CN110673147A - Post-flood evaluation method - Google Patents

Abstract

A post-flood assessment method, comprising: acquiring a GNSS-R original DDM image, and calculating the position of a mirror reflection point of a target area corresponding to the original DDM image; calculating the spatial resolution among the specular reflection points, the transmitting satellite and the satellite-borne receiver, and performing threshold division through the spatial resolution to determine the size of a grid of a final evaluation product; calibrating the power of the original DDM image to obtain a calibrated power value, and calculating the soil humidity sensitive parameter SNR according to the calibrated power value: inverting the soil humidity of the target area, performing threshold processing on the inversion result to obtain a region after disaster damage and calculating the disaster damage area; and generating a disaster area evaluation result. The method can effectively utilize the advantages of the GNSS-R technology, overcomes the defects of space-time resolution, coverage and timeliness in the traditional satellite-borne observation means, does not need to perform data fusion of a multi-source satellite, can quickly respond to the evaluation problem after the disaster, and is suitable for application of flood, typhoon and other disaster positioning, loss evaluation and other problems.

Description

A post-flood assessment method

technical field

The invention relates to the technical field of microwave remote sensing, in particular to a post-flood assessment method.

Background technique

Floods, typhoons, and heavy rainfall in a short period of time will cause local property damage to the people. Using traditional methods to assess the problems of discrete sampling, insufficient coverage, and time-consuming and labor-intensive problems can be effectively compensated for by satellite remote sensing. However, it is difficult to achieve high timeliness and resolution requirements with a single satellite data source.

GNSS-R (Global Navigation Satellite System Refectometry, referred to as GNSS-R) refers to a remote sensing technology that obtains information about the earth's land and oceans by receiving satellite signals reflected from the earth's surface to space. As an emerging technology, this technology has experienced a total of 25 years of development since it was proposed by ESA in 1993. The first experimental satellite was developed by the British Sally Satellite Commercial Company in 2003, and continued to be developed in 2014. UK TechDemoSat- 1. Experimental satellites. Prior to this, the application of GNSS-R technology was concentrated on the inversion of the sea surface wind field. The detection of soil moisture has been in the exploratory stage, and due to the small number of satellites in orbit, the revisit time in the same area has reached 1 year. Time, it is impossible to form products, and it is difficult to meet the needs of applications in terms of temporal and spatial resolution. On December 17, 2016, NASA of the United States inherited the GNSS-R spaceborne receiver developed by the British Sally Satellite Commercial Company, and launched 8 micro-satellites at one time to form the CYGNSS Hurricane GNSS-R constellation for medium and low For tropical cyclone observations in the latitude zone, the network formation of satellites greatly enhances the spatial and temporal resolution, and the revisit time is also increased from 1 year to 1 day. A large number of applications can be realized. At the same time, with the help of the SMAP soil moisture satellite adjusted to the launch satellite frequency in 2015 for GNSS-R soil observation, the sensitive parameters of the L-band GNSS-R soil moisture were developed, which made the observation and research of soil moisture using GNSS-R in this half year. Rapid development.

However, domestic GNSS-R soil moisture observations are mainly concentrated in the ground-based test stage, and GNSS-R soil moisture research is also concentrated in the single-satellite exploration research of the retired British Sally Satellite Commercial Company.

SUMMARY OF THE INVENTION

In view of the above situation, the purpose of the present invention is to provide a post-flood assessment method, which well solves the deficiencies of traditional methods in temporal and spatial resolution, coverage and timeliness, and has a fast response speed.

