A system for selecting a SAR image detection area

Abstract

The application discloses a SAR image detection area selection system and belongs to the technical field of SAR detection. The system solves the problem that the image collected by the SAR detection and image collection in the prior art is random, which may not meet the requirements. The system comprises a radar controller, a data calculation unit, a threshold comparison unit, an image display unit and a data table generation unit. The instruction output end of the radar controller is connected with the data input end of the threshold comparison unit through the data calculation unit. The data output end of the threshold comparison unit is connected with the image display unit and the data table generation unit. The data output end of the data table generation unit is connected with the data input end of the radar controller. The system can be used for the selection of the detection area of the synthetic aperture radar.

Description

Technical Field

[0001] This invention belongs to the field of SAR detection technology, and in particular relates to a SAR image detection area selection system. Background Technology

[0002] In existing technologies, when SAR needs to perform detection, it typically involves direct detection and image acquisition. However, SAR detection and image acquisition using this method are random, and the acquired images may not meet the requirements. Summary of the Invention

[0003] Based on the above analysis, the present invention aims to provide a SAR image detection area selection system, which solves the problem that the random nature of SAR detection and image acquisition in the prior art may result in images that do not meet the requirements.

[0004] The objective of this invention is mainly achieved through the following technical solutions:

[0005] This invention provides a SAR image detection area selection system, including a radar controller, a data calculation unit, a threshold comparison unit, an image display unit, and a data table generation unit;

[0006] The command output terminal of the radar controller is connected to the data input terminal of the threshold comparison unit through the data calculation unit. The data output terminal of the threshold comparison unit is connected to the image display unit and the data table generation unit respectively. The data output terminal of the data table generation unit is connected to the data input terminal of the radar controller.

[0007] Furthermore, the data calculation unit is used to calculate the ground reflectance coefficient matrix, distance resolution matrix, and azimuth resolution matrix of the grid points at different distance resolutions.

[0008] Furthermore, the threshold comparison unit receives the range resolution matrix, azimuth resolution matrix, and ground reflectance matrix respectively, and compares them with the threshold ranges of range resolution, azimuth resolution, and ground reflectance stored in the threshold comparison unit to obtain multiple grid points that simultaneously satisfy the range resolution, azimuth resolution, and ground reflectance, and sends them to the graphical display unit and the data table generation unit respectively.

[0009] Furthermore, the graphical display unit displays multiple grid points that simultaneously satisfy distance resolution, azimuth resolution, and ground reflectivity in a graphical manner.

[0010] Furthermore, the data table generation unit generates parameter tables for multiple grid points that meet the conditions, including range resolution, azimuth resolution, ground reflection coefficient, coordinates, flight parameters of the carrier, off-axis angle, and antenna installation angle, and sends them to the radar controller.

[0011] Furthermore, the SAR controller receives the parameter table and performs image detection of the detection area based on the parameters in the parameter table, which meets the requirements of range resolution, azimuth resolution, and ground reflectivity.

[0012] Furthermore, the SAR image detection area selection system also includes a distortion rate acquisition unit.

[0013] Furthermore, the threshold comparison unit is used to receive the distortion rate and compare the distortion rates corresponding to multiple grid points that simultaneously satisfy the range resolution, azimuth resolution, and ground reflectance with the thresholds stored in the threshold comparison unit. This results in multiple grid points that simultaneously satisfy the range resolution, azimuth resolution, ground reflectance, and distortion rate, which are then sent to the graphical display unit to display a two-dimensional analysis diagram.

[0014] Furthermore, the threshold comparison unit is used to receive the distortion rate and compare the distortion rates corresponding to multiple grid points that simultaneously satisfy the range resolution, azimuth resolution, and ground reflectance with the thresholds stored in the threshold comparison unit. The results of multiple grid points that simultaneously satisfy the range resolution, azimuth resolution, ground reflectance, and distortion rate are sent to the data table generation unit to generate a data table.

[0015] Furthermore, the SAR detection area selection system also includes a memory for storing data calculation units, threshold comparison units, image display units, and data table generation units.

