Electronic device storing a terrain database, method of generating the database, avionics system, monitoring method and related computer program

Abstract

An electronic device (10) for storing a terrain database (15) for an avionics system (20) is on board of an aircraft (5). The terrain database (15) corresponds to a terrestrial area possibly flown over by the aircraft (5), this area being represented in the form of a surface area divided into a grid of cells, each cell corresponding to a section of the terrestrial area, the terrain database (15) having a first resolution and comprising first terrain elevation values each associated with a corresponding cell. The terrain database (15) further comprises, for each cell, an uncertainty value associated with the corresponding first elevation value, at least one uncertainty value being computed from a plurality of second terrain elevation values associated with the cell and derived from a second terrain database (35) having a second resolution higher than the first resolution.

Description

[0001] The application relates to an electronic device for storing a terrain database of a navigation and communication system, the storage device being configured to be loaded on board an aircraft, the terrain database corresponding to a terrain region likely to be flown over by the aircraft, in the form of a surface divided into a grid, each grid corresponding to a section of the terrain region.

[0002] The application also relates to a navigation and communication system configured to be loaded on board an aircraft, comprising or connected to said electronic storage device.

[0003] The application also relates to a generation method of a terrain database for a navigation and communication system, the generation method being implemented by a computer.

[0004] The application also relates to a computer-readable medium comprising a computer program containing software instructions implementing said generation method when executed by a computer.

[0005] The application also relates to a monitoring method of the vertical positioning of an aircraft, the method being implemented by an electronic monitoring device configured to be loaded on board the aircraft and connected to said electronic storage device.

[0006] The application also relates to a computer-readable medium comprising a computer program containing software instructions implementing said monitoring method when executed by a computer.

[0007] The application relates to the field of terrain databases for navigation and communication systems and of navigation and communication systems such as aircraft piloting and monitoring systems using said terrain databases. These systems are generally based on navigation sensors, such as satellite geolocation sensors also known as Global Navigation Satellite System (GNSS) sensors, radio altimeters or pressure sensors allowing the measurement of the barometric altitude; and generally propose a human-machine interface showing the pilot all the information necessary to pilot the aircraft.

[0008] The appearance of so-called synthetic vision systems (SVS) in civil aircraft allows to improve the operating safety by showing the crew a permanent three-dimensional synthetic image of their environment. This image is computed from the position and altitude of the aircraft and from the terrain data from a terrain database loaded on board the aircraft.

[0009] Other monitoring systems such as terrain awareness and warning systems (TAWS) use terrain databases to warn the pilot of a situation where the trajectory of the aircraft will conflict with the terrain.

[0010] However, the algorithms and terrain databases used are generally relatively insensitive to signal errors.

[0011] The object of the application is therefore to propose an electronic device for storing a terrain database of a navigation system, configured to be loaded on board an aircraft and allowing a more reliable terrain database to be provided, in order to reduce the risk of accidents for the aircraft.

[0012] To this end, the application relates to an electronic storage device for storing a terrain database of a navigation system, the storage device being configured to be loaded on board an aircraft, the terrain database corresponding to a terrain region that the aircraft can fly over, the terrain region being represented in the form of a surface divided into a grid, each grid corresponding to a section of the terrain region, the terrain database having a first resolution and comprising first terrain elevation values each associated with a corresponding grid.

[0013] The terrain database also comprises, for each grid, an uncertainty value associated with the corresponding first elevation value, at least one uncertainty value being calculated from a plurality of second terrain elevation values associated with said grid and coming from a second terrain database having a second resolution, the second resolution being higher than the first resolution.

[0014] Thus, by virtue of the electronic storage device according to the application, also known as the terrain database loaded on board the aircraft, also referred to as the first terrain database, comprises, for each elevation value of a section of the terrain region, an uncertainty value associated with the corresponding elevation value, which thus allows the reliability of this elevation value to be known.

[0015] Furthermore, at least one uncertainty value is calculated from a plurality of second elevation values coming from a second database of higher resolution, which allows the uncertainty values to be calculated in a more reliable manner. The person skilled in the art will understand explicitly that the second terrain database provides a higher resolution than the first terrain database, each grid of the first database corresponding to a plurality of grids of the second database, the second elevation values each being associated with a corresponding grid of the second database. In other words, said at least one uncertainty value is calculated from the elevation values of a plurality of sub-grids of the corresponding grid of the first database, each sub-grid corresponding to a corresponding grid of the second database.

[0016] Since the second resolution is higher than the first resolution of the first database, the second terrain database comprises more information than the first database, and therefore requires a greater storage space. The second terrain database is therefore generally stored in an electronic device external to the storage device, which external device is preferably arranged outside the aircraft and for example installed on the ground.

