Patent ID: 12236792

DETAILED DESCRIPTION

In the remainder of the description, the expression “substantially equal to” defines an equality relationship at +/−10%, preferably at +/−5%.

InFIGS.1and2, an aircraft navigation assistance system10includes an acquisition module12, a transposition module14, an evaluation module16, and an assistance module18.

In the embodiment shown inFIG.1, assistance system10further includes a segmentation module20, a validation module22, a command module24, and a user interface26.

Assistance system10is, for example, on board the aircraft whose navigation the system10assists. Alternatively, assistance system10is installed outside the aircraft whose navigation the system10assists. Alternatively, and as will be discussed later, part of system10, for example user interface26, validation module22and command module24, is carried on board the aircraft, with the remainder of system10being installed outside the aircraft.

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

Acquisition module12is configured to acquire a plurality of source bases28of field data, hereafter referred to as source bases28. Acquisition module12is in other words configured to acquire data contained in source bases28.

As may be seen inFIG.4, each source base28corresponds to an area30of a terrain likely to be overflown by the aircraft, divided in a mesh into a plurality of cells32, each corresponding to a sector of area30of the terrain.

Cells32are, 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 90 m and 15 m.

Each source database28is, for example, a terrain database of the same area30of the terrain, source databases28being distinct from each other but corresponding to the same area30of 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.

The resolution of each of the first, second and third bases is, for example, substantially equal to 30 m if area30of the terrain is located at the equator.

For an ALOS-type source base, the terrain is cut according to a grid such that an area30of terrain extending over the earth's surface over a region of 1° longitude by 1° latitude is cut into 3,600 cells by 3,600 cells.

For a source base28of the ASTER GDEM type, the terrain is cut according to a mesh such that an area30of terrain extending over the earth's surface over a region of 1° longitude by 1° latitude is cut into 3,601 cells by 3,601 cells.

For a source base28of the NASADEM type, the terrain is cut according to a mesh such that an area30of terrain extending on the earth's surface over a region of 1° longitude by 1° latitude is cut into 3,601 cells by 3,601 cells.

Each source base28contains, for each cell32, an ELV elevation. Each source database28preferably further includes, for each cell32, a metadata MD associated with ELV elevation.

ELV elevation for a cell32corresponds to a height of the ground within the cell32. ELV elevation corresponds, for example, to a reference value of a terrain height in relation to a reference altitude, typically Mean Sea Level (MSL). Each source base therefore includes, for example, one ELV elevation per cell32.

MD metadata corresponding to ELV elevation reflects an origin of ELV elevation in source database28. MD metadata is in particular indicative of a measured elevation or a predefined elevation.

An MD metadata indicative of a measured elevation is a metadata associated with an ELV elevation that has been measured during the development of source database28. 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 may be described as “authentic” for source base28, and that ELV elevation is derived from source base28's own measurements. Thus, for a given source base28, 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 bases28, i.e., such an elevation does not originate from another source base28. MD metadata thus characterizes, when it is indicative of a measured elevation, a local independence of source base28from other source bases28.

In contrast, MD metadata indicative of a predefined elevation is metadata associated with an ELV elevation that has not been measured during the development of source database28. 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 may be qualified as “not authentic” for source base28, as this ELV elevation comes from measurements that are not specific to source base28. Thus, for a given source base28, an MD metadata indicative of a predefined elevation indicates that the ELV elevation to which the MD metadata corresponds is an elevation dependent elevation of another source base28, i.e., that such an elevation is from another source base28. MD metadata thus characterizes, when indicative of a predefined elevation, a local dependency of source database28on other source databases28.

A metadata MD indicative of a predefined elevation is, for example, associated with an ELV elevation measured during the construction of a source base28which is not source base28containing the ELV elevation. The presence of such an elevation in a source database, and thus of metadata indicative of a predefined elevation, is typically due to a problem with the ELV elevation measurement for cell32when source database28was compiled (e.g., due to inappropriate meteorology for the measurement), with the ELV elevation being replaced by a predefined elevation from another source database28.

