Aircraft three-dimensional positioning method and system based on satellite-borne multi-spectrum thermal infrared imager

Abstract

The invention discloses an aircraft three-dimensional positioning method and system based on a satellite-borne multi-spectrum thermal infrared imager, and the method comprises the steps: (1) carrying out the detection of an aircraft through a machine learning algorithm based on the observation data of the satellite-borne multi-spectrum thermal infrared imager, and obtaining the latitude and longitude information of an aircraft target and the DN value of the aircraft target in a remote sensing image; (2) calculating the brightness temperature T1, T2,..., Tn at the entrance pupil of the multi-spectrum airplane; (3) establishing an aircraft radiation characteristic model to obtain the relationship between the flight height of the aircraft and the brightness temperature at the entrance pupil; (4) acquiring environmental conditions of latitude and longitude positions of the airplane by using multi-source observation data, substituting the environmental conditions into the airplane radiation characteristic model, and establishing a flight height lookup table; and (5) obtaining the flight height corresponding to the brightness temperature at the entrance pupil of the multispectral section obtained in the step (2) through the lookup table, and calculating the average flight height to obtain an inversion result. The method is wide in detection range, does not depend on a radio communication transmission medium, and can realize all-day searching and positioning of a target in a wide area range.

Description

Technical Field

[0001] The invention belongs to the field of remote sensing and aviation safety, and in particular relates to a three-dimensional positioning method and system for an aircraft based on a satellite-borne multi-spectral thermal infrared imager. Background Art

[0002] During the flight of aircraft and other aerial targets, it is crucial to obtain three-dimensional position information, including longitude, latitude and altitude. The measurement of aircraft flight altitude is mainly obtained through ground radar and satellite communication. Surveillance radar is used for detection and control on routes and airports. Secondary radar receives aircraft number, altitude and direction information for traffic control. Automatic Dependent Surveillance-Broadcast (ADS-B) is currently the most important civil aircraft monitoring technology. It determines the position of the aircraft through the satellite navigation system and broadcasts it regularly. The traffic control ground station receives this information as a substitute for secondary radar. Due to the limitation of detection distance, ground radar systems are difficult to cover polar and oceanic areas, and satellite communication systems rely on feedback information from aerial targets. These aircraft detection and information acquisition methods are difficult to meet the application requirements of detection and search for unknown flying targets in a wide area.

[0003] The Chinese patent document with publication number CN111879286A discloses a method for obtaining the flight altitude of an aircraft, which integrates the characteristics of different flight altitude measurement equipment such as laser atmospheric data system, global navigation satellite system, wireless altimeter, etc. to perform data fusion to determine the aircraft altitude information. This method requires obtaining information such as air pressure and temperature through sensors carried by the aircraft, and transmitting the signal to satellites or the ground.

[0004] In order to make the acquired data more accurate, those skilled in the art have also studied sensors. For example, a Chinese patent document with publication number CN210689594U discloses a pressure sensor for real-time monitoring of aircraft flight altitude, including a pressure sensor body, on which is installed a flow-blocking device for hindering airflow from entering the air inlet end of the pressure sensor body when the aircraft is flying. The utility model weakens the airflow when the aircraft is running at high speed, and the wind speed value at the time of the final detection is approximately equal to 0, thereby ensuring the accuracy of the pressure sensor body without affecting the connectivity between the pressure sensor body and the outside world.

[0005] However, the above methods for obtaining the flight altitude of an aircraft cannot realize the search and positioning of unknown targets. Summary of the invention

[0006] The present invention provides a method and system for stereoscopic positioning of aircraft based on a satellite-borne multi-spectral thermal infrared imager, which has a wide detection range, is independent of radio communication transmission media, and utilizes space-based infrared detection means to achieve all-day search and positioning of targets within a wide area.

[0007] A method for stereoscopic positioning of an aircraft based on a satellite-borne multi-spectral thermal infrared imager comprises the following steps:

[0008] (1) Based on the observation data of the satellite-borne multi-spectral thermal infrared imager, the machine learning algorithm is used to detect aircraft and obtain the longitude and latitude information of the aircraft target and the DN value of the aircraft target in the remote sensing image;

[0009] (2) Calculate the brightness temperature T1, T2, ..., T at the entrance pupil of the multi-spectral aircraft n , n is the number of spectrum segments;

[0010] (3) Establish an aircraft radiation characteristic model to obtain the relationship between the aircraft's flight altitude and the brightness temperature at the entrance pupil;

[0011] (4) Using multi-source observation data to obtain the environmental conditions of the aircraft's latitude and longitude, including seasonal climate, surface temperature, and light conditions, and bringing them into the above-mentioned aircraft radiation characteristic model to establish a flight altitude lookup table;

[0012] (5) Obtain the flight height corresponding to the brightness temperature at the entrance pupil of the multi-spectral bands obtained in step (2) from the lookup table, calculate the average flight height, and obtain the inversion result.

