CN117538909A - Inertial navigation assisted Beidou III isomerism constellation stepwise satellite selection method - Google Patents
Inertial navigation assisted Beidou III isomerism constellation stepwise satellite selection method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
- G01S19/28—Satellite selection
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
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Abstract
The invention discloses an inertial navigation-assisted Beidou III isomerism constellation step-by-step star selection method, which comprises the following steps of: step 1, primarily screening Beidou III satellites based on evaluation indexes of satellite observation data quality; step 2, selecting and determining 4 basic satellites with highest priority based on the principle of optimal geometric configuration of satellites; and 3, determining the priority of the remaining satellites from the remaining satellite sets according to the PDOP value contribution degree. The method comprehensively considers the influence of the Beidou heterogeneous constellation characteristics, the observed data quality and the satellite geometric configuration on the positioning result, rapidly and accurately sorts the priorities of all the visible satellites by utilizing the characteristic of short-time accuracy of inertial navigation, selects a certain number of satellites according to the priorities to participate in navigation positioning calculation, and improves the calculation efficiency while not affecting the navigation positioning performance; the step-by-step satellite selection algorithm provided by the invention does not need to fix the number of satellites in advance, and solves the defect that the traditional satellite selection algorithm needs to fix the number of satellites.
Description
Technical Field
The invention relates to the technical field of satellite navigation and positioning, in particular to a step-by-step star selection method for a Beidou III isomerism constellation assisted by inertial navigation.
Background
With the overall operation of the Beidou satellite navigation system, the number of in-orbit satellites of the global satellite navigation system is hundreds, and the number of visible satellites is increased, so that the geometric configuration of the satellites can be improved, the positioning accuracy is improved, and the risk of more abnormal observables is increased. In addition, for the strapdown inertial navigation/satellite integrated navigation system, the original observed quantity such as the pseudo range, the pseudo range rate and the like sent by the satellite receiver board card is generally received through a serial port, and only a certain number of satellite observed quantities can be transmitted due to the limitation of the transmission capacity of hardware equipment. Because the satellite positioning precision obeys the barrel effect, when abnormal observation exists in the satellite observation quantity, the satellite positioning precision is not obviously improved even though more visible satellites exist, even the phenomenon of no ascending and descending can occur, and in order to ensure that the satellite observation quantity participating in positioning can calculate the optimal positioning result, the efficient satellite selection algorithm is necessary to be researched. The traditional satellite selection algorithm mainly considers the elevation angle, the azimuth angle and the maximum volume of tetrahedra, and often adopts a traversal algorithm, and along with the increase of the number of visible satellites, the operation amount is rapidly increased, and the real-time performance of navigation is seriously affected. In recent years, many scholars have combined artificial intelligence with satellite selection algorithms to propose various intelligent satellite selection schemes, but these schemes often have high performance requirements on the equipment or unique requirements on the quality and number of initial samples. Therefore, it is highly desirable to provide an efficient and practical fast star selection method.
Disclosure of Invention
The invention aims to solve the technical problem of providing an inertial navigation-assisted Beidou III isomerism constellation step-by-step satellite selection method, which can solve the problems of poor instantaneity and fixed satellite number in the traditional satellite selection algorithm.
In order to solve the technical problems, the invention provides an inertial navigation-assisted Beidou III isomerism constellation step-by-step star selection method, which comprises the following steps:
step 1, primarily screening Beidou III satellites based on evaluation indexes of satellite observation data quality;
step 2, selecting and determining 4 basic satellites with highest priority based on the principle of optimal geometric configuration of satellites;
and 3, determining the priority of the remaining satellites from the remaining satellite sets according to the PDOP value contribution degree.
Preferably, in step 1, the satellite altitude angle, the signal-to-noise ratio and the pseudorange measurement information are adopted as the evaluation index of the satellite observation data quality.
Preferably, the calculation formula of the satellite altitude angle is:
wherein θ is the altitude angle of the satellite, [ ΔeΔnΔu ]] T For satellite observation vector at user position in station center coordinate system, its calculation formula is
Wherein [ DeltaxDeltayDeltaz ]] T Satellite observation vectors of a geocentric earth fixed coordinate system; s is a coordinate transformation matrix; λ is the latitude of the receiver in the geodetic coordinate system; phi is the longitude of the receiver in the geodetic coordinate system.
