SAR Image Analysis Method Based on Synthetic Aperture Radar Multi-source Data Fusion

Abstract

The present invention relates to the field of synthetic aperture radar imaging, and in particular to a SAR image analysis method based on synthetic aperture radar multi-source data fusion, the method firstly obtains the transmission signal strength and echo signal strength of each polarization channel of the synthetic aperture radar at different times, obtains the state characteristic value of each polarization channel at each time according to the difference between the transmission signal strength and the echo signal strength at each time in each polarization channel, and the echo signal strength at each time in all polarization channels; and analyzes the correlation between the polarization channels to obtain the correlation coefficient, and then fuses the echo signal strength of all polarization channels at the same time through the obtained fusion adjustment parameters to obtain fused signal data at each time; and generates a SAR image based on the fused signal data at all times. The present invention can improve the fusion effect of the echo signal data in the multi-polarization channels and generate radar images with better quality.

Description

Technical Field

[0001] The invention relates to the field of synthetic aperture radar imaging, and in particular to a SAR image analysis method based on synthetic aperture radar multi-source data fusion. Background Art

[0002] Synthetic Aperture Radar (SAR) is a high-resolution imaging radar technology that generates high-resolution ground images by emitting electromagnetic wave signals and receiving echo signals reflected from the ground. Compared with ordinary ground radar, synthetic aperture radar can generate higher resolution images and has important applications in remote sensing monitoring and geographic surveying and mapping.

[0003] Since synthetic aperture radar can transmit and receive electromagnetic wave signals in different polarization channels, the relevant technology usually uses the echo signal intensity data received by synthetic aperture radar in different polarization channels to fuse and then generate a radar image to improve the ability to recognize ground features, which helps to improve the resolution of radar images. However, due to the differences in the changes in echo signal data in different polarization channels, the fusion effect of the echo signal data in multiple polarization channels will be reduced, resulting in poor quality of the generated image. Summary of the invention

[0004] In order to solve the technical problem that the difference in the change of echo signal data in different polarization channels will reduce the fusion effect of echo signal data in multi-polarization channels, thereby resulting in poor quality of generated images, the purpose of the present invention is to provide a SAR image analysis method based on synthetic aperture radar multi-source data fusion, and the technical scheme adopted is as follows:

[0005] The present invention proposes a SAR image analysis method based on synthetic aperture radar multi-source data fusion, the method comprising:

[0006] Obtain the transmission signal strength and echo signal strength of each polarization channel of the synthetic aperture radar at different times;

[0007] Taking any polarization channel as the polarization channel to be measured, taking any time as the time to be measured, and obtaining the state characteristic value of the polarization channel to be measured at the time to be measured according to the difference between the transmission signal strength and the echo signal strength at the time to be measured in the polarization channel to be measured, and the echo signal strength at each time in all polarization channels; taking the combination of any two polarization channels as the target channel group, and obtaining the correlation coefficient between the two polarization channels in the target channel group according to the distribution of the echo signal strength at each time in the two polarization channels in the target channel group and the difference of the state characteristic value at the same time;

[0008] Performing statistical analysis on the echo signal strength at different moments in each polarization channel to obtain the principal component data and principal component direction of each polarization channel; obtaining a fusion adjustment parameter at each moment according to the difference in the principal component directions of two polarization channels in each target channel group and the correlation coefficient of the two polarization channels, and the difference between the echo signal strength of all polarization channels at the same moment and the principal component data; based on the fusion adjustment parameter, fusing the echo signal strength of all polarization channels at the same moment to obtain fused signal data at each moment;

[0009] Generate SAR images based on the fused signal data at all times.

[0010] Further, obtaining the state characteristic value of the polarization channel to be tested at the time to be tested according to the difference between the transmission signal strength and the echo signal strength at the time to be tested in the polarization channel to be tested, and the echo signal strength at each time in all polarization channels includes:

[0011] The difference between the transmission signal strength and the echo signal strength of the polarization channel to be tested at the time to be tested is used as the loss state value of the polarization channel to be tested at the time to be tested;

[0012] The average value of the echo signal strength of each polarization channel at all times is used as the overall receiving strength of each polarization channel; the absolute value of the difference between the echo signal strength of each polarization channel at the time to be tested and the overall receiving strength is used as the receiving signal deviation value of each polarization channel at the time to be tested;

[0013] Taking the accumulated value of the received signal deviation values ​​of all polarized channels at the time to be tested as the overall deviation value at the time to be tested;

[0014] taking a ratio of the received signal deviation value of the polarized channel to be tested at the time to be tested to the overall deviation value at the time to be tested as the abnormal state value of the polarized channel to be tested at the time to be tested;

[0015] The product value of the loss state value and the abnormal state value is normalized to obtain a state characteristic value of the polarization channel to be tested at the time to be tested.

[0016] Further, obtaining the correlation coefficient between the two polarization channels in the target channel group according to the distribution of the echo signal strength at each moment in the two polarization channels in the target channel group and the difference of the state characteristic value at the same moment includes:

[0017] Performing negative correlation mapping on the absolute value of the difference between the state characteristic values ​​of two polarized channels in the target channel group at the same time, to obtain the state similarity between the two polarized channels at the same time;

[0018] Taking the accumulated value of the state similarity between the two polarized channels in the target channel group at all the same times as the first correlation between the two polarized channels;

[0019] The absolute value of the Pearson correlation coefficient between the echo signal strengths of the two polarization channels in the target channel group at all times is used as the second correlation between the two polarization channels;

[0020] Establishing a two-dimensional coordinate system with time as the horizontal coordinate and the echo signal intensity as the vertical coordinate;

[0021] Respectively mapping the echo signal strengths at all times in the two polarization channels in the target channel group to a two-dimensional coordinate system, and performing curve fitting on the echo signal strengths at each time of each polarization channel to obtain a fitting curve for each polarization channel in the target channel group; and obtaining extreme value points on each of the fitting curves;

[0022] Obtaining a third correlation between the two polarization channels according to the distribution of extreme value points on the fitting curves corresponding to the two polarization channels in the target channel value;

[0023] A product value of the first correlation, the second correlation, and the third correlation between two polarization channels in the target channel value is used as a correlation coefficient between the two polarization channels.

