Altitude measurement system and altitude measurement method

Abstract

The present invention comprises: a flight altimeter that is provided to an aircraft and includes at least one of a pressure altimeter and a GPS altimeter; a laser altimeter that is provided to the aircraft; and a control unit that, when the aircraft descends, switches a measurement value to be used between a measurement value of the flight altimeter and a measurement value of the laser altimeter on the basis of use conditions.

Description

Altitude measurement system and altitude measurement method

[0001] The present disclosure relates to an altitude measurement system and an altitude measurement method.

[0002] Conventionally, an automatic landing system for landing a vertical take-off and landing aircraft at a landing target point provided on a ship has been known (see, for example, Patent Document 1). The automatic landing system for a vertical take-off and landing aircraft disclosed in Patent Document 1 controls the vertical take-off and landing aircraft so that the relative position between the vertical take-off and landing aircraft and the landing target point becomes zero.

[0003] Japanese Patent Application Laid-Open No. 2021-062719

[0004] When a vertical take-off and landing aircraft lands at a target landing point, the vertical take-off and landing aircraft uses an altimeter such as a barometric altimeter or a laser altimeter to calculate the relative position in the vertical direction between the vertical take-off and landing point and performs flight operations so that the relative position becomes zero. However, with a barometric altimeter, if the vertical position changes between take-off and landing due to changes in air pressure, it may be difficult to accurately measure the altitude from the target landing point.

[0005] Therefore, an object of the present disclosure is to provide an altitude measurement system and an altitude measurement method that can acquire the altitude of an aircraft with high accuracy even during takeoff and landing.

[0006] The altitude measurement system disclosed herein includes an aircraft-mounted flight altimeter including at least one of a barometric altimeter and a GPS altimeter, a laser altimeter mounted on the aircraft, and a control unit that switches between the measurement value of the flight altimeter and the measurement value of the laser altimeter to be used based on usage conditions when the aircraft is descending.

[0007] The altitude measurement method disclosed herein is performed by an altitude measurement system that, during the descent of an aircraft, switches between the measurement values ​​of a flight altimeter, which includes at least one of a barometric altimeter and a GPS altimeter, and the measurement values ​​of a laser altimeter, based on the conditions of use.

[0008] According to the present disclosure, the altitude of an aircraft can be obtained with high accuracy even during takeoff and landing.

[0009] Fig. 1 is a schematic diagram showing an example of an altitude measurement system according to this embodiment. Fig. 2 is an explanatory diagram showing the landing operation of an aircraft. Fig. 3 is a block diagram related to the determination of whether or not a laser altimeter can be used. Fig. 4 is a block diagram related to the altitude correction process.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, this disclosure is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially identical. Furthermore, the components described below can be combined as appropriate, and when there are multiple embodiments, the respective embodiments can also be combined.

[0011] [Present Embodiment] Fig. 1 is a schematic diagram showing an example of an altitude measurement system according to this embodiment. Fig. 2 is an explanatory diagram showing the landing operation of an aircraft. Fig. 3 is a block diagram related to the determination of whether or not a laser altimeter can be used. Fig. 4 is a block diagram related to the altitude correction process. The altitude measurement system 100 is a system that measures the altitude between an aircraft 1 and a target landing point where the aircraft 1 will land.

[0012] The aircraft 1 is a rotary-wing aircraft (e.g., a vertical take-off and landing aircraft such as a helicopter or a drone). In this embodiment, the aircraft 1 is an unmanned aerial vehicle (UAV). The aircraft 1 may be any aircraft capable of forward, backward, sideways, turning, and hovering, and may be a manned aircraft. The aircraft 1 is equipped with an altitude measurement system 100, and flight is controlled based on altitude information acquired by the altitude measurement system 100.

[0013] 2, the target landing point is provided on a ship 5. Therefore, the aircraft 1 lands (docks) on the ship 5, which is a mobile body that moves on water. However, the target landing point is not limited to the ship 5, and may be provided on a mobile body that moves on land, such as a vehicle, or may be provided on stationary equipment or the ground.

[0014] The altitude measurement system 100 according to this embodiment acquires the altitude between the aircraft 1 and a target landing point on the ship 5. As shown in Fig. 1, the altitude measurement system 100 is configured as a system provided on the aircraft 1. First, the ship 5 will be described with reference to Figs. 1 and 2.