[0016] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0017] The SAR image detection area selection system provided by this invention can pre-calculate the distance resolution, azimuth resolution, and ground reflectance of each grid point in the required detection area before the actual SAR image detection. It obtains a two-dimensional analysis map that reflects the SAR detection capability, as well as a parameter table of distance resolution, azimuth resolution, ground reflectance, coordinates, carrier flight parameters, and off-axis angle corresponding to the grid points that meet the conditions, thereby better guiding the SAR in selecting the detection area.

[0018] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0019] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0020] Figure 1 This is a schematic diagram of the connection between the memory and the housing in the SAR image detection area selection system provided in Embodiment 1 of the present invention;

[0021] Figure 2 This is a schematic diagram of the connection between the first arc-shaped rod and the connecting rod in the SAR image detection area selection system provided in Embodiment 1 of the present invention.

[0022] Figure label:

[0023] 1-Housing; 2-Memory; 3-First arc-shaped rod; 4-Second arc-shaped rod; 5-Connecting pipe; 6-Outer ring; 7-First inner ring; 8-Second inner ring; 9-Baffle. Detailed Implementation

[0024] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of the present invention and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0025] Example 1

[0026] This embodiment provides a SAR image detection area selection system, including a radar controller, a data calculation unit, a threshold comparison unit, an image display unit, and a data table generation unit. The command output terminal of the radar controller is connected to the data input terminal of the threshold comparison unit through the data calculation unit. The data output terminal of the threshold comparison unit is connected to both the image display unit and the data table generation unit. The data output terminal of the data table generation unit is connected to the data input terminal of the radar controller.

[0027] The data calculation unit is used to calculate the ground reflectance coefficient matrix, range resolution matrix, and azimuth resolution matrix of grid points at different range resolutions;

[0028] The threshold comparison unit receives the range resolution matrix, azimuth resolution matrix, and ground reflectance coefficient matrix respectively, and compares them with the threshold ranges of range resolution, azimuth resolution, and ground reflectance coefficient stored in the threshold comparison unit. It then obtains multiple grid points that simultaneously satisfy the range resolution, azimuth resolution, and ground reflectance coefficient and sends them to the graphical display unit and the data table generation unit respectively.

[0029] The graphical display unit displays multiple grid points that simultaneously meet the requirements of distance resolution, azimuth resolution, and ground reflectivity in an image format.

[0030] The data table generation unit generates a parameter table for multiple grid points that meet the conditions, including range resolution, azimuth resolution, ground reflection coefficient, coordinates, carrier flight parameters, off-axis angle, and antenna installation angle, and sends it to the radar controller.

[0031] The SAR controller is used to receive the parameter table and perform image detection of the detection area according to the parameters in the parameter table, which meets the range resolution, azimuth resolution and ground reflectivity.

[0032] Based on the two-dimensional analysis diagram obtained by the above system, the beam coverage area can be divided into multiple regions to obtain the resolution distribution characteristics within the ground beam coverage area under different oblique angles. For example, the resolutions are 1m×1m×sigma (ground reflection coefficient) = -12, 3m×3m×sigma (ground reflection coefficient) = -12 and 5m×5m×sigma (ground reflection coefficient) = -12. In practical applications, for example, the grid points of the circular markers are grid points that satisfy the range resolution and azimuth resolution of 1m × 1m × sigma (ground reflectivity) = -12; the grid points of the star-shaped markers are grid points that satisfy the range resolution and azimuth resolution of 3m × 3m × sigma (ground reflectivity) = -12; and the grid points of the triangular markers are grid points that satisfy the range resolution and azimuth resolution of 5m × 5m × sigma (ground reflectivity) = -12. When the carrier needs to perform image detection with a range resolution and azimuth resolution of 1m × 1m × sigma (ground reflectivity) = -12, the various parameters of the carrier and the radar can be controlled to be consistent with the various parameters corresponding to the grid points of the circular markers, thereby enabling image detection with a range resolution and azimuth resolution of 1m × 1m × sigma (ground reflectivity) = -12, and guiding the radar image detection.