[0024] Further, obtaining a third correlation between the two polarization channels according to the distribution of extreme value points on the fitting curve corresponding to the two polarization channels in the target channel value includes:

[0025] Extract the maximum value point from all extreme value points on the fitting curve corresponding to each polarization channel in the target channel group;

[0026] The Euclidean distance between the maximum points on the two fitting curves is used as the first distance parameter between the two fitting curves;

[0027] The minimum value of the number of extreme points on the two fitting curves is used as the reference number, and the first reference number of extreme points on each fitting curve is used as the extreme points to be tested for each fitting curve;

[0028] The Euclidean distance between the extreme value points to be tested at the same position on the two fitting curves is used as the distance parameter between the extreme value points to be tested, and the average value of the distance parameters between all the extreme value points to be tested at the same position is used as the second distance parameter between the two fitting curves;

[0029] The sum of the first distance parameter and the second distance parameter is normalized to be negatively correlated to obtain a third correlation between the two polarization channels in the target channel value.

[0030] Further, performing statistical analysis on the echo signal strength at different times in each polarization channel to obtain the principal component data and principal component direction of each polarization channel includes:

[0031] The echo signal strength at different times in each polarization channel is input into the principal component analysis algorithm to extract the principal component data and principal component direction of each polarization channel.

[0032] Further, obtaining the fusion adjustment parameter at each moment according to the difference in the principal component directions of the two polarization channels in each target channel group and the correlation coefficient of the two polarization channels, and the difference between the echo signal strength of all polarization channels at the same moment and the principal component data includes:

[0033] Taking the absolute value of the difference between the principal component directions of the two polarization channels in each target channel group as the principal component direction difference value of each target channel group;

[0034] Perform negative correlation mapping on the correlation coefficients between the two polarization channels in each target channel group to obtain the independence parameter of each target channel group;

[0035] The product value of the principal component direction difference value and the independence parameter is used as the difference parameter of each target channel group, and the accumulated value of the difference parameters of all target channel groups is used as the overall difference between the polarization channels;

[0036] According to the difference between the echo signal strength of all polarization channels at the same time and the principal component data and the overall difference, a fusion adjustment parameter at each time is obtained.

[0037] Further, obtaining the fusion adjustment parameter at each moment according to the difference between the echo signal strength of all polarization channels at the same moment and the principal component data and the overall difference includes:

[0038] A time is randomly selected as the target time, and the absolute value of the difference between the echo signal strength of each polarization channel at the target time and the main component data of the polarization channel is used as the fluctuation degree of each polarization channel at the target time;

[0039] The accumulated value of the fluctuation degree of all polarization channels at the target time is used as the overall fluctuation value at the target time;

[0040] The product value of the overall difference and the overall fluctuation value at the target moment is normalized to obtain the fusion adjustment parameter at the target moment.

[0041] Further, based on the fusion adjustment parameter, the echo signal strengths of all polarization channels at the same time are fused to obtain fused signal data at each time, including:

[0042] The average value of the echo signal strength of all polarization channels at the target time is taken as the overall signal strength at the target time;

[0043] Normalizing the absolute value of the difference between the echo signal strength of each polarization channel at the target time and the overall signal strength at the target time to obtain a fusion weight of each polarization channel at the target time;

[0044] Obtaining initial fusion data at the target time according to the fusion weights and echo signal strengths of all polarization channels at the target time;

[0045] The product value of the fusion adjustment parameter and the initial fusion data at the target moment is used as the fusion signal data at the target moment.

[0046] Further, obtaining the initial fusion data at the target time according to the fusion weights and echo signal strengths of all polarization channels at the target time includes:

[0047] Using the fusion weight of each polarization channel at the target time as the weight of the echo signal strength of each polarization channel at the target time;

[0048] The echo signal strengths of all polarization channels at the target time are weighted and summed to obtain the initial fusion data at the target time.

[0049] Furthermore, generating a SAR image based on fused signal data at all times includes:

[0050] Based on synthetic aperture radar technology, SAR images are generated using fused signal data at all times.

[0051] The present invention has the following beneficial effects:

[0052] The present invention takes into account that in the process of fusing echo signal data of different polarization channels of synthetic aperture radar, due to the different changes in echo signal strength in different polarization channels, the fusion effect of multi-polarization channel data is poor, so that the quality of the generated SAR image is poor. Therefore, the present invention first obtains the transmission signal strength and echo signal strength of each polarization channel at different times. Considering that the loss of echo signal strength of the polarization channel at different times and the abnormal conditions of echo signal strength are different, the change state of the echo signal at each moment in the polarization channel can be reflected by the acquired state characteristic value. Considering that the information provided by the echo signal strength in different polarization channels is different, the surface features expressed are also different, so it is necessary to analyze the correlation between different polarization channels, reflect the correlation of echo signal strength between two polarization channels through the acquired correlation coefficient, extract the main component direction and main component data of each polarization channel, and then adjust the fusion process of echo signal strength of all polarization channels at the same time through the acquired fusion adjustment parameter, so as to obtain more effective fusion signal data, and subsequently generate a SAR image with better quality based on the fusion signal data. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0054] Figure 1 A flow chart of a SAR image analysis method based on synthetic aperture radar multi-source data fusion provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0055] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of the specific implementation, structure, features and effects of a SAR image analysis method based on synthetic aperture radar multi-source data fusion proposed by the present invention in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0056] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0057] An embodiment of a SAR image analysis method based on synthetic aperture radar multi-source data fusion:

[0058] A specific solution of a SAR image analysis method based on synthetic aperture radar multi-source data fusion provided by the present invention is described in detail below with reference to the accompanying drawings.