[0017] According to other advantageous aspects of the application, the electronic storage device comprises one or more of the following features, taken separately or in any technically feasible combination:

[0018] - the second terrain database is stored in an electronic device external to the electronic storage device, the external device being preferably arranged outside the aircraft;

[0019] - each uncertainty value is preferably calculated from the plurality of second elevation values associated with the corresponding grid;

[0020] each uncertainty value is preferably calculated from the plurality of second elevation values associated with the corresponding grid;

[0021] - at least one first elevation value is determined from the plurality of second elevation values associated with the corresponding grid;

[0022] the at least one first elevation value is preferably selected from the group comprising: a maximum value of the second elevation values associated with the corresponding grid; a mean value of the second elevation values associated with the corresponding grid; and the maximum value of the second elevation values minus N times a standard deviation of the second elevation values associated with the corresponding grid with respect to the maximum value, N being an integer greater than or equal to 1 ;

[0023] each first elevation value is preferably determined from the second elevation values associated with the corresponding grid; and

[0024] - the first and second resolutions are expressed in angular seconds, the angular seconds value of each resolution defining a size corresponding to one side of the smallest representative feature of the terrain, the higher resolution corresponding to a lower angular seconds value;

[0025] the first resolution is preferably equal to 3 or 6 angular seconds;

[0026] the second resolution is preferably equal to 1 or 2 angular seconds.

[0027] The application also relates to an avionics system configured to be loaded on board an aircraft, the avionics system comprising or being connected to electronic means for storing a terrain database, the electronic storage means being the electronic storage means defined above, and the avionics system comprising electronic monitoring means configured to monitor the height of the aircraft by comparison between, on the one hand, the height from a height sensor such as a satellite geopositioning sensor or a pressure sensor, and, on the other hand, the sum of the first terrain elevation value from the terrain database and the height above ground from a radio altimeter, the comparison being based on the uncertainty value associated with the corresponding first elevation value.

[0028] Thus, the avionics system according to the application allows the reliability of the terrain database loaded on board the aircraft and / or the reliability of the radio altimeter and / or the height sensor such as a satellite geopositioning sensor and / or a pressure sensor to be monitored by its electronic monitoring means.

[0029] Indeed, the constant evolution of the human infrastructure, for example through the construction of new buildings, the levelling of mountains or quarries, changes the actual elevation of the terrain and rapidly reduces the reliability of the terrain database, even making it relatively obsolete. The monitoring of the precision of the terrain database and the generation of alerts to the pilot or to the provider of the database, if necessary, are therefore of great interest.

[0030] On the other hand, the radio altimeter continuously provides the height from the ground, in other words the height above ground level, and this height is subsequently compared with the sum of the terrain elevation provided by the terrain database and the height from the height sensor, which also allows the operation of the radio altimeter and / or of the height sensor to be monitored and alerts to be generated if necessary.

[0031] This also allows the safety of the aircraft to be improved, since radio altimeter malfunctions have in the past been the cause of aircraft accidents. Furthermore, the monitoring of the radio altimeter of the aircraft is also advantageous in the event of an increase in electromagnetic interference, for example associated with the arrival of base stations complying with the 5G standard and which, under certain conditions, can be disturbed in the frequency band of 4.2 to 4.4 GHz, corresponding to the conventional frequency band of the radio altimeter.

[0032] The invention also relates to a generation method for generating a terrain database for an avionics system, the terrain database being stored in an electronic storage device configured to be loaded on board an aircraft, the terrain database corresponding to a terrain region that the aircraft can fly over, the terrain database being represented in the form of a surface divided into a grid, each grid corresponding to a section of the terrain region, the terrain database comprising a first resolution and comprising first terrain elevation values each associated with a corresponding grid.

[0033] The method is computer-implemented and comprises the following steps:

[0034] - calculating, for each grid, an uncertainty value associated with the corresponding first elevation value, at least one uncertainty value being calculated from a plurality of second terrain elevation values associated with said grid and originating from a second terrain database having a second resolution, the second resolution being higher than the first resolution;

[0035] - including each calculated uncertainty value in the terrain database.

[0036] The invention also relates to a computer program containing software instructions which, when executed by a computer, implement the generation method as defined above.

[0037] The invention also relates to a monitoring method for monitoring the vertical positioning of an aircraft, the method being implemented by an electronic monitoring device configured to be loaded on board the aircraft and connected to an electronic device for storing a terrain database.

[0038] The method comprises comparing, on the one hand, the altitude from a height sensor such as a satellite geolocation sensor or a pressure sensor, and on the other hand, the sum of the first topographic elevation value from the topographic database and the height above ground from the radio altimeter, the comparison being based on the uncertainty value associated with the corresponding first elevation value, the topographic database being generated by the generation method defined above.

[0039] According to another advantageous aspect of the application, the monitoring method also comprises generating a warning in the event that an error is determined during said comparison, the generated warning varying according to the error determined and being chosen from the group comprising a warning relating to the topographic database, a warning relating to the height sensor, a warning relating to the radio altimeter, a warning relating to both the height sensor and the radio altimeter, and a global warning.

