RU2393430C1 - Method for high-precision measurement of aircraft trajectory coordinates in flight investigations on long routes - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: method is based on receiving signals from global navigation satellite system spacecraft and involves measurement of phase shift between signals of the aircraft antenna from each satellite navigation system (SNS) spacecraft. After flight, through absolute positioning from phase measurements due to use of exact ephemeredes and exact satellite time determined by the International GPS service through the Internet system, the position of a satellite is calculated from keplerian orbit elements, which are contained in the ephemeride data, and the algorithm for determining coordinates of the aircraft is executed in form of a sequence of calculations, which include calculation of the ionospheric delay using the Klobuchar model and troposphere delay using the Black model, calculating the integer solution from code sequences of the receiver of the satellite navigation system, using the least-squares method to calculate coordinates of the aircraft from phase measurements of the receiver of the satellite navigation system with allowance for phase ambiguity, using an algorithm with a floating solution, the obtained Cartesian ordinates of the aircraft are converted to a geodetic coordinate system. ^ EFFECT: more accurate measurement of trajectory parametres of aircraft. ^ 2 cl, 4 dwg, 1 tbl

Description

The invention relates to the field of aviation, in particular to systems for processing flight test materials (LI) of aircraft (LA), methods for developing and researching systems for tracking aircraft objects, and can be used to determine their accuracy characteristics. The invention can also be used to determine the coordinates of the location of the components of the vector of the phase centers of the antennas of the navigation equipment of users of satellite radio navigation systems.

There is a method of determining the coordinates of the location of the components of the velocity vector of navigation artificial Earth satellites (NISS) and users of satellite radio navigation systems (SRNS), implemented in the SRNS of the second generation of GLONASS and GPS systems (see V.S.Shebshaevich, P.P.Dmitriev, etc. “Network satellite radio navigation systems.” - M.: Radio and Communications, 1993).

Each of the GLONASS and GPS navigation satellites continuously transmits its own navigation messages containing information, on the basis of which navigation instruments of users (NAL) simultaneously navigate radio objects of at least four NLHs on navigating objects (SRNS users), measure pseudorange between navigating users and NLH and make the calculations necessary to solve the navigation problem. The geometrical equivalent of the final algorithm for solving the navigation problem of this method is the construction of position surfaces relative to the NISS used, the intersection point of which is the desired position of users.

The navigation messages transmitted by each NISS contain the following information:

- information on the state of the satellite systems, allowing users to conclude on the advisability of using data transmitted by satellites for navigation definitions;

- corrections to the time standards and satellite frequencies, almanac data on ephemeris (ephemeris — NISS coordinate values in the geocentric coordinate system, calculated for fixed time points based on the results of predicting the movement of the NISS);

- parameters for introducing delay corrections for navigation radio signals of satellites during their propagation through the ionosphere, etc.

The formation of arrays of navigation (service) information (time, ephemeris, parameters for introducing corrections, components of the satellite velocity vector, etc.), as well as their transfer (loading) to the computer memory of the corresponding NESZ, is carried out by control stations (CS) controlling the orbits NISH, the divergence of the NISS time scales with system time and the prediction of the ephemeris of each NISS.

Using the information of the navigation messages received by the NAP and the measurement of the pseudoranges to the selected NLH, the functional relationships are established between the known NLH coordinates and the unknown coordinates of the SRNS users. Determining the coordinates of users comes down to solving a system of navigation equations with 4 unknowns. As a result of solving the system of navigation equations, four unknowns are determined: three coordinates of the user's location (X _P , Y _P , Z _P ) and an amendment to his time scale (correction to his clock).

Similarly, using the results of measurements of quasi-velocities, three components of the user velocity vector are determined (X _P , Y _P , Z _P ) and the correction to the frequency of the local frequency standard used to form time scales.

This method is characterized by the following set of actions:

- determination of the coordinates of the NISS constituting the velocity vector by solving navigation systems of equations;

- prediction of the NESZ GLONASS ephemeris by numerically integrating the differential equations of motion of the NISS;

- measurement of pseudorange from an object to each visible NHSS by measuring the phase shift between pseudo-random sequences (SRP) generated by each satellite, each of which is synchronized according to its own time standard, and SRP formed at the receiving location (in the NAP of the object);

- measurement of quasi-speed by measuring increments of ranges at the carrier frequency using phase locked loop systems (PLL);

- NAP reception of NISS navigation radio signals and measurement of pseudorange, radial pseudo-speeds of NISS;

- determination of the coordinates that make up the user velocity vector by solving systems of navigation equations.