[0059] See also Figure 1 , which shows a flow chart of a SAR image analysis method based on synthetic aperture radar multi-source data fusion provided by an embodiment of the present invention, the method comprising:

[0060] Step S1: Obtain the transmission signal strength and echo signal strength of each polarization channel of the synthetic aperture radar at different times.

[0061] Synthetic Aperture Radar (SAR) is a system that generates high-resolution ground images by emitting electromagnetic wave signals and receiving echo signals reflected from the ground. It has important applications in remote sensing monitoring and geographic surveying and mapping. The SAR system can transmit a series of pulse signals through the antenna. These signals are usually emitted in the form of electromagnetic waves and can cover a certain ground range. When these signals encounter ground targets, they will produce reflected echoes. The special feature of the SAR system is that it can move the position of the antenna and receive echo signals from the same target at different positions. By performing complex mathematical processing on these signals received at different times and positions, it simulates the effect of a large-size antenna, thereby improving the resolution of imaging.

[0062] In a SAR system, different polarization channels can provide different information about surface targets. Therefore, the relevant technology usually uses the received echo signal intensity data of the synthetic aperture radar in different polarization channels to fuse, so as to improve the recognition ability of the ground object features, which helps to improve the resolution of the radar image. However, due to the differences in the changes of the echo signal data in different polarization channels, the fusion effect of the echo signal data in the multi-polarization channels will be reduced, resulting in poor quality of the generated image. Therefore, the present invention proposes a SAR image analysis method based on synthetic aperture radar multi-source data fusion to solve this problem.

[0063] The embodiment of the present invention first uses a synthetic aperture radar to transmit electromagnetic wave signals through a radar transmitter in different polarization channels, and simultaneously receives echo signals through a radar receiver, and obtains the transmission signal strength and echo signal strength at different times during the transmission and reception process, wherein the signal strength can be represented by the power of the signal during transmission and reception. In a SAR system, polarization describes the vibration direction of the electric field vector of an electromagnetic wave, and electromagnetic waves are usually transmitted and received in a horizontally polarized or vertically polarized manner. Combinations of different polarization modes can form different polarization channels. For example, a horizontal-horizontal polarization channel indicates that the synthetic aperture radar transmits and receives electromagnetic waves in a horizontally polarized manner at the same time, and a vertical-vertical polarization channel indicates that the synthetic aperture radar transmits and receives electromagnetic waves in a vertically polarized manner at the same time. Electromagnetic waves are transmitted and received in a polarized manner. These two polarization channels are called similar polarization channels. The horizontal-vertical polarization channel means that electromagnetic waves are transmitted in a horizontally polarized manner and received in a vertically polarized manner. The vertical-horizontal polarization channel means that electromagnetic waves are transmitted in a vertically polarized manner and received in a horizontally polarized manner. These two polarization channels are called cross-polarization channels. Different polarization channels can provide different types of information. Similar polarization channels are usually more sensitive to the smoothness and roughness of the surface, while cross-polarization channels are more sensitive to the shape and directionality of the target. Therefore, by analyzing the signal strength data in different polarization channels, surface features can be better distinguished and identified, and better quality SAR images can be generated.

[0064] Step S2: taking any polarization channel as the polarization channel to be measured, taking any time as the time to be measured, and obtaining the state characteristic value of the polarization channel to be measured at the time to be measured according to the difference between the transmission signal strength and the echo signal strength at the time to be measured in the polarization channel to be measured, and the echo signal strength at each time in all polarization channels; taking the combination of any two polarization channels as the target channel group, and obtaining the correlation coefficient between the two polarization channels in the target channel group according to the distribution of the echo signal strength at each time in the two polarization channels in the target channel group and the difference in the state characteristic value at the same time.

[0065] In synthetic aperture radar technology, the intensity of the reflected echo signal received by the radar receiver is usually analyzed to generate a corresponding image, and the echo signal intensity in different polarization channels can reflect different characteristics of the target. For example, the horizontal-horizontal polarization channel can detect targets with horizontal surface characteristics such as the water surface, the vertical-vertical polarization channel can detect targets with vertical surface characteristics such as buildings, and the cross-polarization channel can detect the shape and direction of the target. Therefore, the echo signal intensity in different polarization channels can be combined for analysis, and the echo signal intensity at each moment in different polarization channels can be fused to generate a SAR image with higher resolution. However, due to the difference in the change of the echo signal intensity in different polarization channels, the fusion effect of the echo signal intensity in the multi-polarization channels will be reduced, resulting in poor quality of the generated image. Therefore, the embodiment of the present invention analyzes the change of the echo signal intensity at each moment in different polarization channels, improves the fusion effect of multi-polarization channel data, and then generates a SAR image with better quality.

[0066] Since there are differences in state characteristics such as loss and abnormal conditions of echo signal strength at different moments in the process of signal propagation, in order to facilitate the analysis of state characteristics of echo signal strength at each moment in different polarization channels, any polarization channel can be used as the polarization channel to be tested, and any moment can be used as the moment to be tested, and then the difference between the transmission signal strength and the echo signal strength at the moment to be tested in the polarization channel to be tested, as well as the echo signal strength at each moment in all polarization channels are analyzed. The state characteristic values ​​obtained reflect the state characteristics of the echo signal strength of the polarization channel to be tested at the moment to be tested. Subsequently, the correlation between the polarization channels can be analyzed in combination with the state characteristic values ​​between different polarization channels at the same moment.