Preferably, the formula of the signal-to-noise ratio is:
where SNR is the signal-to-noise ratio; p (P) s Is the signal power; p (P) n Is the noise power.
Preferably, the calculation formula of the pseudo-range measurement innovation is as follows:
r i ＝ρ i -ρ INS -c(dt r -dt s )-T-I
in the middle of，r i Measurement information for the ith satellite; ρ i Pseudo-range observables for the ith satellite; dt (dt) r And dt (dt) s The clock difference is respectively the receiver and the satellite clock difference; t and I are tropospheric and ionospheric delays, respectively; ρ INS For the geometrical distance between the satellite and the receiver which is reversely calculated by the position of the inertial navigation recursion, the calculation formula is as follows:
in (x) I ,y I ,z I ) A receiver position calculated for the inertial navigation recursion; (x) s ,y s ,z s ) Is the satellite position.
Preferably, in step 1, the preliminary screening of the beidou III satellite based on the evaluation index of satellite observation data quality specifically includes: setting a satellite cut-off height angle and a minimum signal to noise ratio threshold value, and eliminating observation satellites lower than the cut-off height angle and the minimum signal to noise ratio; and constructing a normal step-by-step inspection model by using the pseudo-range measurement information, and detecting and eliminating abnormal observations possibly existing in the observed quantity.
Preferably, the detection and elimination of abnormal observations possibly existing in the observed quantity by using the measurement information are specifically as follows:
first, an assumption test is constructed as follows, to detect whether an observed quantity has an abnormality
H 0 :s＜T,H 1 :s＞T
Wherein H is 0 For the original assumption, it means that no abnormal observed quantity exists, H 1 For alternative hypothesis, it indicates that there is abnormal observed quantity, s is test statistic, and T is test threshold;
the test statistic is constructed by using the sum of squares of the innovation:
wherein R is an innovation vector, U is an innovation covariance matrix, H is an observation matrix, R is a measurement noise covariance matrix,for the prediction state covariance matrix,/>Unit weight variance factor, χ 2 Representing the chi-square step, m and n are the number of observational quantity and state parameters respectively;
the test threshold T is determined by the false alarm rate and the number of redundant observables, i.e
Wherein P is FA M-n represents the number of redundant observers for false alarm rate;
then, if the alternative assumption H1 is satisfied, the abnormal observed quantity is identified and excluded, and the following detection statistics are adopted
Thought s i The observed quantity corresponding to the maximum value in (i=1..m) is taken as the abnormal observed quantity, and is excluded.
Preferably, in step 2, 4 basic satellites with highest priorities are selected and determined based on the principle of optimal geometric configuration of satellites, and the satellite selection criteria are as follows:
criterion 1: if the candidate satellites are IGSO or MEO satellites, selecting the satellite with the largest altitude angle from the IGSO and MEO satellites as the zenith satellite in the basic satellites, otherwise, selecting the satellite with the largest altitude angle from the MEO satellites as the zenith satellite;
criterion 2: and selecting three bottom satellites, and preferentially selecting among MEO satellites. And selecting a combination with three satellite azimuth intervals closest to 120 degrees from the alternative MEO satellite sets. The method comprises the steps of selecting two satellites with azimuth angles between 0 and 120 degrees, wherein the azimuth angle difference between the two satellites is closest to +/-120 degrees, combining the three satellites to be used as one group in base satellite selection, calculating the difference between the azimuth angle difference between the three satellites and 120 degrees to be used as the difference of the base satellite combination, comparing the difference of all base satellite combinations, and selecting the base satellite combination with the smallest difference as the base satellite combination of a base satellite.
Preferably, in step 3, determining the priorities of the remaining satellites from the remaining satellite sets according to the PDOP value contribution degree specifically includes:
based on the contribution degree of the PDOP value, on the basis of satellite observation quality optimization and basic constellation selection, adding more visible satellites into the basic constellation, reducing the PDOP value and meeting the requirement on positioning accuracy; from the remaining satellite candidate sets, the contribution degree of each satellite to the PDOP value is calculated, and the priorities of the remaining satellites are ranked according to the contribution degree.
