28, i.e. that such an elevation comes from another source base 28. The MD metadata thus characterizes, when it is indicative of a predefined elevation, a local dependency of the source base 28. vis-à-vis other source bases 28.

[0070] An MD metadata indicative of a predefined elevation is for example associated with an ELV elevation measured during the development of a source base 28 which is not the source base 28 containing said ELV elevation. The presence of such an elevation in a source base, and therefore of a metadata indicative of a predefined elevation, is typically explained by a problem of ELV elevation measurement for the cell 32 during the development of the source base 28 (for example due to meteorology inappropriate for the measurement), the ELV elevation then being replaced by a predefined elevation coming from another source base 28.

[0071] The transposition module 14 is configured to transpose each source base 28 into a transposed base 34, as schematically illustrated in [Fig.4],

[0072] Each transposed base 34 corresponds to the zone 30 of the terrain, cut according to a reference mesh into a plurality of transposed cells 36.

[0073] As illustrated in [Fig.4], the reference mesh is common to all the transposed bases 34. Thus, two source bases 28 corresponding to an area cut according to a different mesh, correspond, once transposed into two transposed bases 34, to the same area cut according to the reference mesh which is common to these transposed bases 34.

[0074] The reference mesh is for example chosen such that it corresponds to the least fine mesh according to which the terrain is cut, for the plurality of source bases 28. In other words, in this example, the transposed cells 36 cutting the terrain for each transposed base 34 have the dimension of the largest cells among the cells cutting the terrain for each source base 28.

[0075] In a particular example, an area 30 of land extending over the Earth's surface on a region of 1° of longitude by 1° of latitude is divided into 1200 transposed cells by 1200 transposed cells, according to the reference mesh. Each transposed cell is then, for example, approximately in the shape of a square whose side length corresponds to a resolution of 3 arc seconds. The value of the resolution in arc seconds defines the dimension corresponding to a side of a smallest representative element, the smallest representative element here being the transposed cell.

[0076] In the example where a first source base is of the NASADEM type, a second source base is of the ASTER GDEM type and a third source base is of the ALOS type, the transposition module 14 transposes the first source base into a first transposed source base, the second source base into a second transposed source base and respectively the third source base into a third transposed source base, the first, second and third transposed source bases cutting out the area 30 of the terrain according to the reference mesh.

[0077] Each transposed base 34 includes, for each transposed cell 36, a transposed elevation ELV_T. Each transposed base 34 further preferably comprises, for each transposed cell 36, a transposed metadata MD_T associated with the transposed elevation ELV_T.

[0078] The transposition module 14 is thus configured to determine the transposed elevation ELV_T, and where appropriate, the transposed metadata MD_T, for a transposed base 34, from at least one elevation ELV and at least one metadata MD, of the source base 28 being transposed.

[0079] The transposition module 14 is for example configured to determine the transposed elevation ELV_T of each transposed cell 36 from the elevation ELV of a corresponding cell 32 of the transposed source base 28. The corresponding cell 32 is for example the cell 32 of the source base covering the most common surface of the terrain with the transposed cell 36 of the zone 30 of the terrain.

[0080] In a particular embodiment, the transposition module 14 is configured to determine the transposed elevation ELV_T from the ELV elevations of several corresponding cells 32 of the source base 28 being transposed. The transposed elevation ELV_T of the transposed cell 36 corresponds for example to the weighted average of the ELV elevations of the cells 32 corresponding to the transposed cell 36 of the transposed source base 28. The average is for example weighted for each ELV elevation by the ratio of the surface area of ​​the corresponding terrain area 30 of the transposed cell 36 covered by the cell 32, divided by the surface area of ​​the terrain area 30 covered by the transposed cell 36.

[0081] The transposition module 14 is for example configured to determine the transposed metadata MD_T of each transposed cell 36 from the metadata of a corresponding cell 32 of the transposed source base 28. The corresponding cell 32 is for example the cell 32 of the source base 28 covering the most common area of ​​the terrain with the transposed cell 36 of the area 30 of the terrain.

[0082] Alternatively, the transposition module 14 is configured to determine a transposed metadata MD_T indicative of a predefined elevation if the metadata of one of the or the corresponding cell 32 of the transposed source base 28 is indicative of a predefined elevation.