[0033] During implementation, SAR is activated, and the SAR controller sends a detection area prediction command. Based on the detection area prediction command, the ground beam coverage area is determined using the carrier's flight parameters, the radar's antenna installation angle, and scanning range. A grid is drawn within the beam coverage area, and the coordinate matrix of the grid points within the beam coverage area is obtained. The slant angle matrix and slant range matrix corresponding to the grid points within the beam coverage area are calculated based on the carrier's flight parameters and the grid point coordinate matrix. The actual transmit gain matrix and actual receive gain matrix from the antenna to the grid points are calculated based on the off-axis angle. It should be noted that the off-axis angle refers to the angle between the carrier's target pointing direction and the antenna pointing direction. The radar equations are calculated based on the actual transmit gain matrix from the antenna to the grid points, the actual receive gain matrix from the antenna to the grid points, the slant angle matrix, the slant range matrix, the radar's system loss (it should be noted that the radar's system loss is a fixed value; each radar model has a fixed system loss, usually including waveform loss or transmission loss, etc.) and the average power, to obtain the coordinate matrix of the grid points within the grid coverage area. Ground reflectance coefficient matrices at different range resolutions are generated. Based on the radar bandwidth, carrier altitude, and slant range matrix, the range resolution matrix of the grid points is obtained. Based on the carrier's velocity (which can be calculated from the carrier's three-dimensional velocity), wavelength, synthetic aperture time, slant angle matrix, and slant range matrix, the azimuth resolution matrix of the grid points is obtained. The range resolution, azimuth resolution, and ground reflectance coefficient in the range resolution matrix and azimuth resolution matrix of the grid points are filtered according to a threshold range to obtain multiple grid points that simultaneously meet the conditions of range resolution, azimuth resolution, and ground reflectance coefficient. These are then graphically displayed to obtain a two-dimensional analysis map, and a parameter table is generated for the range resolution, azimuth resolution, ground reflectance coefficient, coordinates, carrier flight parameters, off-axis angle, and antenna installation angle corresponding to the multiple grid points that meet the conditions. The SAR controller receives the parameter table and performs image detection of the detection area that meets the range resolution, azimuth resolution, and ground reflectance coefficient based on the parameters in the parameter table.

[0034] It should be noted that the carrier refers to the substrate used to mount the radar, such as aircraft, satellites, spacecraft, and other flying vehicles. The carrier's flight parameters include its coordinates in the navigation coordinate system, pitch attitude, yaw attitude, roll attitude, and three-dimensional velocity.

[0035] Compared with existing technologies, the SAR image detection area selection system provided in this embodiment can pre-calculate the distance resolution, azimuth resolution, and ground reflectance of each grid point in the required detection area before the actual SAR image detection. This results in a two-dimensional analysis map that reflects the SAR detection capability, as well as a parameter table of distance resolution, azimuth resolution, ground reflectance, coordinates, carrier flight parameters, and off-axis angle corresponding to the grid points that meet the conditions. This allows for better guidance in the selection of the SAR detection area.

[0036] Furthermore, in response to the needs of radar detection capability analysis, the previously separately calculated indicators such as range resolution, azimuth resolution, and ground reflection coefficient are comprehensively calculated and filtered. The radar capability boundary is presented in multiple dimensions through two-dimensional images. The position, three-dimensional velocity, and three-dimensional attitude of the carrier are mapped to multiple dimensions such as the radar's effective range, oblique angle, and off-axis angle. The distribution characteristics of resolution within the ground beam coverage area are given, which can more intuitively demonstrate the radar detection capability and make it easier for operators to intuitively understand the radar's detection capability.

[0037] Specifically, in the above data calculation unit, the grid point coordinate matrix adopts the following formula:

[0038] T x =[x1,x2,…,x M ]

[0039] T z =[z1,z2,,z N ]

[0040] Where, x1, x M z1, z N T represents the coordinates of the intersection of the maximum beam coverage area and the two-dimensional coordinate axes on the ground. x T z Let z be a two-dimensional coordinate matrix of grid points, where x is an integer from 1 to M and z is an integer from 1 to N.