[0040] The object of the application is also a computer program comprising software instructions implementing the monitoring method defined above when said software instructions are executed by a computer.

[0041] These features and advantages of the application will become clearer upon reading the following description, given only as a non-restrictive example and with reference to the appended drawings in which:

[0042] Figure 1 is a schematic view of an aircraft comprising an electronic device for storing a topographic database, an avionics system comprising an electronic device for monitoring the vertical positioning of the aircraft, a height sensor and a radio altimeter;

[0043] Figure 2 is a schematic view representing Figure 1 the data contained in the topographic database from Figure 1 the altitude from the height sensor and the sum of the topographic elevation value from said database and the height above ground from the radio altimeter from Figure 1 ;

[0044] Figure 3 is a flowchart of the method for generating a topographic database stored in the storage device from Figure 1 ; and

[0045] Figure 4 is a flowchart of the method for monitoring the vertical positioning of an aircraft according to the application, the method being implemented by the electronic monitoring system from Figure 1 .

[0046] In the remainder of the present description, the expression "substantially equal" defines an equality relationship of plus or minus 10%, preferably plus or minus 5%.

[0047] In Figure 1The aircraft 5 comprises, among others, an electronic device 10 for storing a terrain database 15, an avionics system 20, a height sensor 22 and a radio altimeter 24.

[0048] The aircraft 5 is, for example, an airplane. Alternatively, the aircraft 5 is a helicopter, a vertical take-off and landing aircraft, also known as ADAV or VTOL, or is a drone that can be flown remotely by a pilot.

[0049] The electronic storage device 10 is configured to be loaded on board the aircraft 5. The storage device 10 comprises a terrain database 15 that can be used by the avionics system 20. The storage device 10 is, for example, in the form of a computer memory, or is a hard disk drive.

[0050] In the example shown in Figure 1 , the storage device 10 is distinct from the avionics system 20 and is therefore connected to the avionics system 20 so that the avionics system 20 can use the terrain database 15 contained in the storage device 10.

[0051] In an alternative not shown, the storage device 10 is integrated into the avionics system 20.

[0052] The terrain database 15, also referred to as first database 15 hereinafter, corresponds to a terrain area 26 that the aircraft 5 can fly over, the terrain area 26 being represented as a surface divided into meshes 28, each mesh 28 corresponding to a section of the terrain area 26 and also referred to as first mesh 28 hereinafter, as Figure 2 shown.

[0053] The terrain database 15 has a first resolution R1 and comprises elevation values 30, each associated with a respective mesh 28 and also referred to as first elevation value 30 hereinafter. Each first elevation value 30 is a reference value of the height of the ground 26 within the respective first mesh 28 relative to a reference elevation REF, typically the mean sea level height, also referred to as MSL.

[0054] The terrain database 15 typically comprises a single first elevation value 30 for each respective first mesh 28.

[0055] According to the invention, the terrain database 15 also comprises, for each respective first mesh 28, an uncertainty value δ BD1 associated with the respective first elevation value 30, also referred to as first uncertainty value δ BD1 hereinafter.

[0056] At least one first uncertainty value δ BD1 is calculated from a plurality of second elevation values 32 corresponding to said first mesh 28 and originating from a second terrain database 35 having a second resolution R2, the second resolution R2 being higher than the first resolution R1.

[0057] Since the second terrain database 35 provides a higher resolution than the first terrain database 15, each first grid 28 of the first database 15 corresponds to a plurality of grids 38 of the second database 35, which are also referred to hereinafter as second grids 38 and in Figure 2 Fig. 2. The second grids 38 corresponding to a respective first grid 28 thus form a sub-grid of this respective first grid 28. Each second elevation value 32 is associated with a respective grid 38 of the second database 35.

[0058] Each second elevation value 32 is a reference height value of the terrain 26 within the respective second grid 38 relative to the reference elevation REF. Each second elevation value 32 for example corresponds to the maximum height from the ground 26 relative to the reference elevation REF within the respective second grid 38; in other words, the height of the highest point from the ground 26 relative to the reference elevation REF within the respective second grid 38.

[0059] The first resolution R1 and the second resolution R2 are for example each expressed in angular seconds, denoted arcsec, an angular resolution value thus defining a dimension corresponding to a side of a minimum representative unit. The person skilled in the art will thus understand that the lower the resolution, the greater its value expressed in arcsec.

[0060] The first resolution R1 is for example equal to 3 or 6 arcsec, and the second resolution R2 is for example equal to 1 or 2 arcsec.

[0061] The person skilled in the art will thus understand that the at least one uncertainty value δ BD1 is calculated from the elevation values 32 of the plurality of sub-grids of the respective grid 28 of the first database 15, each sub-grid corresponding to a respective second grid 38 of the second database 35.

