Ground disaster monitoring system based on interferometric synthetic aperture radar

Abstract

The invention discloses a ground disaster monitoring system based on an interferometric synthetic aperture radar, and relates to the technical field of radar survey, and the system comprises an airborne end and a ground control end. The airborne end comprises a synthetic aperture radar antenna, a transmit-receive switch, a transmitter, a receiver, a frequency source, a signal processor, a data recorder and a control and display module. The synthetic aperture radar antenna is connected to the transmitter and the receiver through the transmit-receive switch. The frequency source is connected to the transmitter and the receiver; the transmitter, the receiver and the frequency source are all connected to the signal processor; the synthetic aperture radar antenna is used for transmitting broadband signals or receiving target echoes; the transmitter is used for generating, modulating and amplifying broadband signals; the receiver is used for frequency conversion, amplification and acquisition of echo signals; the frequency source is used for generating clock and local oscillation signals of the whole system; the signal processor is used for time sequence synchronization, parameter control and echo signal processing of the whole system. And detection of natural disasters such as landslide, debris flow, earthquake and flood is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of radar surveying and mapping, and particularly to a geological disaster monitoring system based on an interferometric synthetic aperture radar. Background Art

[0002] Synthetic Aperture Radar (SAR) is a remote sensing system that uses microwave imaging technology to detect ground and sea surface targets. The SAR radar realizes high resolution in the range direction of the target by transmitting a large bandwidth linear frequency modulation signal. During the relative movement between the radar platform and the target, through coherent accumulation and motion compensation, the antenna length is extended in a time-for-space manner to achieve high resolution in the azimuth direction. Since it was proposed and successfully developed in the United States in the 1950s, the SAR radar has developed rapidly and effectively, and has the characteristics of all-weather, all-day, high-precision, large range, and long distance. It has been widely used in agricultural and forestry disaster prevention, remote sensing mapping and navigation, geological exploration, environmental and ocean monitoring, and military fields in various countries.

[0003] In the related art, there is a lack of a geological disaster monitoring system that applies synthetic aperture radar technology. Based on this, the present invention proposes a geological disaster monitoring system based on an interferometric synthetic aperture radar. Summary of the Invention

[0004] The present invention provides a geological disaster monitoring system based on an interferometric synthetic aperture radar to realize the detection of natural disasters such as landslides, debris flows, earthquakes, floods, etc.

[0005] According to one aspect of the present disclosure, there is provided a geological disaster monitoring system based on an interferometric synthetic aperture radar, the system comprising: an airborne end and a ground control end; The airborne end includes: a synthetic aperture radar antenna, a transceiver switch, a transmitter, a receiver, a frequency source, a signal processor, a data recorder, a control and display module; Wherein, the synthetic aperture radar antenna is connected to the transmitter and the receiver through the transceiver switch; the frequency source is connected to the transmitter and the receiver; the transmitter, the receiver and the frequency source are all connected to the signal processor; the signal processor is connected to the data recorder and the control and display module; The synthetic aperture radar antenna is used to transmit a broadband signal or receive a target echo; The transmitter is used to generate, modulate and amplify the broadband signal; The receiver is used to convert the frequency, amplify and collect the echo signal; The frequency source is used to generate the clock and local oscillator signals of the entire system; The signal processor is used for the timing synchronization, parameter control and echo signal processing of the entire system.

[0006] In a possible implementation manner, the system further includes an inertial navigation system, which measures the antenna attitude in real time and transmits it to the signal processor for motion compensation calculation.

[0007] In a possible implementation, the data recorder is used to record the signal echo and the image data processed by the signal processor.

[0008] In a possible implementation, the control and display module is used for the control of the entire system and image display.

[0009] In a possible implementation, the signal processor is used to execute the following method: Generate a reference map of the area to be detected based on the radar echo signal when the aircraft first flies over the geological disaster detection area; Generate a SAR real-time image of the area to be detected based on the radar echo signal when the aircraft second flies over the geological disaster detection area; Geometrically correct the SAR real-time image according to the imaging parameters and inertial navigation parameters; Perform image registration on the geometrically corrected SAR real-time image according to the reference map; Perform change detection on the SAR real-time image after image registration to output a classification difference map; The classification difference map represents the changes in the image; Fuse the classification difference map with the SAR real-time image to obtain a change detection result map; Among them, the change detection includes the following operations: filtering, generating a logarithmic ratio difference map, maximum likelihood initial segmentation, CFAR statistical segmentation based on constant false alarm detection, and target screening.