[0041] In the above data calculation unit, the oblique angle matrix θ and oblique distance matrix R are calculated using the following formulas:

[0042] θ v =arctan(v z / v x )

[0043] θ p =arctan(T) z -P z ) / (T x -P z )

[0044] θ=θ p -θ v

[0045]

[0046] Where θ is the oblique angle matrix, R is the oblique distance matrix, and v x v represents the northward velocity of the carrier in the navigation coordinate system. z For the eastward speed of the carrier in the navigation coordinate system, (P) x ,P y ,P zT represents the coordinates of the carrier in the navigation coordinate system. x T z Let z be a two-dimensional coordinate matrix of grid points, where x is an integer from 1 to M and z is an integer from 1 to N.

[0047] In the aforementioned data calculation unit, the actual transmit gain matrix G from the antenna to the grid point is... tT and the actual receive gain matrix G from the antenna to the grid point rT The calculation uses the following formula:

[0048]

[0049]

[0050] Among them, G t For antenna transmit gain, G r For antenna receive gain, each GAR model has a fixed G value. t and G r Both are known values, G tT G is the actual transmit gain matrix from the antenna to the grid points. rT This is the actual receive gain matrix from the antenna to the grid points. It is the off-axis angle matrix.

[0051] In the above data calculation unit, the ground reflection coefficient matrix is ​​calculated using the following formula:

[0052]

[0053] Where σ is the ground reflection coefficient matrix, R is the slant range matrix, and K = 1.38 × 10⁻⁶. -23 Here, F is the Boltzmann constant, T0 is the noise temperature, and F is the noise temperature. n Let L be the noise figure, L be the system loss, v be the sum of the vehicle's velocities in the northeast plane in the navigation coordinate system, θ be the oblique angle matrix, and P be the noise figure. av For average power, G tT G is the actual transmit gain matrix from the antenna to the grid points. rT Here, SNR is the actual receive gain matrix from the antenna to the grid points, λ is the detection signal-to-noise ratio, and D is the wavelength. r Where is the distance resolution (in this formula, is a specified value), and k = 1.4 is the azimuth broadening factor.

[0054] In the aforementioned data calculation unit, the distance resolution matrix D r The calculation uses the following formula:

[0055]

[0056]

[0057] Among them, D r R is the range resolution matrix, and B is the slant range matrix. r For the bandwidth of the radar, (P) x ,P y ,P z ) represents the coordinates of the carrier in the navigation coordinate system, k is the azimuth expansion factor, c is the speed of light, and β is the ground grazing angle.

[0058] In the aforementioned data calculation unit, the azimuth resolution matrix D a The calculation uses the following formula:

[0059]

[0060] Among them, D a R is the azimuth resolution matrix, k is the azimuth broadening factor, λ is the wavelength, R is the slant range matrix, v is the sum and velocity of the vehicle in the northeast plane in the navigation coordinate system, θ is the slant angle matrix, and T is the azimuth resolution matrix. a The time for synthesizing the aperture is denoted as .

[0061] It is worth noting that in practical applications, the speed and altitude errors of the carrier can also affect the radar's detection capability. Therefore, the SAR image detection area selection system mentioned above also includes a distortion rate acquisition unit.

[0062] The threshold comparison unit receives the distortion rate and compares the distortion rates corresponding to multiple grid points that simultaneously satisfy the range resolution, azimuth resolution, and ground reflectance with the thresholds stored in the threshold comparison unit. This results in multiple grid points that simultaneously satisfy the range resolution, azimuth resolution, ground reflectance, and distortion rate, which are then sent to the graphical display unit to display a two-dimensional analysis diagram and to the data table generation unit.

[0063] It is understood that, in order to realize the storage of the above-mentioned units, the SAR detection area selection system further includes a memory 2 for storing the data calculation unit, threshold comparison unit, image display unit and data table generation unit. For example, the memory 2 can be a chip.

[0064] In order to effectively protect the memory 2, the SAR detection area selection system also includes a housing 1. The memory 2 is located inside the housing 1. The housing 1 can effectively protect the memory 2 and extend its service life.

