CN110673147A - Post-flood evaluation method - Google Patents
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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
Technical Field
The invention relates to the technical field of microwave remote sensing, in particular to a post-flood evaluation method.
Background
The property loss of people can be caused regionally by flood, typhoon and strong rainfall in a short period, the problems of discrete sampling, insufficient coverage, time and labor consumption can be evaluated by adopting the traditional means, the defect can be effectively compensated by adopting the satellite remote sensing means, and the requirement on high timeliness and resolution can be difficultly met by adopting a single satellite data source.
GNSS-R (Global Navigation Satellite system, GNSS-R for short) refers to a remote sensing technology for acquiring information related to the earth's land and sea by receiving transmitted Satellite signals reflected to the space through the earth's surface. The technology is a new technology, is proposed by ESA in 1993, has a development time of 25 years, is developed by Sali satellite commercial company in British in 2003, and is continuously developed in 2014 to UK TechDemosat-1 test satellites, before that, the application of the GNSS-R technology is concentrated on the inversion of sea surface wind fields, the detection of soil humidity is always in an exploration stage, and due to the fact that the number of orbit satellites is small, the revisit time of the same region reaches 1 year, products cannot be formed, and the space-time resolution cannot meet the application requirements. In 2016, 12 and 17 days, NASA in America inherits a GNSS-R satellite-borne receiver developed by Sali satellite commercial company in England, 8 micro satellites are emitted at one time to form a CYGNSS hurricane GNSS-R constellation which is used for tropical cyclone observation in middle and low latitude zones, the space-time resolution is greatly enhanced by networking formation of the satellites, the revisit time is also increased from 1 year to 1 day, and the reflection point of the sub-satellite mirror surface can rapidly traverse a region, so that a large amount of applications except the hurricane observation can be realized. Meanwhile, by means of adjusting SMAP soil humidity satellite to a transmitting satellite frequency point in 2015 for GNSS-R soil observation, sensitive parameters of L-band GNSS-R soil humidity are developed, so that observation research on soil humidity by adopting GNSS-R is developed quickly in the half year.
However, domestic GNSS-R soil moisture observation is mainly focused on the stage of ground test, and the research on GNSS-R soil moisture is also focused on the single-star exploration research of retired American satellites commercial company in British.
Disclosure of Invention
In view of the above-mentioned situation, the present invention aims to provide a post-flood evaluation method, which well solves the shortcomings of the conventional method in terms of spatial and temporal resolution, coverage and timeliness, and has a fast response speed.
The invention provides a post-flood evaluation method, which comprises the following steps:
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:
wherein SNR is soil moisture sensitivity parameter, i.e. signal-to-noise ratio, gammarlIs the reflectivity, PgFor calibrated power values, RtsAnd RrsRespectively the distance from the transmitting satellite to the ground mirror reflection point and the distance from the mirror reflection point to the satellite-borne receiver, N is the noise statistic size of the Doppler time delay image, GrFor the magnitude of the gain of the receiving antenna, GtIn order to transmit the satellite transmit antenna gain,
transmitting power for a transmitting satellite;
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 flood post-disaster assessment method provided by the invention can effectively utilize the advantages of the GNSS-R technology, well solve 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 assessment problem after the disaster, and is suitable for the application of flood, typhoon and other disaster positioning, loss assessment and other problems.
The method for evaluating the flood after the flood, wherein the steps of 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 specifically comprise:
counting the noise of the part before the peak value of the original DDM image to obtain a statistic value CN；
Calculating to obtain the total gain G of the satellite-borne receiver through the auxiliary information;
according to the statistical value CNAnd the total gain G is calculated to obtain a calibrated power value:
wherein C represents a numerical value in an original DDM image, CNIs the noise statistic, G is the total gain of the satellite-borne receiver, PgIs the calibrated power value;
and calculating the soil humidity sensitive parameter SNR according to the calibrated power value.