Preferably, the calculation method of the contribution degree of the PDOP value is that one satellite is added successively from the rest satellite set on the basis of the basic satellite, the PDOP value after adding 1 satellite is calculated, the priority of the correspondingly added satellite is ordered according to the size of the PDOP value after adding one satellite, and the calculation formula of the PDOP is as follows:
wherein q is 11 、q 22 、q 33 Is a diagonal element of the Q matrix; q is a weight coefficient matrix; h is a geometric matrix.
The beneficial effects of the invention are as follows: the method comprehensively considers the influence of the Beidou heterogeneous constellation characteristics, the observed data quality and the satellite geometric configuration on the positioning result, rapidly and accurately sorts the priorities of all the visible satellites by utilizing the characteristic of short-time accuracy of inertial navigation, selects a certain number of satellites according to the priorities to participate in navigation positioning calculation, and improves the calculation efficiency while not affecting the navigation positioning performance; the step-by-step satellite selection algorithm provided by the invention does not need to fix the number of satellites in advance, and solves the defect that the traditional satellite selection algorithm needs to fix the number of satellites.
Drawings
FIG. 1 is a schematic flow chart of the method of the present invention.
FIG. 2 is a graph of the visible star zenith steps for a test epoch according to the present invention.
FIG. 3 is a schematic diagram of the best geometry tetrahedron method of the present invention for selecting the 4 highest priority basis stars.
Detailed Description
As shown in fig. 1, the inertial navigation-assisted Beidou III isomerism constellation step-by-step star selection method comprises the following steps:
step S1: primarily screening the Beidou III satellite based on the evaluation index of satellite observation data quality;
specifically, the specific steps of carrying out preliminary screening on the Beidou III satellite based on the evaluation index of satellite observation data quality are as follows:
step 1): and screening out visible satellites with the height angle smaller than 5 degrees and the signal to noise ratio larger than 20dB from all the current visible satellites to construct a satellite set to be selected.
Specifically, the specific steps for calculating the altitude angle are as follows:
and converting the coordinates of the receiving station under the geocentric geodetic fixed coordinate system into the coordinates under the geodetic coordinate system, and using an iteration method.
Wherein (phi, lambda, h) is the coordinates of the receiver in the geodetic coordinate system; (x, y, z) is the coordinates of the receiver in the geocentric fixed coordinate system; n is the radius of curvature of the unitary mortise of the reference ellipsoid; e is the ellipsoidal eccentricity; a and b are the long and short radii of the reference ellipsoid. First assume phi 0 Equal to zero, in turn calculate N 1 ,h 1 And phi 1 Then phi is added 1 And carrying out iteration, circulating in the way, setting an iteration ending condition, and ending calculation after reaching the condition if delta H is less than or equal to 0.001m to obtain a final coordinate conversion result.
Converting satellite observation vectors at the user position from a geocentric, geodetic, rectangular coordinate system to a station-centric coordinate system having the user position as an origin:
wherein [ DeltaxDeltayDeltaz ]] T And [ ΔeΔnΔu ]] T Satellite observation vectors at the user's location with the receiver location as the origin of coordinates under the geocentric geodetic fixed coordinate system and under the station-centric coordinate system, respectively; s is a coordinate transformation matrix; λ is the latitude of the receiver in the geodetic coordinate system; phi is the longitude of the receiver in the geodetic coordinate system.
The altitude of the satellite is:
where θ is the altitude of the satellite.
Step 2): and reconstructing pseudo-range and pseudo-range rate by using the position and speed calculated by inertial navigation, and calculating measurement information of each satellite. And detecting whether the observed quantity of each satellite is abnormal or not based on normal step hypothesis test by utilizing the measurement information, and eliminating the satellites which are not tested.
Specifically, the measurement information of the ith satellite can be expressed as:
r i ＝ρ i -ρ INS -c(dt r -dt s )-T-I
wherein r is i Measurement information for the ith satellite; ρ i Pseudo-range observables for the ith satellite; dt (dt) r And dt (dt) s The clock difference is respectively the receiver and the satellite clock difference; t and I are tropospheric and ionospheric delays, respectively; ρ INS For the geometrical distance between satellite and receiver calculated reversely by inertial navigation recursion position, the calculation formula is：
In (x) I ,y I ,z I ) A position calculated for inertial navigation recursion; (x) s ,y s ,z s ) Is the satellite position.