[0067] Preferably, in one embodiment of the present invention, a method for acquiring a state characteristic value at a time to be measured in a polarized channel to be measured specifically includes:

[0068] The difference between the transmission signal strength and the echo signal strength of the polarization channel to be tested at the time to be tested is used as the loss state value of the polarization channel to be tested at the time to be tested; the average value of the echo signal strength of each polarization channel at all times is used as the overall receiving strength of each polarization channel; the absolute value of the difference between the echo signal strength and the overall receiving strength of each polarization channel at the time to be tested is used as the receiving signal deviation value of each polarization channel at the time to be tested; the accumulated value of the receiving signal deviation values ​​of all polarization channels at the time to be tested is used as the overall deviation value at the time to be tested; the ratio of the receiving signal deviation value of the polarization channel to be tested at the time to be tested to the overall deviation value at the time to be tested is used as the abnormal state value of the polarization channel to be tested at the time to be tested; the product value of the loss state value and the abnormal state value is normalized to obtain the state characteristic value of the polarization channel to be tested at the time to be tested. The expression of the state characteristic value can be specifically, for example, as follows:

[0069] in, Indicates the state characteristic value of the polarization channel to be tested at the time to be tested; Indicates the transmit signal strength of the polarization channel to be tested at the time to be tested; Indicates the echo signal strength of the polarization channel to be tested at the time to be tested, ; It represents the average value of the echo signal strength at all times in the polarization channel to be measured, that is, the overall receiving strength of the polarization channel to be measured; Indicates The echo signal strength of each polarization channel at the time to be measured; Indicates The average value of the echo signal strength at all times in the polarization channel, i.e. The overall receiving strength of each polarization channel; represents the number of polarization channels, ; Represents the normalization function.

[0070] In the process of obtaining the state characteristic value of the polarization channel to be tested at the time to be tested, the state characteristic value Indicates the loss state and abnormal state of the echo signal strength of the polarization channel to be tested at the time of testing, and the state characteristic value The larger the value is, the more serious the echo signal strength loss of the polarization channel to be tested is at the time of testing, and the more abnormal the echo signal strength is at the time of testing. The larger the value is, the more serious the loss of echo signal strength of the polarization channel to be tested is at the time of testing. The larger the value, the greater the deviation of the received signal of the polarization channel to be tested at the time of testing. The larger the value, the greater the difference between the echo signal strength at the time of measurement and the echo signal strength of the polarization channel to be measured. The larger the value is, the greater the proportion of the received signal deviation value of the polarization channel to be tested at the time to be tested is, which further indicates that the echo signal strength of the polarization channel to be tested at the time to be tested is more abnormal, and the echo signal strength at the time to be tested is more likely to contain key information, then the state characteristic value The larger the state, the larger the state, and the normalization function is used to limit the state eigenvalue to within the range.

[0071] In one embodiment of the present invention, the normalization processing can be specifically, for example, maximum and minimum value normalization processing, and the normalization in subsequent steps can all adopt maximum and minimum value normalization processing. In other embodiments of the present invention, other normalization methods can be selected according to the specific range of numerical values, which will not be described in detail.

[0072] After obtaining the state characteristic value of the polarization channel to be tested at the time to be tested, the state characteristic value at each time in each polarization channel can be obtained by the same method as above. The embodiment of the present invention needs to fuse the data in different polarization channels to generate a SAR image with better quality. Therefore, the correlation between different polarization channels can be analyzed first to improve the subsequent data fusion effect. In order to facilitate the subsequent analysis, the combination of any two polarization channels can be used as the target channel group. Since the change of the echo signal strength at each time in different polarization channels is different, the distribution of the echo signal strength at each time in different polarization channels is also different. Therefore, the distribution of the echo signal strength at each time in the two polarization channels in the target channel group can be analyzed, and combined with the difference in the state characteristic values ​​of the two polarization channels at the same time, the correlation coefficient between the two polarization channels in the target channel group is obtained. The correlation coefficient reflects the correlation of the echo signal strength between the two polarization channels, and the effect of data fusion in different polarization channels can be subsequently improved.

[0073] Preferably, in an embodiment of the present invention, a method for acquiring a correlation coefficient between two polarized channels in a target channel group specifically includes:

[0074] The absolute value of the difference between the state characteristic values ​​of the two polarization channels in the target channel group at the same time is negatively correlated to obtain the state similarity between the two polarization channels at the same time; the cumulative value of the state similarity between the two polarization channels in the target channel group at all the same times is used as the first correlation between the two polarization channels; the absolute value of the Pearson correlation coefficient between the echo signal intensities of the two polarization channels in the target channel group at all times is used as the second correlation between the two polarization channels. The calculation formula of the Pearson correlation coefficient is a technical means well known to those skilled in the art and will not be elaborated here;

[0075] A two-dimensional coordinate system is established with time as the horizontal coordinate and the echo signal strength as the vertical coordinate; the echo signal strengths at all times in the two polarization channels in the target channel group are respectively mapped to the two-dimensional coordinate system, and the echo signal strengths at each time of each polarization channel are curve fitted to obtain a fitting curve of each polarization channel in the target channel group. The curve fitting method can be a polynomial fitting method. In other embodiments of the present invention, a spline curve fitting method can also be used for curve fitting, which is not limited here; based on Newton's method, extreme value points on each fitting curve are obtained, and the extreme value points include maximum value points and minimum value points. Newton's method and polynomial fitting are technical means well known to those skilled in the art, which will not be described in detail here; the maximum value point is extracted from all extreme value points on the fitting curve corresponding to each polarization channel in the target channel group, and the extraction method is: : Among all the extreme points on each fitting curve, the extreme point corresponding to the maximum echo signal intensity is selected as the maximum point; the Euclidean distance between the maximum points on the two fitting curves is used as the first distance parameter between the two fitting curves; the minimum value of the number of extreme points on the two fitting curves is used as the reference number, and the first reference number of extreme points on each fitting curve are used as the extreme points to be tested for each fitting curve; the Euclidean distance between the extreme points to be tested at the same position on the two fitting curves is used as the distance parameter between the extreme points to be tested, and the average value of the distance parameters between all the extreme points to be tested at the same position is used as the second distance parameter between the two fitting curves; the sum of the first distance parameter and the second distance parameter is normalized to be negatively correlated, and the third correlation between the two polarization channels in the target channel value is obtained;