The disadvantages of this method are:

- the presence of a ground network of CS, determining the coordinates of the location of the NESZ (ephemeris);

- Prediction of the ephemeris of each NISZ;

- errors in navigation definitions due to the instability of the frequencies of the NISS generators and reference object generators, the shift of the time scales of objects relative to the NISS time scales, as well as the errors introduced by the wobble (shift) of the start time of the coded sequences introduced to reduce the accuracy of the c / a GPS signal.

Known US patent No. 7.164.383 B2 dated 16.01.07, G01S 5/14 "Navigation system using GPS in the local area".

In a navigation system using GPS in the local area, the differential positioning method (DGPS) is used. The system includes at least three reference stations, a main station located at a short distance from each other (15 - 1500 m) and a LAAS (Local Area Augmentation System) receiver located at a remote site. Each of the reference stations receives GPS signals from satellites, determines the corresponding pseudorange, and transmits them to the main station via communication channels. The main station receives pseudorange from the reference stations, calculates the differential corrections and transmits them to the LAAS receiver. The LAAS receiver receives GPS signals from satellites, differential corrections from the main station and calculates its exact location. The distribution range of differential corrections does not exceed 37 km. The system works in real time.

However, this system, based on relative measurements, has significant range limitations and cannot be used on large long paths.

A known method for determining the location coordinates of the vector of speed, range and trajectory measurements of a navigating object from the navigation radio signals of the spacecraft of satellite radio navigation systems (see RF patent for the invention No. 2152048, G01S 5/00 dated 06.27.02, taken as a prototype), wherein the antenna receiving device installed on the site receives satellite navigation signals containing ephemeris values constituting satellite velocity vectors, as well as information for introducing corrections to the frequency and delay, measure the distance from the object to each satellite by measuring the time shifts of the code sequences generated by the satellite generators relative to the code sequence generated by the object generator using the delayed tracking system (CVD), and also calculate the components of the object’s velocity vector by measuring the received Doppler frequency shifts using carrier tracking systems (CCH) and determine the coordinates of the location and components of the velocity vector of the object. Simultaneously or sequentially in time, the satellite’s radionavigation signals are received and, based on the received ephemeris data, the following are calculated: projections of N vectors — bases connecting the two positions of the phase centers of the antennas of artificial navigation satellites of the Earth (NISS) in orbit, determined by dimensional intervals, by subtracting the same components of the position centers of the phase centers NISS antennas; modules of N vectors - bases, values of guide cosines characterizing the directions of vectors - bases in space; the values of the cosines of the angles between the base vectors, and the position vector of the phase center of the antenna of the user's navigation equipment (NAP) on the object, as well as the values of their angles; the speed of the NISS orbit, the radii of the orbits of the NISS, then measure the distance between the phase center of the antenna of the NAP object and the phase center of the satellite antennas located at the intersection points of the base vectors, establish a system of linear navigation equations between the known values of the direction cosines of the vectors - bases and unknown values of the guides cosines of vectors - ranges, differentiate the equations with respect to time and using measured radial velocities, range increments, rate of change increments I ranges using CCH determine the coordinates of the location, the values of the components of the velocity vectors of the phase center of the antenna NAP by solving the corresponding systems of equations. Using the ephemeris data, the values of the cosines of the angles and the values of the angles between the N -base vectors are determined by solving the equations that determine their functional dependencies. The composition of the ephemeris calculated according to the results of predicting the movement of satellites for specific time instants stores the values of the modules and the values of the direction cosines of the base vectors determined by measured intervals in the satellite’s memory and multiplies them by current measured intervals.

However, this differential method for determining the location coordinates that make up the velocity vector and the aircraft range from the navigation radio signals of the spacecraft of radio navigation systems does not allow flight studies to be carried out with the necessary accuracy at large distances from the base station over long routes.

The technical result to which this invention is directed is to increase the accuracy by the method of absolute positioning by phase measurements (ACE) of the trajectory determination of the coordinates of the location of the aircraft on large long routes during flight research, where there are no ground-based radio navigation stations.

Essential features.

