CN105652292B - GPS multipath effect correction positioning method and system - Google Patents

Abstract

The invention relates to a GPS multipath effect correction positioning method and a system, wherein the method comprises the following steps: s1, calculating the initial position of the receiver according to the GPS pseudo-range observed quantity measured by the receiver; s2, calculating a position correction number according to the estimated distance difference between the reflected signal and the direct signal; and S3, obtaining the corrected position according to the initial position and the position correction number of the receiver. The invention calculates the position correction number according to the estimated distance difference between the reflected signal and the direct signal, further corrects the position of the receiver, reduces the multipath effect, greatly improves the positioning precision of the GPS in the urban building dense area, has simple method and low cost, and can be directly used for the positioning mode of the GPS mobile phone.

Description

A GPS multipath effect correction positioning method and system

technical field

The present invention relates to the technical field of GPS (Global Positioning System) positioning, and more specifically relates to a positioning method and system for correcting GPS multipath effects.

Background technique

GPS technology plays a revolutionary role in the development of positioning technology. GPS can provide high-precision navigation and positioning around the clock. As the price of GPS receivers decreases day by day, GPS receivers have been installed in a large number of mobile phones now, and the sensitivity of the receivers is getting higher and higher.

However, in the urban environment, due to the reflection of GPS signals by a large number of buildings, a strong multipath effect is caused, which greatly reduces the positioning accuracy of GPS, and sometimes the positioning error can reach 200 meters. Over the years, scientists from various countries have done a lot of research on the impact of multipath effects on GPS positioning accuracy, and mainly improved through the following methods: 1) Improve the receiving loop algorithm in the GPS receiver to reduce multipath effects 2) Through various filtering techniques, the impact of satellite observations with multipath effects on the final positioning results is reduced. However, these methods are complicated and still have large errors.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for correcting the position by calculating the position correction number directly according to the distance difference between the reflected signal and the direct signal, aiming at the defect that the multipath effect improvement method of the existing GPS positioning is complicated and the effect is not good. GPS multipath effect correction positioning method and system.

The technical solution adopted by the present invention to solve its technical problems is: construct a kind of GPS multipath effect correction location method, comprise the following steps:

S1. Calculate the initial position of the receiver according to the GPS pseudo-range observations measured by the receiver;

S2. Calculate the position correction number according to the estimated distance difference between the reflected signal and the direct signal;

S3. Obtain a corrected position according to the initial position of the receiver and the position correction number.

In the GPS multipath effect correction positioning method according to the present invention, the position correction number is calculated by the following formula in the step S2:

ΔX＝(A ^T A) ^-1 A ^T Δ;

Among them, A is the satellite coefficient matrix determined by the satellite position coordinates and the initial coordinates of the receiver; Δ=(δ1,δ2,...,δn) ^T ; n is the number of satellites; The distance difference between the i-th satellite reflected signal and the direct signal received, i=1,2,...,n; when the signal-to-noise ratio S/N of the i-th satellite reflected signal is greater than the preset value, δi=0; When the signal-to-noise ratio S/N is smaller than the preset value, the distance difference δi between the reflected signal and the direct signal is calculated.

In the GPS multipath effect correcting positioning method according to the present invention, in the step S2, the direct and direct correlation between the reflected signal and the direct signal is calculated according to the height of the building at the location of the receiver, the width of the street and the zenith angle of the corresponding satellite. The distance of the signal is poor.

In the GPS multipath effect correction positioning method according to the present invention, in the step S2, the distance difference between the reflected signal and the direct signal is calculated according to the average height of the building where the receiver is located.

In the GPS multipath effect correction positioning method according to the present invention, the method also includes steps performed after step S3:

S4. Using the three-dimensional city model, search for the data of the building height and street width at the corrected position obtained in step S3;

S5, calculate the distance difference between the reflected signal and the direct signal according to the data of the building height and the street width and the zenith angle of the corresponding satellite according to the step S4, and solve the position correction number;

S6. Obtain a re-corrected position according to the corrected position obtained in step S3 and the position correction number obtained in step S5.

The present invention also provides a GPS multipath effect correction positioning system, comprising:

The initial position calculation unit is used to calculate the initial position of the receiver according to the GPS pseudo-range observations measured by the receiver;

The first correction number calculation unit is used to calculate the position correction number according to the estimated distance difference between the reflected signal and the direct signal;

The first position correction unit is configured to obtain a corrected position according to the initial position of the receiver and the position correction number.

