CN113420424A - Method for calculating cross-rail and along-rail spatial resolution of GNSS-R mirror reflection point - Google Patents

Method for calculating cross-rail and along-rail spatial resolution of GNSS-R mirror reflection point Download PDF

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CN113420424A
CN113420424A CN202110619742.2A CN202110619742A CN113420424A CN 113420424 A CN113420424 A CN 113420424A CN 202110619742 A CN202110619742 A CN 202110619742A CN 113420424 A CN113420424 A CN 113420424A
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CN113420424B (en
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夏俊明
孙越强
白伟华
杜起飞
王先毅
尹聪
黄飞雄
孟祥广
柳聪亮
胡鹏
刘黎军
蔡跃荣
李伟
曹光伟
吴春俊
刘成
李福�
乔颢
程双双
张璐璐
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National Space Science Center of CAS
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Abstract

The invention discloses a method for calculating the spatial resolution of a GNSS-R mirror reflection point in the cross-rail direction and the along-rail direction, which comprises the following steps: calculating a ambiguity function value of a space area around the specular reflection point by taking the time delay and the Doppler value at the GNSS-R specular reflection point as reference values; calculating an effective scattering area of the specular reflection point by adopting a threshold value method according to the ambiguity function value; the effective scattering area of the specular reflection point is equivalent to an ellipse with the center at the specular reflection point; calculating an equation of two tangent lines which are parallel to the movement speed direction of the mirror reflection point and tangent to the ellipse; calculating the cross-rail spatial resolution at the specular reflection point according to the equation of the two tangent lines; equating the ellipse to a parallelogram with equal area, and calculating the length of the bottom side of the parallelogram; and calculating the product of the movement speed and the incoherent integration time of the specular reflection point, and calculating to obtain the axial spatial resolution of the GNSS-R specular reflection point according to the size relation between the product and the side length of the bottom edge of the parallelogram.

Description

Method for calculating cross-rail and along-rail spatial resolution of GNSS-R mirror reflection point
Technical Field
The invention relates to the technical field of GNSS reflected signal remote sensing, in particular to a method for calculating the spatial resolution of a GNSS-R mirror reflection point in the cross-rail direction and the along-rail direction.
Background
Since the 90 s of the 20 th century, the GNSS-R technology (Global Navigation Satellite Systems reflection) has gradually developed into a new type of remote sensing technology. The technology can be applied to remote sensing detection in the fields of sea surface wind fields, sea surface height, sea surface effective wave height, sea ice coverage, sea ice density, soil humidity and the like by simultaneously receiving direct signals and ground reflection signals transmitted by GNSS satellites, and has the advantages of rich signal sources, all-weather and the like.
The GNSS-R technology belongs to a bistatic radar remote sensing mode, a space-based GNSS-R bistatic radar remote sensing is formed by a GNSS satellite, a ground surface reflecting surface and a Low Earth Orbit satellite (LEO) receiver, and as the ground surface reflecting surface is usually rough, a GNSS ground reflecting signal received by the LEO satellite is essentially a series of multipath signals reflected by a large ground area around a mirror reflecting point. The spatial resolution at the specular reflection point is closely related to various factors such as the height of the receiver, the velocity, the incoherent integration time, the incidence angle and the azimuth angle of the GNSS satellite. At present, the calculation of the spatial resolution of the GNSS-R specular reflection point generally equates the effective observation area to a square, and the side length of the square represents the size of the spatial resolution. Because the reflected signals received by the GNSS-R satellite may appear in different azimuth directions, the effective observation area of the GNSS-R specular reflection point is actually closer to the four parallel sides, and if the current calculation method of the GNSS-R spatial resolution of the equivalent square is adopted, the influence of the azimuth angle of the GNSS satellite on the spatial resolution of the observation quantity of the specular reflection point cannot be accurately reflected.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for calculating the spatial resolution of a GNSS-R mirror reflection point in the cross-rail direction and the along-rail direction.