[0065] In practical applications, considering that the memory 2 is an electronic device, when the carrier is an aircraft, the memory 2 will inevitably be subjected to a certain impact when the carrier lands. The above-mentioned SAR detection area selection system also includes a buffer, and the memory 2 is detachably connected to the housing 1 through the buffer.

[0066] For example, the aforementioned buffer includes a first arc-shaped rod 3, a connecting pipe 5, and a second arc-shaped rod 4. One end of the first arc-shaped rod 3 is slidably connected to one end of the second arc-shaped rod 4 via the connecting pipe 5. The other ends of the first arc-shaped rod 3 and the second arc-shaped rod 4 are connected to the housing 1, and the memory 2 is disposed on the connecting pipe 5. In this way, on the one hand, since both the first arc-shaped rod 3 and the second arc-shaped rod 4 are arc-shaped, when the memory 2 is impacted, the first arc-shaped rod 3 and the second arc-shaped rod 4 can undergo a certain degree of elastic deformation, thereby playing a buffering role. On the other hand, since one end of the first arc-shaped rod 3 is slidably connected to one end of the second arc-shaped rod 4 via the connecting pipe 5, during the elastic deformation process of the first arc-shaped rod 3 and the second arc-shaped rod 4, their ends will approach each other, increasing their elastic deformation, thereby further buffering the impact.

[0067] Considering that any material has a deformation limit, in order to avoid excessive deformation of the first arc rod 3 and the second arc rod 4 leading to damage, it is necessary to appropriately limit the relative sliding displacement between the first arc rod 3 and the second arc rod 4. One end of the connecting pipe 5 is sleeved on the outer wall of the first arc rod 3, and the other end of the connecting pipe 5 is sleeved on the outer wall of the second arc rod. Limiting components are provided between the connecting pipe 5 and the first arc rod 3 and between the connecting pipe 5 and the second arc rod 4.

[0068] For example, the limiting member includes an outer ring 6 disposed on the outer wall of the first arc-shaped rod 3 and the second arc-shaped rod 4, and an inner ring disposed on the inner wall of the connecting pipe 5. The outer ring 6 is a rigid ring, and the inner ring is an elastic ring. The inner diameter of the inner ring is smaller than the outer diameter of the outer ring 6. Along the direction that gradually approaches the midpoint of the connecting pipe 5, the inner diameter of the multiple inner rings gradually decreases.

[0069] Taking the inner and outer rings 6 between the connecting pipe 5 and the first arc-shaped rod 3 as an example, there is one outer ring 6 and two inner rings, namely the first inner ring 7 and the second inner ring 8. The second inner ring 8 is provided with a baffle 9 on the side away from the first inner ring 7. When there is no impact, the outer ring 6 is located on the side of the first inner ring 7 away from the second inner ring 8 and does not contact the first inner ring 7. When the elastic deformation of the first arc-shaped rod 3 is too large, the outer ring 6 squeezes the first inner ring 7 and enters between the first inner ring 7 and the second inner ring 8, and collides with the second inner ring 8, absorbing part of the impact force. The second inner ring 8 can limit the sliding displacement between the first arc-shaped part and the connecting pipe 5 to a certain extent, preventing the outer ring 6 from sliding further. When the first arc-shaped rod 3 approaches the maximum elastic deformation, the outer ring 6 squeezes the second inner ring 8 and abuts against the baffle 9, thereby preventing the outer ring 6 from sliding further and thus avoiding damage to the outer ring 6.

[0070] For example, filtering the distance resolution in the distance resolution matrix, the azimuth resolution in the azimuth resolution matrix, and the ground reflectance in the ground reflectance matrix based on the threshold ranges for distance resolution, azimuth resolution, and ground reflectance, respectively, includes the following steps:

[0071] Step a: Determine whether the distance resolution in the distance resolution matrix is ​​within the distance resolution threshold range. If so, determine whether the grid points corresponding to the distance resolution meet the conditions and obtain multiple grid points that meet the distance resolution.

