# The method of eliminating the influence of tropospheric and ionospheric errors of measurement in single frequency satellite navigation receivers

(57) Abstract:

The invention relates to improving the accuracy of satellite navigation, in particular the elimination of tropospheric and ionospheric errors of measurement ranges in conventional single-frequency receivers through a specific targeted treatment code and phase measurements using only the information available to the satellite receiver in normal mode it works. This solution allows to increase accuracy by eliminating tropospheric and ionospheric errors in conventional single-frequency receiver that uses only standard available satellite navigation and measurement information, which is achievable technical result. The improved accuracy is achieved by including the parameters of the vertical tropospheric and ionospheric delays, as interfering in the number estimated by the results of a joint radio navigation measurements (code and phase) and with the exception thereby influence the current errors (tropospheric and ionospheric) on the results of solving the navigation problem of determining the coordinates and the components of the velocity vector of the object. Good quality assessment of these disturbing, parametro different ionospheric delay and uniform in the troposphere. Processing of measurements carried out as a fixed volume sampling method of least squares (SNK) weighing neravnodushnyh measurement (ideal for stationary users), and the increasing volume with recurrent RNA or standard Kalman filter (FC), which is more convenient for moving objects. For recurrent processing as SNK and FC form the matrix of partial derivatives. 1 C.p. f-crystals.

The invention relates to improving the accuracy of satellite navigation, in particular the elimination of tropospheric and ionospheric errors of measurement ranges in conventional single-frequency receivers through a specific targeted treatment code and phase measurements using only the information available to the satellite receiver in normal mode it works.

When measuring distance to satellites, the main factor atmospheric effects on the accuracy of these measurements is the delay of signal propagation in the troposphere and the ionosphere, jointly manifested in the measurements and making errors from tens to hundreds of meters.

There are ways to reduce these errors [1], [2], entitled “methods of simulation runs of reportmaster in the vicinity of the installation of the receiving antenna - temperature, pressure and humidity. It is also known that in a wide range of variation of these parameters tropospheric delay varies relatively little, so calculating this delay parameters for “standard atmosphere”, it is possible to 70-80% reduction in tropospheric error measurement range. When this residual error will not exceed 10-15 meters. To further improve the accuracy required for the measurement of temperature, pressure and humidity at the installation point of the receiving system, converting these measurements into digital form and a special interface for inputting these data into the navigation computer, which causes complication and cost of the equipment.

The same method applied to ionospheric measurement error is implemented in the satellite navigation system GPS, where as part of the navigation message, the satellites transmit the parameters of the ionospheric model Klobuchar [2].

The closest analogue (prototype) of the proposed method is a method [1], including simultaneous measurements of pseudorange and pseudoradicular speeds, the selection of the navigation information transmitted by the satellites, including the model parameters of the ionospheric errors, the calculation of tropospheric errors on parametrina amendments to the dead-reckoned coordinates and velocities of the object by the method of least squares fixed sample size mentioned pairs of measurements or recurrently in the same way as revenues of the current measurements or the standard procedure of the linear Kalman filter.

The disadvantage of the prototype: low accuracy (not only 70-80% of the tropospheric error and 50% of the ionospheric).

The basis of the invention is to eliminate the disadvantages of the prototype, which is solved in that in the proposed method, the current values of tropospheric and ionospheric errors of measurements of distances and radial velocities are in the form of works of the respective vertical delays on the function of the inclined beam, time-dependent through the modification of the angular coordinates of the satellites mentioned vertical delay include the number of estimated parameters measurements together with such nuisance parameters, as systematic errors of measurement, the matrix of partial derivatives of the measurements by the estimated values as partial derivatives of the above measurements on the vertical delays in the troposphere and the ionosphere include the corresponding functions of the inclined beam for distances and their time derivatives for the radial velocity and injected into the navigation filter diagonal matrix of the noise heterogeneous and significantly neravnodushnyh measurements of pseudorange and pseudoradicular velocities in the form of dispersions of code and phase measurements or their relationships, and in the matrix cast is Karosta coordinates of the object.

As in the troposphere and the ionosphere inclined beam (compared to vertical) is a better path in the environment options, other than vacuum. Therefore, the latency (tropospheric and ionospheric) can be represented as a product of the vertical delay, which varies depending on the properties of the ionosphere (troposphere) on some function of the inclined beam (f_{nl}>1), increasing with decreasing elevation (angle of elevation) of the satellite. This factorization is convenient because the vertical delay describes the slowly time-varying characteristics of the atmosphere, and f_{nl,}depending on the current angular position of the satellite (including those from azimuth, especially for ionosphere) through these known angles (azimuth and altitude) describes the change of the time delay:

where D^{(trails,ion)(}t) is the current tropospheric (ionospheric) measurement error;

- tropospheric (ionospheric) error when the vertical spread of the beam;

- function tilting of the beam is e and phase measurements. They are different in that the code is measured by the delay of fronts ranging code, which is modulated carrier signal, and the phase to RAID the phase of the carrier.