[0013] In step (2), the formula for calculating the brightness temperature at the entrance pupil of the multi-spectral aircraft is as follows:

[0014]

[0015] T i represents the brightness temperature of the i-th spectral band, i = 1, 2, ..., n; k1 and k2 are the coefficients for deriving the brightness temperature from the radiance; is the spectral radiance of the i-th spectral band calculated using the fitting coefficients and the signal response grayscale value.

[0016] The calculation formula is as follows:

[0017]

[0018] Among them, DN i is the value of the signal of the i-th spectrum converted into a digital number by the analog-to-digital converter, that is, the grayscale value in the remote sensing image; a i and b i are the gain coefficient and bias coefficient of the i-th spectral band.

[0019] In step (3), the aircraft radiation characteristic model is established. The specific process is as follows:

[0020] Aircraft entrance pupil radiance L airplane Expressed as

[0021] L airplane(λ)=(L skin (λ)+L atm (λ))·τ atm (λ)+L path (λ)

[0022] Among them, L skin is the aircraft skin radiance, L atm is the atmospheric reflected radiation, τ atm is the atmospheric transmittance, L pat is the path radiation, λ is the wavelength; atmospheric transmittance τ atm and path radiation L path It is related to the flight altitude of the aircraft and is obtained through MODTRAN simulation.

[0023] Aircraft skin radiance L skin Expressed as

[0024]

[0025] Among them, ε skin is the infrared emissivity of the skin, T skin_ave is the average temperature of the aircraft skin, M is the spectral radiation emittance, which satisfies Planck's law;

[0026] The average temperature of the aircraft skin is T skin_ave Expressed as

[0027]

[0028] Among them, T atm is the ambient atmospheric temperature of the aircraft, β is the temperature recovery coefficient, υ is the specific heat ratio; C is a constant, Ma is the flight speed of the aircraft, the unit is Mach number;

[0029] Aircraft ambient air temperature T atm It is related to the aircraft's flight altitude, and the relationship is expressed as:

[0030] T atm =T L -α·H

[0031] Among them, T L is the surface temperature, H is the aircraft altitude, and α is the coefficient. Depending on the climate and weather, the coefficient α ranges from 0.58 to 0.65.

[0032] Convert the radiance at the entrance pupil of the aircraft into the brightness temperature T at the entrance pupil airplane , complete the establishment of the aircraft radiation characteristics model:

[0033]

[0034] Wherein, λ1 and λ2 are the start and end wavelengths of the spectrum band respectively, c1 is the first radiation constant, and c2 is the second radiation constant.

[0035] In step (5), the flight altitudes corresponding to the brightness temperatures at the multi-spectral entrance pupil are H1, H2, …, H n The following conditions should be met:

[0036] Based on the same inventive principle, the present invention also provides an aircraft stereo positioning system based on a satellite-borne multi-spectral thermal infrared imager, characterized in that it includes a memory and one or more processors, wherein the memory stores executable code, and when the one or more processors execute the executable code, they are used to implement the above-mentioned aircraft stereo positioning method.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The method of the present invention does not require the target itself to provide feedback information, which is conducive to discovering unknown targets.

[0039] 2. The method of the present invention is a passive detection method, which improves the concealment of the acquisition of target location information.

[0040] 3. The method of the present invention is applicable to day and night conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The present invention is a flow chart of an aircraft stereo positioning method based on a satellite-borne multi-spectral thermal infrared imager;

[0042] Figure 2 This is the aircraft altitude inversion result in the embodiment of the present invention. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0044] The embodiment of the present invention takes the TIS data carried by the SDGSAT-1 satellite as an example. Figure 1 As shown, a method for stereoscopic positioning of an aircraft based on a satellite-borne multi-spectral thermal infrared imager comprises the following steps:

[0045] Step 1: Use machine learning models to detect aircraft, combine cloud detection to reduce false alarm rates, and obtain the DN value of aircraft targets in space-based remote sensing images. At the same time, obtain the longitude and latitude of the target based on the geographic information in the remote sensing image.