The method for evaluating flood after disaster, wherein the steps of inverting the soil humidity of a target area, performing threshold processing on the inversion result to obtain a region after disaster and calculating the area of the disaster include:
combining the spatial resolution and the grid area of the target area to obtain sensitive parameters needing to be averaged;
substituting the averaged sensitive parameters into a mode function to obtain the soil humidity of the grid area;
and carrying out threshold processing on the inversion result to obtain a region after disaster damage and calculating the disaster damage area.
The post-flood evaluation method for flood comprises the following steps of performing threshold processing on an inversion result to obtain a post-disaster area and calculating a disaster area, and specifically comprises the following steps:
carrying out threshold processing on the inversion result to obtain a contour line of the water content of the soil;
and (5) carrying out statistics on contour line data of the water content of the soil, and calculating the disaster area.
The flood post-disaster evaluation method comprises the following steps of obtaining 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:
determining a time range in which disaster assessment is required;
separating the DDM image acquired by the satellite-borne receiver and corresponding auxiliary information to obtain attribute information corresponding to the original DDM image one by one;
and calculating the position of a specular reflection point of the target area corresponding to the original DDM image.
After the step of separating the DDM image acquired by the satellite-borne receiver and the corresponding auxiliary information to obtain the attribute information corresponding to the original DDM image one to one, the post-flood evaluation method further comprises:
drawing an information query table according to the attribute information;
respectively inquiring the gain G of the receiving antenna according to the information inquiry tablerGain G of transmitting satellite transmitting antennatTransmitting satellite transmission power Prthe value of t.
The flood post-disaster evaluation method comprises the following steps of:
acquiring the coordinate position of the satellite-borne receiver in an ECEF coordinate system;
acquiring the coordinate position of the launching satellite in an ECEF coordinate system;
and calculating to obtain the position of a mirror reflection point of the original DDM image corresponding to the target area by taking the coordinate positions of the satellite-borne receiver and the transmitting satellite as input.
According to the flood post-disaster evaluation method, the coordinate position of the satellite-borne receiver is obtained through auxiliary information.
The flood post-disaster evaluation method comprises the following steps of:
acquiring GNSS satellite signals of the DDM image corresponding to the corresponding moment;
and acquiring the coordinate position of the transmitting satellite in a preset coordinate system by transmitting the satellite ephemeris according to the GNSS satellite signal.
The flood post-disaster evaluation method comprises the following steps of calculating the spatial resolution among the specular reflection point, the transmitting satellite and the satellite-borne receiver, and dividing a threshold value according to the spatial resolution to determine the size of a grid of a final evaluation product, and specifically comprises the following steps:
calculating the height of the satellite-borne receiver and the satellite elevation angle of the transmitting satellite at the mirror reflection point;
and calculating the spatial resolution according to the size of the electromagnetic wave wavelength entering the first Fresnel zone of the emission satellite:
wherein a is transverse resolution, b is longitudinal resolution, lambda is the electromagnetic wave wavelength of the transmitting satellite, h is the height of the satellite-borne receiver, and theta is the satellite elevation angle of the transmitting satellite at the mirror reflection point;
thresholding is performed by spatial resolution to determine the mesh size of the final evaluation product.
Drawings
Fig. 1 is a flowchart of a post-flood evaluation method according to an embodiment of the present invention;
FIG. 2 is a graph showing the inversion of soil moisture in Guangdong province of 2018, using the method of FIG. 1;
fig. 3 is a contour plot of soil moisture content plotted against the inversion results of fig. 2.
Detailed Description
The present invention will be described in detail with reference to the following embodiments in order to make the aforementioned objects, features and advantages of the invention more comprehensible. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art 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.
Aiming at the problems in the background art, the GNSS-R soil humidity detection technology is subjected to attack and customs through investigation of the current soil humidity detection method and the current satellite-borne GNSS-R soil humidity algorithm, the advantages of the technology in space-time resolution and inversion accuracy are verified, and the flood post-disaster assessment method is provided by combining with the geographic information technology.
Referring to fig. 1, the present invention provides a post-flood evaluation method, which includes the following steps S10-S50:
step S10, obtaining GNSS-R original DDM image, and calculating the position of the mirror reflection point of the target area corresponding to the original DDM image.
Specifically, in this step, acquiring a DDM (delay doppler map, DDM for short) image refers to acquiring image data in the image.