The present invention proposes a post-flood assessment method, wherein the assessment method comprises the following steps:

Obtain the original DDM image of GNSS-R, and calculate the position of the specular reflection point of the original DDM image corresponding to the target area;

Calculate the spatial resolution between the specular reflection point, the launching satellite and the onboard receiver, and perform threshold division through the spatial resolution to determine the grid size of the final evaluation product;

The power of the original DDM image is calibrated to obtain the calibrated power value, and the soil moisture sensitive parameter SNR is calculated according to the calibrated power value:

为发射卫星发射功率；Among them, SNR is the soil moisture sensitive parameter, namely the signal-to-noise ratio, Γ _rl is the reflectivity, P _g is the power value after calibration, R _ts and R _rs are the distance from the transmitting satellite to the ground specular reflection point and the specular reflection point to the satellite, respectively The carrier receiver distance, N is the noise statistics of the Doppler time delay image, G ^r is the receiving antenna gain, G ^t is the transmitting satellite transmit antenna gain,

is the transmit power of the launching satellite;

Invert the soil moisture of the target area, and perform threshold processing on the inversion results to obtain the post-disaster area and calculate the affected area;

Generate disaster area assessment results.

The post-flood assessment method proposed by the present invention can effectively utilize the advantages of GNSS-R technology, and can well solve the defects of space-time resolution, coverage and timeliness in traditional satellite-borne observation methods, and does not require multi-source satellite analysis. Data fusion can quickly respond to post-disaster assessment problems, and is suitable for applications such as floods, typhoons and other disaster location, loss assessment and other issues.

The post-flood assessment method, wherein the steps of calibrating the power of the original DDM image to obtain the calibrated power value, and calculating the soil moisture sensitive parameter SNR according to the calibrated power value, specifically include:

Count the noise of the part before the peak of the original DDM image to obtain the statistic C _N ;

The total gain G of the spaceborne receiver is obtained by calculating the auxiliary information;

Calculated from the statistic C _N and the overall gain G to get the calibrated power value:

Among them, C represents the value in the original DDM image, C _N is the noise statistic value, G is the total gain of the spaceborne receiver, and P _g is the power value after calibration;

The soil moisture sensitive parameter SNR is calculated according to the calibrated power value.

In the post-flood assessment method, the steps of inverting the soil moisture in the target area, performing threshold processing on the inversion result to obtain the post-disaster area and calculating the affected area, specifically include:

Combine the spatial resolution and the grid area area of the target area to derive the sensitive parameters that need to be averaged;

Substitute the averaged sensitive parameters into the model function to obtain the soil moisture in the grid area;

Threshold the inversion results to get the post-disaster area and calculate the disaster area.

The post-flood assessment method, wherein the step of performing threshold processing on the inversion result to obtain the post-disaster area and calculating the disaster area specifically includes:

Thresholding the inversion results to obtain soil water content contour lines;

Make statistics on the contour data of soil moisture content, and calculate the affected area.

The post-flood assessment method, wherein the steps of acquiring the GNSS-R original DDM image and calculating the position of the specular reflection point of the original DDM image corresponding to the target area specifically include:

Determining the time frame within which a hazard assessment is required;

Separate the DDM image and the corresponding auxiliary information obtained by the onboard receiver to obtain the attribute information corresponding to the original DDM image one-to-one;

Calculate the position of the specular reflection point of the original DDM image corresponding to the target area.

The post-flood assessment method, wherein, after the step of separating the DDM image and the corresponding auxiliary information obtained by the spaceborne receiver to obtain the attribute information corresponding to the original DDM image one-to-one, the assessment method further includes:

Draw an information query table according to the attribute information;

According to the information look-up table, the values of the receiving antenna gain Gr , the transmitting satellite transmitting antenna gain G ^t and the transmitting satellite transmitting power P _r ^t are respectively inquired.

The post-flood assessment method, wherein the step of calculating the position of the specular reflection point of the original DDM image corresponding to the target area specifically includes:

Obtain the coordinate position of the spaceborne receiver in the ECEF coordinate system;

Obtain the coordinate position of the launching satellite in the ECEF coordinate system;

Using the coordinates of the onboard receiver and the launching satellite as input, the position of the specular reflection point corresponding to the target area of the original DDM image is calculated.

In the post-flood assessment method, the coordinate position of the satellite-borne receiver is obtained through auxiliary information.