Transposition module14is configured to transpose each source base28into a transposed base34, as schematically illustrated inFIG.4.

Each transposed base34corresponds to area30of the terrain, divided according to a reference grid into a plurality of transposed cells36.

As illustrated inFIG.4, the reference mesh is common to all transposed bases34. Thus, two source bases28corresponding to an area cut according to a different mesh correspond, once transposed into two transposed bases34, to the same area cut according to the reference mesh which is common to these transposed bases34.

The reference mesh is for example chosen so that it corresponds to the least fine mesh according to which the terrain is cut, for the plurality of source bases28. In other words, in this example, the transposed cells36cutting the terrain for each transposed base34have the size of the largest cells among the cells cutting the terrain for each source base28.

In one particular example, an area30of land extending across the earth's surface over a region of 1° longitude by 1° latitude is partitioned into 1,200 transposed cells by 1,200 transposed cells, according to the reference grid. Each transposed cell is then, for example, roughly in the form of a square with a side length corresponding to a resolution of 3 arc seconds. The value of the resolution in arc second(s) defines the dimension corresponding to one side of a smallest representative element, the smallest representative element here being the transposed cell.

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, transposition module14transposes the first source base into a first transposed source base, the second source base into a second transposed source base and the third source base into a third transposed source base, respectively, the first, second and third transposed source bases cutting out area30of the terrain according to the reference grid.

Each transposed base34includes, for each transposed cell36, a transposed elevation ELV_T. Each transposed base34preferably further includes, for each transposed cell36, a transposed metadata MD_T associated with transposed elevation ELV_T.

Transposition module14is thus configured to determine transposed elevation ELV_T, and if applicable, transposed metadata MD_T, for a transposed base34, from at least one elevation ELV and at least one metadata MD, of the source base28being transposed.

For example, transposition module14is configured to determine transposed elevation ELV_T of each transposed cell36from elevation ELV of a corresponding cell32of the transposed source base28. Corresponding cell32is, for example, cell32of the source database covering the most common area of the terrain with transposed cell36of zone30of the terrain.

In a particular embodiment, transposition module14is configured to determine transposed elevation ELV_T from elevations ELV of a corresponding plurality of cells32of the source base28being transposed. Transposed elevation ELV_T of transposed cell36is, for example, the weighted average of elevations ELV of cells32corresponding to transposed cell36of transposed source base28. For example, the average is weighted for each ELV elevation by the ratio of the area of corresponding terrain30of transposed cell36covered by cell32, divided by the area of terrain30covered by transposed cell36.

For example, transposition module14is configured to determine transposed metadata MD_T of each transposed cell36from metadata of a corresponding cell32of transposed source database28. Corresponding cell32is, for example, cell32of source database28covering the most common area of the terrain with transposed cell36of terrain area30.

Alternatively, transposition module14is configured to determine a transposed metadata MD_T indicative of a predefined elevation if metadata of a corresponding one of or cell32of transposed source base28is indicative of a predefined elevation.

Evaluation module16is configured to evaluate a local consistency level NCL for at least one transposed cell36of a transposed base34. Evaluation module16is configured to evaluate local consistency level NCL based on a comparison of transposed elevation ELV_T of one of transposed cells36of one of transposed bases34with transposed elevation ELV_T of the corresponding transposed cell36of at least one other of transposed bases34. In other words, evaluation module16is configured to evaluate local coherence level NCL for a transposed cell36based on elevation difference between the transposed cell36and one or more corresponding transposed cells36of other transposed bases34.

In a preferred embodiment, evaluation module16is configured to evaluate local coherence level NCL of a transposed cell36based on the smallest elevation difference between transposed elevation ELV_T of the transposed cell36and transposed elevation ELV_T of the corresponding transposed cell36of each other transposed base34.