In the GPS multipath effect correction positioning system according to the present invention, the first correction number calculation unit calculates the position correction number by the following formula:

ΔX＝(A ^T A) ^-1 A ^T Δ;

Among them, A is the satellite coefficient matrix determined by the satellite position coordinates and the initial coordinates of the receiver; Δ=(δ1,δ2,...,δn) ^T ; n is the number of satellites; The distance difference between the i-th satellite reflected signal and the direct signal received, i=1,2,...,n; when the signal-to-noise ratio S/N of the i-th satellite reflected signal is greater than the preset value, δi=0; When the signal-to-noise ratio S/N is smaller than the preset value, the distance difference δi between the reflected signal and the direct signal is calculated.

In the GPS multipath effect correction positioning system according to the present invention, the first correction calculation unit calculates the reflection according to the height of the building at the location of the receiver, the width of the street, and the zenith angle of the corresponding satellite The distance difference between the signal and the direct signal.

In the GPS multipath correction positioning system according to the present invention, the first correction calculation unit calculates the distance difference between the reflected signal and the direct signal according to the average height of the building where the receiver is located.

In the GPS multipath effect correction positioning system according to the present invention, the system also includes:

A data search unit, configured to use a three-dimensional city model to search for the data of the building height and street width at the corrected position obtained by the first position correction unit;

The second correction number calculation unit is used to calculate the distance difference between the reflected signal and the direct signal according to the data of the building height and street width found by the data search unit and the zenith angle of the corresponding satellite, and solve the position correction number;

The second position correction unit is configured to obtain a re-corrected position according to the corrected position obtained by the first position correction unit and the position correction number obtained by the second correction number calculation unit.

Implementing the GPS multipath effect correction positioning method and system of the present invention has the following beneficial effects: the present invention calculates the position correction number according to the distance difference between the estimated reflected signal and the direct signal, and then corrects the position of the receiver, reducing the number of Because of the path effect, the positioning accuracy of GPS in densely built urban areas is greatly improved, and the method of the present invention is simple and low in cost, and can be directly used in the positioning mode of GPS mobile phones.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

Fig. 1 is a flow chart of a GPS multipath correction positioning method according to a preferred embodiment of the present invention;

Fig. 2 is the schematic diagram of the satellite reflection signal received by the receiver;

Fig. 3 is a block diagram of a GPS multipath correction positioning system according to a preferred embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

In the application of GPS in the urban environment, due to the obstruction of buildings, the satellite signal received by the GPS receiver is itself a reflected signal. This will cause a large error in GPS positioning in an urban environment. Aiming at this kind of situation, the present invention proposes a new method suitable for GPS urban positioning and reducing multipath effect, so that the positioning accuracy of GPS in densely built urban areas is greatly improved. The invention can be directly used in the positioning mode of the GPS mobile phone.

Please refer to FIG. 1 , which is a flow chart of a GPS multipath correction positioning method according to a preferred embodiment of the present invention. As shown in Figure 1, the GPS multipath effect correction positioning method provided by this embodiment includes the following steps:

First, in step S1, the initial position of the receiver is calculated according to the GPS pseudo-range observations measured by the receiver.

Assume that the equation for linearizing GPS pseudorange observations is:

AX＝L＝L ₀ +Δ+e; (1)

In the formula, A is the coefficient matrix, which is determined by the satellite position coordinates and the initial coordinates of the receiver. X is the position vector. L is the GPS pseudo-range observation, and _L0 is the error-free observation. Δ is the error caused by the reflected signal, and e is all other error vectors of GPS pseudorange observations. The GPS pseudorange observations are pseudorange or carrier phase signals.

It can be known from formula (1) that when the GPS pseudo-range observations of the receiver are known, the initial position of the receiver can be calculated by the following formula:

When a mobile terminal such as a mobile phone has a built-in GPS receiver, the initial position of the receiver can be calculated according to the GPS pseudorange observations measured by the receiver through formula (2).

Subsequently, in step S2, a position correction number is calculated according to the estimated distance difference between the reflected signal and the direct signal.

Preferably, the position correction number is calculated by the following formula in the step S2:

ΔX＝(A ^T A) ^-1 A ^T Δ; (3)

Among them, A is the satellite coefficient matrix determined by the satellite position coordinates and the initial coordinates of the receiver; Δ=(δ1,δ2,........,δn) ^T ; n is the number of satellites.