To obtain the specified technical result in the method of high-precision measurements of the trajectory coordinates of the aircraft in flight research on long-distance paths, based on the reception of signals from spacecraft of global navigation satellite systems, the following operations are carried out:

- measurement of the phase shift between the received signals of each spacecraft of the satellite navigation system (SNA) and the signals of the receiver of the aircraft;

- determination of the current position of the aircraft in the ground computer by solving equations compiled from measurements of the phase shifts of the SNA signals;

- solving the navigation problem of determining geodetic coordinates: B, L, H (geodesic B is latitude, L is longitude, H is the height above the ellipsoid) in the WGS-84 coordinate system;

according to the invention, after the flight, the coordinates of the aircraft are determined by the method of absolute positioning by phase measurements (ACE). For this, accurate ephemeris and exact satellite times are used. The exact ephemeris and exact satellite times are determined by the International GPS Service (MTS) via the Internet. The satellite coordinates are calculated from the elements of the Keplerian orbit contained in the ephemeris data. The algorithm for determining the coordinates of the aircraft is implemented in the form of a sequence of calculations, including taking into account the delay of the ionospheric delay according to the Klobuchar model and the troposphere of the delay according to the Black model, fixing an integer solution by the code sequences of the SNA receiver, determining by the least squares coordinates of the aircraft according to the phase measurements of the SNA receiver with phase resolution ambiguities using a floating-point algorithm. The resulting rectangular coordinates of the location of the aircraft are converted into a geodetic coordinate system.

It should be noted that the accuracy of the GPS satellite ephemeris measurement is 2-3 m, and satellite clock errors can reach 10 ns, which can lead to positioning errors of up to 3 m. Therefore, it is advisable to use accurate ephemeris corrections and accurate amended hours satellites. To process data using the ACE method, data (files) of the exact ephemeris and time are necessary, which means that it is impossible to process in ACE mode on the day the data are received. Accurate ephemeris and time files are generated by organizations and structures of the MGS, using data from satellite receivers distributed around the world. These files are laid out on the Internet with no access restrictions. The delays in the appearance of exact ephemeris files and watch correction files on the Internet are from 1 to 8 days.

Thus, in contrast to the differential phase mode of processing used in the prototype, which requires the deployment of base stations with known geodetic coordinates, the ACE method allows the use of data from only one two-frequency receiver located on the aircraft, which allows the processing of flight data on long-haul routes without using data of ground base stations with an accuracy of 10-40 cm.

Tropospheric errors in the SNA signal processing system are compensated by modeling tropospheric vertical delay and using a Kalman filter, and phase two-frequency measurements are used to account for ionospheric errors to form a combination of phases that is free from the influence of the atmosphere.

To ensure convergence of the solution when processing phase measurements of SNA signals conducted on an aircraft, measurements are taken for a period of time before takeoff and after landing.

The list of figures in the drawings.

To clarify the invention, figure 1 shows a functional diagram of the measurement of the signals of the SNA and their ground processing, which shows:

1 - artificial Earth satellites (AES) of a satellite navigation system (SNA);

2 - aircraft (LA);

3 - antenna;

4 - receiver SNS;

5 - a complex of on-board trajectory measurements (KBTI);

6, 7 - coordinates of the location of the takeoff and landing of the aircraft;

8 - research organizations, IGU;

9 - Internet system;

10 - ground computer;

11 - satellite equipment;

12 - satellite antenna;

13 - satellite transmitter;

14 - phase rangefinder system (FDS);

15, 21 - electronic generator (EG);

16 - aircraft onboard equipment;

17 - aircraft onboard antenna;

18 - radio receiver (RPM) aircraft;

19 - meter B, L, H;

20 - shaper hardware signal.

Figure 2 shows an example of a structural diagram of the equipment of the transmitting part on the satellite and the receiving part on the aircraft.

Figure 3 shows an example of determining the amplitude carrier (L _1, L ₂ ) and phase modulation of the signals received by the receiver in the aircraft, where 22 is the amplitude of the carrier frequency of the SNA signal, 23 is phase modulation.

Figure 4 shows examples of measuring the fractional and full phase of the carrier frequency of the SNA signal, where 24 is the phase of the signal received from the satellite with Doppler shift, 25 is the carrier created in the receiver, 26 is the beat signal along the time axis.

The method is as follows.