[0062] Each first uncertainty value δ BD1 is preferably calculated from the plurality of second elevation values 32 corresponding to the respective first grid 28 of the first database 15.

[0063] Each first uncertainty value δ BD1 is for example chosen from the group comprising:

[0064] - the difference between the maximum and the minimum of the plurality of second elevation values 32 associated with the respective first grid 28; and

[0065] - the standard deviation of the second elevation values 32 associated with the respective first grid 28 relative to said maximum.

[0066] In Figure 2In the example, the first uncertainty value δ BD1 It is equal to the difference between the maximum and minimum values ​​of the multiple second elevation values ​​32 associated with the corresponding first grid 28. In other words, in this example, the first uncertainty value δ BD1 It is equal to the difference between the maximum value of the second elevation value 32 associated with the corresponding first grid 28 and the minimum value of the second elevation value 32.

[0067] As an optional supplementary approach, at least one first elevation value 30 is determined from a plurality of second elevation values ​​32 corresponding to a corresponding first grid 28. According to this optional supplementary approach, each first elevation value 30 is preferably determined from the plurality of second elevation values ​​32 corresponding to a corresponding first grid 28.

[0068] Each first elevation value 30, determined from a plurality of second elevation values ​​32 associated with the corresponding first grid 28, is selected, for example, from a group containing the following:

[0069] - The maximum value of the second elevation value 32 associated with the corresponding first grid 28;

[0070] - The average value of the second elevation value 32 associated with the corresponding first grid 28; and

[0071] - The maximum value of the second elevation value 32 minus N multiplied by the standard deviation of the second elevation value 32 associated with the corresponding first grid 28 relative to the maximum value, where N is an integer greater than or equal to 1.

[0072] exist Figure 2 In the example, the first elevation value 30 is equal to the maximum value of the second elevation value 32 corresponding to the first grid 28.

[0073] As an optional supplement, the terrain database 15 also includes, for each first grid 28, an uncertainty value δ based solely on data contained in the second database 35. BD2 This is also referred to as the second uncertainty value δ in the following text. BD2 .

[0074] Each second uncertainty value δ BD2 For example, each height deviation, also known as an elevation deviation, is calculated from multiple height deviations and is associated with a corresponding second grid 38, corresponding to the difference between the maximum and minimum elevations of the terrain 26 within the second grid 38. Each second uncertainty value δ BD2 For example, the corresponding first grid 28 of the first database 15 is equal to the maximum value among multiple elevation deviations of the second grid 38 of the second database 35, which is different from the first grid 28 of the first database 15. Figure 2 As shown.

[0075] Considering that the second resolution R2 is greater than the first resolution R1, each second uncertainty value δ BD2 for the corresponding first grid 28 being less than each first uncertainty value δ BD1 where the ratio between the first resolution R1 and the value in arcsec of the second resolution R2 is generally equal to 3.

[0076] each second uncertainty value δ BD2 is thus increased, for example, by a predetermined constant, generally based on the second resolution R2 of the second database 35.

[0077] The avionics system 20 is configured to be loaded on board the aircraft 5 and connected to the electronic storage device 10, such as Figure 1 as shown.

[0078] In an alternative not shown, the avionics system 20 comprises the electronic storage device 10.

[0079] The avionics system 20 is, for example, chosen from the group comprising:

[0080] - an aircraft flight management system, also known as flight management system (FMS);

[0081] - a terrain awareness and warning system (TAWS);

[0082] - a navigation information display system, also known as navigation display (ND); and

[0083] - a primary flight display (PFD) with or without synthetic vision system (SVS).

[0084] The avionics system 20 comprises an electronic device 40 for monitoring the vertical positioning of the aircraft 5.

[0085] The altitude sensor 22 is itself known and is, for example, a satellite geolocation sensor, also known as global navigation satellite system (GNSS), such as a global positioning system sensor (GPS), a GLONASS sensor, a Galileo sensor, or a pressure sensor for measuring the barometric altitude, such as a pitot sensor.

[0086] The radio altimeter 24 is itself known.

[0087] The second terrain database 35 is stored in an electronic device 45 external to the electronic storage device 10. The electronic device 45 in which the second terrain database 35 is stored is preferably arranged outside the aircraft 5.

[0088] The electronic monitoring device 40 is configured to monitor the altitude of the aircraft 5. The monitoring device 40 comprises a processor 41 for processing the altitude ALTMSL and the first elevation value 30 and the ground clearance H from the radio altimeter 24 RA Module 50 compares the sums.

[0089] As an optional supplement, the monitoring device 40 includes a module 52 for generating a warning when the comparison module 50 detects an error.

[0090] exist Figure 1 In one example, the electronic monitoring device 40 includes, for example, an information processing unit 60 formed by a memory 62 and a processor 64 associated with the memory 62.

