RU2645875C1 - Method of increasing of navigation parameters differential correction accuracy in a long-wave positioning system - Google Patents

Abstract

FIELD: radio engineering and communication.

SUBSTANCE: invention relates to radio engineering and can be used to improve the mobile objects coordinates determining accuracy using the long-wave radio navigation systems equipment. Method for increasing of navigational parameters differential correction accuracy in a long-wave positioning system using the local differential substation (LDSS), which allows to determine the corrected distances to the navigation receiver of the user R_nri (i = 1, 2, …, K), which are determined by dividing the measured distances to the user's navigation receiver R_usi (i = 1, 2, …, K) by the refractive index n_i, R_nri=R_usi/n_i, (i = 1, 2, …, K), which is calculated from the measured R_usi and actual R_fli distances between navigation stations and LDSS in the form n_i=R_usi/R_fli, (i = 1, 2, …, K).

EFFECT: technical result of the invention consists in eliminating the error in estimating distances and increasing the accuracy of determining the coordinates of the user's navigation receiver.

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Description

The invention relates to radio engineering and can be used to improve the accuracy of determining the coordinates of moving objects using the equipment of long-wave radio navigation systems.

The location of the user's navigation receiver in the long-wave range of radio waves is estimated from the measured distances from the navigation receiver to the navigation stations using various navigation systems, including Loran-C, Chaika, Mars-75, etc.

Due to the different propagation conditions of the radio waves in the estimation of distances, errors arise due to the presence of signal delays caused by a change in the propagation velocity of the radio waves above the earth's surface.

Long-wave (DW) radio waves propagate in the lower atmosphere — the troposphere. In the troposphere, the propagation velocity of radio waves is [1]

where c = 299694 m / s is the speed in vacuum, n is the refractive index of the atmosphere. The coefficient n for radio waves depends on weather conditions and can be calculated by the formula of Smith and Weintraub: [2, 3]

(n-1) 10 ⁶ = A (P + B),

Where

A = 77.6 / T; B = 4810e / T; T = 273.2 + t ° C;

P is the atmospheric pressure in millibars;

e is the vapor pressure (humidity) in millibars.

Due to a decrease in the propagation speed, signal delays occur, introducing errors into the measured distances between the navigation stations and the navigation receiver of the navigation signals user, which worsens the location estimate of the navigation receiver of the user.

Since the distances between the navigation stations and the user's navigation receiver are hundreds of kilometers, it is impossible to estimate the atmospheric pressure, temperature and humidity of water vapor, and this leads to an error in estimating the refractive index from these parameters and, as a result, to an error in the measured distances.

There is a way to reduce errors in measuring distances from navigation stations to the LDPS and the user's navigation receiver by using the differential mode [4]. Differential mode is based on the fact that any two closely located receivers experience the same atmospheric effects. In this mode, use a local differential substation with known coordinates, located at a distance of several tens of kilometers from the receiver.

Corrections associated with a change in the propagation velocity are measured in the form of differences between the actual distances R _fli (i = 1, 2, ..., K) from LDPS to NS _i and the measured distances R _ili

These corrections are transmitted to the consumer receiver, which takes them into account when estimating distances. At the same time, the receiver measures the distances R _ipi (i = 1, 2, ..., K) to the HC _i taking into account atmospheric phenomena. The adjusted distances are then determined.

Thus, by applying the differential mode, signal transmission delays in the troposphere can be eliminated.

The disadvantage of this method is that the corrections ΔR _{li are} calculated for the distances between the LDPS and NS _i , while there are other distances between the navigation receiver of the user and NS _i , because of this, the corrections will have errors.

The aim of the invention is to eliminate the existing error in the estimation of distances and improve the accuracy of determining the coordinates of the navigation receiver of the user.

This goal is achieved by calculating the refractive indices of the troposphere n _i , (i = 1, 2, ..., K) through the actual R _fli and the measured R _ili distances between the LDPS and NS _i

which provide corrected distances R _spi between the navigation stations and the navigation receiver of the user

The invention is illustrated in the figure.

In FIG. 1 shows a layout of the navigation stations, the LDPS and the vessel with the user's navigation receiver, FIG. 2 shows a table of input data for modeling; FIG. 3 shows a table of correction results for existing algorithms; FIG. 4 shows a table of correction results by the proposed algorithm.

A method of improving the accuracy of differential correction of navigation parameters in the long-wavelength positioning system is as follows. Navigation stations 1 (HC ₁ , HC ₂ , HC ₃ , ..., HC _K ) transmit the navigation signals that receive LDPS 2 and the navigation receiver 3.

LDPS 2 receives the navigation signal from the navigation stations 1 and measures the distances R _ipi (i = 1, 2, ..., K) to each navigation station 1 and then calculates the refractive indices of the troposphere n _i , (i = 1, 2, ... , K) through the actual R _flo and the measured R _il distances between the LDPS 2 and navigation stations 1 according to the formula (4)

n _i = R _il / R _fli , (i = 1, 2, ..., K).

The calculated refractive indices of the troposphere n _i are transmitted to the navigation receiver of user 3.

User navigation receiver 3 measures distances to navigation stations 1 and calculates the corrected distances R _spi to these navigation stations by dividing each measured distance R _ipi from navigation stations 1 to navigation receiver of user 4 by the troposphere refractive index n _i according to formula (5)

R _spi = R _ipi / n _i .