δi is the estimated distance difference between the i-th satellite reflection signal received by the receiver and the direct signal, i=1,2,...,n. When the signal-to-noise ratio S/N of the i-th satellite reflection signal is greater than the preset value k1, the signal is considered to be a direct signal, so the distance difference between the i-th satellite reflection signal and the direct signal is δi=0; when the signal-to-noise ratio When the S/N is less than the preset value k1, the signal is considered as a reflected signal, and the distance difference δi between the reflected signal and the direct signal is calculated by a certain method.

Finally, in step S3, the corrected position is obtained according to the initial position of the receiver and the position correction number.

From formula (1), it can be deduced that

Therefore, the corrected position can be calculated based on the initial position of the receiver and the position correction number by the following formula:

In the first preferred embodiment of the present invention, in the above step S2, the distance difference between the reflected signal and the direct signal can be calculated according to the height h of the building where the receiver is located, the width D of the street, and the zenith angle α of the corresponding satellite , as the estimated distance difference between the reflected signal and the direct signal.

Please refer to Figure 2, which is a schematic diagram of satellite reflection signals received by the receiver. As shown in FIG. 2 , point O is the position of the receiver. In the present invention, it is assumed that the receiver is located on the center line of the street between two buildings of equal height. Because the direct signal of the satellite is blocked by the building, the actual signal received by the receiver is actually the reflected signal after being reflected by the building, so the distance of the signal propagation is longer than that of the direct signal. If it is not corrected, it will cause errors in GPS positioning.

Suppose the street width is D and the building height is h. Therefore, the maximum zenith angle of the direct signal of the satellite that the receiver can receive is When the satellite zenith angle α>α0, the satellite signal will be blocked by buildings. In actual situations, we can use the signal-to-noise ratio S/N of the received satellite signal to judge whether the received signal is a direct signal or a reflected signal. When the S/N is greater than the preset value k1, it can be considered that the received signal is a reflected signal.

According to Figure 2, the distance difference δi between the direct signal and the reflected signal can be calculated:

δi=OC-OD;

Suppose the satellite zenith angle is α>α0, s1=OA, s2=OB, s3=AC, s4=AB, s5=OD, s6=OC;

s2=s1cos(α-α0); (7)

s4=s1sin(α-α0); (9)

s5=s2-s3; (10)

The distance difference between the reflected signal and the direct signal is δi:

δi=s6-s5; (12)

Through the above formula, the distance difference between the reflected signal and the direct signal can be calculated according to the building height h and street width D where the receiver is located, and the zenith angle α of the received signal source satellite. In a preferred embodiment of the present invention, the data of building height h and street width D corresponding to the initial position can be searched from the database according to the initial position of the receiver calculated in step S1. Since the initial position calculated in step S1 is not the exact position of the receiver, the distance difference between the reflected signal and the direct signal calculated by these methods is not an accurate value, but an estimated distance difference between the reflected signal and the direct signal. In the second preferred embodiment of the present invention, in step S2, the distance difference between the reflected signal and the direct signal can be approximately calculated by the following simplified formula:

Among them, h is the average height of the building where the receiver is located. In some embodiments of the present invention, the average data of the building height h corresponding to the initial position can be obtained from the database according to the initial position of the receiver calculated in step S1, for example, in a certain city or region, calculate The average height h of buildings in the city or region. In some other embodiments of the present invention, the distance difference between the reflected signal and the direct signal may also be estimated by directly setting a reasonable average value for the building height h. The distance difference between the reflected signal and the direct signal calculated by these methods is not an exact value, but an estimated distance difference between the reflected signal and the direct signal.

In a third preferred embodiment of the present invention, a more accurate receiver location can be calculated using a three-dimensional city model. In recent years, 3D city models have been widely used and used in different applications. Therefore, the data of these high-precision 3D urban building models can be obtained through mobile terminals, and the multipath signal path correction can be accurately calculated by the following methods:

First, in step S1, formula (2) is used to calculate the initial position of the receiver according to the GPS pseudo-range observation L measured by the receiver.

Subsequently, in step S2, judge whether the satellite signal received by the receiver is a direct signal or a reflected signal according to the signal-to-noise ratio S/N of the i-th satellite reflected signal, and when the S/N is greater than the preset value k1, it is a direct signal , δi=0; when the S/N is smaller than the preset value k1, it is a reflected signal, and δi is calculated from the average height of the building where the receiver is located using formula (13). Then calculate the position correction number by formula (3).