[0046] Step 2: Calculation of the aircraft's multi-spectral entrance pupil brightness temperature

[0047] The thermal infrared radiation imager carried by the SDGSAT-1 satellite has three spectral bands, namely 8-10.5μm (B1), 10.3-11.3μm (B2) and 11.5-12.5μm (B3). The brightness temperature T of the i-th spectral band i The calculation expression is:

[0048]

[0049] where k1 and k2 are coefficients for deriving the brightness temperature from the radiance. is the spectral radiance of the i-th spectral band calculated using the fitting coefficient and the signal response gray value. The calculation expression is:

[0050]

[0051] Among them, DN i It is the value of the signal of the i-th spectrum converted into a digital number by the analog-to-digital converter, that is, the grayscale value in the remote sensing image. i and b i are the gain coefficient and bias coefficient of the i-th spectral band.

[0052] like Figure 2 As shown in (a), the latitude and longitude position of the aircraft target in the image is E5.48 / N43.16, and the DN values ​​of the three spectrum segments are 1534 (B1), 1794 (B2), and 1244 (B3), which are converted into entrance pupil brightness temperature:

[0053] T1=264.27K

[0054] T2=267.83K

[0055] T3=266.60K

[0056] Step 3: Establishing the aircraft radiation characteristics model

[0057] The aircraft radiation signal reaching the entrance pupil includes the skin thermal radiation generated by aerodynamic heating when the aircraft is flying at high speed, the heating of the aircraft caused by atmospheric reflection and sunlight, and path radiation.

[0058] Entrance pupil radiance L airplane It can be expressed as

[0059] L airplane (λ)=(L skin (λ)+L atm (λ))·τ atm (λ)+L path (λ)

[0060] Among them, L skin is the aircraft skin radiance, L atm is the atmospheric reflected radiation, τatm is the atmospheric transmittance, L path is the path radiation, λ is the wavelength. τ atm and L path It is related to the flight altitude and can be obtained through MODTRAN simulation.

[0061] Spectral infrared radiance L of aircraft skin skun It can be expressed as

[0062]

[0063] Among them, ε skin is the infrared emissivity of the skin, T skin_ave is the average temperature of the skin, M is the spectral radiation emittance, and it satisfies Planck's law.

[0064] The average temperature of the aircraft skin is T skin_ave It can be expressed as

[0065]

[0066] Among them, T atm is the ambient air temperature of the aircraft, β is the temperature recovery coefficient, υ is the specific heat ratio, C is a constant, Ma is the aircraft flight speed, and the unit is Mach number.

[0067] Ambient temperature T atm The relationship with height can be expressed as

[0068] T atm =T L -α·H

[0069] Among them, T L is the surface air temperature, H is the aircraft flight altitude, and α is a coefficient, which usually ranges from 0.58 to 0.65 depending on the climate and weather.

[0070] Convert the radiance at the entrance pupil of the aircraft into the brightness temperature T at the entrance pupil airplane , complete the establishment of the aircraft radiation characteristics model:

[0071]

[0072] Wherein, λ1 and λ2 are the start and end wavelengths of the spectrum band respectively, c1 is the first radiation constant, and c2 is the second radiation constant.

[0073] Step 4: Based on the above model, the local environmental conditions are obtained by combining multi-source remote sensing information, and a height lookup table is established such as Figure 2 As shown in (c). The inversion results show that the height of the three spectral segments is

[0074] H1=9.52km

[0075] H2=9.65km

[0076] H3=9.84km

[0077] The inversion result of the height is 9.67km, and the difference of the inversion height of the three spectrum segments is 0.32km, which meets the accuracy requirement (<1km).

[0078] In summary, this scheme uses the satellite-borne multi-spectral thermal infrared imager to achieve three-dimensional positioning of the aircraft.

[0079] Based on the same inventive principle, an embodiment of the present invention also provides an aircraft stereo positioning system based on a satellite-borne multi-spectral thermal infrared imager, comprising a memory and one or more processors, wherein the memory stores executable code, and when one or more processors execute the executable code, it is used to implement the aircraft stereo positioning method mentioned in the above embodiment.