[0072] Step b: Determine whether the azimuth resolution of multiple grid points that meet the distance resolution is within the azimuth resolution threshold range. If so, determine whether the grid point corresponding to the azimuth resolution meets the condition, and obtain multiple grid points that simultaneously meet the distance resolution and azimuth resolution.

[0073] Step c: Determine whether the ground reflectance coefficient of multiple grid points that simultaneously satisfy the range resolution and azimuth resolution is within the ground reflectance coefficient threshold range. If so, determine whether the grid point corresponding to the ground reflectance coefficient meets the condition, and obtain multiple grid points that simultaneously satisfy the range resolution, azimuth resolution and ground reflectance coefficient.

[0074] Alternatively, filtering can be performed on the distance resolution in the distance resolution matrix, the azimuth resolution in the azimuth resolution matrix, and the ground reflectance in the ground reflectance matrix based on the threshold ranges for distance resolution, azimuth resolution, and ground reflectance, respectively. This includes the following steps:

[0075] Step a': Determine whether the azimuth resolution in the azimuth resolution matrix is ​​within the azimuth resolution threshold range. If so, determine whether the grid points corresponding to the azimuth resolution meet the conditions and obtain multiple grid points that meet the azimuth resolution.

[0076] Step b': Determine whether the distance resolution of multiple grid points that meet the azimuth resolution is within the distance resolution threshold range. If so, determine whether the grid point corresponding to the distance resolution meets the condition, and obtain multiple grid points that simultaneously meet the azimuth resolution and distance resolution.

[0077] Step c': Determine whether the ground reflectance coefficient of multiple grid points that simultaneously satisfy the azimuth resolution and range resolution is within the ground reflectance coefficient threshold range. If so, determine whether the grid point corresponding to the ground reflectance coefficient satisfies the condition, and obtain multiple grid points that simultaneously satisfy the range resolution, azimuth resolution and ground reflectance coefficient.

[0078] Alternatively, filtering can be performed on the distance resolution in the distance resolution matrix, the azimuth resolution in the azimuth resolution matrix, and the ground reflectance in the ground reflectance matrix based on the threshold ranges for distance resolution, azimuth resolution, and ground reflectance, respectively. This includes the following steps:

[0079] Step a”: Determine whether the ground reflection coefficient in the ground reflection coefficient matrix is ​​within the ground reflection coefficient threshold range. If so, determine whether the grid point corresponding to the ground reflection coefficient meets the condition and obtain multiple grid points that meet the ground reflection coefficient.

[0080] Step b”: Determine whether the azimuth resolution of multiple grid points that satisfy the ground reflectance coefficient is within the azimuth resolution threshold range. If so, determine whether the grid point corresponding to the azimuth resolution satisfies the condition and obtain multiple grid points that simultaneously satisfy the ground reflectance coefficient and azimuth resolution.

[0081] Step c”: Determine whether the distance resolution of multiple grid points that simultaneously satisfy the ground reflectance coefficient and azimuth resolution is within the distance resolution threshold range. If so, determine whether the grid point corresponding to the distance resolution satisfies the condition, and obtain multiple grid points that simultaneously satisfy the distance resolution, azimuth resolution and ground reflectance coefficient.

[0082] Alternatively, filtering can be performed on the distance resolution in the distance resolution matrix, the azimuth resolution in the azimuth resolution matrix, and the ground reflectance in the ground reflectance matrix based on the threshold ranges for distance resolution, azimuth resolution, and ground reflectance, respectively. This includes the following steps:

[0083] Step A: Determine whether the ground reflection coefficient in the ground reflection coefficient matrix is ​​within the ground reflection coefficient threshold range. If so, determine whether the grid point corresponding to the ground reflection coefficient meets the condition and obtain multiple grid points that meet the ground reflection coefficient.

[0084] Step B: Determine whether the distance resolution of multiple grid points that satisfy the ground reflectance coefficient is within the distance resolution threshold range. If so, determine whether the grid point corresponding to the distance resolution satisfies the condition, and obtain multiple grid points that simultaneously satisfy the ground reflectance coefficient and distance resolution.