The method of high-precision measurements of the trajectory coordinates of the aircraft in flight research on long-distance routes works as follows. On airplane 2, the antenna 3 of the SNA 4 receiver is located, with the help of which phase measurements are made at two frequencies L ₁ and L _{2 of} navigation satellites - 1 GPS and GLONASS constellations. During the flight, the information of the SNA receiver, issued in the RS-232 format, is recorded in the on-board unit of the complex of on-board trajectory measurements (KBTI) - 5 with a frequency of 1 Hz. Processing the registered signals of the SNA receivers and determining the coordinates of the aircraft’s location is carried out after a flight in the ground computer - 10, using the exact ephemeris and exact time files received by research organizations 8 and downloaded from the Internet 9, see Fig. 1.

The coordinates of the antenna of the SNA receiver are calculated in the coordinate system associated with the ellipsoid WGS-84 (World Geodetic System of 1984). The coordinate system is rigidly connected with the Earth. The center of the rectangular coordinate system is located in the conditional center of the Earth. The X and Y axes lie in the equatorial plane, the first of them intersects the zero meridian. The Z axis makes up the right three with the X and Y axes, is directed towards the north pole and is parallel to the axis of the Earth's own rotation.

The “raw” code and phase measurements of the SNA receiver contain errors that depend on a number of reasons. Errors in the measurement of pseudorange to navigation satellites cause errors in finding the navigation parameters of the antenna of the SNA receiver. The most significant of them are:

- satellite clock error;

- error of the clock of the SNA receiver;

- errors in the satellite ephemeris;

- signal distortion when passing through the layers of the ionosphere;

- signal distortion during the passage of troposphere layers;

- multipath;

- random noise of the SNA receiver;

- ambiguity of phase measurements.

The ranging signal is generated on the satellite 11 by the shaper of the ranging signal (FDS) 14 from the oscillations of the reference generator (EG) 15, see FIG. 2. A similar generator 21 on the aircraft 2 using a hardware signal shaper (FAS) 20 generates a signal in a format similar to the rangefinder. With the phase method of measuring the range, the FDS and FAS form in-phase low-frequency oscillations with high long-term frequency stability. The meter 19 (IZM), which is part of the onboard equipment of the aircraft, compares the signal received from the satellite 11 with the hardware signal and determines the distance in terms of the delay time or phase difference.

SNA data is based on determining the difference to several satellites. The advantage of the SNA is the exclusion of the methodological error ΔD _c when measuring the phase shift between the signals received from several satellites. Moreover, time standards - phases on all satellites are tied to a single scale with high accuracy.

The carrier wavelength is small compared to code pseudorange - about 19 cm for L ₁ and 24 cm for L ₂ . Because Since the resolution of measurements is 1-2% of the wavelength, the phase of the carrier can be measured with millimeter accuracy, compared with an accuracy of several meters for code measurements. But the phase measurement is not enough, because it is impossible to distinguish (on L ₁ and L ₂ ) one wave from another. Information about the transmission time for the signal on L ₁ cannot be fixed on the carrier wave, therefore, the main phase measurement lies in the range from 0 to 360 ° - this is a fractional phase (120-45 ° is the beat signal), 27, see Fig. 4 .

To obtain the full phase of the carrier in the receiver 18 of the on-board equipment - 16, tracking of an integer number of carrier wavelengths (B) is supported, which results in the observation of a continuous (accumulated) phase (360 ° N + 120 °) to (360 ° (N + B ) + 45 °), 26, see figure 4:

,

,

(Т_А) - дробная фаза, измеренная как угол в пределах от 0 до 360°, где 360° соответствует ~19 см для фазы L₁ и 24 см для фазы L₂, а C_R - текущий отсчет по счетчику переходов через ноль, который регистрирует только число целых циклов со времени захвата. Начальный отсчет по счетчику

равен 0, член в квадратных скобках является целым числом. Нижний индекс А относится к приемнику РПМ 18, верхний индекс i - к спутнику 11. Соотношение между фазой

