Maritime monitoring station integrity monitoring method after wide-area correction product broadcasting

Abstract

The invention relates to a method for monitoring the integrity of an offshore monitoring station after wide-area correction product broadcasting. The method comprises the following steps: broadcasting the observed quantity of a satellite subjected to differential correction to the offshore monitoring station equipped with an atomic clock by using a satellite communication link; the offshore monitoring station equipped with the atomic clock calculates a pseudo-range residual vector based on a least square method by using the received differently corrected observed quantity; the offshore monitoring station equipped with the atomic clock uses the obtained pseudo-range residual vector to construct detection statistics; the seaborne monitoring station equipped with the atomic clock calculates an inspection threshold of credible monitoring according to a given false alarm rate; the atomic clock equipped offshore monitoring station compares the detection statistics to the test threshold of trusted monitoring to perform integrity monitoring.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation technology, and in particular to a method for monitoring the integrity of a marine monitoring station after a wide-area correction product is broadcast. Background Art

[0002] The Global Navigation Satellite System (GNSS) has powerful functions such as navigation, positioning, and timing. It can provide all-round, all-weather, and all-time navigation and positioning services, covering multiple typical application scenarios such as sea, land, and air. It is widely used in transportation, military, agriculture and other fields, such as vehicle-mounted navigation systems, unmanned driving, intelligent traffic control, and marine intelligent operations.

[0003] The vast ocean is rich in natural resources. As people's development and exploration of the ocean become more and more extensive, the requirements for equipment and technology in marine engineering have become higher. The accuracy and reliability of satellite navigation positioning results are the key to ensuring the normal operation of marine engineering equipment and high-tech ships. Positioning technology based on wide-area differential real-time correction service has become one of the effective methods for navigation and positioning of ships on the ocean with the characteristics of single antenna and low cost. It can provide high-precision positioning results that meet ship navigation. With the expansion of the application of satellite navigation and positioning technology in marine engineering, in applications related to life safety, the reliability of navigation and positioning results has gradually become the primary performance indicator. Marine monitoring stations are of great significance to ensuring the high accuracy and reliability of user positioning results.

[0004] When traditional trusted marine monitoring stations monitor the integrity of the positioning domain after broadcasting, they first obtain a position estimate through the wide-area differential real-time correction service, compare it with their own precisely known position to obtain the error, and compare the error with the preset threshold to evaluate the reliability of the navigation positioning result. However, except for some marine monitoring stations built on islands or fixed-position beacons, due to the complex marine environment, the increase in risk sources that affect positioning accuracy, and the limited signal transmission, most marine monitoring stations cannot obtain the true coordinate information of their own positions. At this time, the accuracy and reliability of the user positioning results obtained cannot be guaranteed.

[0005] Therefore, in order to meet the requirements of high-reliability and high-precision navigation and positioning performance, the offshore monitoring station needs to complete the integrity monitoring and inform the users of the monitoring results without obtaining the real coordinate information of its own position, so as to avoid broadcasting the navigation and positioning results with poor positioning accuracy and reliability to the users. Summary of the invention

[0006] To solve the above problems, the present invention proposes a method for monitoring the integrity of marine monitoring stations after the broadcast of wide-area correction products, comprising the following steps:

[0007] Step S1) using a satellite communication link to broadcast the satellite observations that have been differentially corrected to a marine monitoring station equipped with an atomic clock;

[0008] Step S2) the marine monitoring station equipped with an atomic clock uses the received differentially corrected observations to calculate a pseudorange residual vector based on a least squares method;

[0009] Step S3) The marine monitoring station equipped with an atomic clock uses the obtained pseudorange residual vector to construct a detection statistic;

[0010] Step S4) the marine monitoring station equipped with an atomic clock calculates a verification threshold for reliable monitoring according to a given false alarm rate;

[0011] Step S5) The marine monitoring station equipped with an atomic clock compares the detection statistic obtained in step S3 with the verification threshold of the credible monitoring obtained in step S4 to perform integrity monitoring.

[0012] The beneficial effects of the present invention are:

[0013] In order to solve the technical problem that the accuracy and reliability of user positioning results cannot be guaranteed due to the inability of marine monitoring stations to obtain the true value of their own positions, the present invention proposes a method for monitoring the integrity of marine monitoring stations after the broadcast of wide-area correction products. The marine monitoring station is equipped with an atomic clock, and can perform integrity monitoring on the wide-area correction products in the absence of true coordinate information of the marine monitoring station's own position. Compared with the integrity monitoring method of the positioning domain disclosed in the prior art using a user receiver that is not equipped with an atomic clock, the monitoring method provided by the present invention constructs a chi-square detection statistic with higher fault detection sensitivity, and can still generate highly reliable integrity monitoring information in the absence of the true value of the marine monitoring station's position, thereby assisting marine users in achieving high-precision and highly reliable navigation positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A flow chart of a method for monitoring the integrity of marine monitoring stations after the broadcast of a wide-area correction product provided by the present invention. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] The following are examples and the attached Figure 1, the technical solution of the present invention is further specifically described.