In order to achieve the above object, the present invention provides a method for calculating the cross-rail and along-rail spatial resolution of a GNSS-R specular reflection point, the method comprising:
calculating a ambiguity function value of a space area around the specular reflection point by taking the time delay and the Doppler value at the GNSS-R specular reflection point as reference values;
calculating an effective scattering area of the specular reflection point by adopting a threshold value method according to the ambiguity function value;
the effective scattering area of the specular reflection point is equivalent to an ellipse with the center at the specular reflection point;
calculating an equation of two tangent lines which are parallel to the movement speed direction of the mirror reflection point and tangent to the ellipse;
calculating the cross-rail spatial resolution at the specular reflection point according to the equation of the two tangent lines;
equating the ellipse to a parallelogram with equal area, and calculating the length of the bottom side of the parallelogram;
and calculating the product of the movement speed and the incoherent integration time of the specular reflection point, and calculating to obtain the axial spatial resolution of the GNSS-R specular reflection point according to the size relation between the product and the side length of the bottom edge of the parallelogram.
As an improvement of the above method, the ambiguity function value of the spatial region around the specular reflection point is calculated by taking the time delay and the doppler value at the GNSS-R specular reflection point as reference values; the method specifically comprises the following steps:
by time delay tau at GNSS-R mirror reflection pointrefAnd Doppler value frefCalculating the ambiguity function value WAF of the space area around the GNSS-R mirror reflection point as a reference value as follows:
WAF(τ-τref，f-fref)＝Λ2(τ-τref)S2(f-fref)
wherein, f represents the Doppler frequency of the reflection signal of any reflection point, tau represents the propagation delay of the reflection signal of any reflection point, and Λ and S are respectively the autocorrelation function and Doppler filtering Sinc function of the pseudo random code adopted by the GNSS-R:
Figure BDA0003099072830000021
wherein, TiIs the receiver coherent integration time.
As an improvement of the above method, the effective scattering area of the specular reflection point is calculated by using a threshold method according to the ambiguity function value; the method specifically comprises the following steps:
taking the maximum ambiguity function value WAF from the ambiguity function values WAFmax；
Using a threshold method, will be greater than WAFmaxThe spatial region of/2 is defined as the effective observation region of the specular reflection point.
As an improvement of the above method, the effective scattering area of the specular reflection point is equivalent to an ellipse centered at the specular reflection point; the method specifically comprises the following steps:
and (3) equating the effective observation area of the GNSS-R mirror reflection point to be an ellipse centered at the GNSS-R mirror reflection point, wherein any point (x, y) of the ellipse satisfies the following formula:
Figure BDA0003099072830000022
wherein a is an ellipse major semiaxis which is equal to the maximum distance between any two points on the boundary of the effective scattering area; b is an ellipse minor semi-axis which is equal to the minimum distance between any two points on the boundary of the effective scattering area, alpha is the included angle between the ellipse major axis and the X axis, and theta is the included angle between the connecting line between the point (X, y) and the origin and the X axis.
As an improvement of the above method, the equation of two tangent lines parallel to the moving speed direction of the specular reflection point and tangent to the ellipse is calculated; the method specifically comprises the following steps:
velocity of motion V at specular reflection pointspWhen the direction is not parallel to the Y axis:
two tangent lines y1，y2Satisfies the following formula:
Figure BDA0003099072830000036
wherein the slopes of the two tangent lines are both k, and k is equal to the velocity V at the specular reflection pointspSlope of the vector, c1And c2The intercept of the two tangent lines respectively satisfies the following formula:
Figure BDA0003099072830000031
wherein, the parameter values at two tangent points of the two tangents to the ellipse are respectively theta and theta + pi, and the parameter value theta is:
Figure BDA0003099072830000032
velocity of motion V at specular reflection pointspWhen the direction is parallel to the Y axis:
two tangent lines x1，x2Satisfies the following formula:
Figure BDA0003099072830000037
c3and c4The intercept of the two tangent lines respectively satisfies the following formula:
Figure BDA0003099072830000033
wherein, the parameter values at two tangent points of the two tangents to the ellipse are respectively theta and theta + pi, and the parameter value theta is:
Figure BDA0003099072830000034
as an improvement of the above method, the cross-rail spatial resolution at the specular reflection point is calculated according to an equation of two tangent lines; the method specifically comprises the following steps:
velocity of motion V at specular reflection pointspWhen the direction is not parallel to the Y axis, the cross-rail spatial resolution R at the specular reflection point is obtained by two tangent linescrossComprises the following steps:
Figure BDA0003099072830000035
velocity of motion V at specular reflection pointspWhen the direction is parallel to the Y axis, the cross-track spatial resolution R at the mirror reflection point is obtained by two tangent linescrossComprises the following steps:
Rcross＝|c3-c4|。
as an improvement of the above method, the ellipse is equivalent to a parallelogram with equal area, and the length of the bottom side of the parallelogram is calculated; the method specifically comprises the following steps:
equating the ellipse to a parallelogram with an equal area, a center coinciding with the specular reflection point and a bottom side parallel to the speed direction of the specular reflection point, wherein the length L of the bottom side of the parallelogram is as follows:
Figure BDA0003099072830000041
as an improvement of the above method, the product of the movement speed of the specular reflection point and the incoherent integration time is calculated, and the spatial resolution of the GNSS-R specular reflection point along the axial direction is calculated according to the magnitude relation between the product and the side length of the bottom side of the parallelogram; the method specifically comprises the following steps:
according to the movement velocity V of the mirror reflection pointspProduct V of the sum of the incoherent integration time TspT and the size relation between the T and the length L of the bottom edge of the parallelogram to obtain the spatial resolution R of the GNSS-R specular reflection point in the cross-rail direction and the along-rail directionparallelComprises the following steps:
Figure BDA0003099072830000042
compared with the prior art, the invention has the advantages that:
1. according to the method, the GNSS-R mirror reflection point elliptic effective scattering area is equivalent to a parallelogram model with the same area, the center of the parallelogram model is coincided with the mirror reflection point, and the bottom edge of the parallelogram model is parallel to the movement speed direction of the mirror reflection point, and a technical scheme for calculating the cross-rail and along-rail spatial resolution of the GNSS-R mirror reflection point based on the equivalent parallelogram model is provided;
2. according to the invention, the cross-rail direction and the along-rail direction spatial resolution of the GNSS-R mirror reflection point under different threshold values can be obtained by calculating through modifying the size of the ambiguity function value threshold value defined by the GNSS-R mirror reflection point effective observation area;
3. according to the technical scheme, the elliptic effective scattering area of the GNSS-R mirror reflection point is equivalent to a parallelogram model, and the spatial resolution of the mirror reflection point is described by using the two-dimensional spatial resolution along the orbit direction and the cross orbit direction at the GNSS-R mirror reflection point, so that the influence of the GNSS satellite azimuth on the spatial resolution at the GNSS-R mirror reflection point can be reflected more accurately.
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FIG. 1 is a flow chart of a method for calculating the cross-track and along-track spatial resolution of GNSS-R specular reflection points in accordance with the present invention;
FIG. 2 is a graph of an ambiguity function distribution for a spatial region around a GNSS-R specular reflection point;
FIG. 3 is an elliptical effective observation area of GNSS-R specular reflection points and its major and minor axes;
FIG. 4 shows two tangents of the GNSS-R specular reflection point elliptical effective observation area parallel to the direction of the velocity of movement of the specular reflection point and the distance between the tangents;
FIG. 5 is an equivalent parallelogram and bottom edge of an elliptical effective observation area of GNSS-R specular reflection points;
FIG. 6 is the along-track and cross-track spatial resolution when the GNSS-R specular reflection point velocity of motion multiplied by the incoherent integration time is less than the length of the parallelogram base;
FIG. 7 is an along-track and cross-track spatial resolution when the GNSS-R specular reflection point velocity of motion multiplied by the incoherent integration time is greater than the length of the parallelogram base.
Detailed Description
The invention provides a new technology for calculating the spatial resolution of a GNSS-R in the cross-rail direction and the along-rail direction by adopting a parallelogram equivalent approximate model. The concrete description is as follows:
(1) utilizing time delay tau at GNSS-R mirror reflection pointrefAnd Doppler value JrefAnd calculating the ambiguity function value WAF of the space area around the GNSS-R mirror reflection point as a reference value.
The ambiguity function WAF of the GNSS-R describes the magnitude of the contribution of different reflection surface elements to the reference point receiver observations within the spatial area of the reflection surface. The mathematical expression of the ambiguity function of GNSS-R is:
WAF(τ-τref，f-fref)＝Λ2(τ-τref)S2(f-fref) (1)
in the formula, f represents the Doppler frequency of a reflection signal of any reflection point, tau represents the propagation delay of the reflection signal of any reflection point, and Λ and S are respectively the autocorrelation function and Doppler filtering Sinc function of a pseudo random code adopted by the GNSS-R. The Sinc function of the doppler filter, related to the receiver coherent integration time Ti:
Figure BDA0003099072830000051
(2) and calculating the effective scattering area of the specular reflection point according to the value of the WAF by adopting a threshold value method. In all reflective surface elements, the contribution will be greater than the WAFmaxThe space area of/2 is defined as the effective observation area of the GNSS-R mirror reflection point, wherein, WAFmaxThe maximum ambiguity function value.