[0091] exist Figure 1 In this example, the comparison module 50 and the generation module 52, as an optional supplement, are each implemented as a software program or software block executable by the processor 64. The memory 62 of the electronic monitoring device 40 is therefore able to store the height ALT values ​​from the height sensor 22. MSL and the first elevation value 30 and the ground clearance H from the radio altimeter 24 RA The software compares the sums. As an optional supplement, the memory 62 of the electronic monitoring device 40 can also store software for generating warnings if the comparison software detects a corresponding error. The processor 64 is therefore able to execute the comparison software and the generation software as an optional supplement.

[0092] In an alternative not shown, the comparison module 50 and the generation module 52, as an optional supplement, are each implemented as a programmable logic component, such as a field-programmable gate array (FPGA) or an application-specific integrated circuit, such as an application-specific integrated circuit (ASIC).

[0093] When the electronic monitoring device 40 is implemented as one or more software programs—in other words, as a computer program—it can also be recorded on a computer-readable medium (not shown). A computer-readable medium is, for example, a medium capable of storing electronic instructions and coupled to a bus of a computer system. Examples of such media include optical discs, magneto-optical discs, ROM memory, RAM memory, any type of non-volatile memory (e.g., EPROM, EEPROM, FLASH, NVRAM), magnetic cards, or optical cards. Thus, a computer program containing software instructions is stored on the readable medium.

[0094] Comparison module 50 is configured to compare one side by Figure 2 The first reference numeral 70 in the figure indicates the altitude ALT from the altitude sensor 22. MSL And, on the other hand, the first topographic elevation value 30 from the topographic database 15 and the ground clearance H from the radio altimeter 24.RA and the comparison of the sum by Figure 2 Also indicated in the figure by a second reference numeral 72, which is also of the shape of an aircraft, is a second elevation value.

[0095] The comparison module 50 is preferably configured to perform the comparison also on the basis of a first uncertainty value δ BD1 the altitude ALT MSL and the corresponding first elevation value 30 with the height above ground H RA of the sum.

[0096] For example, the comparison module 50 is configured to perform the comparison according to the following equation: [1]

[0098] ALT MSL + δ MSL = H RA + δ RA + ELV BD1 + δ BD1

[0099] wherein ALT MSL represents the altitude from the altitude sensor 22;

[0100] δ MSL represents the uncertainty value associated with the altitude ALT MSL from the altitude sensor 22;

[0101] H RA represents the height above ground from the radio altimeter 24;

[0102] δ RA represents the uncertainty value associated with the height above ground H RA from the radio altimeter 24;

[0103] ELV BD1 represents the corresponding first elevation value 30 from the first terrain database 15; and

[0104] δ BD1 represents the first uncertainty value associated with the first elevation value ELV BD1 .

[0105] the uncertainty value δ MSL associated with the altitude ALT MSL from the altitude sensor 22, for example corresponds to the information given by the Vertical Figure of Merit (VFOM) when the altitude sensor 22 is a GPS sensor providing an altitude enhanced by a Space Based Augmentation System (SBAS) correction, such as Wide Area Augmentation System (WAAS) correction. Alternatively, the uncertainty value δ MSL associated with the altitude ALT MSLThis is a predetermined value, for example, an uncertainty value of approximately 56 ft (feet) when the altitude sensor 22 is a pressure sensor, corresponding to a deviation of 2 hPa in the lowest atmosphere. In another alternative, it is related to altitude ALT. MSL The associated uncertainty value δ MSL The altitude sensor 22 is a pressure sensor, specifically based on the distance between the aircraft 5 and the airport, which transmits the barometric pressure-corrected altitude value known as QNH altitude.

[0106] With the ground clearance H from radio altimeter 24 RA The associated uncertainty value δ RA For example, this is represented in the accuracy table of radio altimeter 24, such as the first table shown below.

[0107] [Table 1]

[0108] Height (ft) Vertical velocity (ft / s) delta RA ]]> -20 to 75 0 to 20 ±1.5 ft 75 to 2500 0 to 25 ±2％ 2500 to 5000 0 to 25 ±3％

[0109] As an optional supplement, the comparison module 50 is configured to use a second uncertainty value δ associated with the first elevation value 30. BD2 Perform height ALT from height sensor 22 MSL And the first elevation value of 30 and the height above the ground H RA Comparison between sums.

[0110] According to this optional supplementary scheme, the comparison module 50 is configured, for example, to perform the comparison according to the following equation: [2]

[0112] ALT MSL +δ MSL =H RA +δ RA +ELV BD1 +δ BD1 +δ BD2

[0113] Where δ BD2 It also indicates that it is related to the first high value ELV BD1 The associated second uncertainty value.

[0114] As an alternative supplement, comparison module 50 is configured to calculate the sum of squares of uncertainty values, which is determined by Δ max This means that it is equal to the height ALT. MSL The associated uncertainty value δ MSL and height H above the ground RA The associated uncertainty value δ RA and the corresponding first uncertainty value δ of the first grid 28 BD1Also, when needed, the second uncertainty value δ of the first grid 28. BD2 The sum of squares.