The post-flood assessment method, wherein, the step of acquiring the coordinate position of the launch satellite under the ECEF coordinate system specifically includes:

Obtain the GNSS satellite signal corresponding to the DDM image at the corresponding moment;

According to the GNSS satellite signal and the precise ephemeris of the transmitting satellite, the coordinate position of the transmitting satellite in the preset coordinate system is obtained.

The post-flood assessment method, wherein the calculation of the spatial resolution between the specular reflection point, the launch satellite and the spaceborne receiver, and the threshold division by the spatial resolution to determine the grid size of the final assessment product , including:

Calculate the height of the onboard receiver and the satellite elevation angle of the launching satellite at the mirror reflection point;

The spatial resolution is calculated according to the size of the first Fresnel zone entered by the wavelength of the electromagnetic wave of the transmitting satellite:

Among them, a is the lateral resolution, b is the longitudinal resolution, λ is the electromagnetic wave wavelength of the transmitting satellite, h is the height of the onboard receiver, and θ is the satellite elevation angle of the transmitting satellite at the specular reflection point;

Thresholding is performed by spatial resolution to determine the grid size for the final evaluation product.

Description of drawings

1 is a flowchart of a post-flood assessment method proposed by an embodiment of the present invention;

Fig. 2 shows the result of inversion of soil moisture in Guangdong Province for the whole year of 2018 by using the method in Fig. 1;

FIG. 3 is a contour map of soil moisture content drawn from the inversion results in FIG. 2 .

Detailed ways

In order to make the above objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention will be described in detail below. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

In the present invention, unless otherwise expressly specified and limited, the terms "installed", "connected", "connected", "fixed" and other terms should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection , or integrally connected; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or the internal communication between the two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

In view of the problems in the background technology, the present application has carried out research on the GNSS-R soil moisture detection technology by investigating the current soil moisture detection methods and the current spaceborne GNSS-R soil moisture algorithm, and verified that the technology has high spatial and temporal resolution and Taking advantage of the inversion accuracy, combined with geographic information technology, a post-flood assessment method is proposed.

Referring to FIG. 1, the present invention proposes a post-flood assessment method, and the assessment method includes the following steps S10-S50:

In step S10, the GNSS-R original DDM image is acquired, and the position of the specular reflection point of the original DDM image corresponding to the target area is calculated.

Specifically, in this step, acquiring a DDM (Delay Doppler Map, Delay Doppler Map, DDM for short) image refers to acquiring image data in the image.

The post-flood assessment method, wherein the steps of acquiring the GNSS-R original DDM image and calculating the position of the specular reflection point of the original DDM image corresponding to the target area specifically include:

Step S101 , determining the time range in which the disaster assessment needs to be performed, so as to perform accurate time positioning, so as to avoid the occurrence of assessment errors and affect the assessment results.

Step S102, separate the DDM image obtained by the onboard receiver and the corresponding auxiliary information to obtain attribute information corresponding to the original DDM image one-to-one. It should be noted that, in this step, the original DDM image is determined through attribute information.

The post-flood assessment method, wherein, after the step of separating the DDM image and the corresponding auxiliary information obtained by the spaceborne receiver to obtain the attribute information corresponding to the original DDM image one-to-one, the assessment method further includes:

Step S1021, drawing an information query table according to the attribute information, so as to facilitate subsequent query of related information;

Step S1022 , according to the information look-up table, the values of the receiving antenna gain Gr , the transmitting satellite transmitting antenna gain G ^t , and the transmitting satellite transmit power P _r ^t are respectively inquired.

Step S103: Calculate the position of the specular reflection point of the original DDM image corresponding to the target area.

The post-flood assessment method, wherein the step of calculating the position of the specular reflection point of the original DDM image corresponding to the target area specifically includes:

Step S1031, obtaining the coordinate position of the spaceborne receiver in the ECEF coordinate system;

It should be noted that, in this step, the coordinate position of the on-board receiver is obtained through auxiliary information, that is, through an information look-up table. The ECEF (Earth-Centered, Earth-Fixed) coordinate system means that the origin O of the coordinate system is the earth's center of mass, the z-axis is parallel to the earth's axis and points to the North Pole, the x-axis points to the intersection of the prime meridian and the equator, and the y-axis is perpendicular to the The xOz plane (that is, the intersection of 90° east longitude and the equator) constitutes a right-handed coordinate system.