The flood post-disaster evaluation method comprises the following steps of obtaining 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:
and S101, determining a time range in which disaster assessment is required to be performed so as to perform accurate time positioning and avoid the assessment result from being influenced by assessment errors.
Step S102, separating the DDM image obtained by the satellite-borne receiver and the corresponding auxiliary information to obtain the attribute information corresponding to the original DDM image one by one. In this step, the original DDM image is determined by the attribute information.
After the step of separating the DDM image acquired by the satellite-borne receiver and the corresponding auxiliary information to obtain the attribute information corresponding to the original DDM image one to one, the post-flood evaluation method further comprises:
step S1021, drawing an information query table according to the attribute information so as to facilitate the query of the subsequent related information;
step S1022, respectively inquiring the receiving antenna gain G according to the information look-up tablerGain G of transmitting satellite transmitting antennatTransmitting satellite transmission power Prthe value of t.
Step S103, calculating the position of the specular reflection point of the target area corresponding to the original DDM image.
The flood post-disaster evaluation method comprises the following steps of:
step S1031, acquiring a coordinate position of the satellite-borne receiver in an ECEF coordinate system;
it should be noted that, in this step, the coordinate position of the satellite borne receiver is obtained through the attached information, that is, through the information lookup table. The ECEF (Earth-Centered, Earth-Fixed) coordinate system means that the origin O of the coordinate system is the Earth centroid, the z-axis is parallel to the Earth axis and points to the north pole, the x-axis points to the intersection point of the meridian and the equator, and the y-axis is perpendicular to the xOz plane (i.e. the intersection point of the east longitude 90 ° and the equator) to form a right-hand coordinate system.
Step S1032, acquiring the coordinate position of the launching satellite in an ECEF coordinate system;
the flood post-disaster evaluation method comprises the following steps of:
acquiring GNSS satellite signals of the DDM image corresponding to the corresponding moment;
and acquiring the coordinate position of the transmitting satellite in a preset coordinate system by transmitting the satellite ephemeris according to the GNSS satellite signal.
And step S1033, calculating to obtain the position of the mirror reflection point of the original DDM image corresponding to the target area by taking the coordinate positions of the satellite-borne receiver and the transmitting satellite as input.
Step S20, calculating the space resolution among the mirror reflection point, the transmitting satellite and the satellite-borne receiver, and dividing the threshold value according to the space resolution to determine the mesh size of the final evaluation product;
the flood post-disaster evaluation method comprises the following steps of calculating the spatial resolution among the specular reflection point, the transmitting satellite and the satellite-borne receiver, and dividing a threshold value according to the spatial resolution to determine the size of a grid of a final evaluation product, and specifically comprises the following steps:
step S201, calculating the height of the satellite-borne receiver and the satellite elevation angle of the transmitting satellite at the mirror reflection point.
In the step, the height h of the satellite-borne receiver and the satellite elevation angle theta of the launching satellite at the specular reflection point are calculated and obtained according to the geometric position relation of the satellite-borne receiver, the specular reflection point and the transmitter in an ECEF coordinate system.
Step S202, according to the size of the electromagnetic wave wavelength entering the first Fresnel area of the emission satellite, calculating the spatial resolution:
wherein a is the transverse resolution, b is the longitudinal resolution, lambda is the electromagnetic wave wavelength of the transmitting satellite, h is the height of the satellite-borne receiver, and theta is the satellite elevation angle of the transmitting satellite at the mirror reflection point.
Step S203, threshold division is performed by spatial resolution to decide the mesh size of the final evaluation product.
Step S30, 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:
wherein SNR is soil moisture sensitivity parameter, i.e. signal-to-noise ratio, gammarlIs the reflectivity, PgFor calibrated power values, RtsAnd RrsRespectively the distance from the transmitting satellite to the ground mirror reflection point and the distance from the mirror reflection point to the satellite-borne receiver, N is the noise statistic size of the Doppler time delay image, GrFor the magnitude of the gain of the receiving antenna, GtFor transmitting satellite transmitting antenna gain, PrAnd t is the transmitting power of the transmitting satellite.