[0115] According to this optional supplementary scheme, the comparison module 50 is therefore configured to be relative to the sum of squares Δ of the uncertainty value. max The comparison of one aspect is also represented as ELV. BD1 The first elevation value of 30 and the height above the ground H RA The sum of the height ALT from the height sensor 22 on the other hand MSL The absolute value difference between them. The comparison module 50 is therefore configured to operate when the absolute value difference is less than or equal to the sum of squares Δ. max In other words, if the following inequality (3) is satisfied, and no error related to the altitude of aircraft 5 is detected, and conversely, if the absolute difference is greater than the sum of squares Δ max In other words, an error is detected when the following inequality (4) is satisfied. [3]

[0117] |H RA +ELV BD1 -ALT MSL |≤Δ max

[0118] Where |.| represents absolute value; and

[0119] Δ max It represents the sum of squares of the uncertainty values. [4]

[0121] |H RA +ELV BD1 -ALT MSL |>Δ max

[0122] If an error is detected when inequality (4) is satisfied, the comparison module 50 is also configured to measure the height ALT from the height sensor 22. MSL If the error is determined to be associated with the first terrain database 15, and the error is either SBAS corrected altitude or QNH corrected barometric pressure corrected altitude, and inequality (4) is satisfied during the time period between the first predetermined time T1 and the second predetermined time T2.

[0123] The first predetermined time T1 corresponds, for example, to the time during which the aircraft 5 is allowed to fly across the diagonals of at least two first grids 28. When the aircraft 5 is an airplane, the first predetermined time T1 is, for example, equal to 10 seconds when the first resolution R1 is equal to 6 arcsec and the speed of the aircraft 5 is substantially equal to 100 knots.

[0124] The second predetermined time T2 corresponds for example to a time allowing the aircraft 5 to fly over the diagonal of at least twelve first meshes 28 and is thus for example equal to six times the first predetermined time T1.

[0125] In addition, if the inequality (4) is satisfied over a time greater than the second predetermined time T2 and if the integrity of the position of the aircraft 5 from the altitude sensor 22, also called HPL in the case where the altitude sensor 22 is a satellite geolocation sensor, is less than or equal to a predetermined threshold HPL HQ , then the comparison module 50 is configured to determine that the error is associated with the altitude sensor 22 when the aircraft 5 is equipped with two distinct radio altimeters 24 and the altitudes above ground from these two distinct radio altimeters 24 are consistent; and to determine that the error is associated with the radio altimeter 24 when the altitudes above ground from these two separate radio altimeters 24 are not consistent.

[0126] As a further complementary solution, if the inequality (4) is satisfied over a time period greater than the second predetermined time period T2 and if the positioning integrity HPL is less than or equal to a predetermined threshold HPL HQ , but the aircraft 5 is equipped with a single radio altimeter 24, then the comparison module 50 is configured to determine that the error is associated with the altitude sensor 22 and / or the radio altimeter 24.

[0127] As another complementary solution, if the inequality (4) is satisfied over a time period greater than the second predetermined time period T2 and if the positioning integrity HPL is greater than a predetermined threshold HPL HQ , then the comparison module 50 is configured to detect an inconsistency between the first terrain database 15 and the position provided by the altitude sensor 22 and then to suspend the altitude monitoring of the aircraft 5 over a predetermined delay time.

[0128] As an optional complementary solution, the generation module 52 is configured to generate a warning when an error is determined by the comparison module 50.

[0129] For example, the generation module 52 is configured to generate a warning relating to the terrain database 15 when the comparison module 50 pre-determines that the error is associated with the first terrain database 15, to generate a warning relating to the altitude sensor 22 when the comparison module 50 pre-determines that the error is associated with said altitude sensor 22, to generate a warning relating to the radio altimeter 24 when the comparison module 50 pre-determines that the error is associated with said radio altimeter 24, to generate a warning relating to the altitude sensor 22 and to the radio altimeter 24 when the comparison module 50 pre-determines that the error is associated with the altitude sensor 22 and / or with the radio altimeter 24, and to generate a global warning and then to suspend the height monitoring of the aircraft 5 for a predetermined delay time when the comparison module 50 pre-determines an inconsistency between the first terrain database 15 and the position provided by the altitude sensor 22.

[0130] Reference will now be made to a flowchart representing a method of generating a first terrain database 15 stored in the storage means 10 according to the application, Figure 3 Reference will then be made to a flowchart representing a method of monitoring the height of the aircraft 5 implemented by the electronic monitoring device 40 according to the application, Figure 4 The operation of the application will be described.

[0131] During an initial step 100, at least one uncertainty value δ BD1 , associated with the corresponding first elevation value 30, is calculated for each first grid 28 of the first database 15. BD2 At least one of the calculated uncertainty values δ BD1 is calculated from a plurality of second elevation values 38 corresponding to said first grid 28 and taken from the second terrain database 35.