[0076] The product of the first correlation, the second correlation and the third correlation between the two polarized channels in the target channel value is used as the correlation coefficient between the two polarized channels. The expression of the correlation coefficient can be specifically, for example, as follows:

[0077]

[0078]

[0079] in, represents the correlation coefficient between two polarization channels in the target channel group; represents the first correlation between two polarization channels in the target channel group; represents the second correlation between two polarization channels in the target channel group; represents the third correlation between two polarization channels in the target channel group; and Respectively represent the two polarization channels in the target channel group in the first The state characteristic value at a moment; Represents the number of all moments in the polarization channel, and the number of moments in different polarization channels is the same; It represents the Euclidean distance between the maximum value point on one fitting curve and the maximum value point on the other fitting curve on the two fitting curves corresponding to the two polarization channels in the target channel group, that is, the first distance parameter between the two fitting curves; Represents the first The extreme point to be tested and the first point on another fitting curve The Euclidean distance between the extreme points to be tested; and They respectively represent the number of extreme points on the two fitting curves corresponding to the two polarization channels in the target channel group; represents the minimum value function, then Indicates the reference quantity; Indicated by natural constant An exponential function with base ; It represents the first adjustment parameter. To prevent the denominator from being 0, the first adjustment parameter is set to 0.01. Its specific value can also be set by the implementer according to the specific implementation scenario and is not limited here.

[0080] In the process of obtaining the correlation coefficient between two polarization channels in the target channel group, the correlation coefficient The larger the value, the more relevant the echo signal strengths of the two polarization channels at each moment are. The larger the value, the more similar the loss and abnormality of the two polarization channels in the target channel group at the same time are. Therefore, the first correlation The larger the value, the more similar the overall losses and anomalies of the two polarization channels are. The larger the value is, the greater the second correlation between the two polarization channels in the target channel group is, indicating that the echo signal strengths at each moment in the two polarization channels are more correlated. The larger the first distance parameter between the two fitting curves is, The smaller the second distance parameter between the two fitting curves is, the The smaller the value, the more similar the fluctuation characteristics of the echo signal strength on the two fitting curves are, which further indicates that the echo signal strength at each moment in the two polarization channels is more correlated. The bigger it is.

[0081] The above method can be used to obtain the correlation coefficient between two polarization channels in each target channel group, thereby obtaining the correlation coefficient between any two polarization channels. Subsequently, further analysis can be performed in combination with the correlation coefficient between the polarization channels to obtain the adjustment parameters for data fusion.

[0082] Step S3: Statistically analyze the echo signal strength at different times in each polarization channel to obtain the principal component data and principal component direction of each polarization channel; obtain the fusion adjustment parameter at each time according to the difference in the principal component directions of the two polarization channels in each target channel group and the correlation coefficient of the two polarization channels, and the difference between the echo signal strength and the principal component data of all polarization channels at the same time; based on the fusion adjustment parameter, fuse the echo signal strength of all polarization channels at the same time to obtain the fusion signal data at each time.

[0083] Since the echo signal strengths at different moments in different polarization channels vary differently, if the echo signal strengths in different polarization channels are directly fused, the final fusion effect will be reduced, resulting in the generated SAR image failing to achieve an ideal effect. Therefore, the fusion process needs to be adjusted. In the embodiment of the present invention, first, statistical analysis is performed on the echo signal strengths at different moments in each polarization channel to obtain the principal component data and principal component direction of each polarization channel. Subsequently, the fusion adjustment parameters at each moment can be obtained based on the difference in principal component directions and correlation coefficients between different polarization channels and the difference in echo signal strength at each moment in the polarization channel and the principal component data of the polarization channel. Subsequently, the fusion process of the data in different polarization channels can be adjusted based on the fusion adjustment parameters to improve the final fusion effect.

[0084] Preferably, in one embodiment of the present invention, the echo signal strength at different times in each polarization channel can be input into a principal component analysis algorithm to extract the principal component data and principal component direction of each polarization channel, wherein the principal component direction is expressed in the form of an angle radian system. The principal component analysis algorithm is a technical means well known to those skilled in the art and will not be described in detail herein.

[0085] After extracting the principal component direction and principal component data of each polarization channel, the difference in the principal component directions of the two polarization channels in each target channel group and the correlation coefficient of the two polarization channels can be analyzed. At the same time, the difference in the echo signal strength and the principal component data of all polarization channels at the same time can be combined to obtain the fusion adjustment parameters at each moment. In the subsequent process, the data fusion process at each moment can be adjusted based on the fusion adjustment parameters to obtain more accurate fusion data at each moment.

[0086] Preferably, in an embodiment of the present invention, a method for obtaining the fusion adjustment parameter at each moment specifically includes:

[0087] The absolute value of the difference between the principal component directions of the two polarization channels in each target channel group is used as the principal component direction difference value of each target channel group; the correlation coefficient between the two polarization channels in each target channel group is negatively correlated to obtain the independence parameter of each target channel group; the product value of the principal component direction difference value and the independence parameter is used as the difference parameter of each target channel group, and the accumulated value of the difference parameters of all target channel groups is used as the overall difference between the polarization channels; for the convenience of analysis, a moment can be arbitrarily selected as the target moment, and the absolute value of the difference between the echo signal strength of each polarization channel at the target moment and the principal component data of the polarization channel is used as the fluctuation degree of each polarization channel at the target moment; the accumulated value of the fluctuation degree of all polarization channels at the target moment is used as the overall fluctuation value of the target moment; the product value of the overall difference and the overall fluctuation value of the target moment is normalized to obtain the fusion adjustment parameter of the target moment. The expression of the fusion adjustment parameter can be specifically, for example, as follows:

[0088] in, Indicates Fusion adjustment parameters at each moment; and Respectively represent The principal component directions of the two polarization channels in the target channel group; Indicates The correlation coefficient between two polarization channels in the target channel group; Indicates the number of target channel groups. Since there are 4 different polarization channels in total, the number of target channel groups formed by combining two of them is 6; Indicates In the polarization channel The echo signal strength at a certain moment; Indicates The principal component data of polarization channels; represents the number of polarization channels; represents the normalization function; It represents the second adjustment parameter. To prevent the denominator from being 0, the second adjustment parameter is set to 0.01. Its specific value can also be set by the implementer according to the specific implementation scenario and is not limited here.