It should be noted that, in this step, the distance R between the transmitting satellite and the ground specular reflection pointtsAnd the distance R from the mirror reflection point to the satellite borne receiverrsThe gain G of the receiving antenna is calculated by the coordinates of the transmitting satellite and the specular reflection point in an ECEF coordinate systemrGain G of transmitting satellite transmitting antennatAnd transmitting satellite transmission power Pr tCan be obtained by looking up a table in an information look-up table.
The method for evaluating the flood after the flood, wherein the steps of 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 specifically comprise:
counting the noise of the part before the peak value of the original DDM image to obtain a statistic value CN；
Calculating to obtain the total gain G of the satellite-borne receiver through the auxiliary information;
according to the statistical value CNAnd the total gain G is calculated to obtain a calibrated power value:
wherein C represents a numerical value in an original DDM image, CNIs the noise statistic, G is the total gain of the satellite-borne receiver, PgIs the calibrated power value;
and calculating the soil humidity sensitive parameter SNR according to the calibrated power value.
And step S40, inverting the soil humidity of the target area, performing threshold processing on the inversion result to obtain a disaster area, and calculating the disaster area.
The method for evaluating flood after disaster, wherein the steps of inverting the soil humidity of a target area, performing threshold processing on the inversion result to obtain a region after disaster and calculating the area of the disaster include:
step S401, combining the spatial resolution and the grid area of the target area to obtain sensitive parameters needing to be averaged;
step S402, substituting the averaged sensitive parameters into a mode function to obtain the soil humidity of the grid area;
step S403, performing threshold processing on the inversion result to obtain a region after disaster and calculating a disaster area.
The post-flood evaluation method for flood comprises the following steps of performing threshold processing on an inversion result to obtain a post-disaster area and calculating a disaster area, and specifically comprises the following steps:
step S4031, performing threshold processing on the inversion result to obtain a soil water content contour line;
step S4032, the contour line data of the soil water content is counted, and the disaster area is calculated.
Step S50, a disaster area evaluation result is generated.
In conclusion, the flood post-disaster assessment method provided by the invention can effectively utilize the advantages of the GNSS-R technology, well solve 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 assessment problem after the disaster, and is suitable for the application of flood, typhoon and other disaster positioning, loss assessment and other problems.
Experimental validation examples
The experiment selects the Guangdong province in China in 2018 as an example, and the soil humidity in the Guangdong province in 2018 in the whole year is inverted by adopting the process flow of the steps of the invention, and the obtained result is shown in figure 2. Then, contour drawing of the soil water content was performed, and the results are shown in fig. 3. The disaster area and the disaster area can be visually seen from the figure, and the city, the county and the corresponding district can be accurately positioned.
The water content of the soil is more than 0.4cm after 12 months all year by adopting threshold value analysis3/cm3Can be obtained all year roundThe influence of flood disasters is received in 10 months and 12 months, and the affected area reaches 2500km2The disaster area is mainly Shenzhen city, and the query of meteorological data shows that 9 month and 11 month Guangdong provinces are respectively influenced by typhoon mangosteen and rabbit, so that a large amount of rainfall in a short time is influenced, a certain flood disaster is caused, and the water content of the soil in the next month is particularly increased sharply.
And (4) experimental conclusion: according to the experimental result table name, the method can well and quickly complete the statistics of the flood disaster affected area and the positioning of the affected area under the condition of only adopting GNSS-R satellite data, and can be suitable for application of typhoon in most coastal areas, flood disaster evaluation in inland areas and the like.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above 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 express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A post-flood evaluation method is characterized by comprising the following steps:
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:
wherein SNR is soil moisture sensitivity parameter, i.e. signal-to-noise ratio, gammarlIs the reflectivity, PgFor calibrated power values, RtsAnd RrsRespectively the distance from the transmitting satellite to the ground mirror reflection point and the distance from the mirror reflection point to the satellite-borne receiver, N is the noise statistic size of the Doppler time delay image, GrFor the magnitude of the gain of the receiving antenna, GtIn order to transmit the satellite transmit antenna gain,
transmitting power for a transmitting satellite;
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.