и расстоянием

имеет вид

, гдеwhere T _A is the time of receiver A,

(T _A ) is the fractional phase, measured as an angle in the range from 0 to 360 °, where 360 ° corresponds to ~ 19 cm for phase L ₁ and 24 cm for phase L ₂ , and C _R is the current count for the zero transition counter, which only records the number of whole cycles since capture. Countdown

equals 0, the term in square brackets is an integer. The lower index A refers to the receiver RPM 18, the upper index i refers to satellite 11. The relationship between the phase

and distance

has the form

where

- есть целая неоднозначность, a v содержит все смещения и ошибки, влияющие на это измерение. Величина (f₀/c) переводит расстояние в единицы циклов. - постоянная во времени величина для каждой отдельной пары «приемник-спутник». Чтобы преобразовать эти наблюдения фазы в расстояние, необходимо определить неоднозначность циклов. Если целое число

определено, то полученное «фазовое расстояние» (или «расстояние по несущей») будет очень точным расстоянием (на уровне нескольких миллиметров).

- there is a whole ambiguity, av contains all the biases and errors that affect this dimension. The value (f ₀ / c) translates the distance into units of cycles. - constant in time value for each separate pair of "receiver-satellite". To convert these phase observations to distances, it is necessary to determine the ambiguity of the cycles. If an integer

defined, the resulting "phase distance" (or "distance along the carrier") will be a very accurate distance (at the level of several millimeters).

The number of whole N cycles is not observed, the receiver 18 LA 4 only takes into account the change in it. Loss of capture of the counter signal leads to loss of counting cycles in the continuous phase. The initial value of the ambiguity N is determined, which is the problem of resolving the ambiguity of the phase measurements.

At receiver 18, a signal at an intermediate frequency is digitally converted and monitors codes and phases using a program in a microcomputer. The receiver 18 performs the following operations: initial capture of satellite 1 signals, tracking code and phase signals, extracting a navigation message, determining user coordinates, monitoring the current status of satellites in constellation 1. These receiver operations are controlled by a microprocessor. The program for the microprocessor is an instruction manual for the receiver 18, is installed in its memory.

The microprocessors of the ground computer 10 operate with a digital representation of the pseudorange and carrier phase. They are obtained by converting at some point in the digital stream, which filter this data in order to reduce the influence of noise or to obtain reliable values of the position and speed of the object. The ground computer 10 has a keyboard and a display for user interface, for entering commands, options, surveillance data, auxiliary information.

Ground processing using calculator 10 involves the operation of inputting phase shift measurement data between the received signals of each spacecraft of the satellite navigation system (SNA) and the signals of the aircraft receiver from KBTI 5 (registrar).

Then, by absolute positioning by phase measurements due to the use of accurate ephemeris and the exact satellite time determined by the International GPS Service (MGS) 8 via the Internet 9, satellite positions are calculated using the elements of the Kepler’s orbit that are contained in the ephemeris data, and the algorithm for determining the coordinates of the aircraft is implemented in the form of a sequence of calculations, including taking into account the delay of the ionospheric delay according to the Klobuchar model and the troposphere of the delay according to the Black model, fixing an integer solution SNA by code sequences of the receiver, the determination method of least squares on the aircraft coordinates SNA receiver phase measurements with a resolution of the phase ambiguity algorithm using the floating solution, converting the obtained rectangular coordinate locations LA geodetic coordinate system. To ensure convergence in the algorithm of the floating solution of the required accuracy, static measurements of the SNS signals are carried out before takeoff and after landing the aircraft.

When solving the positioning problem in the process of processing satellite data, it is necessary to know the position of the satellites and the exact moment of time the signal was emitted by the satellite, to determine which it is necessary to have satellite clock time errors.

The position of the satellite is calculated by the elements of the Keplerian orbit, which are contained in the ephemeris data transmitted in the navigation message of each satellite. The satellite position determination algorithm is implemented as a sequence of calculations (Interface control document. INTERFACE CONTROL DOCUMENT, Navstar GPS Space Segment / Navigation User Interfaces / Revision IRN-200C-004, April 12, 2000. ARTNC RESEARCH CORPORATION 2250 E. Imperial Highway, Suite 450 EI Segundo, CA 90245-3509).

Years of experience in satellite measurements show that the accuracy of satellite on-board ephemeris is 2-3 m, and satellite clock errors can reach up to 10 ns (i.e., up to 3 m).