[0083] The evaluation module 16 is configured to evaluate a local consistency level NCL for at least one transposed cell 36 of a transposed base 34. The evaluation module 16 is configured to evaluate the local consistency level NCL as a function of the comparison of the transposed elevation ELV_T of one of the transposed cells 36 of one of the transposed bases 34 with the transposed elevation ELV_T of the corresponding transposed cell 36 of at least one other of the transposed bases 34. In other words, the evaluation module 16 is configured to evaluate the local consistency level NCL for a transposed cell 36 as a function of the elevation difference between said transposed cell 36 and one or more corresponding transposed cells 36 of other transposed bases 34.

[0084] In a preferred variant, the evaluation module 16 is configured to evaluate the local coherence level NCL of a transposed cell 36 as a function of the smallest elevation difference between the transposed elevation ELV_T of said transposed cell 36 and the transposed elevation ELV_T of the corresponding transposed cell 36 of each other transposed base 34.

[0085] Furthermore, and preferably, the evaluation module 16 is for example configured to evaluate the local consistency level NCL for each transposed cell 36 of a respective transposed base 34, as a function of the transposed metadata MD_T of said transposed cell 36 and the transposed metadata MD_T of the corresponding transposed cell 36 of each other transposed base 34. In other words, and since a transposed metadata MD_T is indicative of the dependence or independence of a transposed elevation ELV_T of a given transposed base 34 with respect to transposed elevations of other transposed bases 34, the evaluation module 16 evaluates the local consistency level NCL for each transposed cell 36 as a function of the dependence or independence of the transposed elevation ELV_T of said transposed cell 36 and the corresponding transposed cell 36 of each other transposed base 34.

[0086] In particular, and according to this variant, the evaluation module 16 is configured to evaluate the local coherence level NCL as a function only of ELV_T elevations of transposed cells 36 whose MD_T metadata is indicative of a measured elevation, and in particular of the comparison of such ELV_T elevations. In other words terms, for a given transposed base 34, the evaluation module 16 is configured to evaluate the local consistency level NCL for a transposed cell 36 based only on ELV_T elevations of corresponding transposed cells 36 of other transposed bases 34 independent of the ELV_T elevation of the transposed cell 36 of the given transposed base 34.

[0087] The evaluation module 16 is then configured to evaluate the local coherence level NCL of a transposed cell 36 as a function of the smallest elevation difference between the transposed elevation ELV_T of said transposed cell 36 and the transposed elevation ELV_T of the corresponding transposed cell 36 of each other transposed base 34, the transposed metadata MD_T associated with each of the compared transposed elevations ELV_T being indicative of a measured elevation.

[0088] In the example where a first source base is of the NASADEM type, a second source base is of the ASTER GDEM type and a third source base is of the ALOS type, and following the transposition of these bases, the local coherence level NCL for a transposed cell 36 of one of these bases is determined as a function of at least one elevation difference between the transposed elevation ELV_T of the transposed cell 36 and the transposed elevation ELV_T of the transposed cell 36 of one of the other transposed bases 34.

[0089] In particular, and in the preferred variant, the transposed elevation ELV_T of the transposed cell 36 of one of the transposed bases 34 is compared with the transposed elevation ELV_T of each of the corresponding transposed cells 36 for which the transposed metadata MD_T is indicative of a measured elevation. The smallest elevation difference resulting from such comparisons then serves as a basis for evaluating the local coherence level NCL of the transposed cell 36.

[0090] In a particular example, the local consistency level is selected from a high consistency level, a medium consistency level, and a low consistency level.

[0091] The evaluated local coherence level of a transposed cell 36 is for example a high coherence level if the smallest elevation difference between the transposed elevation ELV_T of the transposed cell 36 and the transposed elevation ELV_T of each of the corresponding transposed cells of the other transposed bases 34 is less than or equal to 15m.

[0092] The evaluated local coherence level of a transposed cell 36 is for example an average coherence level if the smallest elevation difference between the transposed elevation ELV_T of the transposed cell 36 and the transposed elevation ELV_T of each of the corresponding transposed cells of the other transposed bases 34 is greater than 15m and less than or equal to 30m.

[0093] The evaluated local coherence level of a transposed cell 36 is for example a low coherence level if the smallest elevation difference between the transposed elevation ELV_T of transposed cell 36 and the transposed elevation ELV_T of each of the corresponding transposed cells of the other transposed bases 34 is greater than 30m and less than or equal to 100m.