It is known ([3], [4] and other textbooks and monographs on the propagation of radio waves) that the troposphere introduces the same delay as the signal envelope (ranging code), and the phase of the carrier. From the same textbooks it is known that the ionosphere introduces a delay equal size, but of different sign in the envelope and the phase of the carrier, and the code is always lagging behind the true delay (in vacuum), and the phase of the carrier ahead of her. This is because in the ionosphere (dispersing medium) in contrast to the troposphere, the group velocity less than the speed in vacuum, and the phase by the same amount more. So the code range when the measurement signal is transmitted to the ionosphere, is always higher than the true, and the phase is always less than its (the same value).

In accordance with the foregoing, the expression for the measured satellite receiver code D^{code}and phase D^{phase}distances beam when passing through the atmosphere can be written as:

where D^{code}(t) - the current is awn (current integer number of phase cycles plus the fractional part of the phase cycle);

D^{East}(t) is the true current range to the satellite;

D^{ion}(t) is the current ionospheric measurement error;

D^{trails}(t) - current tropospheric error measurements.

IonosphericD^{ion}and tropospheric D^{trails}measurement error is expressed by the formula (1).

It should be noted that the full phase range D^{phase}in conventional single-frequency receivers are not available, as it requires knowledge integer number of phase cycles (wavelengths =19 cm) lying down on the track propagation length of up to 20,000 km). This number is lost when the capture signal to the support carrier and the recovery afterwards is not subject. Even in dual-frequency receivers to calculate this number of phase cycles encounters considerable difficulties due to the relatively small spacing of these frequencies.

However, in the conventional single-frequency receivers available measurements of radial velocities V_{r}that represent the rate of change of the phase range, and naturally do not contain the unknown (but constant) initial number f is the radial velocity;

- derivative of the phase range ( rate of change of the full phase);

V^{East}_{r}(t) the true radial velocity;

- the rate of change of the current ionospheric errors;

- the rate of change of current tropospheric errors.

We will substitute the expressions for tropospheric and ionospheric errors from the formula (1) in formula (4) and, after differentiation, we get:

where- the rate of change of the function of the inclined beam in the ionosphere:

- the rate of change of the function of the inclined beam in the troposphere.

Thus, the prototype of the proposed method is the method of modeling the propagation path of radio waves [1], more precisely the way to solve the navigation task, taking into account the calculated values of the tropospheric and ionospheric errors (tropospheric parameters “standard atmosphere”, ionospheric - model data transmitted by the GPS satellites).

This solution allows to increase accuracy by eliminating tropospheric and ionospheric errors in conventional single-frequency receiver that uses only standard available to him, satellite navigation and measurement information. The improved accuracy is achieved by including the parameters of the vertical tropospheric and ionospheric delays, as interfering in the number estimated by the results of a joint radio navigation measurements (code and phase) and with the exception thereby influence the current errors (tropospheric and ionospheric) on the results of solving the navigation problem of determining the coordinates and the components of the velocity vector of the object. Good quality assessment of these nuisance parameters (joint observability) is provided by the signs of partial derivatives of the radial velocity and range of different ionospheric delay and W (with the inclusion of interfering in the number of surveyed) proposed to increase the informational redundancy of assessment for extracting coordinate information from measurements of radial velocities [5] (suspended processing joint code and phase measurements), where insufficient information content of the measurements of radial velocities for estimating coordinates in this sredneformatnykh satellite navigation systems repeatedly compensated for by their high accuracy compared to code (by 2-3 orders of magnitude), i.e., weight measurements of radial velocities in joint processing code ranges in the 10^{4}-10^{6}more recent.

Considering the above we can describe the principle of processing of satellite measurements of the proposed method. Processing the measurements are performed at a fixed volume sampling method of least squares (SNK) weighing neravnodushnyh measurement (ideal for stationary users), and the increasing volume with recurrent RNA or standard Kalman filter (FC), which is more convenient for moving objects. For recurrent processing as SNK and FC form the matrix of partial derivatives in the form of:

where a, b, and C are partial derivatives of code ranges for the object coordinates x, y, z;

, ,its systematic error;

the other elements are parameters of the troposphere and ionosphere f_{nl}above.

Note that an analytical expression for the partial derivatives of the radial velocity coordinates of the object are not always convenient for calculations, so it is rational to form them numerically, as derivedby setting the final increment arguments.