[0017] The present invention provides a method for monitoring the integrity of a marine monitoring station after a GNSS wide-area correction product is broadcast. The method monitors the integrity of a positioning domain after the broadcast, that is, monitors whether the positioning error of a positioning result obtained by a user is within an allowable range.

[0018] The method for monitoring the integrity of marine monitoring stations after the wide-area correction product is broadcast comprises the following steps:

[0019] Step S1) The satellite observations corrected by the differential correction are broadcast to the marine monitoring station equipped with the atomic clock by using the satellite communication link.

[0020] Differential correction of satellite observations can be achieved using existing known methods.

[0021] Step S2) The marine monitoring station equipped with an atomic clock uses the received differentially corrected observations to calculate the pseudorange residual vector based on the least squares method.

[0022] The satellite observations broadcast have been differentially corrected by the wide-area correction product. The measurement equation of the GNSS system is as follows:

[0023] y=Hx+ε (1)

[0024] In formula (1), y represents the n×1 dimensional residual observation, x represents the 4×1 dimensional position vector and clock error, H is the n×4 dimensional observation matrix, which is a linearized matrix consisting of the direction cosine vectors from each satellite to the user receiver and the elements in the 4th column are all 1, ε is the n×1 dimensional measurement error vector, and n is the number of observed satellites.

[0025] According to the least squares estimation criterion, the least squares method is used to estimate and solve equation (1), and the solution obtained is:

[0026]

[0027] In formula (2), represents the position vector and clock error estimated by the least squares method, y represents the residual observation of n×1 dimension, H is the observation matrix of n×4 dimension, n is the number of observed satellites, W is the weighting matrix, the superscript T represents the transposed matrix, and the superscript -1 represents the inverse matrix, for example W -1 is the inverse matrix of W, which is expressed as:

[0028]

[0029] In formula (3), σ iIt represents the standard deviation of the pseudorange error of satellite i, which consists of four error terms: satellite clock error and ephemeris error σ flt , ionospheric delay error σ UDRE , tropospheric delay error σ tropo and the airborne receiver and multipath error σ air , these terms are combined to form σ i , which is expressed as follows:

[0030]

[0031] In formula (4), σ i represents the standard deviation of the pseudorange error of satellite i, σ flt,i represents the satellite clock and ephemeris error of satellite i, σ UDRE,i represents the ionospheric delay error of satellite i, σ tropo,i represents the tropospheric delay error of satellite i, σ air,i represents the onboard receiver and multipath error of satellite i.

[0032] The pseudorange residual vector v is:

[0033]

[0034] In formula (5), v represents the pseudorange residual vector, y represents the n×1-dimensional residual observation, represents the position vector and clock error estimated by the least squares method, H is the n×4-dimensional observation matrix, I n is the n×n unit matrix, n is the number of observed satellites, W is the weighting matrix, the superscript T indicates the transposed matrix, the superscript -1 indicates the inverse matrix, W -1 The matrix form of is shown in equation (3).

[0035] The purpose of calculating the pseudorange residual vector v is to identify and detect faults.

[0036] Step S3) The marine monitoring station equipped with an atomic clock uses the obtained pseudorange residual vector to construct a detection statistic.

[0037] The specific method includes: using the pseudorange residual vector to calculate the pseudorange residual square sum:

[0038] SSE=v T v (6)

[0039] In formula (6), SSE is the sum of squares of pseudorange residuals, v represents the pseudorange residual vector, and the superscript T represents the transpose.

[0040] Usually, when the measurement error vector ε follows a normal distribution, the pseudorange residual sum of squares SSE follows a chi-square distribution with n-4 degrees of freedom (χ 2Distribution), n is the number of observed satellites, and the factors that constrain the degree of freedom include the error components in the three directions of the northeast sky and the clock error. In the field of satellite navigation, the northeast sky includes: east, north, and sky, of which the east and north are horizontal directions, and the sky is a vertical direction.

[0041] In the present invention, an atomic clock is equipped at the marine monitoring station. When the atomic clock is used as the receiver clock, the user clock and the satellite clock are completely consistent, and the influence of the clock error can be completely ignored. In this way, the marine monitoring station can ignore the influence of the clock error by equipping the atomic clock. Therefore, the pseudo-range residual sum of squares SSE constructed by the present invention obeys the χ2 with n-3 degrees of freedom. 2 The distribution removes the clock error term, which can improve the sensitivity of fault detection.

[0042] The method to construct the test statistic is as follows:

[0043]

[0044] In formula (7), T represents the detection statistic, SSE is the sum of squares of pseudorange residuals, and n is the number of observed satellites.