[0094] For example, if the smallest elevation difference between the transposed elevations ELV_T of a transposed cell 36 corresponds to the elevation difference between a transposed elevation ELV_T whose value is 126 m (for example resulting from the transposition of the elevation ELV of a source base of the NASADEM type) and a transposed elevation ELV_T whose value is 101 m (for example resulting from the transposition of the elevation ELV of a source base of the ALOS type), the difference between these transposed elevations ELV_T is equal to 25 m and the local coherence level NCL of the transposed cell 36 is evaluated as average.

[0095] In other examples, the local coherence level NCL is expressed directly as the value of the smallest elevation difference between the transposed elevation ELV_T of the transposed cell 36 and the transposed elevation ELV_T of each of the corresponding transposed cells of the other transposed bases 34. The local coherence level NCL is then expressed for example in meters. A high local coherence level NCL then corresponds to a small elevation difference, expressed in meters, for example an elevation difference less than or equal to 50m, 30m, 15m or 10m. Conversely, the low local coherence level NCL corresponds to a large elevation difference expressed in meters, for example an elevation difference greater than 50m, 80m or 100m.

[0096] The assistance module 18 is configured to determine data D for assistance with the navigation of the aircraft, as a function of the local coherence level NCL evaluated for at least one of the transposed cells 36.

[0097] The first embodiment illustrated in [Fig. 1], for which a confidence index IC at a given consistency level NC forms the assistance data D generated by the assistance module 18, will now be presented.

[0098] The segmentation module 20 is configured to segment the area 30 of the terrain corresponding to at least one of the transposed bases 34 into a plurality of areas of interest 38.

[0099] The segmentation module 20 is in particular configured to segment the area 30 of the terrain so that each area of ​​interest 38 comprises a plurality of adjacent transposed cells 36. As illustrated schematically in [Fig.5], each area of ​​interest 38 of the same transposed base 34 comprises for example the same number of transposed cells 36.

[0100] In a particular example, each area of ​​interest 38 comprises a set of 120 transposed cells by 120 transposed cells.

[0101] In such an example, and in the case where the reference mesh is such that a region of 1° of longitude by 1° of latitude is divided into 1200 cells transposed by 1200 transposed cells 36, such a region of 1° of longitude by 1° of latitude includes one hundred areas of interest 38.

[0102] Each area of ​​interest is then, for example, substantially in the shape of a square, the length of one side of which corresponds to an angle equal to 6 minutes of arc, or in other words to a length of approximately 6 nautical miles, noted Nm (from the English Nautical mile).

[0103] The assistance module 18 is configured to determine, for the area of ​​interest 38, a confidence index IC at a given consistency level NC.

[0104] The confidence index IC then forms the assistance data and is determined as a function of the local coherence level NCL of each transposed cell 36 of the area of ​​interest 38.

[0105] The confidence index IC in a given coherence level NC is for example determined as a function of the proportion, on the area of ​​interest 38, of transposed cells 36 whose local coherence level NCL is greater than or equal to said given coherence level NC.

[0106] By way of example, for a given coherence level NC equal to an average coherence level, the confidence index IC in the average coherence level corresponds to the proportion of cells, in the area of ​​interest 38, whose local coherence level NCL is average or high.

[0107] It will be understood that alternatively, the assistance module 18 is configured to determine, for the area of ​​interest 38, a level of consistency for a given confidence index.

[0108] With reference to [Fig.4], the user interface 26 is configured to receive, from a user, a target consistency level NCC and a limit confidence index ICL in said target consistency level NCC.

[0109] In the variant shown, the user interface 26 is provided with a keyboard and a screen. Alternatively, the user interface 26 is for example provided with a touch screen.

[0110] The target consistency level NCC corresponds to a consistency level, as defined above for the local consistency levels NCL, that the user of the system 10 wishes to evaluate on the area of ​​interest 38.

[0111] The limit confidence index ICL in said target coherence level NCC corresponds for example to a minimum confidence index that the user wishes to obtain in the target coherence level NCC on the area of ​​interest 38.

[0112] Pairs of limit confidence index ICL and target consistency level NCC arise for example from regulations or user requirements.

[0113] For example, a confidence limit index ICL of 95% at a coherence level of 30m is required for the use of a transposed base 34, or a corresponding source base 28, for the navigation of an aircraft in an airport area.

[0114] For example, a confidence limit index ICL of 80% at a coherence level of 80m is required for the use of a transposed base, or a corresponding source base 28, for the navigation of an aircraft outside an airport area.