Consider an example of modeling the existing and proposed differential correction algorithms with the location of objects in accordance with FIG. 1. At the same time, we take into account that the surface values of the refractive index (n-1) 10 ⁶ over the globe are in the range of 240-400, and those brought to sea level are 290-390 units [5].

In Table 1, as an example, the coordinates of four navigation stations 1, an object with a navigation receiver of user 3, LDPS 2 and initial refractive indices (n-1) 10 ^{6 of the} troposphere along the paths from navigation stations 1 to LDPS 2 and the navigation receiver of the user are given as input data 3.

The actual distances between the navigation stations 1 and LDPS 2, as well as between the navigation stations 1 and the navigation receiver of the user, we calculate, respectively, according to the formulas

where x _i , y _i , i = 1, 2, ..., K are the coordinates of the navigation stations 1, x _l , y _l are the coordinates of the LDPS 2, x _p , y _p are the coordinates of the navigation receiver of user 3.

The measured distances between the navigation stations 1 and LDPS 2, as well as between the navigation stations 1 and the navigation receiver of user 3, are calculated using the formulas

Corrections in the form of differences between the measured distances R _fli from LDPS 2 to four navigation stations 1 and the actual distances R or _i are equal

These corrections are transmitted to the navigation receiver of user 3, which takes them into account when correcting distances in the existing differential correction method

Given the source data shown in Table 1, and the calculation results in Table 2 are presented:

- differences between the measured and actual distances from the navigation stations to the LDPS, i.e. corrections related to changes in the propagation velocity of radio waves;

- differences between the measured and actual distances from the navigation stations to the receiver;

- differences between the corrected and actual distances from the navigation stations to the receiver, that is, correction errors.

Note that the calculations were performed under the assumption that the LDPS 2 and user 3 receivers measure distances without errors. That is, in this numerical experiment, only correction errors are estimated due to the different locations of the LDPS 2 and the navigation receiver of user 3.

From the calculation results it can be seen that in this example, the maximum error in the correction of distances using LDPS 2 by the existing algorithm is 13.7 m.

Further, for the same initial data, we obtain the results of the correction of distances by the proposed algorithm.

An estimate of the refractive indices will be obtained in accordance with formula (4)

n _i = R or _i / R _fl , i = 1, 2, ..., K.

The corrected distances between the navigation stations 1 and the user's navigation receiver will be found using (5)

R _spi = R _ipi / n _i , i = 1, 2, ..., K.

The simulation results are shown in Table 3.

From Table 3 it can be seen that the calculated refractive indices (n-1) 10 ⁶ on the paths between the navigation stations 1 and LPS 2 coincided with the initial ones, and the correction errors are zero.

That is, taking into account the fact that the medium of passage of radio waves from navigation stations 1 to LDPS 2 and navigation receiver of user 3 experiences the same atmospheric effects, the proposed distance estimation algorithm using a local differential substation allows more accurate measurements of the distances between navigation stations 1 and user navigation receiver 3.

The existing and proposed methods for correcting the measurement of distances between navigation stations 1 and navigation receiver of user 2 using a local differential substation are considered.

In the existing method, the correction corrections for the distances between the navigation stations 1 and the navigation receiver of the user 3 are calculated as the differences between the measured and actual distances from the LDPS 2 to the navigation stations 1. However, due to the fact that there are other distances between the navigation receiver of the user 3 and the navigation stations 1 , these corrections have errors.

In the proposed algorithm, based on the measured and actual distances between the LDPE 2 and the navigation stations 1, the refractive indices of the propagation medium are calculated, which are used to correct the measured distances from the navigation receiver of user 3 to the navigation stations 1.

Since the differential mode is based on the fact that the same atmospheric phenomena act on the medium of radio waves propagation from navigation stations 1 to LDPS 2 and the navigation receiver of user 3, the proposed correction method gives more accurate estimates of distances.

Literature

1. Monakov A.A. Theoretical Foundations of Radar / SPbGUAP. St. Petersburg: 2002, 70 p.

2. Bean B.R., Dutton E.D. Radio meteorology. L .: Gidrometizdat, 1971.362 s.

3. Gudenko S.Yu. The influence of the troposphere on the radar observation of objects // National University "Odessa Maritime Academy". Navigation. 2016. Issue. 26.S. 84-92.

4. Antonovich K.M. The use of satellite radio navigation systems in geodesy. In 2 t. T. 2. M .: FSUE “Kartgeocenter”, 2006. 360 s.

5. Serapinas BB Global positioning systems. M .: IKF “Catalog”, 2002. 106 p.

Claims (4)

A method for improving the accuracy of differential correction of navigation parameters in a long-wavelength positioning system using a local differential substation (LPS), including generating corrections to the measured distances between the navigation stations and the user's navigation receiver, characterized in that the adjusted distances to the user's navigation receiver R _spi (i = 1, 2, ..., K) are determined by dividing the measured distances to the user's navigation receiver R _ipi (i = 1, 2, ..., K) by the coefficients refractive index n _i , R _spi = R _ipi / n _i , (i = 1, 2, ..., K), which is calculated on the basis of the measured R _il and the actual R _{fli the} distances between the navigation stations and the LDPS in the form n _i = R _il / R _fli , (i = 1, 2, ..., K).

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