In addition, and preferably, evaluation module16is, for example, configured to evaluate local consistency level NCL for each transposed cell36of a respective transposed base34, based on transposed metadata MD_T of the transposed cell36and transposed metadata MD_T of the corresponding transposed cell36of each other transposed base34. 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 base34on transposed elevations of other transposed bases34, evaluation module16evaluates local consistency level NCL for each transposed cell36based on dependence or independence of transposed elevation ELV_T of the transposed cell36and the corresponding transposed cell36of each other transposed base34.

In particular, and according to this embodiment, evaluation module16is configured to evaluate local coherence level NCL based only on ELV_T elevations of transposed cells36whose MD_T metadata is indicative of a measured elevation, and in particular on the comparison of such ELV_T elevations. In other words, for a given transpose base34, evaluation module16is configured to evaluate local coherence level NCL for a transpose cell36based only on ELV_T elevations of corresponding transpose cells36of other transpose bases34independent of ELV_T elevation of the transpose cell36of the given transpose base34.

Evaluation module16is then configured to evaluate local consistency level NCL of a transposed cell36based on the smallest elevation difference between transposed elevation ELV_T of the transposed cell36and transposed elevation ELV_T of the corresponding transposed cell36of each other transposed base34, transposed metadata MD_T associated with each of the compared transposed elevations ELV_T being indicative of a measured elevation.

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 transposition of these bases local coherence level NCL for a transposed cell36of one of these bases is determined as a function of at least one elevation difference between transposed elevation ELV_T of the transposed cell36and transposed elevation ELV_T of the transposed cell36of one of the other transposed bases34.

In particular, and in the preferred embodiment, transposed elevation ELV_T of the transposed cell36of one of the transposed bases34is compared with transposed elevation ELV_T of each of the corresponding transposed cells36for which transposed metadata MD_T is indicative of a measured elevation. The smallest elevation difference resulting from such comparisons is then used as a basis for assessing local coherence level NCL of the transposed cell36.

In one particular example, local consistency level NCL is chosen from a high consistency level, a medium consistency level and a low consistency level.

The assessed local coherence level of a transposed cell36is, for example, a high coherence level if the smallest elevation difference between transposed elevation ELV_T of the transposed cell36and transposed elevation ELV_T of each of the corresponding transposed cells of the other transposed bases34is less than or equal to 15 m.

The assessed local coherence level of a transposed cell36is, for example, a medium coherence level if the smallest elevation difference between the transposed elevation ELV_T of the transposed cell36and transposed elevation ELV_T of each of the corresponding transposed cells of the other transposed bases34is greater than 15 m and less than or equal to 30 m.

The assessed local coherence level of a transposed cell36is, for example, a low coherence level if the smallest elevation difference between transposed elevation ELV_T of the transposed cell36and the transposed elevation ELV_T of each of the corresponding transposed cells of the other transposed bases34is greater than 30 m and less than or equal to 100 m.

As an example, if the smallest elevation difference between transposed ELV_T elevations of a transposed cell36is the elevation difference between a transposed ELV_T elevation with a value of 126 m (e.g., resulting from transposing ELV elevation of a NASADEM type source base) and a transposed ELV_T elevation with a value of 101 m (e.g., resulting from transposing ELV elevation of an ALOS type source base), the difference between these transposed ELV_T elevations is equal to 25 m and local coherence level NCL of the transposed cell36is evaluated as average.

In other examples, local coherence level NCL is expressed directly as the value of the smallest elevation difference between transposed elevation ELV_T of the transposed cell36and transposed elevation ELV_T of each of the corresponding transposed cells of the other transposed bases34. Local coherence level NCL is then expressed, for example, in meters. A high NCL then corresponds to a low elevation difference, expressed in meters, e.g., an elevation difference of 50 m, 30 m, 15 m or 10 m or less. Conversely, a low NCL corresponds to a large difference in elevation expressed in meters, for example, a difference in elevation of more than 50 m, 80 m or 100 m.