The GPS time correction algorithm at the time the satellite emits the PRN signal is as follows (control interface document ICD-GPS-200C, clause 20.3.3.3.1):

t = t _sv -Δt _sv the adjusted GPS time at the time of the emission of the PRN signal by the satellite, Where PRN Satellite pseudo-random signal t _sv GPS time at the time of emission of the PRN signal Δt _sv offset (error) of the satellite clock

The error of the satellite clock is determined from the equation:

Where

a _f0 , a _f1 , a _f2 polynomial coefficients (from a navigation message); t _oc reference time of the clock data (from the navigation message); Δt _r = Fe (A) ^1/2 sinE _k correction for the relativistic effect;

constant = -4.442807633 (10) ^-10 sec / (m) ^1/2 ; µ = 3.986005 · 10 ¹⁴ Earth's gravitational constant; s = 2.9979245810 ⁸ speed of light.

To increase the accuracy of calculating the distance to the satellite, it is necessary to know the signal delay during the passage of the ionosphere and troposphere.

Ionospheric delays with the absolute measurement method give errors in the distance up to 20-30 m or more. The ionosphere model obtained from eight parameters of the satellite navigation message allows taking into account up to 50% of the ionospheric delay. The following is a model of the ionosphere for correcting the ionospheric delay (“Klobuchar model” (K. Antonovich. Use of satellite radio navigation systems in geodesy. In 2 vols. T.2. Monograph / K. M. Antonovich; GOU VPO “Siberian State Geodetic Academy” . - M.: FGUP Kartotsentr, 2006. - 360 p.).

AMP is the amplitude coefficient.

T _iono correction _is determined for L1 frequency. For frequency L2, the correction is determined by the coefficient γ

t = 4.32 * 10 ⁴ λ _i + GPS time (sec)

0≤t <86400: otherwise, if t≥86400, then subtract 86400 seconds;

if t <0, then add 86400 seconds.

Designation of the elements used in calculating the ionospheric delay:

- Elements transmitted by the satellite in the navigation message:

α _n are the coefficients of the cubic equation representing the amplitude of the vertical delay (4 coefficients of 8 bits each);

β _n are the coefficients of the cubic equation representing the period of the ionospheric model (4 coefficients of 8 bits each).

- Elements generated by a ground computer:

E - satellite elevation angle (half cycles);

A - satellite azimuth (half cycles);

u - geodetic latitude of the user (half-cycle) WGS-84;

λ _u - geodetic longitude of the user (half-cycle) WGS-84.

- Calculated elements:

χ - phase (radians);

F is the slope factor;

t is local time (sec);

ϕ _m is the geomagnetic latitude of the earth projection of the point of intersection of the line of sight with the ionospheric layer (the average layer height is assumed to be 350 km) (half-cycles);

λ _i is the geodetic longitude of the earth projection of the point of intersection of the line of sight with the ionospheric layer (half-cycles);

ψ is the central earth angle between the user’s position and the earth projection of the point of intersection of the line of sight with the ionospheric layer (half-cycles).

With two-frequency measurements, it is possible to estimate the ionospheric delay and obtain a pseudorange free from the influence of the ionosphere.

Where

A - A = 40.3 · TEC is an unknown parameter;

TEC — electron density in the ionosphere;

P _L1 is the pseudorange measured at the frequency L1;

P _L2 is the pseudorange measured at the frequency L2;

f _L1 - carrier frequency L1;

f _L1 - carrier frequency L2.

Pseudorange, free from the influence of the ionosphere, contains errors of the satellite clock, ephemeris and troposphere. In addition, it is much more noisy than the pseudorange measured on L1 and L2 (about 3 times more).

With two-frequency phase measurements, it becomes possible to estimate the ionospheric phase advance (Antonovich K.M. Use of satellite radio navigation systems in geodesy. In 2 vols. T.1. Monograph / K.M. Antonovich; GOU VPO Siberian State Geodetic Academy. - M .: FSUE “Kartotsentr”, 2006. - 360 p.).

Where

f _L1 - carrier frequency L1;

f _L2 - carrier frequency L2;

λ _L1 - wavelength L1;

λ _L2 - wavelength L2;

Ф _L1 is the phase of the carrier, measured at a frequency of L1;

Ф _L2 - carrier phase, measured at the frequency L2;

N _L1 - the whole ambiguity at the frequency L1;

N _L2 - the whole ambiguity at the frequency L2.