[0010] In a possible implementation, performing image registration on the geometrically corrected SAR real-time image according to the reference map includes: Perform rough registration according to the geographical coordinates; Large window correlation matching reaches pixel-level accuracy; Small window correlation matching reaches sub-pixel-level accuracy; Full map resampling.

[0011] Compared with the prior art, the beneficial effects of the present invention are: The geological disaster monitoring system based on an interferometric synthetic aperture radar according to an embodiment of the present disclosure, the system comprising: an airborne end and a ground control end; the airborne end comprising: a synthetic aperture radar antenna, a transceiver switch, a transmitter, a receiver, a frequency source, a signal processor, a data recorder, a control and display module; wherein, the synthetic aperture radar antenna is connected to the transmitter and the receiver through the transceiver switch; the frequency source is connected to the transmitter and the receiver; the transmitter, the receiver and the frequency source are all connected to the signal processor; the signal processor is connected to the data recorder and the control and display module; the synthetic aperture radar antenna is used for transmitting a broadband signal or receiving a target echo; the transmitter is used for generating, modulating and amplifying the broadband signal; the receiver is used for frequency conversion, amplification and acquisition of the echo signal; the frequency source is used for generating the clock and local oscillator signals of the entire system; the signal processor is used for timing synchronization, parameter control and echo signal processing of the entire system.

[0012] Using the interference mode of the SAR radar, three-dimensional elevation measurement is realized by using multi-antenna single interference or single-antenna repeat-pass interference, and stereo mapping is realized for areas such as hills, mountains, and plains, so as to realize the detection of natural disasters such as landslides, debris flows, earthquakes, and floods. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A block diagram of a geological disaster monitoring system based on an interferometric synthetic aperture radar according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0014] Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the drawings. Identical reference numerals in the drawings denote elements having the same or similar functions. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0015] The special term "exemplary" herein means "serving as an example, embodiment or illustration". Any embodiment described herein as "exemplary" is not necessarily to be construed as superior or better than other embodiments.

[0016] In addition, in order to better illustrate the present disclosure, numerous specific details are given in the following detailed description. Those skilled in the art should understand that the present disclosure can be implemented without some specific details. In some instances, methods, means, elements and circuits well known to those skilled in the art are not described in detail so as to highlight the gist of the present disclosure.

[0017] According to one aspect of the present disclosure, there is provided a geological disaster monitoring system based on an interferometric synthetic aperture radar, the system comprising: an airborne end and a ground control end; The airborne end comprises: a synthetic aperture radar antenna, a transceiver switch, a transmitter, a receiver, a frequency source, a signal processor, a data recorder, a control and display module; Among them, the synthetic aperture radar antenna is connected to the transmitter and receiver through a transmit-receive switch; the frequency source is connected to the transmitter and receiver; the transmitter, receiver, and frequency source are all connected to the signal processor; the signal processor is connected to the data recorder and the control and display module; The synthetic aperture radar antenna is used to transmit broadband signals or receive target echoes; The transmitter is used to generate, modulate, and amplify broadband signals; The receiver is used to convert the frequency, amplify, and collect echo signals; The frequency source is used to generate the clock and local oscillator signals for the entire system; The signal processor is used for the timing synchronization, parameter control, and echo signal processing of the entire system.

[0018] In a possible implementation, the system further includes an inertial navigation system, which measures the antenna attitude in real time and transmits it to the signal processor for motion compensation calculation.

[0019] In a possible implementation, the data recorder is used to record the signal echoes and the image data processed by the signal processor.

[0020] In a possible implementation, the control and display module is used for the control of the entire system and image display.

[0021] In a possible implementation, the system further includes a radar power supply, which is used to provide power for the airborne terminal.