Specifically, the method for primarily screening the Beidou III satellite based on satellite observation data quality evaluation indexes comprises the steps of firstly, setting a satellite cut-off height angle and a minimum signal to noise ratio threshold value, and eliminating observation satellites lower than the cut-off height angle and the minimum signal to noise ratio; then, a normal step-by-step inspection model is constructed by using the pseudo-range measurement information, and abnormal observations possibly existing in the observed quantity are detected and eliminated.
Specifically, the specific method for detecting and eliminating the abnormal observation possibly existing in the observed quantity by using the pseudo-range measurement information comprises the following steps:
the following hypothesis test is constructed to detect whether an observed quantity has an abnormality
H 0 :s＜T,H 1 :s＞T
Wherein H is 0 For the original assumption, it means that no abnormal observed quantity exists, H 1 For the alternative hypothesis, s is the test statistic, and T is the test threshold, indicating that there is an abnormal observed quantity.
Specifically, the test statistic is constructed by using the sum of squares of the innovation:
wherein R is an innovation vector, U is an innovation covariance matrix, H is an observation matrix, R is a measurement noise covariance matrix,for the prediction state covariance matrix,/>Unit weight variance factor, χ 2 The method is characterized in that the method represents the chi-square step, and m and n are the number of observables and state parameters respectively.
The test threshold T is determined by the false alarm rate and the number of redundant observables, i.e
Wherein P is FA For false alarm rate, m-n represents the number of redundant observers, and the false alarm rate can be set as P FA ＝0.01。
Then, if the alternative assumption H1 holds, the abnormal observed quantity is identified and excluded. The following detection statistics are adopted
Thought s i The observed quantity corresponding to the maximum value in (i=1..m) is taken as the abnormal observed quantity, and is excluded.
Step S2: selecting and determining 4 basic satellites with highest priorities based on the principle of optimal geometric configuration of satellites;
specifically, the following criteria are used to select the 4 base satellites with the highest priorities.
Criterion 1: if the candidate satellites are IGSO or MEO satellites, selecting the satellite with the largest altitude angle from the IGSO and MEO satellites as the zenith satellite in the basic satellites, otherwise, selecting the satellite with the largest altitude angle from the MEO satellites as the zenith satellite;
criterion 2: and selecting three bottom satellites, and preferentially selecting among MEO satellites. And selecting a combination with three satellite azimuth intervals closest to 120 degrees from the alternative MEO satellite sets. The satellites with azimuth angles between 0 and 120 degrees are selected from two satellites with azimuth angles closest to +/-120 degrees, and the three satellites are combined to be used as one group in bottom star selection. The difference between the azimuth angle difference between the three satellites and 120 ° is calculated as the difference of the base angle combination. And comparing the difference values of all the bottom star combinations, and selecting the bottom star combination with the smallest difference value as the bottom star combination of the basic satellite.
Step S3: determining the priority of the remaining satellites from the remaining satellite sets according to the PDOP value contribution degree;
specifically, the method for sequencing the priorities of the remaining satellites is to add more visible satellites to a basic constellation based on the contribution degree of the PDOP value on the basis of satellite observation quality optimization and basic constellation selection, so that the PDOP value is reduced, and the requirement on positioning accuracy is met. From the remaining satellite candidate sets, the contribution degree of each satellite to the PDOP value is calculated, and the priorities of the remaining satellites are ranked according to the contribution degree.
Specifically, the calculation formula of PDOP is:
wherein q is 11 、q 22 、q 33 Is a diagonal element of the Q matrix; q is a weight coefficient matrix; h is a geometric matrix.
The embodiment of the invention provides a group of test results of a Beidou III isomerism constellation step-by-step star selection method based on inertial navigation assistance, and static single-point positioning calculation is carried out by adopting two schemes respectively:
scheme 1: inertial navigation assisted Beidou III isomerism constellation step-by-step star selection method;
scheme 2: all-star calculation;
the test was performed using BDS/INS combination sports car data from day 17 of 8 months 2023, observations at 20 minutes 25 seconds epoch time 07. Single point location resolution is performed using Matlab software. The relevant parameters are shown in the following table.