(3) And (3) enabling the effective scattering area at the specular reflection point to be equivalent to an ellipse with the center at the specular reflection point, wherein the size of the long axis of the ellipse is equal to the maximum value of the distance between any two points on the boundary of the effective scattering area, and the size of the short axis of the ellipse is equal to the minimum value of the distance between any two points on the boundary of the effective scattering area.
The parametric equation of the ellipse is that,
Figure BDA0003099072830000052
in the formula, X and Y are coordinates of an X axis and a Y axis corresponding to any point of the ellipse, a is the size of a major semi-axis of the ellipse, b is the size of a minor semi-axis of the ellipse, alpha is an included angle between the major axis of the ellipse and the X axis, and theta is an included angle between a connecting line between any point and an origin of the ellipse and the X axis.
(4) And calculating tangent equations of two tangents which are parallel to the movement speed direction of the mirror reflection point and tangent to the ellipse.
Let the slope of the tangent be k, k being equal to the velocity V at the specular reflection pointspThe slope of the vector. The parameter values at two tangent points of the tangent line tangent to the ellipse are respectively theta and theta + pi, and the calculation formula of the parameter value theta is
Figure BDA0003099072830000061
a. Velocity of motion V at specular reflection pointspWhen the direction is not parallel to the Y axis
Substituting theta and theta + pi into the parameter equation to obtain two tangent equations
Figure BDA0003099072830000066
c1And c2Respectively, are as follows,
Figure BDA0003099072830000062
b. velocity V at specular reflection pointspWhen the direction is parallel to the Y axis
After substituting theta and theta + pi into the parameter equation, two tangent equations can be obtained
Figure BDA0003099072830000067
c3And c4Respectively, are as follows,
Figure BDA0003099072830000063
(5) calculating the distance between the two tangent line equations, wherein the distance is the cross-rail spatial resolution at the GNSS-R mirror reflection point;
Figure BDA0003099072830000064
(6) equating the ellipse to a parallelogram with equal area, the center coinciding with the mirror reflection point and the bottom side parallel to the speed direction of the mirror reflection point, and calculating the bottom side length L of the parallelogram;
Figure BDA0003099072830000065
(7) according to the movement velocity V of the mirror reflection pointspProduct of non-coherent integration time TspT, and the size relation between the length L of the bottom edge of the parallelogram, and calculating the along-track spatial resolution R of the GNSS-R mirror reflection pointpatallel，
Figure BDA0003099072830000071
The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and examples.
Example 1
As shown in fig. 1, an embodiment 1 of the present invention provides a method for calculating the cross-track and along-track spatial resolutions of GNSS-R specular reflection points. The method comprises the following specific steps:
(1) using the formula (1) and (2)Calculating the time delay tau of the specular reflection pointrefAnd Doppler value frefFor reference values, the ambiguity function values WAF for the spatial region around the GNSS-R specular reflection point are calculated, as shown in fig. 2.
(2) Calculating the effective scattering area of the specular reflection point according to the value of WAF by using threshold method, wherein the contribution of all the reflection surface elements is larger than the WAFmaxThe/2 space area is an effective observation area corresponding to the GNSS-R product, wherein the WAFmaxThe effective observation area of the GNSS-R specular reflection point ellipse for the maximum ambiguity function value is shown as the area inside the bold ellipse in FIG. 3.
(3) And (3) enabling the effective scattering area at the specular reflection point to be equivalent to an ellipse with the center at the specular reflection point, wherein the size of the long axis of the ellipse is equal to the maximum value of the distance between any two points on the boundary of the effective scattering area, and the size of the short axis of the ellipse is equal to the minimum value of the distance between any two points on the boundary of the effective scattering area. The major axis and the minor axis of the GNSS-R mirror reflection point ellipse are shown as the bold line segment in FIG. 3.
(4) Two tangent equations parallel to the moving speed direction of the specular reflection point and tangent to the ellipse are calculated by using equations (3) to (8). Two tangent lines of the GNSS-R mirror reflection point elliptic effective observation area, which are parallel to the movement speed direction of the mirror reflection point, are shown as two parallel dotted lines in FIG. 4.