[0022] When the SAR radar passes through the reconnaissance and surveillance area for the first time, the reference map production mode is started to generate a change reference map of the reconnaissance and surveillance area, which is used as the reference for subsequent change detection. When the SAR radar repeatedly passes through the reconnaissance and surveillance area, the change detection mode is started, and the SAR image of the reconnaissance and surveillance area obtained in real time is automatically compared with the reference map of this area generated before to perform automatic target change detection and generate a classification difference map. Considering the sensitivity of the human eye to colors, the targets on the classification difference map are represented in color to indicate the presence or absence of the targets while maintaining their original shapes and distribution characteristics, which is more in line with human cognitive habits and is convenient for intelligence map analysis personnel to confirm change information and identify targets.

[0023] In order to reduce the influence of route changes on change detection, all SAR image data needs to be geometrically corrected according to the imaging parameters to ensure that the corrected SAR images are arranged due south and due north, which is convenient for later intelligence map analysis personnel to interpret the maps.

[0024] In the image registration stage, a hierarchical registration strategy is adopted to achieve precise registration between the reference image and the real-time image. First, according to the geographical coordinate information, the common parts in the reference image and the real-time image are extracted. At this time, the registration accuracy is within 10 - 30 pixels. Second, within the image range, a small number of (such as 3×3 = 9) control points are evenly selected, large window data is taken, and the registration accuracy of the two images is improved to within 1 pixel using the criterion of correlation coefficient. Finally, through sampling processing, registration is performed at the sub-pixel level to achieve sub-pixel registration at the control points. Through the control point information, fitting is performed within the entire image range, and resampling is carried out on the real-time image to achieve precise matching with the reference image.

[0025] In the change detection stage, the logarithmic ratio method is used to construct an initial difference map, which is used as the basis for change detection. Based on a full analysis of the statistical characteristics of the changed and unchanged regions, maximum likelihood initial segmentation and CFAR-based statistical segmentation are sequentially adopted to complete the segmentation of the initial difference map.

[0026] In the change detection stage, the logarithmic ratio method is used to construct an initial difference map, which is used as the basis for change detection. Based on a full analysis of the statistical characteristics of the changed and unchanged regions, maximum likelihood initial segmentation and CFAR-based statistical segmentation are sequentially adopted to complete the segmentation of the initial difference map.

[0027] In a possible implementation, the signal processor is used to execute the following method: Generate a reference map of the area to be detected according to the radar echo signal when the aircraft first flies over the geological disaster detection area; Generate a SAR real-time image of the area to be detected according to the radar echo signal when the aircraft second flies over the geological disaster detection area; Geometrically correct the SAR real-time image according to the imaging parameters and inertial navigation parameters; Perform image registration on the geometrically corrected SAR real-time image according to the reference map; Perform change detection on the SAR real-time image after image registration and output a classification difference map; The classification difference map represents the changes in the image; Fuse the classification difference map with the SAR real-time image to obtain a change detection result map; Among them, change detection includes the following operations: filtering, generating a logarithmic ratio difference map, maximum likelihood initial segmentation, CFAR statistical segmentation based on constant false alarm detection, and target screening.

[0028] Change detection is a technology that determines the change characteristics and processes of ground objects based on multiple images obtained at different times in the same area. It mainly realizes the recognition of the transformation of ground object types or the changes in internal conditions and states by extracting and analyzing the spectral feature differences or spatial structure feature differences between images. The most prominent manifestation is the changes between gray values or local textures, and on this basis, the changes in the shape, position, quantity, and other attributes of the region of interest are obtained.

[0029] In a possible implementation, image registration is performed on the geometrically corrected SAR real-time image according to a reference image, including: Performing rough registration according to geographical coordinates; Performing large-window correlation matching to achieve pixel-level accuracy; Performing small-window correlation matching to achieve sub-pixel-level accuracy; Performing full-image resampling.