Subsequently, in step S3, according to the initial position of the receiver obtained in step S1 and the position correction number obtained in step S2, formula (5) is used to obtain a corrected position.

Subsequently, in step S4, the data of building height h and street width D at the corrected position obtained in step S3 are searched by using the three-dimensional city model.

Subsequently, in step S5, according to the data of the building height h and the street width D found in step S4, together with the zenith angle α of the satellite of the received signal source, the difference between the reflected signal and the direct signal is calculated by formula (12). The distance difference, and solve the position correction number by formula (3).

Finally, in step S6, the re-corrected position is obtained according to the corrected position obtained in step S3 and the position correction number obtained in step S5, that is, the position of the receiver is recalculated using formula (5).

Through the method of the third preferred embodiment, the influence of the initial large error of the receiver on the final result can be avoided, making the GPS positioning more accurate.

Please refer to FIG. 3 , which is a block diagram of a GPS multipath correction positioning system according to a preferred embodiment of the present invention. As shown in FIG. 3 , the GPS multipath effect correction positioning system 100 provided in this embodiment includes: an initial position calculation unit 10 , a first correction number calculation unit 20 and a first position correction unit 30 .

The initial position calculation unit 10 is used for calculating the initial position of the receiver according to the GPS pseudo-range observations measured by the receiver. The realization principle and process of the initial position calculation unit 10 are consistent with step S1 in the GPS multipath effect corrected positioning method, and formula (2) can also be used to calculate the initial position of the receiver.

The first correction number calculation unit 20 is used for calculating the position correction number according to the estimated distance difference between the reflected signal and the direct signal. The implementation principle and process of the first correction number calculation unit 20 are consistent with step S2 in the GPS multipath effect correction positioning method, and the position correction number can also be calculated by formula (3).

The first position correction unit 30 is used for calculating the corrected position according to the initial position of the receiver obtained by the initial position calculation unit 10 and the position correction number obtained by the first correction number calculation unit 20 . The implementation principle and process of the first position correction unit 30 are consistent with step S3 in the GPS multipath effect correction positioning method, and the corrected position can also be calculated by using formula (5).

In the fourth preferred embodiment of the present invention, the above-mentioned first correction number calculation unit 20 can calculate the reflected signal and direct The distance of the signal is poor. For example, through the method in the first preferred embodiment of the system, at first judge whether the satellite signal received by the receiver is a direct signal or a reflected signal according to the signal-to-noise ratio S/N of the i-th satellite reflected signal, when the S/N When it is greater than the preset value k1, it is a direct signal, and δi=0; when the S/N is smaller than the preset value k1, it is a reflected signal. Use formula (12) to calculate the distance difference δi between the reflected signal and the direct signal, and then use formula (3) Calculate the position correction.

In the fifth preferred embodiment of the present invention, the first correction calculation unit 20 can calculate the distance difference between the reflected signal and the direct signal according to the average height h of the building where the receiver is located. For example, it is realized by the method in the second preferred embodiment of the system. First, judge the direct signal or the reflected signal according to the signal-to-noise ratio, and then use the formula (13) to calculate δi from the average height of the building where the receiver is located, and then use the formula ( 3) Calculate the position correction number.

In the sixth preferred embodiment of the present invention, on the basis of the fifth preferred embodiment, a data search unit, a second correction number calculation unit and a second position correction unit may be added.

Wherein, the data searching unit is used for searching the data of building height h and street width D at the corrected position obtained by the first position correcting unit 30 by using the three-dimensional city model.

The second correction number calculation unit is used to find the data of building height h and street width D obtained according to the data search unit, together with the zenith angle α of the satellite of the received signal source by formula (12) to calculate the reflection signal and The distance difference of the direct signal, and solve the position correction number by formula (3).

The second position correction unit is used to calculate the corrected position again according to the corrected position obtained by the first position correction unit 30 and the position correction number obtained by the second correction number calculation unit, that is, adopt formula (5) to calculate the receiver again s position.

In summary, the GPS multipath effect correction positioning method and system of the present invention consider the influence of multipath effect on the direct signal, and calculate the position correction number according to the distance difference between the reflected signal and the direct signal, and then perform the position correction on the receiver. Correction reduces the multipath effect and greatly improves the positioning accuracy of GPS in densely built urban areas. The invention has low cost, simple calculation method and accurate result, and can be directly used in the positioning mode of the GPS mobile phone.