[0089] In the process of obtaining the fusion adjustment parameters at each moment, the fusion adjustment parameters Used to adjust the subsequent data fusion of different polarization channels and adjust the fusion parameters The larger the value is, the greater the weight is when adjusting the echo signal strength fusion at that moment. The principal component direction difference value of each target channel group is The larger the value, the greater the difference in echo signal strength between the two polarization channels in the target channel group, and the greater the weight required in the subsequent fusion adjustment. Therefore, the fusion adjustment parameter The larger the independence parameter of each target channel group is, The larger the value, the less correlated the echo signal strengths of the two polarization channels in the target channel group are, and the greater the weight required in the subsequent fusion adjustment. Therefore, the fusion adjustment parameter The larger the value, the greater the difference parameter of all target channel groups. The accumulated value of the polarization channels is obtained to obtain the overall difference between the polarization channels. The greater the overall difference, the greater the difference in echo signal strength between the polarization channels, and the less correlated the echo signal strength between the polarization channels, so the fusion adjustment parameter The larger the polarization channel is, the greater the fluctuation of the polarization channel at each moment. The larger the value, the greater the fluctuation of the echo signal strength of the polarization channel at that moment. Therefore, the overall fluctuation value at each moment is The larger the value is, the greater the fluctuation of the echo signal strength at that moment is, which means that the echo signal strength at that moment is more important in the subsequent data fusion, and the greater the weight required in the fusion adjustment at that moment is. Therefore, the fusion adjustment parameter The larger the value, the more the fusion adjustment parameters are limited to range, which is convenient for subsequent adjustment of data fusion.

[0090] After obtaining the fusion adjustment parameters at each moment, the data fusion process of the echo signal strength of different polarization channels at the same moment can be adjusted based on the fusion adjustment parameters to obtain the fused signal data at each moment, thereby improving the final data fusion effect, so that better quality SAR images can be generated based on the fused signal data at each moment in the subsequent process.

[0091] Preferably, in an embodiment of the present invention, the method for acquiring fusion signal data at each moment specifically includes:

[0092] The average value of the echo signal strength of all polarization channels at the target time is used as the overall signal strength at the target time; the absolute value of the difference between the echo signal strength of each polarization channel at the target time and the overall signal strength at the target time is normalized to obtain the fusion weight of each polarization channel at the target time; the initial fusion data at the target time is obtained according to the fusion weight and echo signal strength of all polarization channels at the target time; the product value of the fusion adjustment parameter at the target time and the initial fusion data is used as the fusion signal data at the target time. The expression of the fusion signal data can be specifically, for example, as follows:

[0093] in, Indicates Fusion signal data at each moment; Indicates Fusion adjustment parameters at each moment; Indicates In the polarization channel The echo signal strength at a certain moment; Indicates In the polarization channel The echo signal strength at a certain moment; represents the number of polarization channels; Represents the normalization function.

[0094] In the process of acquiring fusion signal data at each moment, Indicates The overall signal strength at a given moment is The larger the value is, the greater the difference between the echo signal strength of the polarization channel at that moment and the overall signal strength of all polarization channels at that moment is, which means that the information contained in the echo signal strength of the polarization channel at that moment is more important. Therefore, the result of normalization is used as the fusion weight of the polarization channel at that moment. The larger the value is, the greater the proportion of the echo signal strength of the polarization channel at that moment is. Then, the echo signal strengths of different polarization channels at the same moment are weighted and summed to obtain the initial fusion data at each moment. , realize the preliminary fusion of data in different polarization channels, use the fusion adjustment parameters to adjust the initial fusion data at each moment, and obtain the fusion signal data at each moment , so as to improve the fusion effect of the echo signal strength of different polarization channels at the same time.

[0095] After obtaining the fused signal data at each moment, a SAR image with better quality can be generated based on the fused signal data at each moment in the subsequent process.

[0096] Step S4: Generate a SAR image based on the fused signal data at all times.

[0097] Since the fused signal data at each moment combines the information features in different polarization channels and the fusion effect is better, a better quality SAR image can be generated based on the fused signal data at all moments.

[0098] Preferably, in one embodiment of the present invention, based on synthetic aperture radar technology, SAR images are generated using fused signal data at all times. The SAR images have higher resolution and stronger ability to recognize ground objects, so the overall quality of the generated SAR images is better. Synthetic aperture radar technology is a technical means well known to those skilled in the art and will not be elaborated here.

[0099] In summary, the embodiment of the present invention first obtains the transmission signal strength and echo signal strength of each polarization channel of the synthetic aperture radar at different times, and obtains the state characteristic value of each polarization channel at each time according to the difference between the transmission signal strength and the echo signal strength at each time in each polarization channel and the echo signal strength at each time in all polarization channels; obtains the correlation coefficient between the two polarization channels according to the distribution of the echo signal strength at each time in the two polarization channels in the target channel group and the difference in the state characteristic value at the same time; and extracts the principal component data and principal component direction of each polarization channel; obtains the fusion adjustment parameter at each time according to the difference in the principal component direction of the two polarization channels in each target channel group and the correlation coefficient of the two polarization channels, and the difference between the echo signal strength and the principal component data of all polarization channels at the same time; based on the fusion adjustment parameter, the echo signal strength of all polarization channels at the same time is fused to obtain the fusion signal data at each time; and generates the SAR image based on the fusion signal data at all times.