In the processing of RNA at a fixed sample size n matrix H of dimension 2n10 form of the above formula (6) pairs of rows with indices i (i=i...n), corresponding to the numbers of pairs of measurements in the sample.

The matrix R noise measurements for recurrent processing each incoming pair of measurements with respect to the matrix H by the formula (6) is written as:

where =10^{4}:10^{6}- the ratio of the variances of the noise measurement errors pseudorutile speed to the pseudorange error.

To process a fixed amount of n pairs of joint measurements of pseudorange and pseudoradicular speeds, where for each i pair matrix H generated by forms of the UIS elements of the main diagonal, equal to I and.

Amendments to the dead-reckoned the values of the estimated coordinates and velocities, as well as to the dead-reckoned the values of the nuisance parameters - systematic measurement errors of vertical delays in the troposphere and the ionosphere, calculated by the method of least squares weighting neravnodushnyh measurements using the matrix R according to the formula:

where L is a matrix of dimension n2 differences of measured and dead-reckoned pairs of measurements (pseudorange and pseudoradicular speeds).

Sources of information

1. GLONASS. Global satellite navigation system. Under. ed C. N. Kharisov, A. I. Perov, V. A. Boldin. M: IPGR, 1999.

2. The interface control document GPS.

3. Dolukhanov M. P. Propagation of radio waves. M: Communications, 1972.

4. Grodinsky, P. Propagation of radio waves M.: Higher school, 1975.

5. Volosov P.F., Dubinko Y. S., B. Mordvinov,, Taverns C. D. Marine complexes satellite navigation. Leningrad: Sudostroenie, 1983.

1. The method of eliminating the influence of tropospheric and ionospheric errors of measurement in single-frequency prosta, the selection of the navigation information transmitted by the satellites, including the model parameters of the ionospheric errors, the calculation of tropospheric errors on the parameters of the standard atmosphere in the model of a spherical layer with an exponential decrease of density with height, calculation of the amendments to the dead-reckoned coordinates and velocities of the object by the method of least squares fixed sample size mentioned pairs of measurements or recurrently in the same way as revenues of the current measurements or standard procedure in the same way as revenues of the current measurements, either in the standard procedure of the linear Kalman filter, characterized in that what's the current values of tropospheric and ionospheric errors of measurements of distances and radial velocities are in the form of works of the respective vertical delays on the function of the inclined beam, time-dependent through the modification of the angular coordinates of the satellites mentioned vertical delay include the number of estimated parameters measurements together with such nuisance parameters, as systematic errors of measurement, the matrix of partial derivatives of the measurements by the estimated values as partial derivatives mentioned beam for distances and their time derivatives for the radial velocity and injected into the navigation filter diagonal matrix of the noise heterogeneous and significantly neravnodushnyh measurements of pseudorange and pseudoradicular velocities in the form of dispersions of code and phase measurements or their relationship.

2. The method according to p. 1, characterized in that the matrix of partial derivatives of the measurements estimated parameters additionally include partial derivatives of the radial velocity with respect to the coordinates of the object.

**Same patents:**

FIELD: digital cartography and symbolic circuits.

SUBSTANCE: method includes forming matrix for transforming image or objects coordinates distortion matrix on certain digital plans and symbolic circuits relatively to true geographic coordinates received for tracked objects via navigation devices of users, by combining plans or symbolic circuits with precise terrain chart. Distortion matrix is included in contour of displaying objects on plans and circuits, on basis of true geographic coordinates of tracked objects, sent in by users. A layer of plan or circuit of terrain transformed according to matrix is formed, on which tracked objects are marked by certain graphic symbols. Data, received on circuit, for example, route and movement speed of each tracked object, is relayed to certain users with visualization of symbolic circuit on indication device of each user. Device for realization of method has digital terrain chart, received information processing device, information indication device, n components of subscribers complex. Each component has device for determining coordinates on terrain connected by its input to output of controlling device, directly or through encoder/decoder. Outputs of control device are connected to inputs of information indication device and to device for connecting to radio channel. Device for connecting each subscriber component to radio channel is connected by its input to output of control device and is connected to group device for connecting to radio channel belonging to base portion of device for receiving digital cartographic material. Another input and output of group device for connecting to radio channel are connected directly to output and input of coordinates transforming and controlling device or respectively to output and input of second encoder/decoder, connected by other its input and output respectively to output and input of device for coordinates transformation and control. Another input of coordinates transformation and control device is connected to output of distortion matrix storage device. Next input and output of coordinates transformation and control device are connected respectively to output and input of block, containing digital terrain charts and to output and input of block, containing symbolic circuits or plans of same terrain.

EFFECT: higher speed of operation, higher effectiveness.

2 cl, 1 dwg