Assistance module18is configured to determine an aircraft navigation assistance datum D, based on local coherence level NCL evaluated for at least one of the transposed cells36.

The first embodiment illustrated inFIG.1, for which a confidence index IC in a given consistency level NC forms assistance data D generated by assistance module18, is now presented.

Segmentation module20is configured to segment area30of terrain corresponding to at least one of transposed bases34into a plurality of areas of interest38.

In particular, segmentation module20is configured to segment area30of the terrain so that each area of interest38includes a plurality of adjacent transposed cells36. As illustrated schematically inFIG.5, each area of interest38of the same transposed base34includes, for example, the same number of transposed cells36.

In one particular example, each area of interest38includes a set of 120 transposed cells per 120 transposed cells.

In such an example, and in the case where the reference mesh is such that a region of 1° longitude by 1° latitude is partitioned into 1,200 transposed cells by 1,200 transposed cells36, such a region of 1° longitude by 1° latitude includes one hundred areas of interest38.

Each area of interest is then, for example, substantially in the shape of a square with a side length corresponding to an angle equal to 6 arc minutes, or in other words a length of about 6 nautical miles, noted Nm.

Assistance module18is configured to determine, for area of interest38, a confidence index IC at a given consistency level NC.

Confidence index IC then forms the support data and is determined according to local coherence level NCL of each transposed cell36of area of interest38.

Confidence index IC in a given NC coherence level is determined, for example, according to the proportion, over area of interest38, of transposed cells36whose local coherence level NCL is greater than or equal to the given NC coherence level.

For example, for a given NC level of coherence equal to an average level of coherence, the confidence index IC in the average level of coherence corresponds to the proportion of cells, in area of interest38, whose local coherence level NCL is average or high.

It will be understood that, alternatively, assistance module18is configured to determine, for area of interest38, a consistency level for a given confidence index.

With reference toFIG.4, user interface26is configured to receive, from a user, a target consistency level NCC and a confidence limit index ICL in the target consistency level NCC.

In the embodiment shown, user interface26has a keyboard and a display. Alternatively, user interface26is, for example, provided with a touch screen.

Target coherence level NCC corresponds to a coherence level, as defined above for local coherence levels NCL, that the user of system10wishes to evaluate on area of interest38.

The limiting confidence index ICL in the target consistency level NCC corresponds, for example, to a minimum confidence index that the user wishes to obtain in target consistency level NCC over area of interest38.

Pairs of limit confidence index ICL and target consistency level NCC are derived, for example, from regulations or user requirements.

For example, an ICL of 95% at a coherence level of 30 m is required for the use of a transposed base34, or a corresponding source base28, for aircraft navigation in an airport area.

Again, for example, a limiting confidence index ICL of 80% at a coherence level of 80 m is required for use of a transposed base, or a corresponding source base28, for navigation of an aircraft outside an airport area.

Validation module22is configured to validate an area of interest38if the determined confidence index IC in the target consistency level NCC is greater than or equal to the limit confidence index ICL, and to reject an area of interest38if the determined confidence index IC is less than the limit confidence index ICL.

As illustrated inFIG.5, command module24is, for example, configured to command display of an enabled state if area of interest38is enabled by enabling module22, or a rejected state if area of interest38is rejected by enabling module22. In particular, command module24is connected to user interface26to command display of the enabled or rejected status on user interface26. In the example shown inFIG.5, rejected areas of interest38are hatched on user interface26, while validated areas of interest38are not hatched on user interface26.

In an embodiment that is not illustrated, command module24is configured to generate an alert when an aircraft overflies a rejected area of interest38.

Alternatively or additionally, command module24is configured to command generation of an aircraft trajectory outside rejected area(s) of interest38. Such a trajectory is, for example, further displayed on user interface26, as represented by a curve C inFIG.5.

Command module24is, for example, configured to obtain an initial trajectory of the aircraft, and to generate the trajectory of the aircraft from the initial trajectory, so that the trajectory of the aircraft extends entirely outside rejected area(s) of interest38.