[0100] A multi-polarization channel data fusion method embodiment for SAR imaging:

[0101] In the related art, the echo signal strength data received by the synthetic aperture radar in different polarization channels are fused to generate a radar image. However, due to the differences in the changes in the echo signal data in different polarization channels, the fusion effect of the echo signal strength data in multiple polarization channels is poor.

[0102] In order to solve this problem, this embodiment provides a multi-polarization channel data fusion method for SAR imaging, including:

[0103] Step S1: obtaining the transmission signal strength and echo signal strength of each polarization channel of the synthetic aperture radar at different times;

[0104] Step S2: taking any polarization channel as the polarization channel to be measured, taking any time as the time to be measured, and obtaining the state characteristic value of the polarization channel to be measured at the time to be measured according to the difference between the transmission signal strength and the echo signal strength at the time to be measured in the polarization channel to be measured, and the echo signal strength at each time in all polarization channels; taking the combination of any two polarization channels as the target channel group, and obtaining the correlation coefficient between the two polarization channels in the target channel group according to the distribution of the echo signal strength at each time in the two polarization channels in the target channel group and the difference in the state characteristic value at the same time;

[0105] Step S3: Statistically analyze the echo signal strength at different times in each polarization channel to obtain the principal component data and principal component direction of each polarization channel; obtain the fusion adjustment parameter at each time according to the difference in the principal component directions of the two polarization channels in each target channel group and the correlation coefficient of the two polarization channels, and the difference between the echo signal strength and the principal component data of all polarization channels at the same time; based on the fusion adjustment parameter, fuse the echo signal strength of all polarization channels at the same time to obtain the fusion signal data at each time.

[0106] Among them, steps S1 to S3 have been described in detail in the above-mentioned embodiment of a SAR image analysis method based on synthetic aperture radar multi-source data fusion, and will not be repeated here.

[0107] The beneficial effects brought by this embodiment are as follows: the present invention takes into account that the fusion effect of multi-polarization channel data is poor due to the different changes in echo signal strength in different polarization channels, and therefore first obtains the transmission signal strength and echo signal strength of each polarization channel at different times, and takes into account that the loss of echo signal strength and the abnormal conditions of echo signal strength of the polarization channel at different times are different, so the change state of the echo signal at each time in the polarization channel can be reflected by the acquired state characteristic value, and the correlation between different polarization channels can be analyzed based on the state characteristic value later, and considering that the information provided by the echo signal strength in different polarization channels is different, the surface features expressed are also different, so it is necessary to analyze the correlation between different polarization channels, reflect the correlation of echo signal strength between two polarization channels by the acquired correlation coefficient, and extract the main component direction and main component data of each polarization channel, and then adjust the fusion process of the echo signal strength of all polarization channels at the same time by the acquired fusion adjustment parameter, so as to improve the final data fusion effect.

[0108] It should be noted that the sequence of the above embodiments of the present invention is only for description and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0109] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

Claims

1. A SAR image analysis method based on synthetic aperture radar multi-source data fusion, characterized in that: The method comprises: Obtain the transmission signal strength and echo signal strength of each polarization channel of the synthetic aperture radar at different times; Taking any polarization channel as the polarization channel to be measured, taking any time as the time to be measured, and obtaining the state characteristic value of the polarization channel to be measured at the time to be measured according to the difference between the transmission signal strength and the echo signal strength at the time to be measured in the polarization channel to be measured, and the echo signal strength at each time in all polarization channels; taking the combination of any two polarization channels as the target channel group, and obtaining the correlation coefficient between the two polarization channels in the target channel group according to the distribution of the echo signal strength at each time in the two polarization channels in the target channel group and the difference of the state characteristic value at the same time; Performing statistical analysis on the echo signal strength at different moments in each polarization channel to obtain the principal component data and principal component direction of each polarization channel; obtaining a fusion adjustment parameter at each moment according to the difference in the principal component directions of two polarization channels in each target channel group and the correlation coefficient of the two polarization channels, and the difference between the echo signal strength of all polarization channels at the same moment and the principal component data; based on the fusion adjustment parameter, fusing the echo signal strength of all polarization channels at the same moment to obtain fused signal data at each moment; Generate SAR images based on the fused signal data at all times.

2. The SAR image analysis method based on synthetic aperture radar multi-source data fusion according to claim 1 is characterized in that: The obtaining, according to the difference between the transmission signal strength and the echo signal strength at the time to be tested in the polarized channel to be tested and the echo signal strength at each time in all polarized channels, the state characteristic value at the time to be tested in the polarized channel to be tested comprises: The difference between the transmission signal strength and the echo signal strength of the polarization channel to be tested at the time to be tested is used as the loss state value of the polarization channel to be tested at the time to be tested; The average value of the echo signal strength of each polarization channel at all times is used as the overall receiving strength of each polarization channel; the absolute value of the difference between the echo signal strength of each polarization channel at the time to be tested and the overall receiving strength is used as the receiving signal deviation value of each polarization channel at the time to be tested; Taking the accumulated value of the received signal deviation values ​​of all polarized channels at the time to be tested as the overall deviation value at the time to be tested; taking a ratio of the received signal deviation value of the polarized channel to be tested at the time to be tested to the overall deviation value at the time to be tested as the abnormal state value of the polarized channel to be tested at the time to be tested; The product value of the loss state value and the abnormal state value is normalized to obtain a state characteristic value of the polarization channel to be tested at the time to be tested.