[0115] The validation module 22 is configured to validate a zone of interest 38 if the confidence index IC determined at the target consistency level NCC is greater than or equal to the limit confidence index ICL, and to reject a zone of interest 38 if said determined confidence index IC is less than the limit confidence index ICL.

[0116] As illustrated in [Fig. 5], the control module 24 is for example configured to control the display of a validated state if the area of ​​interest 38 is validated by the validation module 22, or a rejected state if the area of ​​interest is rejected by the validation module 22. In particular, the control module 24 is connected to the user interface 26 to control the display of the validated or rejected state on the user interface 26. In the example of [Fig. 5], the rejected areas of interest 38 are hatched on the user interface 26 while the validated areas of interest 38 are devoid of hatching on the user interface 26.

[0117] In a variant not illustrated, the control module 24 is configured to generate an alert when an aircraft flies over a rejected area of ​​interest 38.

[0118] Alternatively or in addition, the control module 24 is configured to control the generation of an aircraft trajectory outside the rejected area(s) of interest 38. Such a trajectory is for example further displayed on the user interface, as represented by a curve C in [Fig.5].

[0119] The control module 24 is for example configured to obtain an initial trajectory of the aircraft, and to generate the trajectory of the aircraft from this initial trajectory, so that the trajectory of the aircraft extends entirely outside the rejected zone(s) of interest 38.

[0120] The second embodiment, illustrated in [Fig.2], for which a target elevation ELV_C forms the data generated by the assistance module 18, will now be presented.

[0121] In this embodiment, and as illustrated in [Fig.6], the assistance module 18 is configured to determine a target base 40 of terrain data, corresponding to the area 30 of the terrain, divided according to the reference mesh into a plurality of target cells 42.

[0122] As illustrated in [Fig.6], each target cell 42 corresponds to a transposed cell 36 of each transposed base 34, the reference mesh being common to the target base 40 and to the transposed bases 34.

[0123] The target base 40 includes, for each target cell 42, a target elevation ELV_C forming the assistance data D.

[0124] In particular, the assistance module 18 is configured, according to this embodiment, to determine the target elevation ELV_C of the target cell 42 as a function of the transposed elevations ELV_T of at least two corresponding transposed cells 36, the local coherence level NCL of which is higher than the local coherence level NCL of the other corresponding transposed cells 36.

[0125] The assistance module 18 is for example configured to determine the target elevation ELV_C of the target cell 42 as a function of the transposed elevations ELV_T of at least two corresponding transposed cells 36 by implementing a Kalman filter for merging the transposed elevations ELV_T of at least two transposed cells 36.

[0126] In a particular example, the assistance module 18 is configured to determine the target elevation ELV_C of the target cell 42 as a function of the transposed elevations ELV_T of the two corresponding transposed cells 36, whose local coherence level NCL is higher than the local coherence level NCL of the other corresponding transposed cells 36. Thus, in this example, the target elevation ELV_C of a target cell 42 is determined as a function only of the two transposed elevations ELV_T of transposed cells 36 having the highest local coherence level.

[0127] In the examples of figures 1 and 2 illustrating the first and second embodiments previously described, the assistance system 10 comprises an information processing unit 50 formed for example of a memory 52 and a processor 54 associated with the memory 52.

[0128] In the examples of figures 1 and 2, the acquisition module 12, the transposition module 14, the evaluation module 16, the assistance module 18, and in the example of [Fig.l], the segmentation module 20, the validation module 22 and the control module 24, are each produced in the form of software, or a software brick, executable by the processor 54.

[0129] The memory 52 of the assistance system 10 is then capable of storing software for acquiring a plurality of source bases 28, software for transposing each source base 28 into a respective transposed base 34, software for evaluating a local coherence level NCL for at least one transposed cell 36 of a respective transposed base 34, and software for assisting with navigation of the aircraft. In the example of [Fig.l], the memory is further capable of storing software for segmenting the terrain area corresponding to at least one of the bases transposed into a plurality of areas of interest, software for validating an area of ​​interest 38 and software for controlling display and / or trajectory generation.

[0130] The processor 54 is then able to execute each of the software programs among the acquisition software, the transposition software, the evaluation software, the software assistance, and, in the example of [Fig.l], the segmentation software, the validation software and the control software.