The second embodiment, shown inFIG.2, for which a target elevation ELV_C forms the data generated by assistance module18, is now presented.

In this embodiment, and as illustrated inFIG.6, assistance module18is configured to determine a target base40of terrain data, corresponding to area30of the terrain, cut according to the reference mesh into a plurality of target cells42.

As illustrated inFIG.6, each target cell42corresponds to a transposed cell36of each transposed base34, the reference mesh being common to target base40and transposed bases34.

Target base40includes, for each target cell42, a target elevation ELV_C forming assistance data D.

In particular, assistance module18is configured, according to this embodiment, to determine target elevation ELV_C of target cell42as a function of transposed elevations ELV_T of at least two corresponding transposed cells36, whose local coherence level NCL is higher than the local coherence level NCL of the other corresponding transposed cells36.

For example, assistance module18is configured to determine target elevation ELV_C of target cell42based on transposed elevations ELV_T of at least two corresponding transposed cells36by implementing a Kalman filter for merging transposed elevations ELV_T of at least two transposed cells36.

In a particular example, assistance module18is configured to determine target elevation ELV_C of target cell42based on transposed elevations ELV_T of the two corresponding transposed cells36, whose local coherence level NCL is greater than the local coherence level NCL of the other corresponding transposed cells36. Thus, in this example, target elevation ELV_C of a target cell42is determined based only on the two transposed elevations ELV_T of transposed cells36with the highest local coherence level.

In the examples ofFIGS.1and2illustrating the first and second embodiments previously described, assistance system10includes an information processing unit50formed, for example, by a memory52and a processor54associated with memory52.

In the examples ofFIGS.1and2, acquisition module12, transposition module14, evaluation module16, assistance module18, and, in the example ofFIG.1, segmentation module20, validation module22and control module24, are each realized in the form of software, or a software brick, executable by processor54.

Memory52of assistance system10is then adapted to store software for acquiring a plurality of source bases28, software for transposing each source base28into a respective transposed base34, software for evaluating a local coherence level NCL for at least one transposed cell36of a respective transposed base34, and software for assisting navigation of the aircraft. In the example ofFIG.1, the memory is further adapted to store software for segmentation of the terrain area corresponding to at least one of the bases transposed into a plurality of areas of interest, software for validation of an area of interest38, and software for display command and/or trajectory generation.

Processor54is then able to execute each of acquisition software, transposition software, evaluation software, support software, and, in the example ofFIG.1, segmentation software, validation software and command software.

In a non-illustrated embodiment, the system includes two separate information processing units, each unit including, for example, a memory and a processor associated with the memory, one of the units being carried on board an aircraft while the other of the units is installed outside the aircraft. Acquisition module12, transposition module14, evaluation module16, assistance module18and segmentation module20are each, for example, implemented as software or a software brick that may be run by the processor of the unit installed outside the aircraft. The validation software and the command software are, for example, each realized as a software package, or a software brick, executable by the processor of the unit on board the aircraft.

In a variant not shown, reception module12, speech recognition module14, evaluation module16, acquisition module18, and, for example, segmentation module20, validation module22and control module24, are each produced in the form of a programmable logic component, such as a FPGA (Field-Programmable Gate Array), or as a dedicated integrated circuit, such as an ASIC (Application-Specific Integrated Circuit).

When assistance system10is in the form of one or more software, that is to say in the form of a computer program, it is also capable of being stored on a computer-readable medium, not shown. The computer-readable medium is, for example, a medium that stores electronic instructions and is coupled with a bus from a computer system. For example, the readable medium is an optical disk, magneto-optical disk, ROM memory, RAM memory, any type of non-volatile memory (for example EPROM, EEPROM, FLASH, NVRAM), magnetic card or optical card. The readable medium in such a case stores a computer program including software instructions.