2. The method for post-flood evaluation according to claim 1, wherein the step of 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 specifically comprises:
counting the noise of the part before the peak value of the original DDM image to obtain a statistic value CN；
Calculating to obtain the total gain G of the satellite-borne receiver through the auxiliary information;
according to the statistical value CNAnd the total gain G is calculated to obtain a calibrated power value:
wherein C represents a numerical value in an original DDM image, CNIs the noise statistic, G is the total gain of the satellite-borne receiver, PgIs the calibrated power value;
and calculating the soil humidity sensitive parameter SNR according to the calibrated power value.
3. The method for post-flood evaluation according to claim 1, wherein the steps of inverting the soil humidity of the target area, performing threshold processing on the inversion result to obtain the post-flood area, and calculating the flood area specifically include:
combining the spatial resolution and the grid area of the target area to obtain sensitive parameters needing to be averaged;
substituting the averaged sensitive parameters into a mode function to obtain the soil humidity of the grid area;
and carrying out threshold processing on the inversion result to obtain a region after disaster damage and calculating the disaster damage area.
4. The flood post-disaster assessment method according to claim 3, wherein said step of performing threshold processing on the inversion result to obtain a disaster-stricken area and calculating a disaster-stricken area specifically comprises:
carrying out threshold processing on the inversion result to obtain a contour line of the water content of the soil;
and (5) carrying out statistics on contour line data of the water content of the soil, and calculating the disaster area.
5. The flood post-disaster assessment method according to claim 1, wherein the step of obtaining a 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 comprises:
determining a time range in which disaster assessment is required;
separating the DDM image acquired by the satellite-borne receiver and corresponding auxiliary information to obtain attribute information corresponding to the original DDM image one by one;
and calculating the position of a specular reflection point of the target area corresponding to the original DDM image.
6. The post-flood evaluation method according to claim 5, wherein after the step of separating the DDM image acquired by the satellite-borne receiver and the corresponding auxiliary information to obtain the attribute information corresponding to the original DDM image one to one, the evaluation method further comprises:
drawing an information query table according to the attribute information;
respectively inquiring the gain G of the receiving antenna according to the information inquiry tablerGain G of transmitting satellite transmitting antennatTransmitting satellite transmission power
The value of (c).
7. The flood post-disaster assessment method according to claim 5, wherein the step of calculating the position of the specular reflection point of the target area corresponding to the original DDM image specifically comprises:
acquiring the coordinate position of the satellite-borne receiver in an ECEF coordinate system;
acquiring the coordinate position of the launching satellite in an ECEF coordinate system;
and calculating to obtain the position of a mirror reflection point of the original DDM image corresponding to the target area by taking the coordinate positions of the satellite-borne receiver and the transmitting satellite as input.
8. The post-flood assessment method according to claim 7, wherein the coordinate position of said satellite based receiver is obtained by means of satellite information.
9. The post-flood evaluation method according to claim 7, wherein the step of obtaining the coordinate position of the launch satellite in the ECEF coordinate system specifically comprises:
acquiring GNSS satellite signals of the DDM image corresponding to the corresponding moment;
and acquiring the coordinate position of the transmitting satellite in a preset coordinate system by transmitting the satellite ephemeris according to the GNSS satellite signal.
10. The method according to claim 1 or 7, wherein the step of calculating spatial resolutions between the specular reflection point, the transmitting satellite and the satellite-borne receiver and performing threshold division by the spatial resolutions to determine the mesh size of the final evaluation product comprises:
calculating the height of the satellite-borne receiver and the satellite elevation angle of the transmitting satellite at the mirror reflection point;
and calculating the spatial resolution according to the size of the electromagnetic wave wavelength entering the first Fresnel zone of the emission satellite:
wherein a is transverse resolution, b is longitudinal resolution, lambda is the electromagnetic wave wavelength of the transmitting satellite, h is the height of the satellite-borne receiver, and theta is the satellite elevation angle of the transmitting satellite at the mirror reflection point;
thresholding is performed by spatial resolution to determine the mesh size of the final evaluation product.
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