[0045] The prior art monitors the integrity of the positioning domain through user receivers. User receivers are limited by manufacturing costs and volume and cannot be equipped with atomic clocks. Therefore, compared with the prior art that uses user receivers that are not equipped with atomic clocks, the present invention uses an offshore monitoring station equipped with an atomic clock, which can eliminate the adverse effects caused by clock error and has more advantages in estimating the pseudorange residual vector based on the least squares method and constructing detection statistics.

[0046] Step S4) The marine monitoring station equipped with an atomic clock calculates a verification threshold for reliable monitoring according to a given false alarm rate.

[0047] The present invention is to carry out integrity monitoring of the positioning domain, that is, to monitor whether the positioning error of the positioning result obtained by the user is within the allowable range. The positioning error can be divided into vertical positioning error and horizontal positioning error. First, taking the horizontal positioning error as an example, a mutually exclusive hypothesis is established based on whether the expectation of the observation deviation after wide-area difference correction is 0, and the following fault-free hypothesis H is made. 0 and the faulty assumption H 1 :

[0048] No fault assumption H 0 :SSE~χ 2 (n-3)

[0049] There is a fault assumption H 1 :SSE~χ 2 (λ,n-3)

[0050] The assumption is that the observed deviation is 0, which is the fault-free assumption H 0 , when the observed deviation is not 0, there is a fault hypothesis H 1 , λ is the non-centralization parameter, and n is the number of observed satellites.

[0051] It can be seen that when the observed deviation is 0, the pseudorange residual sum of squares SSE obeys the standard chi-square distribution with n-3 degrees of freedom (χ 2 distribution); when the observed deviation is not 0, the pseudorange residual sum of squares SSE follows a non-standard chi-square distribution with n-3 degrees of freedom (χ 2 distribution), there is a non-centrality parameter λ.

[0052] According to the assumptions, when there are no faulty satellites, that is, there is no anomaly in the wide-area correction product, if an alarm message is detected, it is a false alarm (erroneous alarm).

[0053] When the false alarm rate P is given FA When , the detection threshold value t can be determined as follows:

[0054]

[0055] Among them, P r (*) indicates the probability of occurrence of * event, SSE indicates the sum of squares of pseudorange residuals, t is the detection threshold, e is the horizontal protection level, HAL is the horizontal protection limit, and f(x) is the probability density function. represents the probability density function of the chi-square distribution with n-3 degrees of freedom, where x is the independent variable, n is the number of observed satellites, and P FA Indicates the false alarm rate.

[0056] When the false alarm rate P is given FA When the value of is, because the horizontal protection level e is a known value and the horizontal protection limit HAL is a preset value, the detection threshold value t can be obtained through equation (8).

[0057] Based on equation (9), it can be seen that when the sum of squares of pseudorange residuals SSE is greater than the detection threshold t, it indicates that there is a satellite failure or an abnormality in the wide-area correction product.

[0058] The above method is also applicable to the positioning error in the vertical direction. According to whether the expectation of the observation deviation after wide-area difference correction is 0, a mutually exclusive hypothesis is established, and the no-fault hypothesis H is made. 0 and the faulty assumption H 1 ,The method of establishing mutually exclusive hypotheses is the same process as given above, and will not be repeated here.

[0059] When the false alarm rate P is given FA When , the detection threshold value t can be determined as follows:

[0060]

[0061] Among them, P r (*) indicates the probability of occurrence of * event, SSE indicates the sum of squares of pseudorange residuals, t is the detection threshold, e v is the vertical protection level, VAL is the vertical protection limit, f(x) is the probability density function, then represents the probability density function of the chi-square distribution with n-3 degrees of freedom, where x is the independent variable, n is the number of observed satellites, and P FA Indicates the false alarm rate.

[0062] When the false alarm rate P is given FA The vertical protection level is e v is a known value, the vertical protection limit VAL is a preset value, and the detection threshold value t can be obtained through equation (8-2).

[0063] Based on equation (9-2), it can be seen that when the sum of squares of pseudorange residuals SSE is greater than the detection threshold t, it indicates that there is a satellite failure or an abnormality in the wide-area correction product.

[0064] Calculate the verification threshold T for trusted monitoring D The method is:

[0065]

[0066] In formula (10), T D represents the verification threshold of credible monitoring, t is the detection threshold value, and n is the number of observed satellites.

[0067] It should be emphasized here that for vertical positioning error and horizontal positioning error, the given false alarm rate P FA are the same, and the calculated detection threshold value t is also the same, so the calculated reliable monitoring test threshold T D It is consistent in the horizontal and vertical directions.