With reference toFIG.3, a method for assisting navigation of an aircraft100, implemented by electronic assistance system10, is now presented.

In an initial acquisition operation110, acquisition module12acquires a plurality of source bases28, as described above. As seen above, each source database contains, for each of its cells32, an ELV elevation, and contains, for example, an MD metadata. Acquisition module12then communicates the plurality of acquired source bases28to transposition module14.

Transposition module14then transposes each source base28into a transposed base34in a transposition operation120. As illustrated inFIG.4and described above, the reference mesh according to which each transposed base34in area30of the terrain is cut, is common to all transposed bases34. Each transposed base in transposition operation120then includes, for each transposed cell36, a transposed elevation ELV_T, or even further a transposed metadata MD_T. Transposition module14then communicates the plurality of transposed bases34, resulting from transposition of the plurality of source bases28, to evaluation module16.

Evaluation module16then evaluates, in a subsequent evaluation operation130, a local consistency level NCL for at least one transposed cell36of a respective transposed base34. In particular, local coherence level NCL for transposed cell36of a respective transposed base34is determined based on comparison of transposed elevation ELV_T of the transposed cell36with transposed elevation ELV_T of the corresponding transposed cell36of at least one other transposed base34. Evaluation module16then communicates to support module18the local consistency level NCL for at least one transposed cell36of a transposed base34.

In a subsequent operation140of determining an aircraft navigation assistance datum, assistance module18determines an aircraft navigation assistance datum D as a function of evaluated local consistency level NCL of at least one transposed cell36of one of transposed bases34.

As seen above, in a first embodiment, assistance data D is formed by a confidence index IC in a given consistency level NC. In operation140of determining an aircraft navigation assistance datum, segmentation module20segments terrain area30into a plurality of areas of interest38. Support module18then determines, for area of interest38, confidence index IC in a coherence level NC based on local coherence level NCL of each transposed cell36of the area of interest38.

As seen above, in a second embodiment, assistance data D is, for example, formed by a target elevation ELV_C of a target cell42of a target base40. During operation140of determining aircraft navigation assistance data, assistance module18then determines target elevation ELV_C of target cell42as a function of transposed elevations ELV_T of at least two corresponding transposed cells36, whose local coherence level NCL is higher than the local coherence level NCL of the other corresponding transposed cells36.

The use of an evaluation module16configured to evaluate local coherence level NCL of a transposed cell36as a function of the smallest elevation difference between the transposed elevation of the cell36and the transposed elevation of the corresponding transposed cell36of each other transposed base34is particularly advantageous since it makes it possible to exclude from the evaluation of local coherence level NCL the transposed bases34whose transposed elevations ELV_T of the corresponding cells36are remote from the transposed elevation ELV_T of the cell, the probability that the transposed elevations ELV_T of corresponding cells of such transposed bases are erroneous being high.

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

The use of the metadata for the evaluation of the local consistency level NCL of each transposed cell36, 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 the cell32and transposed elevation ELV_T of corresponding transposed cell36of each other transposed base34, is particularly advantageous as it allows only ELV_T elevation data having been measured during elaboration of source base28resulting in transposed base34to be considered. Thus, the use of metadata avoids, for example, evaluation of local consistency level NCL based on comparison of data from the same measurements, or in other words, avoids comparison of mutually dependent data for the calculation of local consistency level NCL, thus improving quality of the evaluation of local confidence level NCL and thus of navigation assistance.

Determining a confidence index IC in a consistency level NC over an area of interest38and, where appropriate, validating and commanding a display or the generation of a trajectory as a function of such a confidence index IC in a consistency level NC over an area of interest38, makes it possible to take into account possible local errors in source bases28in the navigation assistance, and where appropriate, to display validation information or to generate a trajectory in a more reliable manner.

Determining target elevation of target cell42as a function of transposed elevations ELV_T of at least two corresponding transposed cells36further enables a target base40to be formed whose ELV_C elevation values are more accurate than the ELV elevation values of source bases28.