[0132] During this step 100, a first uncertainty value δ BD1 is calculated, for example, for each first grid 28 of the first database 15. Each first uncertainty value δ BD1 is preferably calculated from a plurality of second elevation values 32 corresponding to the corresponding first grid 28.

[0133] Each first uncertainty value δ BD1 calculated from a plurality of second elevation values 32 is generally equal to the difference between the maximum and the minimum of the plurality of second elevation values 32 associated with the corresponding first grid 28, or alternatively to the standard deviation of the second elevation values 32 associated with the corresponding first grid 28 with respect to said maximum.

[0134] During this step 100, additionally or alternatively, a second uncertainty value δ BD2 is calculated for each corresponding first grid 28. Each second uncertainty value δ BD2Preferably, only on the basis of the data contained in the second database 35. Each second uncertainty value δ BD2 Generally calculated from a plurality of height deviations, each associated with a respective second grid 38. Each second uncertainty value δ BD2 For example, equal to the maximum of the plurality of height deviations of the different second grid 38 corresponding to said first grid 28. Each second uncertainty value δ BD2 Preferably increased by a predetermined constant, generally based on the second resolution R2.

[0135] During a next step 110, each calculated uncertainty value δ BD1 , δ BD2 is then contained in the first terrain database 15 to be stored in the storage device 10 and then loaded on board the aircraft 5.

[0136] During the flight of the aircraft 5, the monitoring device 40 then compares, by means of its comparison module 50 and during an initial step 200 of the monitoring method, the altitude ALT MSL from the height sensor 22 and the sum of the first terrain height value 30 from the first terrain database 15 and the height above ground H RA from the radio altimeter 24.

[0137] The comparison is performed during step 200, for example according to equation (1) or according to equation (2). The comparison module 50 thus generally detects the absence of error concerning the altitude of the aircraft 5 when inequality (3) is satisfied, and conversely detects the presence of error concerning the altitude of the aircraft 5 when inequality (4) is satisfied.

[0138] At the end of the comparison step 200, the monitoring device 40 continues with a next optional step 210 during which the generation module 52 generates a warning when the presence of error is detected in the previous step 200. In addition, as mentioned above, the generated warning is a warning concerning the terrain database 15, or a warning concerning the height sensor 22, or a warning concerning the radio altimeter 24, or a warning concerning the height sensor 22 and the radio altimeter 24, or a global warning, on the basis of the error previously detected.

[0139] Thus, by means of the storage device 10 according to the application, the first terrain database 15 to be loaded on board the aircraft 5 also comprises, for each first height value 30, at least one uncertainty value δ BD1 , δ BD2 associated with the respective height value 30, the uncertainty value δ BD1 , δ BD2 Thus allowing a better knowledge of the reliability of this height value 30.

[0140] In addition, at least one first uncertainty value δ BD1 is calculated from a plurality of second altitude values 32 from the database 35 of higher second resolution R2, thus allowing to have uncertainty values which are more reliably calculated.

[0141] The monitoring device 40 according to the application then allows to more accurately monitor the height of the aircraft 5 by subsequently comparing the sum of the altitude ALT MSL from the height sensor 22 and the first altitude value 30 with the height above ground H RA from the radio altimeter 24 and also taking into account the uncertainty value δ BD1 , δ BD2 associated with the respective first altitude value 30 and contained in the first terrain database 15.

[0142] It is thus conceivable that the electronic storage device 10 according to the application provides a more reliable terrain database 15, thus reducing the risk of accidents of the aircraft 5.

Claims

1. An electronic storage device (10) for storing a terrain database (15) of a navigation system (20), said electronic storage device (10) being configured to be on-board a flying vehicle (5), said terrain database (15) corresponding to a terrain region (26) likely to be flown over by said flying vehicle (5), this terrain region (26) being represented in the form of a surface divided into a grid (28) of cells, each of said cells (28) corresponding to a section of said terrain region (26), said terrain database (15) having a first resolution (R1) and comprising first terrain elevation values (30) each associated with a corresponding cell (28) of said grid (28), characterized in that Said topographic database (15) comprises, for each of said meshes (28), also an uncertainty value (delta BD1 ) associated with the respective first topographic elevation value (30), at least one of said uncertainty values (delta BD1 ) being calculated from a plurality of second topographic elevation values (32) associated with said mesh (28) and deriving from a second topographic database (35) having a second resolution (R2) higher than said first resolution (R1).

2. The electronic storage device (10) according to claim 1, wherein said second terrain database being stored in an electronic device external to said electronic storage device.

3. The electronic storage device (10) according to claim 2, wherein said electronic device being arranged outside said flying vehicle.