TABLE 1 Star selection experiment parameters
Fig. 2 is a zenith step chart of the visible satellites of the Beidou satellite, wherein the satellite cut-off altitude is set to be 5 degrees, the signal to noise ratio threshold is set to be 20dB, and the number of the visible satellites is 18. Fig. 3 is a diagram of the best geometric tetrahedron method to select the 4 base satellites with the highest priority. Table 2 is the result of prioritizing the remaining satellites based on PDOP value contribution. Table 3 shows the time consumption, PDOP value and three-dimensional positioning error statistics of the inertial navigation assisted beidou III heterogeneous constellation step-by-step satellite selection method and single-point positioning calculation of all satellites.
TABLE 2 prioritization results for remaining satellites
Table 2 single epoch selection 10 post-star positioning solution result statistical analysis table
| Star selecting method | Solution time(s) | PDOP value | Three-dimensional positioning error (m) |
| Scheme one | 0.0310 | 1.815 | 7.77 |
| Scheme II | 0.0725 | 1.396 | 7.17 |
The statistical result shows that the total star calculation amount is larger, the satellite PDOP value is smaller, and the positioning error is basically equivalent to that of the star selection algorithm provided by the invention.
According to the method, the characteristics of high short-time precision of inertial navigation are utilized to perform primary screening on the observation quality of satellites, 4 basic satellites with highest priority are selected by using an optimal geometric tetrahedron method, the problem of poor instantaneity caused by the fact that a traditional satellite selection algorithm needs to traverse is avoided, meanwhile, the priorities of the rest satellites are ordered based on the PDOP contribution degree, and then the optimal satellite selection quantity is added, so that the defect that the traditional satellite selection algorithm needs to fix the quantity of satellites is overcome, and positioning precision is guaranteed.
Claims (10)
1. The inertial navigation assisted Beidou III isomerism constellation step-by-step star selection method is characterized by comprising the following steps of:
step 1, primarily screening Beidou III satellites based on evaluation indexes of satellite observation data quality;
step 2, selecting and determining 4 basic satellites with highest priority based on the principle of optimal geometric configuration of satellites;
and 3, determining the priority of the remaining satellites from the remaining satellite sets according to the PDOP value contribution degree.
2. The inertial navigation assisted Beidou III heterogeneous constellation step-by-step satellite selection method of claim 1, wherein in the step 1, satellite observation data quality evaluation indexes adopt satellite altitude angle, signal-to-noise ratio and pseudo-range measurement information.
3. The inertial navigation-assisted Beidou III isomerism constellation step-by-step satellite selection method of claim 2, wherein a calculation formula of a satellite altitude angle is as follows:
wherein θ is the altitude angle of the satellite, [ ΔeΔnΔu ]] T The calculation formula of the satellite observation vector under the station center coordinate system is as follows
Wherein [ DeltaxDeltayDeltaz ]] T The satellite observation vector is the satellite observation vector of a geocentric geodetic fixed coordinate system, and lambda is the latitude of the receiver under the geodetic coordinate system; phi is the longitude of the receiver in the geodetic coordinate system.
4. The inertial navigation-assisted Beidou III isomerism constellation step-by-step star selection method of claim 2, wherein a signal-to-noise ratio calculation formula is as follows:
where SNR is the signal-to-noise ratio; p (P) s Is the signal power; p (P) n Is the noise power.
5. The inertial navigation assisted Beidou III isomerism constellation step-by-step star selection method of claim 2, wherein a calculation formula of pseudo-range measurement information is as follows:
r i ＝ρ i -ρ INS -c(dt r -dt s )-T-I
wherein r is i Measurement information for the ith satellite; ρ i Pseudo-range observables for the ith satellite; dt (dt) r And dt (dt) s The clock difference is respectively the receiver and the satellite clock difference; t and I are tropospheric and ionospheric delays, respectively; ρ INS For the geometrical distance between the satellite and the receiver which is reversely calculated by the position of the inertial navigation recursion, the calculation formula is as follows:
in (x) I ,y I ,z I ) A receiver position calculated for the inertial navigation recursion; (x) s ,y s ,z s ) Is the satellite position.