3. The SAR image analysis method based on synthetic aperture radar multi-source data fusion according to claim 1 is characterized in that: The obtaining the correlation coefficient between the two polarization channels in the target channel group according to the distribution of the echo signal strength at each moment in the two polarization channels in the target channel group and the difference of the state characteristic value at the same moment comprises: Performing negative correlation mapping on the absolute value of the difference between the state characteristic values ​​of two polarized channels in the target channel group at the same time, to obtain the state similarity between the two polarized channels at the same time; Taking the accumulated value of the state similarity between the two polarized channels in the target channel group at all the same times as the first correlation between the two polarized channels; The absolute value of the Pearson correlation coefficient between the echo signal strengths of the two polarization channels in the target channel group at all times is used as the second correlation between the two polarization channels; Establishing a two-dimensional coordinate system with time as the horizontal coordinate and the echo signal intensity as the vertical coordinate; Respectively mapping the echo signal strengths at all times in the two polarization channels in the target channel group to a two-dimensional coordinate system, and performing curve fitting on the echo signal strengths at each time of each polarization channel to obtain a fitting curve for each polarization channel in the target channel group; and obtaining extreme value points on each of the fitting curves; Obtaining a third correlation between the two polarization channels according to the distribution of extreme value points on the fitting curves corresponding to the two polarization channels in the target channel value; A product value of the first correlation, the second correlation, and the third correlation between two polarization channels in the target channel value is used as a correlation coefficient between the two polarization channels.

4. The SAR image analysis method based on synthetic aperture radar multi-source data fusion according to claim 3 is characterized in that: The obtaining, according to the distribution of extreme value points on the fitting curves corresponding to the two polarization channels in the target channel value, a third correlation between the two polarization channels comprises: Extract the maximum value point from all extreme value points on the fitting curve corresponding to each polarization channel in the target channel group; The Euclidean distance between the maximum points on the two fitting curves is used as the first distance parameter between the two fitting curves; The minimum value of the number of extreme points on the two fitting curves is used as the reference number, and the first reference number of extreme points on each fitting curve is used as the extreme points to be tested for each fitting curve; The Euclidean distance between the extreme value points to be tested at the same position on the two fitting curves is used as the distance parameter between the extreme value points to be tested, and the average value of the distance parameters between all the extreme value points to be tested at the same position is used as the second distance parameter between the two fitting curves; The sum of the first distance parameter and the second distance parameter is normalized to be negatively correlated to obtain a third correlation between the two polarization channels in the target channel value.

5. The SAR image analysis method based on synthetic aperture radar multi-source data fusion according to claim 1 is characterized in that: The statistical analysis of the echo signal strength at different times in each polarization channel to obtain the principal component data and principal component direction of each polarization channel includes: The echo signal strength at different times in each polarization channel is input into the principal component analysis algorithm to extract the principal component data and principal component direction of each polarization channel.

6. The SAR image analysis method based on synthetic aperture radar multi-source data fusion according to claim 1 is characterized in that: The obtaining, according to the difference between the principal component directions of the two polarization channels in each target channel group and the correlation coefficient of the two polarization channels, and the difference between the echo signal strengths of all polarization channels at the same time and the principal component data, the fusion adjustment parameter at each moment includes: Taking the absolute value of the difference between the principal component directions of the two polarization channels in each target channel group as the principal component direction difference value of each target channel group; Perform negative correlation mapping on the correlation coefficients between the two polarization channels in each target channel group to obtain the independence parameter of each target channel group; The product value of the principal component direction difference value and the independence parameter is used as the difference parameter of each target channel group, and the accumulated value of the difference parameters of all target channel groups is used as the overall difference between the polarization channels; According to the difference between the echo signal strength of all polarization channels at the same time and the principal component data and the overall difference, a fusion adjustment parameter at each time is obtained.

7. The SAR image analysis method based on synthetic aperture radar multi-source data fusion according to claim 6 is characterized in that: The obtaining of the fusion adjustment parameter at each moment according to the difference between the echo signal strength of all polarization channels at the same moment and the principal component data and the overall difference comprises: A time is randomly selected as the target time, and the absolute value of the difference between the echo signal strength of each polarization channel at the target time and the main component data of the polarization channel is used as the fluctuation degree of each polarization channel at the target time; The accumulated value of the fluctuation degree of all polarization channels at the target time is used as the overall fluctuation value at the target time; The product value of the overall difference and the overall fluctuation value at the target moment is normalized to obtain the fusion adjustment parameter at the target moment.

8. The SAR image analysis method based on synthetic aperture radar multi-source data fusion according to claim 7 is characterized in that: The step of fusing the echo signal strengths of all polarization channels at the same time based on the fusion adjustment parameter to obtain fused signal data at each time includes: The average value of the echo signal strength of all polarization channels at the target time is taken as the overall signal strength at the target time; Normalizing the absolute value of the difference between the echo signal strength of each polarization channel at the target time and the overall signal strength at the target time to obtain a fusion weight of each polarization channel at the target time; Obtaining initial fusion data at the target time according to the fusion weights and echo signal strengths of all polarization channels at the target time; The product value of the fusion adjustment parameter and the initial fusion data at the target moment is used as the fusion signal data at the target moment.

9. The SAR image analysis method based on synthetic aperture radar multi-source data fusion according to claim 8, characterized in that: The step of obtaining the initial fusion data at the target time according to the fusion weights and echo signal strengths of all polarization channels at the target time includes: Using the fusion weight of each polarization channel at the target time as the weight of the echo signal strength of each polarization channel at the target time; The echo signal strengths of all polarization channels at the target time are weighted and summed to obtain the initial fusion data at the target time.

10. The SAR image analysis method based on synthetic aperture radar multi-source data fusion according to claim 1, characterized in that: The generating of the SAR image based on the fused signal data at all times comprises: Based on synthetic aperture radar technology, SAR images are generated using fused signal data at all times.

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