[0085] Step C: Determine whether the azimuth resolution of multiple grid points that simultaneously satisfy the ground reflectance coefficient and range resolution is within the azimuth resolution threshold range. If so, determine whether the grid point corresponding to the azimuth resolution satisfies the condition, and obtain multiple grid points that simultaneously satisfy the range resolution, azimuth resolution and ground reflectance coefficient.

[0086] Alternatively, filtering can be performed on the distance resolution in the distance resolution matrix, the azimuth resolution in the azimuth resolution matrix, and the ground reflectance in the ground reflectance matrix based on the threshold ranges for distance resolution, azimuth resolution, and ground reflectance, respectively. This includes the following steps:

[0087] Step A': Determine whether the azimuth resolution in the azimuth resolution matrix is ​​within the azimuth resolution threshold range. If so, determine whether the grid points corresponding to the azimuth resolution meet the conditions and obtain multiple grid points that meet the azimuth resolution.

[0088] Step B': Determine whether the distance resolution of multiple grid points that meet the azimuth resolution is within the ground reflectance threshold range. If so, determine whether the grid point corresponding to the ground reflectance meets the condition, and obtain multiple grid points that simultaneously meet the azimuth resolution and ground reflectance.

[0089] Step C': Determine whether the distance resolution of multiple grid points that simultaneously satisfy the azimuth resolution and ground reflectance is within the distance resolution threshold range. If so, determine whether the grid point corresponding to the distance resolution satisfies the condition, and obtain multiple grid points that simultaneously satisfy the distance resolution, azimuth resolution and ground reflectance.

[0090] Alternatively, filtering can be performed on the distance resolution in the distance resolution matrix, the azimuth resolution in the azimuth resolution matrix, and the ground reflectance in the ground reflectance matrix based on the threshold ranges for distance resolution, azimuth resolution, and ground reflectance, respectively. This includes the following steps:

[0091] Step A”: Determine whether the distance resolution in the distance resolution matrix is ​​within the distance resolution threshold range. If so, determine whether the grid points corresponding to the distance resolution meet the conditions and obtain multiple grid points that meet the distance resolution.

[0092] Step B”: Determine whether the azimuth resolution of multiple grid points that meet the distance resolution is within the ground reflectance threshold range. If so, determine whether the grid point corresponding to the ground reflectance meets the condition and obtain multiple grid points that simultaneously meet the distance resolution and ground reflectance.

[0093] Step C”: Determine whether the azimuth resolution of multiple grid points that simultaneously satisfy the range resolution and ground reflectance coefficient is within the azimuth resolution threshold range. If so, determine whether the grid point corresponding to the azimuth resolution satisfies the condition, and obtain multiple grid points that simultaneously satisfy the range resolution, azimuth resolution and ground reflectance coefficient.

[0094] Alternatively, filtering can be performed on the distance resolution in the distance resolution matrix, the azimuth resolution in the azimuth resolution matrix, and the ground reflectance in the ground reflectance matrix based on the threshold ranges for distance resolution, azimuth resolution, and ground reflectance, respectively. This includes the following steps:

[0095] Simultaneously, it is determined whether the distance resolution in the distance resolution matrix is ​​within the distance resolution threshold range, whether the azimuth resolution in the azimuth resolution matrix is ​​within the azimuth resolution threshold range, and whether the ground reflection coefficient in the ground reflection coefficient matrix is ​​within the ground reflection coefficient threshold range.

[0096] If the range resolution, azimuth resolution, and ground reflectance are all within their respective threshold ranges, then the grid points corresponding to the range resolution, azimuth resolution, and ground reflectance are determined to meet the conditions, and multiple grid points that simultaneously meet the range resolution, azimuth resolution, and ground reflectance are obtained.