[0068] At the test threshold T of the trusted monitoring D The chi-square distribution with n-3 degrees of freedom is also applied in the calculation process of . Therefore, compared with the user receiver without atomic clocks disclosed in the prior art, the offshore monitoring station equipped with atomic clocks has a higher accuracy in calculating the test threshold T of reliable monitoring. D It also has more advantages.

[0069] Step S5) The marine monitoring station equipped with an atomic clock compares the detection statistic obtained in step S3 with the verification threshold of the credible monitoring obtained in step S4 to perform integrity monitoring.

[0070] The marine monitoring station equipped with an atomic clock compares the detection statistic T obtained in step 3 with the verification threshold T of the reliable monitoring obtained in step 4. D When the detection statistic T is less than or equal to the test threshold T of reliable monitoring, D When the detection statistic T is greater than the test threshold T of reliable monitoring, it indicates that the current real-time wide-area correction product is normal and the positioning result is available; when ... D The current real-time wide-area correction product is marked as abnormal and the positioning result is unavailable. The marine monitoring station broadcasts the integrity monitoring results of the wide-area correction product to users via communication satellites.

[0071] The above content is a further detailed description of the present invention in combination with specific implementation methods. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as within the scope of protection required by the present invention.

Claims

1. A method for monitoring the integrity of marine monitoring stations after the broadcast of wide-area correction products, comprising: Step S1) using a satellite communication link to broadcast the satellite observations that have been differentially corrected to a marine monitoring station equipped with an atomic clock; Step S2) the marine monitoring station equipped with an atomic clock uses the received differentially corrected observations to calculate a pseudorange residual vector based on a least squares method; Step S3) The marine monitoring station equipped with an atomic clock uses the obtained pseudorange residual vector to construct a detection statistic; Step S4) the marine monitoring station equipped with an atomic clock calculates a verification threshold for reliable monitoring according to a given false alarm rate; Step S5) The marine monitoring station equipped with an atomic clock compares the detection statistic obtained in step S3 with the verification threshold of the credible monitoring obtained in step S4 to perform integrity monitoring.

2. The method for monitoring the integrity of marine monitoring stations after the wide-area correction product is broadcast according to claim 1, wherein in step S2, the method for calculating the pseudorange residual vector is: Where v represents the pseudorange residual vector, y represents the n×1 dimensional residual observation, represents the position vector and clock error estimated by the least squares method, H is the n×4-dimensional observation matrix, I n is the n×n identity matrix, n is the number of observed satellites, W is the weighting matrix, W -1 is the inverse matrix of W, which is expressed as: where σ i represents the standard deviation of the pseudorange error of satellite i, and its expression is as follows: where σ flt,i represents the satellite clock and ephemeris error of satellite i, σ UDRE,i represents the ionospheric delay error of satellite i, σ tropo,i represents the tropospheric delay error of satellite i, σ air,i represents the onboard receiver and multipath error of satellite i.

3. The method for monitoring the integrity of marine monitoring stations after the broadcast of wide-area correction products according to claim 2, wherein in step S3, the method for constructing the detection statistic comprises the following steps: First, use the pseudorange residual vector to calculate the pseudorange residual sum of squares: SSE = v T v, Where SSE is the sum of squares of pseudorange residuals, and v represents the pseudorange residual vector; Next, construct the test statistic: Where T is the detection statistic, SSE is the sum of squares of pseudorange residuals, and n is the number of observed satellites.

4. The method for monitoring the integrity of marine monitoring stations after the broadcast of wide-area correction products according to claim 1, wherein in step S4, the method for calculating the verification threshold of credible monitoring is: Where T D represents the verification threshold of credible monitoring, t is the detection threshold value, and n is the number of observed satellites; The method for obtaining the detection threshold value t is as follows: Where P r (*) indicates the probability of occurrence of * event, SSE indicates the sum of squares of pseudorange residuals, t indicates the detection threshold, e indicates the horizontal protection level, HAL indicates the horizontal protection limit, and e v is the vertical protection level, VAL is the vertical protection limit, represents the probability density function of the chi-square distribution with n-3 degrees of freedom, where n is the number of observed satellites, P FA Indicates the false alarm rate.

5. According to the method for monitoring the integrity of marine monitoring stations after the broadcast of wide-area correction products as described in claim 1, wherein in step S5, during the process of performing integrity monitoring, when the detection statistic is less than or equal to the inspection threshold of credible monitoring, it is marked that the current real-time wide-area correction product is normal and the positioning result is available; when the detection statistic is greater than the inspection threshold of credible monitoring, it is marked that the current real-time wide-area correction product is abnormal and the positioning result is unavailable.

6. According to the method for monitoring the integrity of marine monitoring stations after the broadcast of wide-area correction products as described in claim 1, in step S5, the marine monitoring station equipped with an atomic clock broadcasts the monitoring results of the integrity of the wide-area correction products to users via communication satellites.

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