(5) Calculating the distance between the two tangent line equations by using a formula (9), wherein the distance is the cross-rail spatial resolution at the GNSS-R specular reflection point; the distance between two tangent lines of the GNSS-R specular reflection point elliptical effective observation area parallel to the movement speed direction of the specular reflection point is shown by a double arrow between two parallel dotted lines in FIG. 4.
(6) The ellipse is equivalent to a parallelogram with equal area, the center coinciding with the mirror reflection point and the bottom side parallel to the speed direction of the mirror reflection point, and the bottom side length of the parallelogram is calculated according to the formula (10). The equivalent parallelogram and the length of the bottom side of the GNSS-R mirror reflection point elliptic effective observation area are shown in FIG. 5.
(7) According to the movement velocity V of the mirror reflection pointspProduct of non-coherent integration time TspAnd T, the size relation between the T and the length L of the bottom edge of the parallelogram, and calculating the along-track spatial resolution of the GNSS-R specular reflection point according to the formula (11).
The spatial resolution along and across the rail direction when the GNSS-R specular reflection point motion velocity multiplied by the incoherent integration time is less than the length of the bottom side of the parallelogram, as indicated by the double-arrow line segment in FIG. 6.
The spatial resolution along and across the rail direction when the GNSS-R specular reflection point motion velocity multiplied by the incoherent integration time is greater than the length of the bottom side of the parallelogram, as indicated by the double-arrow line segment in FIG. 7.
The scheme comprises the following technical characteristics:
an effective observation region of the GNSS-R specular reflection point defined as a region 1/2 in which a ambiguity function value is greater than a maximum ambiguity function value in a scattering region with the specular reflection point as a reference point;
the boundary of the effective observation area of the GNSS-R specular reflection point is approximate to an ellipse of which the center is superposed with the specular reflection point, the size of the long axis of the ellipse is equal to the maximum value of the distance between any two points on the boundary of the effective scattering area, and the size of the short axis of the ellipse is equal to the minimum value of the distance between any two points on the boundary of the effective scattering area;
a GNSS-R mirror reflection point effective observation area is equivalent to a parallelogram with an equal area, a center superposed with the mirror reflection point and a bottom side parallel to the movement speed direction of the mirror reflection point;
4, the calculation formula of the cross-rail spatial resolution of the GNSS-R mirror reflection point is a formula (9);
the calculation formula of the GNSS-R specular reflection point along-the-axis spatial resolution is formula (11).
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (8)

1. A method of computing a GNSS-R specular reflection point cross-rail to along-rail spatial resolution, the method comprising:
calculating a ambiguity function value of a space area around the specular reflection point by taking the time delay and the Doppler value at the GNSS-R specular reflection point as reference values;
calculating an effective scattering area of the specular reflection point by adopting a threshold value method according to the ambiguity function value;
the effective scattering area of the specular reflection point is equivalent to an ellipse with the center at the specular reflection point;
calculating an equation of two tangent lines which are parallel to the movement speed direction of the mirror reflection point and tangent to the ellipse;
calculating the cross-rail spatial resolution at the specular reflection point according to the equation of the two tangent lines;
equating the ellipse to a parallelogram with equal area, and calculating the length of the bottom side of the parallelogram;
and calculating the product of the movement speed and the incoherent integration time of the specular reflection point, and calculating to obtain the axial spatial resolution of the GNSS-R specular reflection point according to the size relation between the product and the side length of the bottom edge of the parallelogram.
2. The method for calculating the spatial resolution of a GNSS-R specular reflection point along and along an orbit of claim 1, wherein the ambiguity function value of a spatial region around the specular reflection point is calculated using the time delay and doppler values at the GNSS-R specular reflection point as reference values; the method specifically comprises the following steps:
by time delay tau at GNSS-R mirror reflection pointrefAnd Doppler value frefCalculating the ambiguity function value WAF of the space area around the GNSS-R mirror reflection point as a reference value as follows:
WAF(τ-τref,f-fref)＝Λ2(τ-τref)S2(f-fref)
wherein, f represents the Doppler frequency of the reflection signal of any reflection point, tau represents the propagation delay of the reflection signal of any reflection point, and Λ and S are respectively the autocorrelation function and Doppler filtering Sinc function of the pseudo random code adopted by the GNSS-R:
Figure FDA0003099072820000011
wherein, TiIs the receiver coherent integration time.