[0097] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A system for selecting a region of interest in a SAR image, characterized by The radar controller, the data calculation unit, the threshold comparison unit, the graphical display unit and the data table generation unit are included. The instruction output end of the radar controller is connected with the data input end of the data calculation unit and the threshold comparison unit, the data output end of the threshold comparison unit is connected with the graphical display unit and the data table generation unit respectively, and the data output end of the data table generation unit is connected with the data input end of the radar controller. The data calculation unit is used for calculating the ground reflection coefficient matrix, the distance resolution matrix and the azimuth resolution matrix of the grid points under different distance resolutions. The threshold comparison unit receives the distance resolution matrix, the azimuth resolution matrix and the ground reflection coefficient matrix respectively, compares them with the threshold range of the distance resolution, the threshold range of the azimuth resolution and the threshold range of the ground reflection coefficient stored in the threshold comparison unit, obtains the multiple grid points satisfying the distance resolution, the azimuth resolution and the ground reflection coefficient at the same time, and sends them to the graphical display unit and the data table generation unit respectively. The graphical display unit displays the multiple grid points satisfying the distance resolution, the azimuth resolution and the ground reflection coefficient at the same time in the form of images. The data table generation unit generates the parameter table of the distance resolution, the azimuth resolution, the ground reflection coefficient, the coordinate, the flight parameter of the carrier, the off-axis angle and the antenna installation angle corresponding to the multiple grid points satisfying the conditions, and sends the parameter table to the radar controller. The controller of the SAR receives the parameter table and performs image detection on the detection area satisfying the distance resolution, the azimuth resolution and the ground reflection coefficient according to the parameters in the parameter table. The ground reflection coefficient matrix calculation adopts the following formula: where σ is the ground reflection coefficient matrix, R is the slant range matrix, K = 1.38 x 10 -23 is the Boltzmann constant, T0 is the noise temperature, F n is the noise factor, L is the system loss, v is the and velocity of the carrier in the north-east plane in the navigation coordinate system, θ is the angle of sight matrix, P av is the average power, G tT is the actual transmitting gain matrix of the antenna to the grid point, G rT is the actual receiving gain matrix of the antenna to the grid point, SNR is the detection signal-to-noise ratio, λ is the wavelength, D r is the distance resolution, in the formula, D r is a specified value, k = 1.4 is the azimuth spread factor; Distance resolution matrix D r The calculation employs the following formula: where D r is the distance resolution matrix, R is the slant range matrix, B r is the bandwidth of the radar, (P x ,P y ,P z ) is the coordinate of the carrier in the navigation coordinate system, k is the azimuth spread factor, c is the speed of light, and β is the ground contact angle. Azimuth resolution matrix D a The calculation employs the following formula: where D a is the azimuth resolution matrix, k = is the azimuth broadening factor, λ is the wavelength, R is the slant range matrix, v is the and velocity of the carrier in the North-East-Plane in the navigation coordinate system, Θ is the squint angle matrix, T a is the synthetic aperture time.

2. The system for selecting a SAR image investigation zone according to claim 1, characterized in that, The SAR image detection area selection system further includes a distortion rate acquisition unit.

3. The system for selecting a SAR image investigation zone according to claim 2, characterized in that, The threshold comparison unit receives the distortion rate, compares the distortion rate corresponding to the multiple grid points satisfying the distance resolution, the azimuth resolution and the ground reflection coefficient at the same time with the threshold stored in the threshold comparison unit, obtains the multiple grid points satisfying the distance resolution, the azimuth resolution, the ground reflection coefficient and the distortion rate at the same time, and sends them to the graphical display unit to display the two-dimensional analysis graph.

4. The system for selecting a SAR image investigation zone according to claim 2, characterized in that, The threshold comparison unit receives the distortion rate, compares the distortion rate corresponding to the multiple grid points satisfying the distance resolution, the azimuth resolution and the ground reflection coefficient at the same time with the threshold stored in the threshold comparison unit, obtains the multiple grid points satisfying the distance resolution, the azimuth resolution, the ground reflection coefficient and the distortion rate at the same time, and sends them to the data table generation unit to generate the data table.

5. The system for selecting a SAR image investigation zone according to claim 1, characterized in that, The SAR image detection area selection system further includes a memory for storing the data calculation unit, the threshold comparison unit, the graphical display unit and the data table generation unit.

Images