[0015] 1, the ship 5 includes a navigation device 70, a data transmission device 80, and an operation display unit 90. The ship 5 also includes a marker 7 that serves as a target for the aircraft 1 when it lands (docks).

[0016] The navigation device 70 is, for example, an inertial navigation system (INS) (registered trademark), and acquires the pitch and roll attitude angles, heading, speed, acceleration, and position coordinates in a global coordinate system of the ship 5. In the present embodiment, the navigation device 70 is described as being an inertial navigation system, but is not particularly limited thereto, and any navigation device 70 may be used. In the present embodiment, the navigation device 70 is an inertial navigation system including a GPS (Global Positioning System) to improve the accuracy of position measurement. In the present embodiment, the navigation device 70 is described as being an inertial navigation system including a GPS, but is not particularly limited to a GPS, and any system capable of measuring position with high accuracy may be used. For example, a system using a quasi-zenith satellite system may be used. Alternatively, a system omitting a GPS or the like may be used as long as the position can be measured with high accuracy using only the navigation device 70. The navigation device 70 may also acquire at least some of the various data using a sensor.

[0017] The data transmission device 80 exchanges various signals with the data transmission device 40 installed on the aircraft 1 via wireless communication.

[0018] The operation and display unit 90 is a user interface through which an operator on board the vessel 5 grasps the control status and inputs various instructions. The instructions input on the operation and display unit 90 are transmitted from the data transmission device 80 to the data transmission device 40. The control status of the aircraft 1 is transmitted from the data transmission device 40 to the data transmission device 80. In other words, the data transmission devices 40 and 80 are capable of two-way communication.

[0019] The marker 7 is provided on the deck of the ship 5. The marker 7 is an AR marker that is color-coded in two colors, for example, black and white, and serves as a marker for the aircraft 1 to capture the position of the target landing point.

[0020] (Aircraft) Next, a description will be given of the aircraft 1. As shown in Fig. 1, the aircraft 1 includes a camera 10, a navigation device 20, a control unit 30, and a data transmission device 40.

[0021] The camera 10 is an imaging device mounted on the aircraft 1 via a gimbal (not shown). The camera 10 may be a monocular camera, a compound eye camera, an infrared camera, or the like, as long as it can capture an image of the marker 7. The camera 10 is provided to capture an image of the marker 7 provided at the target landing point from the aircraft 1. The imaging direction of the camera 10 can be adjusted via a gimbal (not shown).

[0022] Like the navigation device 70, the navigation device 20 is, for example, an inertial navigation system including a GPS. Like the navigation device 70, the navigation device 20 may also be an inertial navigation system including a GPS or the like, or an inertial navigation system excluding a GPS or the like; there is no particular limitation. The navigation device 20 including a GPS acquires the pitch and roll attitude angles of the aircraft 1, the aircraft's heading, the aircraft's speed, the aircraft's acceleration, and position coordinates in the Earth's coordinate system. The navigation device 20 may also include an attitude angle sensor that detects the attitude angle of the aircraft 1, a speed detection sensor that detects the aircraft's speed, an acceleration detection sensor that detects the aircraft's acceleration, and a sensor that detects the aircraft's heading. The navigation device 20 outputs the acquired attitude angles, aircraft speed, aircraft acceleration, and position coordinates of the aircraft 1 to the control unit 30.

[0023] The control unit 30 includes an integrated circuit such as a CPU (Central Processing Unit), etc. The control unit 30 has an image processing unit 32, a guidance calculation unit 34, and a flight control unit 36.

[0024] The image processing unit 32 performs image processing on the image captured by the camera 10 to detect the center position of the marker 7. The image processing unit 32 outputs the calculated center position of the marker 7 to the guidance calculation unit 34.

[0025] The guidance calculation unit 34 calculates control variables for the aircraft 1 to guide the aircraft 1 to the target landing point. The control variables are variables for adjusting the aircraft speed, attitude angle, rate of change of attitude angle, etc. of the aircraft 1. To calculate the control variables, the guidance calculation unit 34 calculates the relative coordinate position between the aircraft 1 and the target landing point. Specifically, the guidance calculation unit 34 calculates the relative position between the aircraft 1 and the target landing point and the relative altitude between the aircraft 1 and the target landing point as the relative coordinate position. The guidance calculation unit 34 also calculates the relative speed between the aircraft 1 and the target landing point, etc. The relative position is the distance between the aircraft 1 and the target landing point of the ship 5 in the horizontal direction. The relative altitude is the distance between the aircraft 1 and the target landing point of the ship 5 in the vertical direction. The guidance calculation unit 34 calculates the relative altitude to the landing target point based on the altitude of the aircraft 1 detected by the altitude sensor 25.