Step S1032, obtaining the coordinate position of the launching satellite under the ECEF coordinate system;

The post-flood assessment method, wherein, the step of acquiring the coordinate position of the launch satellite under the ECEF coordinate system specifically includes:

Obtain the GNSS satellite signal corresponding to the DDM image at the corresponding moment;

According to the GNSS satellite signal and the precise ephemeris of the transmitting satellite, the coordinate position of the transmitting satellite in the preset coordinate system is obtained.

Step S1033, taking the coordinate positions of the onboard receiver and the transmitting satellite as input, calculate and obtain the position of the mirror reflection point of the original DDM image corresponding to the target area.

Step S20, calculating the spatial resolution between the specular reflection point, the transmitting satellite and the onboard receiver, and performing threshold division according to the spatial resolution to determine the grid size of the final evaluation product;

The post-flood assessment method, wherein the calculation of the spatial resolution between the specular reflection point, the launch satellite and the spaceborne receiver, and the threshold division by the spatial resolution to determine the grid size of the final assessment product , including:

Step S201, calculating the height of the onboard receiver and the satellite elevation angle of the transmitting satellite at the mirror reflection point.

In this step, the height h of the spaceborne receiver and the satellite elevation angle θ of the transmitting satellite at the specular reflection point are calculated and obtained according to the geometric position relationship of the spaceborne receiver, the specular reflection point and the transmitter in the ECEF coordinate system.

Step S202, according to the size of the electromagnetic wave wavelength of the transmitting satellite entering the first Fresnel zone to calculate the spatial resolution:

Among them, a is the lateral resolution, b is the longitudinal resolution, λ is the electromagnetic wave wavelength of the transmitting satellite, h is the height of the onboard receiver, and θ is the satellite elevation angle of the transmitting satellite at the specular reflection point.

In step S203, threshold division is performed according to the spatial resolution to determine the grid size of the final evaluation product.

Step S30, calibrate the power of the original DDM image to obtain the calibrated power value, and calculate the soil moisture sensitive parameter SNR according to the calibrated power value:

Among them, SNR is the soil moisture sensitive parameter, namely the signal-to-noise ratio, Γ _rl is the reflectivity, P _g is the power value after calibration, R _ts and R _rs are the distance from the transmitting satellite to the ground specular reflection point and the specular reflection point to the satellite, respectively Carrier receiver distance, N is the noise statistics of the Doppler time delay image, G ^r is the gain of the receiving antenna, G ^t is the transmitting antenna gain of the transmitting satellite, and P _r t is the transmitting power of the transmitting satellite.

It should be noted that, in this step, the distance R _ts from the transmitting satellite to the ground mirror reflection point and the distance R _rs from the mirror reflection point to the satellite onboard receiver are calculated from the coordinates of the transmitting satellite and the mirror reflection point in the ECEF coordinate system, and the receiving The antenna gain G ^r , the transmit satellite transmit antenna gain G ^t and the transmit satellite transmit power P _r ^t can be obtained from the information look-up table.

The post-flood assessment method, wherein the steps of calibrating the power of the original DDM image to obtain the calibrated power value, and calculating the soil moisture sensitive parameter SNR according to the calibrated power value, specifically include:

Count the noise of the part before the peak of the original DDM image to obtain the statistic C _N ;

The total gain G of the spaceborne receiver is obtained by calculating the auxiliary information;

Calculated from the statistic C _N and the overall gain G to get the calibrated power value:

Among them, C represents the value in the original DDM image, C _N is the noise statistic value, G is the total gain of the spaceborne receiver, and P _g is the power value after calibration;

The soil moisture sensitive parameter SNR is calculated according to the calibrated power value.