[0131] In a variant not illustrated, the system comprises two separate information processing units, each unit being for example formed of a memory and a processor associated with the memory, one of the units being on board an aircraft while the other of the units is installed outside the aircraft. The acquisition module 12, the transposition module 14, the evaluation module 16, the assistance module 18 and the segmentation module 20 are for example each produced in the form of software, or a software brick, executable by the processor of the unit installed outside the aircraft. The validation software and the control software are for example each produced in the form of software, or a software brick, executable by the processor of the unit on board the aircraft.

[0132] In a variant not shown, the acquisition module 12, the transposition module 14, the evaluation module 16, the acquisition module 18, and for example the segmentation module 20, the validation module 22 and the control module 24, are each produced in the form of a programmable logic component, such as an FPGA (Field Programmable Gate Array), or in the form of a dedicated integrated circuit, such as an ASIC (Application Specific Integrated Circuit).

[0133] When the assistance system 10 is produced in the form of one or more software programs, that is to say in the form of a computer program, it is furthermore capable of being recorded on a medium, not shown, readable by a computer. The computer-readable medium is, for example, a medium capable of storing electronic instructions and of being coupled to a bus of a computer system. By way of example, the readable medium is an optical disk, a magneto-optical disk, a ROM memory, a RAM memory, any type of non-volatile memory (for example EPROM, EEPROM, FLASH, NVRAM), a magnetic card or an optical card. A computer program comprising software instructions is then stored on the readable medium.

[0134] With reference to [Fig. 3], a method 100 for assisting the navigation of an aircraft, implemented by the electronic assistance system 10, will now be presented.

[0135] During an initial acquisition step 110, the acquisition module 12 acquires a plurality of source bases 28, as described previously. As seen above, each source base contains, for each of its cells 32, an ELV elevation, and contains for example an MD metadata. The acquisition module 12 then communicates the plurality of source bases 28 acquired to the transposition module 14.

[0136] The transposition module 14 then transposes each source base 28 into a transposed base 34 during a transposition step 120. As illustrated in [Fig.4] and as described above, the reference mesh according to which each transposed base 34 of the area 30 of the terrain is cut is common to all the transposed bases 34. Each base transposed during the transposition step 120 then includes, for each transposed cell 36, a transposed elevation ELV_T, or even further a transposed metadata MD_T. The transposition module 14 then communicates the plurality of transposed bases 34, resulting from the transposition of the plurality of source bases 28, to the evaluation module 16.

[0137] The evaluation module 16 then evaluates, during a subsequent evaluation step 130, a local consistency level NCL for at least one transposed cell 36 of a respective transposed base 34. The local consistency level NCL for the transposed cell 36 of a respective transposed base 34 is in particular determined as a function of the comparison of the transposed elevation ELV_T of said transposed cell 36 with the transposed elevation ELV_T of the corresponding transposed cell 36 of at least one other transposed base 34. The evaluation module 16 then communicates to the assistance module 18 said local consistency level NCL for at least one transposed cell 36 of a transposed base 34.

[0138] During a subsequent step 140 of determining a piece of aircraft navigation assistance data, the assistance module 18 determines a piece of aircraft navigation assistance data D as a function of the evaluated local coherence level NCL of at least one transposed cell 36 of one of the transposed bases 34.

[0139] As seen above, in a first embodiment, the assistance data D is formed by a confidence index IC in a given coherence level NC. During the step 140 of determining a piece of aircraft navigation assistance data, the segmentation module 20 segments the terrain area 30 into a plurality of areas of interest 38. The assistance module 18 then determines, for the area of ​​interest 38, the confidence index IC in a coherence level NC as a function of the local coherence level NCL of each transposed cell 36 of the area of ​​interest 38.

[0140] As seen above, in a second embodiment, the assistance data D is for example formed by a target elevation ELV_C of a target cell 42 of a target base 40. During the step 140 of determining a piece of data for assisting the navigation of the aircraft, the assistance module 18 then determines the target elevation ELV_C of the target cell 42 as a function of the transposed elevations ELV_T of at least two corresponding transposed cells 36, the local coherence level NCL of which is higher than the local coherence level NCL of the other corresponding transposed cells 36.