6. The inertial navigation-assisted Beidou III isomerism constellation step-by-step satellite selection method of claim 1, wherein in the step 1, preliminary screening of the Beidou III satellite based on an evaluation index of satellite observation data quality is specifically: setting a satellite cut-off height angle and a minimum signal to noise ratio threshold value, and eliminating observation satellites lower than the cut-off height angle and the minimum signal to noise ratio; and constructing a normal step-by-step inspection model by using the pseudo-range measurement information, and detecting and eliminating abnormal observations possibly existing in the observed quantity.
7. The inertial navigation-assisted Beidou III isomerism constellation step-by-step star selection method of claim 6, wherein detection and elimination of abnormal observations possibly existing in observables by using measurement information are specifically as follows:
first, an assumption test is constructed as follows, to detect whether an observed quantity has an abnormality
H 0 :s＜T,H 1 :s＞T
Wherein H is 0 For the original assumption, it means that no abnormal observed quantity exists, H 1 For alternative hypothesis, it indicates that there is abnormal observed quantity, s is test statistic, and T is test threshold;
the test statistic is constructed by using the sum of squares of the innovation:
wherein R is an innovation vector, U is an innovation covariance matrix, H is an observation matrix, R is a measurement noise covariance matrix,for the prediction state covariance matrix,/>Unit weight variance factor, χ 2 Representing the chi-square step, m and n are the number of observational quantity and state parameters respectively;
the test threshold T is determined by the false alarm rate and the number of redundant observables, i.e
Wherein P is FA M-n represents the number of redundant observers for false alarm rate;
then, if the alternative assumption H1 is satisfied, the abnormal observed quantity is identified and excluded, and the following detection statistics are adopted
Thought s i The observed quantity corresponding to the maximum value in (i=1..m) is taken as the abnormal observed quantity, and is excluded.
8. The inertial navigation-assisted Beidou III isomerism constellation step-by-step satellite selection method of claim 1, wherein in the step 2, 4 basic satellites with highest priority are selected and determined based on a satellite optimal geometric configuration principle, and the satellite selection criterion is as follows:
criterion 1: if the candidate satellites are IGSO or MEO satellites, selecting the satellite with the largest altitude angle from the IGSO and MEO satellites as the zenith satellite in the basic satellites, otherwise, selecting the satellite with the largest altitude angle from the MEO satellites as the zenith satellite;
criterion 2: selecting three bottom satellites preferentially from MEO satellites, selecting a combination with the azimuth interval closest to 120 degrees from three satellites in the set of alternative MEO satellites, selecting two satellites with azimuth angles between 0 and 120 degrees and azimuth differences closest to +/-120 degrees from the satellites, combining the three satellites to form a group in the selection of the bottom satellites, calculating the difference between the azimuth differences of the three satellites and 120 degrees to form the difference of the bottom angle combination, comparing the difference of all the bottom angle combinations, and selecting the bottom angle combination with the smallest difference as the bottom angle combination of the basic satellite.
9. The inertial navigation assisted beidou III heterogeneous constellation step-by-step satellite selection method of claim 1, wherein in step 3, determining the priority of the remaining satellites from the remaining satellite set according to the PDOP value contribution degree is specifically as follows:
based on the contribution degree of the PDOP value, on the basis of satellite observation quality optimization and basic constellation selection, adding more visible satellites into the basic constellation, reducing the PDOP value and meeting the requirement on positioning accuracy; from the remaining satellite candidate sets, the contribution degree of each satellite to the PDOP value is calculated, and the priorities of the remaining satellites are ranked according to the contribution degree.
10. The inertial navigation assisted Beidou III heterogeneous constellation step-by-step satellite selection method is characterized in that a calculation method of the contribution degree of the PDOP value is that one satellite is gradually added from a residual satellite set on the basis of a basic satellite, the PDOP value after 1 satellite is added is calculated, the priorities of the correspondingly added satellites are ordered according to the size of the PDOP value after one satellite is added, and the calculation formula of the PDOP is as follows:
wherein q is 11 、q 22 、q 33 Is a diagonal element of the Q matrix; q is a weight coefficient matrix; h is a geometric matrix.
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