[0026] The guidance calculation unit 34 also calculates the relative speed between the aircraft 1 and the target landing point. More specifically, the guidance calculation unit 34 calculates the relative speed between the aircraft 1 and the target landing point based on the relative position and the aircraft speed.

[0027] The guidance calculation unit 34 then calculates a control amount by feedback control (e.g., PID control) based on the relative position, relative altitude, relative speed, and aircraft acceleration. Note that the feedback control is not limited to PID control, but may be P control, PI control, PD control, etc. The guidance calculation unit 34 outputs the calculated control amount to the flight control unit 36.

[0028] 2, in calculating such control variables, the guidance calculation unit 34 controls the aircraft 1 in a plurality of control modes to guide the aircraft 1 to a target landing point and land it. The plurality of control modes include an approach mode, a hovering mode including a high-altitude hovering mode and a low-altitude hovering mode, and a landing mode.

[0029] The approach mode is a mode in which, in response to a command from the ship 5, the aircraft 1 approaches the deck of the ship 5 and hovers over a marker 7 that is the target landing point. The high-altitude hovering mode is a mode in which the aircraft 1 captures a marker 7 on the deck with the camera 10 and hovers. The low-altitude hovering mode is a mode in which the aircraft 1 descends and hovers at a lower altitude than in the high-altitude hovering mode. That is, the low-altitude hovering mode consists of a descent mode in which the aircraft 1 descends from the high-altitude hovering mode to a low altitude, and a hovering mode in which the aircraft 1 hovers at a low altitude after descending. The landing mode is a mode in which the aircraft 1 lands at a target landing point.

[0030] The flight control unit 36 ​​controls each component of the aircraft 1 in accordance with the control amount calculated by the guidance calculation unit 34 to fly the aircraft 1. The flight control unit 36 ​​controls the blade pitch angle, rotation speed, etc. of each rotor in accordance with the control amount, and adjusts the aircraft speed, attitude angle, rate of change of attitude angle, etc. of the aircraft 1. In this way, the aircraft 1 is guided to the target landing point. Note that in this embodiment, the guidance calculation unit 34 is described as a functional unit separate from the flight control unit 36, but the flight control unit 36 ​​and the guidance calculation unit 34 may be an integrated functional unit. In other words, the processing of the guidance calculation unit 34 may be performed in the flight control unit 36.

[0031] The data transmission device 40, like the data transmission device 80 described above, is included in the altitude measurement system 100 described below, and exchanges various signals with the data transmission device 80 installed on the ship 5 via wireless communication.

[0032] The altitude sensor 25 will now be described. The altitude sensor 25 has a flight altimeter 25a including at least one of a barometric altimeter and a GPS altimeter, and a laser altimeter 25b. The barometric altimeter measures altitude based on barometric pressure. The GPS altimeter measures altitude based on position coordinates in the Earth coordinate system. The laser altimeter 25b measures altitude by emitting a laser and receiving the reflected laser wave. The flight altimeter 25a and the laser altimeter 25b are switched depending on the flight mode and flight state of the aircraft 1.

[0033] (Altitude Measurement System) Next, switching control of the altitude measurement system 100 will be described with reference to FIG. 3 . The control circuit shown in FIG. 3 is incorporated, for example, in the guidance calculation unit 34. Based on the usage conditions, the control circuit executes switching control from the altimeter 25a to the laser altimeter 25b when the availability flag for the laser altimeter 25b is set. Here, the switching control switches between the measurement values ​​of the altimeter 25a and the laser altimeter 25b to be used based on the usage conditions. In this case, the use of only the measurement values ​​may be switched while measurements are being performed by the altimeter 25a and the laser altimeter 25b, or the use of the measurement values ​​may be switched by switching between the execution of measurements by the altimeter 25a and the laser altimeter 25b. In the following description of the switching control, the use of the altimeter 25a and the laser altimeter 25b is simply referred to as switching the use of the altimeter 25a and the laser altimeter 25b.