[0080] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for stereoscopic positioning of an aircraft based on a satellite-borne multi-spectral thermal infrared imager, characterized in that: The following steps are involved: (1) Based on the observation data of the satellite-borne multi-spectral thermal infrared imager, the machine learning algorithm is used to detect aircraft and obtain the longitude and latitude information of the aircraft target and the DN value of the aircraft target in the remote sensing image; (2) Calculate the brightness temperature T1, T2, ..., T at the entrance pupil of the multi-spectral aircraft n , n is the number of spectrum segments; (3) Establish an aircraft radiation characteristic model to obtain the relationship between the aircraft's flight altitude and the brightness temperature at the entrance pupil; (4) Using multi-source observation data to obtain the environmental conditions of the aircraft's latitude and longitude, including seasonal climate, surface temperature, and light conditions, and bringing them into the above-mentioned aircraft radiation characteristic model to establish a flight altitude lookup table; (5) Obtain the flight height corresponding to the brightness temperature at the entrance pupil of the multi-spectral bands obtained in step (2) from the lookup table, calculate the average flight height, and obtain the inversion result.

2. The aircraft stereo positioning method based on a satellite-borne multi-spectral thermal infrared imager according to claim 1, characterized in that: In step (2), the formula for calculating the brightness temperature at the entrance pupil of the multi-spectral aircraft is as follows: T i represents the brightness temperature of the i-th spectral band, i = 1, 2, ..., n; k1 and k2 are the coefficients for deriving the brightness temperature from the radiance; is the spectral radiance of the i-th spectral band calculated using the fitting coefficients and the signal response grayscale value.

3. The aircraft stereo positioning method based on a satellite-borne multi-spectral thermal infrared imager according to claim 2, characterized in that: The calculation formula is as follows: Among them, DN i is the value of the signal of the i-th spectrum converted into a digital number by the analog-to-digital converter, that is, the grayscale value in the remote sensing image; a i and b i are the gain coefficient and bias coefficient of the i-th spectral band.

4. The aircraft stereo positioning method based on a satellite-borne multi-spectral thermal infrared imager according to claim 3, characterized in that: In step (3), the aircraft radiation characteristic model is established. The specific process is as follows: Aircraft entrance pupil radiance L airplane Expressed as L airplane (λ)=(L skin (λ)+L atm (l))·t atm (λ)+L path (l) Among them, L skin is the aircraft skin radiance, L atm is the atmospheric reflected radiation, τ atm is the atmospheric transmittance, L path is the path radiation, λ is the wavelength; Aircraft skin radiance L skin Expressed as Among them, ε skin is the infrared emissivity of the skin, T skin_ave is the average temperature of the aircraft skin, M is the spectral radiation emittance, which satisfies Planck's law; The average temperature of the aircraft skin is T skin_ave Expressed as Among them, T atm is the ambient atmospheric temperature of the aircraft, β is the temperature recovery coefficient, ν is the specific heat ratio; C is a constant, Ma is the flight speed of the aircraft, the unit is Mach number; Aircraft ambient air temperature T atm It is related to the aircraft's flight altitude, and the relationship is expressed as: T atm =T L -α·H Among them, T L is the surface air temperature, H is the aircraft flight altitude, and α is the coefficient; Convert the radiance at the entrance pupil of the aircraft into the brightness temperature T at the entrance pupil airplane , complete the establishment of the aircraft radiation characteristics model: Wherein, λ1 and λ2 are the start and end wavelengths of the spectrum band respectively, c1 is the first radiation constant, and c2 is the second radiation constant.

5. The aircraft stereo positioning method based on a satellite-borne multi-spectral thermal infrared imager according to claim 4, characterized in that: Atmospheric transmittance τ atm and path radiation L path It is related to the flight altitude of the aircraft and is obtained through MODTRAN simulation.

6. The aircraft stereo positioning method based on a satellite-borne multi-spectral thermal infrared imager according to claim 4, characterized in that: Depending on the climate and weather, the coefficient α ranges from 0.58 to 0.

65.

7. The aircraft stereo positioning method based on a satellite-borne multi-spectral thermal infrared imager according to claim 1, characterized in that: In step (5), the flight altitudes corresponding to the brightness temperatures at the multi-spectral entrance pupil are H1, H2, …, H n The following conditions must be met: i -H j |<1km, i≠j.

8. An aircraft stereo positioning system based on a satellite-borne multi-spectral thermal infrared imager, characterized in that: The invention comprises a memory and one or more processors, wherein the memory stores executable codes, and when the one or more processors execute the executable codes, the aircraft stereo positioning method according to any one of claims 1 to 7 is implemented.

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