3. The method for calculating the spatial resolution of GNSS-R specular reflection points along and along the rail of claim 2, wherein the effective scattering area of the specular reflection points is calculated by using a threshold method according to the ambiguity function values; the method specifically comprises the following steps:
taking the maximum ambiguity function value WAF from the ambiguity function values WAFmax；
Using a threshold method, will be greater than WAFmaxThe spatial region of/2 is defined as the effective observation region of the specular reflection point.
4. The method of claim 3, wherein the effective scattering area of the specular reflection point is equivalent to an ellipse centered at the specular reflection point; the method specifically comprises the following steps:
and (3) equating the effective observation area of the GNSS-R mirror reflection point to be an ellipse centered at the GNSS-R mirror reflection point, wherein any point (x, y) of the ellipse satisfies the following formula:
Figure FDA0003099072820000021
wherein a is an ellipse major semiaxis which is equal to the maximum distance between any two points on the boundary of the effective scattering area; b is an ellipse minor semi-axis which is equal to the minimum distance between any two points on the boundary of the effective scattering area, alpha is the included angle between the ellipse major axis and the X axis, and theta is the included angle between the connecting line between the point (X, y) and the origin and the X axis.
5. The method for calculating the GNSS-R specular reflection point's cross-track and along-track spatial resolution of claim 4, wherein the method calculates the equation of two tangent lines parallel to the velocity direction of the movement of the specular reflection point and tangent to the ellipse; the method specifically comprises the following steps:
velocity of motion V at specular reflection pointspWhen the direction is not parallel to the Y axis:
two tangent lines y1，y2Satisfies the following formula:
Figure FDA0003099072820000022
wherein, the slopes of the two tangent lines are both k, and k is equal to the motion speed V at the mirror reflection pointspSlope of the vector, c1And c2The intercept of the two tangent lines respectively satisfies the following formula:
Figure FDA0003099072820000023
wherein, the parameter values at two tangent points of the two tangents to the ellipse are respectively theta and theta + pi, and the parameter value theta is:
Figure FDA0003099072820000024
velocity of motion V at specular reflection pointspWhen the direction is parallel to the Y axis:
two tangent lines x1，x2Satisfies the following formula:
Figure FDA0003099072820000025
c3and c4The intercept of the two tangent lines respectively satisfies the following formula:
Figure FDA0003099072820000026
wherein, the parameter values at two tangent points of the two tangents to the ellipse are respectively theta and theta + pi, and the parameter value theta is:
Figure FDA0003099072820000027
6. the method for calculating the cross-rail and along-rail spatial resolution of GNSS-R specular reflection points of claim 5, wherein the cross-rail spatial resolution at the specular reflection points is calculated according to the equation of two tangent lines; the method specifically comprises the following steps:
velocity of motion V at specular reflection pointspWhen the direction is not parallel to the Y axis, the cross-rail spatial resolution R at the specular reflection point is obtained by two tangent linescrossComprises the following steps:
Figure FDA0003099072820000031
velocity of motion V at specular reflection pointspWhen the direction is parallel to the Y axis, the cross-track spatial resolution R at the mirror reflection point is obtained by two tangent linescrossComprises the following steps:
Rcross＝|c3-c4|。
7. the method for calculating the GNSS-R specular reflection point cross-track and along-track spatial resolution of claim 6, wherein the ellipse is equivalent to a parallelogram with equal area, and the length of the bottom side of the parallelogram is calculated; the method specifically comprises the following steps:
equating the ellipse to a parallelogram with an equal area, a center coinciding with the specular reflection point and a bottom side parallel to the speed direction of the specular reflection point, wherein the length L of the bottom side of the parallelogram is as follows:
Figure FDA0003099072820000032
8. the method for calculating the spatial resolution of the GNSS-R specular reflection point along the axial direction according to claim 7, wherein the product of the movement velocity of the specular reflection point and the incoherent integration time is calculated to obtain the spatial resolution of the GNSS-R specular reflection point along the axial direction according to the size relationship between the product and the length of the bottom side of the parallelogram; the method specifically comprises the following steps:
according to the movement velocity V of the mirror reflection pointspProduct V of the sum of the incoherent integration time TspT and the size relation between the length L of the bottom edge of the parallelogram to obtain the axial spatial resolution R of the GNSS-R mirror reflection point along the trackparallelComprises the following steps:
Figure FDA0003099072820000033
CN202110619742.2A 2021-06-03 2021-06-03 Computing method for cross track direction and along track direction spatial resolution of GNSS-R mirror reflection point Active CN113420424B (en)

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