Step S40, invert the soil moisture of the target area, and perform threshold processing on the inversion result to obtain the post-disaster area and calculate the disaster area.

In the post-flood assessment method, the steps of inverting the soil moisture in the target area, performing threshold processing on the inversion result to obtain the post-disaster area and calculating the affected area, specifically include:

Step S401, combine the spatial resolution and the grid area area of the target area to obtain the sensitive parameter that needs to be averaged;

Step S402, substituting the averaged sensitive parameters into the pattern function to obtain the soil moisture in the grid area;

In step S403, threshold processing is performed on the inversion result to obtain the post-disaster area and calculate the disaster area.

The post-flood assessment method, wherein the step of performing threshold processing on the inversion result to obtain the post-disaster area and calculating the disaster area specifically includes:

Step S4031, performing threshold processing on the inversion results to obtain soil moisture content contour lines;

Step S4032, perform statistics on the contour data of soil moisture content, and calculate the affected area.

Step S50, generating a disaster-affected area assessment result.

To sum up, the post-flood assessment method proposed by the present invention can effectively utilize the advantages of GNSS-R technology, and can well solve the defects of temporal and spatial resolution, coverage and timeliness in traditional spaceborne observation methods, without the need for Data fusion of multi-source satellites can quickly respond to post-disaster assessment problems, and is suitable for applications such as floods, typhoons and other disaster positioning and loss assessment.

Experimental verification example

In the experiment, Guangdong Province, China in 2018 was taken as an example, and the step process of the present invention was used to invert the soil moisture in Guangdong Province for the whole year of 2018. The results are shown in Figure 2. Then, the soil moisture content contour line was drawn, and the result was shown in Figure 3. From the figure, the affected area and the size of the affected area can be seen intuitively, and it can be accurately located to each city, county and corresponding jurisdiction.

By analyzing the soil moisture content of more than 0.4cm ³ /cm ³ in 12 months of the year by using the threshold value, it can be concluded that the flood disasters were affected in October and December of the year, and the disaster area reached 2500km ² , and the disaster area was mainly Shenzhen City, through the inquiry of meteorological data, it can be known that Guangdong Province was affected by typhoons "Mangosteen" and "Jade Rabbit" in September and November respectively, which caused a large amount of rainfall in a short period of time and caused a certain flood disaster, which was embodied in the following month. The soil moisture content increased sharply.

Experimental conclusion: the experimental results are listed, the invention can well and quickly complete the statistics of flood disaster-affected areas and the location of disaster-affected areas under the condition of only using GNSS-R satellite data, and can be adapted to most coastal areas. applications such as disaster assessment of typhoons and floods in inland areas.

In the description of this specification, description with reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples", etc., mean specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the patent of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (10)

1. a post-flood assessment method, is characterized in that, described assessment method comprises the steps: Obtain the original DDM image of GNSS-R, and calculate the position of the specular reflection point of the original DDM image corresponding to the target area; Calculate the spatial resolution between the specular reflection point, the launching satellite and the onboard receiver, and perform threshold division through the spatial resolution to determine the grid size of the final evaluation product; The power of the original DDM image is calibrated to obtain the calibrated power value, and the soil moisture sensitive parameter SNR is calculated according to the calibrated power value:

Among them, SNR is the soil moisture sensitive parameter, namely the signal-to-noise ratio, Γ _rl is the reflectivity, P _g is the power value after calibration, R _ts and R _rs are the distance from the transmitting satellite to the ground specular reflection point and the specular reflection point to the satellite, respectively The carrier receiver distance, N is the noise statistics of the Doppler time delay image, G ^r is the receiving antenna gain, G ^t is the transmitting satellite transmit antenna gain,