[0141] The use of an evaluation module 16 configured to evaluate the local coherence level NCL of a transposed cell 36 as a function of the smallest elevation difference between the transposed elevation of said cell 36 and the transposed elevation of the corresponding transposed cell 36 of each other transposed base 34 is particularly advantageous since it makes it possible to exclude from the evaluation of the level of local consistency NCL the transposed bases 34 whose transposed elevations ELV_T of the corresponding cells 36 are far from the transposed elevation ELV_T of said cell, the probability that the transposed elevations ELV_T of corresponding cells of such transposed bases are erroneous being high.

[0142] The chosen consistency levels are particularly relevant in the field of aircraft navigation assistance.

[0143] The use of metadata for the evaluation of the local consistency level NCL of each transposed cell 36, and in particular the evaluation of the local consistency level NCL as a function of the smallest elevation difference between the transposed elevation ELV_T of said cell 32 and the transposed elevation ELV_T of the corresponding transposed cell 36 of each other transposed base 34, is particularly advantageous since it makes it possible to consider only the elevation data ELV_T having been measured during the development of the source base 28 resulting in the transposed base 34.Thus, the use of metadata avoids, for example, evaluating the local consistency level NCL based on the comparison of data from the same measurements, or in other words, avoids the comparison of data dependent on each other for the calculation of the local consistency level NCL, thus improving the quality of the evaluation of the local confidence level NCL and therefore of the navigation assistance.

[0144] The determination of a confidence index IC in a coherence level NC on an area of ​​interest 38 and, where appropriate, the validation and control of a display or the generation of a trajectory as a function of such a confidence index IC in a coherence level NC on an area of ​​interest 38, makes it possible to take into consideration possible local errors of the source bases 28 in the navigation assistance, and where appropriate, to display validation information or to generate a trajectory more reliably.

[0145] Determining the target elevation of the target cell 42 as a function of the transposed elevations ELV_T of at least two corresponding transposed cells 36 further makes it possible to form a target base 40 whose elevation values ​​ELV_C are more precise than the elevation values ​​ELV of the source bases 28.

Claims

Claims

1. Electronic system (10) for assisting the navigation of an aircraft, comprising: - an acquisition module (12) configured to acquire a plurality of source bases (28) of terrain data, each source base (28) corresponding to an area (30) of terrain likely to be flown over by the aircraft, divided according to a mesh into a plurality of cells (32), each corresponding to a sector of the area (30) of the terrain; each source base (28) containing, for each cell (32), an elevation (ELV), - a transposition module (14) configured to transpose each source base (28) into a respective transposed base (34) of terrain data, each transposed base (34) corresponding to said area (30) of the terrain, divided according to a reference mesh into a plurality of transposed cells (36), the reference mesh being common to all the transposed bases (34), each transposed base (34) including, for each transposed cell (36), a transposed elevation (ELV_T), - an evaluation module (16) configured to evaluate a local consistency level (NCL), reflecting a vertical precision, for at least one transposed cell (36) of a respective transposed base (34), as a function of the comparison of the transposed elevation (ELV_T) of said cell (36) with the transposed elevation (ELV_T) of the corresponding transposed cell (36) of at least one other transposed base (34), And - an assistance module (18) configured to determine a data item (D) for assisting the navigation of the aircraft, as a function of the local consistency level (NCL) evaluated for said at least one transposed cell (36), each source base (28) further containing, for each cell (32), a metadata item (MD) associated with the elevation (ELV), each transposed base (34) including, for each transposed cell (36), a transposed metadata item (MD_T), the evaluation module (16) then being configured to evaluate the local consistency level (NCL) for each transposed cell (36) of a respective transposed base (34), as a function of the transposed metadata item (MD_T) of said cell (36) and the transposed metadata item (MD_T) of the corresponding cell (36) of each other base transposed (34), the metadata (MD) being indicative of a measured elevation or a predefined elevation, the evaluation module (16) then being configured to evaluate the local coherence level (NCL) based solely on the comparison of elevations of transposed cells (36) whose metadata (MD_T) is indicative of a measured elevation.

2. System (10) according to claim 1, wherein the evaluation module (16) is configured to evaluate the local coherence level (NCL) as a function of the smallest elevation difference between the transposed elevation (ELV_T) of said cell (36) and the transposed elevation (ELV_T) of the corresponding transposed cell (36) of each other transposed base (34).

3. System (10) according to claim 2, in which the local consistency level (NCL) is chosen from a high consistency level, a medium consistency level and a low consistency level, the local consistency level (NCL) evaluated being: - a high consistency level if the smallest elevation difference is less than or equal to 15m; - a medium consistency level if the smallest elevation difference is greater than 15m and less than or equal to 30m; - a low consistency level if the smallest elevation difference is greater than 30m and less than or equal to 100m.