The present invention has been described based on specific embodiments, but those skilled in the art will understand that various changes and equivalent substitutions can be made without departing from the scope of the present invention. In addition, many modifications may be made to adapt the technique to a particular situation or material without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed herein, but include all embodiments falling within the scope of the appended claims.

Claims (8)

1. a kind of GPS multipath effects correct localization method, which is characterized in that include the following steps：

S1, the initial position that receiver is calculated according to the GPS pseudo range observed quantities that receiver measures；

S2, the range difference calculation position correction for reflecting signal and direct signal according to estimation；

S3, corrected according to the initial position and Position Corrections number of the receiver after position；

Pass through the following formula calculation position correction in the step S2：

Δ X=(A^TA)^-1A^TΔ；

Wherein, X is position vector；A is the satellite coefficient matrix determined by coordinate of the satellite position and receiver initial coordinate；Δ= (δ 1, δ 2 ... .., δ n)^T；N is number of satellite；δ i be i-th satellite reflection signal receiving of the receiver of estimation with it is straight Meet the range difference of signal, i=1,2 ..., n；When the signal-to-noise ratio S/N of i-th of satellite reflection signal is more than preset value, δ i=0； When signal-to-noise ratio S/N is less than preset value, the range difference δ i of reflection signal and direct signal are calculated.

2. GPS multipath effects according to claim 1 correct localization method, which is characterized in that basis in the step S2 The zenith angle of the depth of building of the receiver present position, street width and corresponding satellite calculate the reflection signal with The range difference of direct signal.

3. GPS multipath effects according to claim 1 correct localization method, which is characterized in that basis in the step S2 The building average height of the receiver present position calculates the range difference of the reflection signal and direct signal.

4. GPS multipath effects according to claim 3 correct localization method, which is characterized in that the method is additionally included in The step of being performed after step S3：

S4, using D Urban model, search the depth of building at the position after the correction that the step S3 is obtained and street The data of width；

S5, according to the step S4 depth of buildings searched and the data of street width and the zenith angle meter of corresponding satellite The range difference of reflection signal and direct signal is calculated, and solves Position Corrections number；

The Position Corrections number that position and step S5 after S6, the correction obtained according to step S3 obtain corrected again after position It puts.

5. a kind of GPS multipath effects correct alignment system, which is characterized in that including：

Initial position computing unit, the GPS pseudo range observed quantities for being measured according to receiver calculate the initial position of receiver；

First correction computing unit corrects for the reflection signal according to estimation and the range difference calculation position of direct signal Number；

Correct unit, the position after being corrected for the initial position according to the receiver and Position Corrections number in first position It puts；

The first correction computing unit passes through the following formula calculation position correction：

Δ X=(A^TA)^-1A^TΔ；

Wherein, X is position vector；A is the satellite coefficient matrix determined by coordinate of the satellite position and receiver initial coordinate；Δ= (δ 1, δ 2 ... .., δ n)^T；N is number of satellite；δ i be i-th satellite reflection signal receiving of the receiver of estimation with it is straight Meet the range difference of signal, i=1,2 ..., n；When the signal-to-noise ratio S/N of i-th of satellite reflection signal is more than preset value, δ i=0； When signal-to-noise ratio S/N is less than preset value, the range difference δ i of reflection signal and direct signal are calculated.

6. GPS multipath effects according to claim 5 correct alignment system, which is characterized in that the first correction meter Unit is calculated according to calculating the zenith angle of the depth of building of the receiver present position, street width and corresponding satellite Reflect the range difference of signal and direct signal.

7. GPS multipath effects according to claim 5 correct alignment system, which is characterized in that the first correction meter Calculate the distance that unit calculates the reflection signal and direct signal according to the building average height of the receiver present position Difference.

8. GPS multipath effects according to claim 7 correct alignment system, which is characterized in that the system also includes：

Data searching unit, for utilizing D Urban model, after searching the correction that the first position correction unit obtains The data of depth of building and street width at position；

Second correction computing unit, for the depth of building and street width searched according to the data searching unit Data and the zenith angle of corresponding satellite calculate the range difference of reflection signal and direct signal, and solve Position Corrections number；

Unit is corrected in the second position, for correcting the position and described second after the obtained correction of unit according to the first position The Position Corrections number that correction computing unit obtains corrected again after position.