is the transmit power of the launching satellite; Invert the soil moisture of the target area, and perform threshold processing on the inversion results to obtain the post-disaster area and calculate the affected area; Generate disaster area assessment results. 2. The post-flood assessment method according to claim 1, wherein the power of the original DDM image is calibrated to obtain the power value after calibration, and the step of calculating the soil moisture sensitive parameter SNR according to the power value after the calibration, specifically include: Count the noise of the part before the peak of the original DDM image to obtain the statistic C _N ; The total gain G of the spaceborne receiver is obtained by calculating the auxiliary information; Calculated from the statistic C _N and the overall gain G to get the calibrated power value: Among them, C represents the value in the original DDM image, C _N is the noise statistic value, G is the total gain of the spaceborne receiver, and P _g is the power value after calibration; The soil moisture sensitive parameter SNR is calculated according to the calibrated power value. 3. post-flood assessment method according to claim 1, is characterized in that, the soil moisture of described inversion target area, carries out threshold value processing to inversion result to obtain post-disaster area and calculates the step of disaster-affected area, specifically comprises : Combine the spatial resolution and the grid area area of the target area to derive the sensitive parameters that need to be averaged; Substitute the averaged sensitive parameters into the model function to obtain the soil moisture in the grid area; Threshold the inversion results to get the post-disaster area and calculate the disaster area. 4. The post-flood assessment method according to claim 3, wherein the inversion result is subjected to threshold processing to obtain the post-disaster area and the step of calculating the affected area, specifically comprising: Thresholding the inversion results to obtain soil water content contour lines; Make statistics on the contour data of soil moisture content, and calculate the affected area. 5. post-flood assessment method according to claim 1, is characterized in that, the described acquisition GNSS-R original DDM image, and the step of calculating the specular reflection point position of original DDM image corresponding target area, specifically comprises: Determining the time frame within which a hazard assessment is required; Separate the DDM image and the corresponding auxiliary information obtained by the onboard receiver to obtain the attribute information corresponding to the original DDM image one-to-one; Calculate the position of the specular reflection point of the original DDM image corresponding to the target area. 6. The post-flood assessment method according to claim 5, characterized in that, after the step of separating the DDM images obtained by the spaceborne receiver and the corresponding auxiliary information to obtain the attribute information corresponding to the original DDM images one-to-one , the evaluation method further includes: Draw an information query table according to the attribute information; According to the information look-up table, the receiving antenna gain Gr , the transmitting satellite transmitting antenna gain G ^t and the transmitting satellite transmitting power are respectively inquired ^.

value of . 7. The post-flood assessment method according to claim 5, wherein the step of calculating the specular reflection point position of the original DDM image corresponding to the target area specifically comprises: Obtain the coordinate position of the spaceborne receiver in the ECEF coordinate system; Obtain the coordinate position of the launching satellite in the ECEF coordinate system; Using the coordinates of the onboard receiver and the launching satellite as input, the position of the specular reflection point corresponding to the target area of the original DDM image is calculated. 8 . The post-flood assessment method according to claim 7 , wherein the coordinate position of the satellite-borne receiver is obtained through auxiliary information. 9 . 9. post-flood assessment method according to claim 7, is characterized in that, the described step of obtaining the coordinate position of launching satellite under ECEF coordinate system, specifically comprises: Obtain the GNSS satellite signal corresponding to the DDM image at the corresponding moment; According to the GNSS satellite signal and the precise ephemeris of the transmitting satellite, the coordinate position of the transmitting satellite in the preset coordinate system is obtained. 10. The post-flood assessment method according to claim 1 or 7, wherein the spatial resolution between the calculation specular reflection point, the transmitting satellite and the spaceborne receiver is calculated, and threshold division is performed by the spatial resolution, The steps to determine the grid size for the final evaluation product include: Calculate the height of the onboard receiver and the satellite elevation angle of the launching satellite at the mirror reflection point; The spatial resolution is calculated according to the size of the first Fresnel zone entered by the wavelength of the electromagnetic wave of the transmitting satellite: Among them, a is the lateral resolution, b is the longitudinal resolution, λ is the electromagnetic wave wavelength of the transmitting satellite, h is the height of the onboard receiver, and θ is the satellite elevation angle of the transmitting satellite at the specular reflection point; Thresholding is performed by spatial resolution to determine the grid size for the final evaluation product.

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