[0034] The induction calculation unit 34 has a first AND circuit 51, an OR circuit 52, and a second AND circuit 53 as circuits for determining the use conditions.

[0035] The first AND circuit 51 outputs an output signal to raise the usable flag when the altitude measured by the flight altimeter 25a is lower than a preset altitude (threshold value) and the intensity of the reflected wave acquired by the laser altimeter 25b is higher than the threshold value.

[0036] The OR circuit 52 outputs an output signal to raise the available flag when the altitude measured by the laser altimeter 25b is lower than a preset altitude, or when an output signal from the first AND circuit 51 is input.

[0037] The second AND circuit 53 sets the available flag when the aircraft 1 is in the low altitude hovering mode and the output signal from the OR circuit 52 is input.

[0038] In addition to the above circuits, a circuit enclosed by a dotted line in Fig. 3 may be further added. This circuit determines whether the relative position between the aircraft and the target landing point is within a predetermined range, and includes a first threshold circuit 55, a second threshold circuit 56, a third AND circuit 57, and a timer 58.

[0039] The first threshold circuit 55 receives the relative position between the aircraft 1 and the target landing point in the X direction on the horizontal plane, and outputs an output signal to raise a usable flag if the relative position in the X direction is within a threshold value (for example, ±2.0 m).

[0040] The second threshold circuit 56 receives the relative position between the aircraft 1 and the target landing point in the Y direction on the horizontal plane, and outputs an output signal to raise an available flag if the relative position in the Y direction is within a threshold value (e.g., ±2.0 m).

[0041] The third AND circuit 57 outputs an output signal for raising the usable flag when it receives the output signal from the first threshold circuit 55 and the output signal from the second threshold circuit 56.

[0042] The timer 58 outputs an output signal for setting up an available flag when an output signal is continuously input from the third AND circuit 57 for a predetermined time (e.g., 0.5 seconds). The circuit enclosed by the dotted line in Fig. 3 may be omitted.

[0043] When the enable flag is set in the circuit shown in Fig. 3, the guidance calculation unit 34 switches to using the laser altimeter 25b and calculates a control amount based on the vertical altitude in the circuit shown in Fig. 4. In the circuit shown in Fig. 4, PID control and the like are performed so that the difference (ΔALT) obtained by subtracting the relative altitude between the aircraft 1 and the target landing point from the target altitude in low altitude hovering mode becomes zero.

[0044] The circuit shown in FIG. 4 includes a first changeover switch 61, a subtractor 62, a second changeover switch 63, an integrator 64, an adder 65, a limiter 66, a third changeover switch 67, and a storage unit 68.

[0045] The first selector switch 61 is a switch for switching between the flight altimeter 25a and the laser altimeter 25b. When the availability flag for the laser altimeter 25b is set, the first selector switch 61 switches to the laser altimeter 25b side. The altitude measured by the flight altimeter 25a is referred to as altitude (1), and the altitude measured by the laser altimeter 25b is referred to as altitude (2).

[0046] The subtractor 62 is a circuit that subtracts the relative altitude input from the first changeover switch 61 from the target altitude input from the limiter 66. The subtractor 62 outputs the difference (ΔALT) between the target altitude and the relative altitude to a control unit that executes PID control or the like.

[0047] The second changeover switch 63 is a switch that is connected when the low altitude hovering mode is executed, and when the low altitude hovering mode is executed, it outputs the descent rate of the aircraft 1, i.e., the rate of change of altitude when the aircraft 1 is descending.

[0048] The integrator 64 receives the target altitude for the high-altitude hovering mode as an initial value, and also receives the descent rate from the second selector switch 63. The integrator 64 outputs the target altitude obtained by subtracting the descent altitude, which is integrated based on the descent rate, from the target altitude, which is the initial value.

[0049] The adder 65 adds the correction value output from the storage unit 68 to the target altitude output from the integrator 64, and outputs the corrected target altitude.

[0050] The limiter 66 is set with a target altitude for the low altitude hovering mode as a lower limit value, and outputs a corrected target altitude that is equal to or greater than the lower limit value so that the corrected target altitude does not fall below the lower limit value.