[0030] During the actual flight of a certain type of airborne radar, changes in targets such as vehicles, aircraft, and corner reflectors within the airport are monitored. The actual detection performance is verified by examining the detection rate and false alarm rate. The detection rate and false alarm rate are defined as follows: Detection rate Pd: Number of detected changing targets / Number of actual changing targets; False alarm rate Pf: Number of detected false targets / Total number of detections. The number of actual changing targets refers to the number of targets that actually change in the assessment area found by the image interpretation analyst by comparing two SAR images before and after the change. The total number of detections refers to the number of detected targets remaining after the image interpretation analyst performs image interpretation analysis on the change situations given in the classification difference map, combining the images before and after the change, and removing false alarms caused by factors such as scene changes in the classification difference map. The number of detected changing targets refers to the number of targets in the total detected targets that match the actual changing targets. The number of detected false targets refers to the number of targets in the total detected targets that have not changed. During the experiment, the radar real-time change detection performance is verified by moving corner reflectors and vehicles. The change detection results are represented by green for newly added targets and red for disappearing targets. The SAR image automatic target change detection technology first associates the reference image and the image to be detected through image registration, and then uses the reference image as prior information to extract the information of interest in the image to be detected, capable of extracting changes in artificial targets (aircraft, vehicles, corner reflectors) in the monitoring area, discarding redundant information, and presenting the results in the form of a classification difference map, which is simple and intuitive and is conducive to image interpretation by the interpreter. The target detection rate in the monitoring area reaches 100%, the false alarm rate is low, it can work for multiple flights with long flight hours, and the real-time performance is high, which proves the robustness and effectiveness of the monitoring system.

[0031] The embodiments of the present disclosure have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art in the technical field without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other ordinary skill in the art in the technical field to understand the embodiments disclosed herein.

Claims

1. A geological disaster monitoring system based on interferometric synthetic aperture radar, characterized in that: The system comprises: an airborne terminal and a ground control terminal; The airborne end includes: synthetic aperture radar antenna, transceiver switch, transmitter, receiver, frequency source, signal processor, data recorder, control and display module; The synthetic aperture radar antenna is connected to the transmitter and the receiver through a transceiver switch; the frequency source is connected to the transmitter and the receiver; the transmitter, the receiver and the frequency source are all connected to the signal processor; the signal processor is connected to the data recorder, the control and display module; Synthetic aperture radar antennas are used to transmit broadband signals or receive target echoes; The transmitter is used to generate, modulate and amplify broadband signals; The receiver is used for frequency conversion, amplification and collection of echo signals; The frequency source is used to generate the clock and local oscillator signal of the entire system; The signal processor is used for timing synchronization, parameter control and echo signal processing of the entire system.

2. The geological disaster monitoring system based on interferometric synthetic aperture radar according to claim 1 is characterized in that: The system also includes an inertial navigation system, which measures the antenna attitude in real time and transmits the attitude to a signal processor for motion compensation calculation.

3. The geological disaster monitoring system based on interferometric synthetic aperture radar according to claim 1, characterized in that: The data recorder is used to record the signal echo and the image data processed by the signal processor.

4. The geological disaster monitoring system based on interferometric synthetic aperture radar according to claim 1, characterized in that: The control and display module is used for the control and image display of the entire system.

5. The geological disaster monitoring system based on interferometric synthetic aperture radar according to claim 1, characterized in that: The signal processing machine is used to execute the following method: Generate a reference map of the area to be detected based on the radar echo signal when the aircraft first flies over the geological disaster detection area; Generate a SAR real-time image of the area to be detected based on the radar echo signal when the aircraft flies over the geological disaster detection area for the second time; perform geometric correction on the SAR real-time image based on imaging parameters and inertial navigation parameters; Image registration is performed on the geometrically corrected SAR real-time image according to the reference image; Perform change detection on the SAR real-time image after image registration and output a classification difference map; The classification difference map is fused with the SAR real-time image to obtain the change detection result map; The classified difference graph shows the changes in the image; Among them, change detection includes the following operations: filtering, generating logarithmic ratio difference map, maximum likelihood initial segmentation, CFAR statistical segmentation based on constant false alarm detection, and target screening.

6. The geological disaster monitoring system based on interferometric synthetic aperture radar according to claim 5 is characterized in that: Image registration is performed on the geometrically corrected SAR real-time image according to the reference image, including: Coarse registration based on geographic coordinates; Large window correlation matching achieves pixel-level accuracy; Small window correlation matching achieves sub-pixel accuracy; Resample the entire image.

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