4. The electronic storage device (10) of claim 1, wherein, at least one of said uncertainty values (δ BD1 ) is selected for each said grid from the group consisting of: a difference between a maximum value and a minimum value of a plurality of said second terrain elevation values (32) associated with the respective said grid (28); and a standard deviation of said second terrain elevation values (32) associated with the respective said grid (28) relative to said maximum value.

5. The electronic storage device (10) of claim 4, wherein each of the uncertainty values (δ BD1 ) is calculated from a plurality of the second terrain elevation values (32) associated with the corresponding grid (28).

6. The electronic storage device (10) of claim 1, wherein, at least one of said first terrain elevation values (30) being determined from a plurality of said second terrain elevation values (32) associated with a corresponding cell (28) of said grid (28).

7. The electronic storage device (10) according to claim 6, wherein at least one of said first terrain elevation values (30) is selected from the group comprising: a maximum of said second terrain elevation values (32) associated with a corresponding cell (28) of said grid (28); an average of said second terrain elevation values (32) associated with a corresponding cell (28) of said grid (28); and a maximum of said second terrain elevation values (32) minus N times a standard deviation of said second terrain elevation values (32) associated with a corresponding cell (28) of said grid (28) with respect to said maximum, N being an integer greater than or equal to 1.

8. The electronic storage device (10) according to claim 6, wherein each of said first terrain elevation values (30) is also determined from said second terrain elevation values (32) associated with a corresponding cell (28) of said grid (28).

9. The electronic storage device (10) of claim 1, wherein, said first resolution (R1) and said second resolution (R2) being expressed in angular seconds, the value in angular seconds of each of said resolutions (R1, R2) defining a dimension corresponding to a side of the smallest unit representing the terrain, a higher resolution thus corresponding to a lower value in angular seconds.

10. The electronic storage device (10) according to claim 9, wherein the first resolution (R1) is equal to 3 or 6 angular seconds.

11. The electronic storage device (10) according to claim 10, wherein the second resolution (R2) is equal to 1 or 2 angular seconds.

12. A navigation system (20) configured to be on-board a flying vehicle (5), said navigation system (20) comprising or being connected to an electronic storage device (10) for storing a terrain database (15), characterized in that said electronic storage device (10) being according to claim 1, and wherein said avionics system (20) comprises an electronic monitoring device (40) configured to monitor the altitude of said aircraft (5) by comparison between, on the one hand, an altitude (ALT MSL ) from an altitude sensor (22), and, on the other hand, a sum of a first terrain elevation value (30, ELV BD1 ) from said terrain database (15) and an altitude above ground level (H RA ) from a radio altimeter (24), said comparison being based on an uncertainty value (δ BD1 ) associated with the corresponding said first terrain elevation value (30).

13. A generation method for generating a terrain database (15) of an avionics system (20), said terrain database (15) being stored in an electronic storage device (10) configured to be loaded on board an aircraft (5), said terrain database (15) corresponding to a terrain region (26) likely to be flown over by said aircraft (5), this terrain region (26) being represented in the form of a surface divided into meshes (28), each of said meshes (28) corresponding to a section of said terrain region (26), said terrain database (15) having a first resolution (Rl) and comprising first terrain elevation values (30) each associated with a respective said mesh (28), said method being computer-implemented and comprising the steps of: calculating (100), for each of said meshes (28), a value of uncertainty (δ BD1 ) associated with the corresponding first terrain elevation value (30) BD1 ), at least one of said values of uncertainty (δ BD1 ) is calculated from a plurality of second terrain elevation values (32) associated with said mesh (28) and deriving from a second terrain database (35) having a second resolution (R2) higher than said first resolution (R1). including (110) each computed said uncertainty value in said terrain database.

14. A computer-readable medium comprising a computer program containing software instructions implementing the generation method according to claim 13 when executed by a computer.

15. A monitoring method for monitoring the vertical positioning of an aircraft (5), said method being implemented by an electronic monitoring device (40) configured to be loaded on board said aircraft (5) and connected to an electronic device (10) for storing a terrain database (15), The method comprises comparing (200) between, on the one hand, the altitude (ALT MSL ) from the altitude sensor (22), and, on the other hand, the sum of the first terrain elevation value (30, ELV BD1 ) from the terrain database (15) and the height above ground (H RA ) from the radio altimeter (24), the comparison being based on the uncertainty value (delta BD1 ) associated with the corresponding first terrain elevation value (30), the terrain database (15) being generated by the generation method according to claim 13.

16. The monitoring method of claim 15, wherein, said method further comprising generating (210) a warning in the event of an error being determined in said comparison (200), the generated warning being a function of the determined error and being selected from the group comprising a warning relating to said terrain database (15), a warning relating to said altitude sensor (22), a warning relating to said radio altimeter (24), a warning relating to both said altitude sensor (22) and said radio altimeter (24) and a global warning.

17. A computer-readable medium comprising a computer program containing software instructions implementing the monitoring method according to claim 15 when executed by a computer.

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