4. System (10) according to any one of the preceding claims, wherein the system (10) comprises: - a segmentation module (20) configured to segment the area (30) of the terrain corresponding to at least one of the transposed bases (34) into a plurality of areas of interest (38), each area of ​​interest (38) comprising a plurality of adjacent transposed cells (36); the assistance module (18) being configured to determine, for the area of ​​interest (38), a confidence index (IC) at a given coherence level, the confidence index (IC) forming the assistance data (D) and being determined as a function of the local coherence level (NCL) of each transposed cell (36) of the area of ​​interest (38).

5. System (10) according to claim 4, in which the confidence index (CI) in a given level of coherence is determined as a function of the proportion, on the area of ​​interest (38), of transposed cells (36) of which the local consistency level (LCL) is greater than or equal to said given consistency level.

6. System (10) according to claim 4 or 5, wherein the system (10) comprises: - a user interface (26) configured to receive, from a user, a target consistency level (NCC) and a limit confidence index (ICL) in said target consistency level (NCC); and - a validation module (22) configured to: + validate an area of ​​interest (38) if the confidence index (IC) determined in the target consistency level (NCC) is greater than or equal to the limit confidence index (ICL); + reject an area of ​​interest if the confidence index (IC) determined in the target consistency level (NCC) is less than the limit confidence index (ICL); and - a control module (24), configured to: + control a display of a validated state if the area of ​​interest (38) is validated by the validation module (22), or a rejected state if the area of ​​interest (38) is rejected by the validation module (22);and / or + command the generation of an aircraft trajectory outside the rejected area(s) of interest (38).;

7. System (10) according to any one of the preceding claims, in which the assistance module (18) is configured to determine a target base (40) of terrain data, corresponding to the area (30) of the terrain, divided according to the reference mesh into a plurality of target cells (42); the target base (40) including, for each target cell (42), a target elevation (ELV_C) forming the assistance data (D), the assistance module (18) then being configured to determine the target elevation (ELV_C) of the target cell (42) as a function of the transposed elevation (ELV_T) of at least two corresponding transposed cells (36), the local coherence level (NCL) of which is higher than the local coherence level (NCL) of the other corresponding transposed cells (36).

8. Method (100) for assisting the navigation of an aircraft, implemented by an electronic system (10) for assisting the navigation of an aircraft, the method (100) comprising the following steps: - acquisition (110) of a plurality of source bases (28) of terrain data, each source base (28) corresponding to an area (30) of terrain likely to be overflown by the aircraft, divided according to a

9. meshing into a plurality of cells (32), each corresponding to a sector of the area (30) of the terrain; each source base (28) containing, for each cell (32), an elevation (ELV), - transposition (120) of each source base (28) into a respective transposed base (34) of terrain data, each transposed base (34) corresponding to said area (30) of the terrain, cut according to a reference mesh into a plurality of transposed cells (36), the reference mesh being common to all the transposed bases (34), each transposed base (34) including, for each transposed cell (36), a transposed elevation (ELV_T), - evaluation (130) of a local coherence level (NCL), reflecting a vertical precision, for at least one transposed cell (36) of a respective transposed base (34), as a function of the comparison of the transposed elevation (ELV_T) of said cell (36) with the transposed elevation (ELV_T) of the corresponding transposed cell (36) of at least one other transposed base (34), and - determination (140) of assistance data (D) for the navigation of the aircraft, as a function of the evaluated local coherence level (NCL) of at least one transposed cell (36) of one of the transposed bases (34), each source base (28) further containing, for each cell (32), a metadata (MD) associated with the elevation (ELV), each transposed base (34) including, for each transposed cell (36), a transposed metadata (MD_T), during the evaluation step, the local coherence level (NCL) is evaluated as a function further of the transposed metadata (MD_T) of said cell (36) and of the transposed metadata (MD_T) of the corresponding cell (36) of each other transposed base (34), the metadata (MD) being indicative of a measured elevation or a predefined elevation, the local coherence level (NCL) being evaluated in function only of the comparison of transposed cell elevations (36) whose metadata (MD_T) is indicative of a measured elevation. A computer program comprising software instructions which, when executed by a computer, implement a method (100) according to the preceding claim.

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