[0051] The third selector switch 67 is connected when the laser altimeter 25b is in use, and outputs a correction value when the laser altimeter 25b is in use. The correction value is the difference between the altitude (2) of the laser altimeter 25b and the altitude (1) of the flight altimeter 25a, and this difference is the value acquired the previous time the laser altimeter 25b was used.

[0052] The storage unit 68 stores the correction value, which is the difference acquired when the laser altimeter 25b is switched to this time.

[0053] In the circuit shown in FIG. 4, the difference in altitude when switching from the flight altimeter 25a to the laser altimeter 25b is added to the target altitude output from the integrator 64 in the adder 65, thereby correcting the target altitude.

[0054] (Altitude Measurement Method) Referring again to FIG. 3 , the altitude measurement method executed by the altitude measurement system 100 according to this embodiment will be described. In this altitude measurement method, the use of the flight altimeter 25a and the laser altimeter 25b is switched based on the usage conditions of the altitude sensor 25. In this altitude measurement method, the control unit 30 (guidance calculation unit 34) determines, in the first AND circuit 51, whether the usage conditions are met: the altitude measured by the flight altimeter 25a is lower than a preset setting altitude, and the reflection intensity acquired by the laser altimeter 25b is higher than a threshold value. If the control unit 30 determines that the usage conditions are met in the first AND circuit 51, the control unit 30 determines, in the OR circuit 52, whether the usage conditions are met: the altitude measured by the laser altimeter 25b is lower than a preset decision altitude, or whether the usage conditions in the first AND circuit 51 are met. The decision altitude is the altitude at which it is determined whether to land. Although the OR circuit 52 uses the condition that the altitude measured by the laser altimeter 25b is lower than a preset decision altitude (threshold value), the condition may instead be that the barometric altitude or GPS altitude reaches the decision altitude. When the OR circuit 52 determines that the use condition is satisfied, the control unit 30 uses the second AND circuit 53 to determine whether the use condition is satisfied, that is, whether the aircraft 1 is in low-altitude hovering mode and the use condition of the OR circuit 52 is satisfied. When the second AND circuit 53 determines that the use condition is satisfied, the control unit 30 outputs an enable flag for the laser altimeter 25b and switches to use of the laser altimeter 25b. Although the second AND circuit 53 uses the AND condition that the aircraft 1 is in low-altitude hovering mode, this need not be an AND condition. In other words, although use of the laser altimeter 25b is permitted when the aircraft 1 is in low-altitude hovering mode, this is not limited to this.

[0055] As described above, the altitude measurement system 100 and the altitude measurement method described in this embodiment can be understood, for example, as follows.

[0056] The altitude measurement system 100 according to the first aspect includes an altimeter 25a provided on the aircraft 1 and including at least one of a barometric altimeter and a GPS altimeter, a laser altimeter 25b provided on the aircraft 1, and a control unit 30 that switches between the measurement values ​​of the altimeter 25a and the laser altimeter 25b to be used based on usage conditions when the aircraft 1 is descending.

[0057] With this configuration, the measurement values ​​of the flight altimeter 25a or the laser altimeter 25b can be switched between and used based on the usage conditions, allowing more appropriate measurement values ​​to be used and enabling altitude to be measured with high accuracy according to the usage conditions.

[0058] In a second aspect, in the altitude measurement system 100 according to the first aspect, the control unit 30 switches to using the measurement value of the laser altimeter 25b when the altitude measured by the laser altimeter 25b is lower than a preset decision altitude as a condition of use.

[0059] According to this configuration, if the altitude measured by the laser altimeter 25b is lower than the decision altitude, the altitude can be measured with high accuracy by switching to the more accurate laser altimeter 25b.

[0060] As a third aspect, in the altitude measurement system 100 according to the first or second aspect, the control unit 30 switches to using the measurement value of the laser altimeter 25b when the usage conditions are that the altitude measured by the flight altimeter 25a is lower than a preset altitude and the reflection intensity acquired by the laser altimeter 25b is higher than a threshold value.

[0061] According to this configuration, when the altitude measured by the flight altimeter 25a is lower than the set altitude and the reflection intensity of the laser altimeter 25b is higher than the threshold value, that is, when altitude measurement using the laser altimeter 25b is possible, the altitude can be measured with high accuracy by switching to and using the laser altimeter 25b.

[0062] As a fourth aspect, in the altitude measurement system 100 according to the first aspect, the control unit 30 allows switching to use of the measurement values ​​of the laser altimeter 25b when the aircraft 1 is in a predetermined flight mode as a usage condition.

[0063] According to this configuration, when the aircraft 1 is in a predetermined flight mode, that is, a flight mode that requires highly accurate altitude measurement, the laser altimeter 25b can be used.

[0064] As a fifth aspect, in the altitude measurement system 100 according to the first or second aspect, the control unit 30 allows switching to use of the measurement value of the laser altimeter 25b when the relative position between the aircraft 1 landing at the target landing point and the target landing point is within a predetermined range as a usage condition.

[0065] With this configuration, the laser altimeter 25b can be used when the aircraft 1 is within a predetermined range including the target landing point, which prevents the laser altimeter 25b from being used on the sea surface away from the target landing point.

[0066] As a sixth aspect, in the altitude measurement system 100 according to any one of the third and fourth aspects, the control unit 30 corrects the difference in altitude when switching between the measurement value of the flight altimeter 25a and the measurement value of the laser altimeter 25b.

[0067] According to this configuration, when switching from the flight altimeter 25a to the laser altimeter 25b, any difference in altitude can be corrected, so that the altitude can be measured with higher accuracy.

[0068] The altitude measurement method according to the seventh aspect is performed by an altitude measurement system 100 that switches between the measurement values ​​of a flight altimeter 25a, which includes at least one of a barometric altimeter and a GPS altimeter, and the measurement values ​​of a laser altimeter 25b, based on the conditions of use, when the aircraft 1 descends.

[0069] With this configuration, if the altitude measured by laser altimeter 25b is lower than the set altitude, the altitude can be measured with high accuracy by switching to laser altimeter 25b. Also, if the altitude measured by flight altimeter 25a is lower than the set altitude and the reflection intensity of laser altimeter 25b is higher than the threshold, that is, if altitude measurement using laser altimeter 25b is possible, the altitude can be measured with high accuracy by switching to laser altimeter 25b.

[0070] REFERENCE SIGNS LIST 1 aircraft 5 ship 7 marker 10 camera 20 navigation device 25 altitude sensor 25a flight altimeter 25b laser altimeter 30 control unit 32 image processing unit 34 guidance calculation unit 36 ​​flight control unit 40 data transmission device 51 first AND circuit 52 OR circuit 53 second AND circuit 55 first threshold circuit 56 second threshold circuit 57 third AND circuit 58 timer 61 first selector switch 62 subtractor 63 second selector switch 64 integrator 65 adder 66 limiter 67 third selector switch 68 memory unit 70 navigation device 80 data transmission device 90 operation display unit 100 altitude measurement system

Claims

1. An altitude measurement system comprising: a flight altimeter installed on an aircraft and including at least one of a barometric altimeter and a GPS altimeter; a laser altimeter installed on the aircraft; and a control unit that switches between the measurement value of the flight altimeter and the measurement value of the laser altimeter to be used based on usage conditions when the aircraft is descending.

2. The altitude measurement system according to claim 1, wherein the control unit switches to using the measurement value of the laser altimeter when the altitude measured by the laser altimeter is lower than a preset decision altitude as a condition of use.

3. The altitude measurement system of claim 1, wherein the control unit switches to using the measurement value of the laser altimeter when the usage conditions are that the altitude measured by the flight altimeter is lower than a preset altitude and the reflection intensity obtained by the laser altimeter is higher than a threshold value.

4. The altitude measurement system according to claim 1, wherein the control unit allows switching to use of the measurement values ​​of the laser altimeter when the aircraft is in a predetermined flight mode as a condition of use.

5. The altitude measurement system of claim 1, wherein the control unit allows switching to use of the measurement values ​​of the laser altimeter when the relative position between the aircraft landing at the target landing point and the target landing point is within a predetermined range as a condition of use.

6. The altitude measurement system according to claim 1, wherein the control unit corrects the difference in altitude when switching between the measurement value of the flight altimeter and the measurement value of the laser altimeter.

7. An altitude measurement method implemented by an altitude measurement system that switches between the measurement values ​​of a flight altimeter, including at least one of a barometric altimeter and a GPS altimeter, and the measurement values ​​of a laser altimeter, based on the conditions of use, when an aircraft is descending.

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