Estimation of the ionospheric delay by phase measurements turns out to be accurate (of the order of 1 cm), but contains whole ambiguities, the determination of which is a rather difficult task. Noisy estimates of ionospheric delay by codes can be smoothed out by estimates of differential delay (between epochs) from phase measurements. The obtained smoothed estimates usually have a decimeter level of accuracy after the satellite has ascended to an elevation angle of 300.

Tropospheric delays give errors in distances to the satellite from 2.5 m at the zenith to 26 m at an elevation angle of 50. To estimate the tropospheric delay, you can use the Black model. Black's tropospheric delay formula is the sum of the integrals of the hydrostatic and wet components of the refraction of the parameters along the path of the beam:

The hydrostatic part of the tropospheric delay is represented by the expression:

,

,

and the wet component

,

,

Where

N _h - hydrostatic refractive index;

N _w - wet refractive index;

ρ is the geometric distance in a straight line from the user to the satellite;

- гидростатическая часть тропосферной задержки;

- hydrostatic part of the tropospheric delay;

P _A is the pressure in the atmospheres;

T _A - temperature in degrees Kelvin;

E ⁱ is the satellite elevation angle in degrees;

L is L = 0.85;

H _{S, h} - height H _{S, h} = 14898 (T _A - 4.12);

H _{S, w} - height H _{S, h} = 13000 m above the user;

r _A is the radius vector to the station;

k ^w - coefficient of climatic conditions.

The values of the coefficient k ^w are given in the table: Climatic conditions k ^w Summer in the tropics or mid-latitudes 0.28 Spring or fall in mid-latitudes 0.20 Winter in the middle latitudes (sea) 0.12 Winter in the middle latitudes (continent) 0.06 Polar regions 0.05

For absolute positioning by phase measurements, there are mathematical models that can reduce positioning errors resulting from the passage of a satellite signal through the ionosphere and troposphere. However, onboard ephemeris errors (2-3 m) and satellite clock errors (up to 3 m) remain. To minimize these errors, accurate orbits are used (exact ephemeris files and satellite exact time files). Exact ephemeris and accurate corrections of satellite clocks are post-processing products. They are represented by the International GPS Service (MGS) and other services after observations and have a declared accuracy of less than 5 cm in position and 0.1 ns in time.

The International GPS Service (MGS) is an international scientific organization (officially started operating on January 1, 1994) that collects, archives, distributes GLONASS / GPS observations from receivers and uses them to calculate high-precision satellite ephemeris, Earth rotation parameters, coordinates and station speeds tracking and satellites, as well as information on the ionosphere and troposphere. The IGU consists of a network of observation stations located around the world, Data Centers, Analysis Centers, Analysis Coordinator, Central Bureau and Governing Council. Accurate orbit data can be obtained via the Internet 9 system directly from the IGU website ( www.igscb.jpl.nasa.gov ) without restriction of access. Since they are calculated from data collected from all stations of the world network, they are the best available accurate orbits.

A successful solution of the claimed method is based on continuous measurement of the phase of the carrier from as many satellites as possible. This is a typical situation when measuring on airplanes. If there is a good quality of continuous two-frequency phase measurements, the ACE method provides accuracy in the kinematic mode of 10-40 cm. In the static mode, the accuracy significantly depends on the observation time: 24 hours - 2 cm, 8 hours - 4 cm, 2 hours - 10 cm.

After solving the navigation problem, the rectangular coordinates are converted into geodetic coordinates: B, L, H (geodetic: B - latitude, L - longitude, H - height above the ellipsoid) in the WGS-84 coordinate system.

Thus, the claimed method achieves an increase in the accuracy of the trajectory determination of the coordinates of the location of the aircraft on large long routes during flight research, where there are no ground-based radio navigation stations. In addition, unlike the differential phase mode of processing, which requires the deployment of base stations with known geodetic coordinates, the ACE method uses data from only one two-frequency receiver located at a remote site, which allows you to process aircraft flight data on long-haul routes with an accuracy of 10-40 cm The claimed method can be used to determine the accuracy characteristics and study of tracking systems of aviation objects.

Claims (2)

1. A method for high-precision measurements of the trajectory coordinates of an aircraft (LA) in flight research on long-distance paths, based on the reception of signals from spacecraft of global navigation satellite systems, including measuring the phase shift between the received signals of each spacecraft of a satellite navigation system (SNA) and the signals of the receiver of the aircraft, in the ground computer, determining the current position of the aircraft by solving equations compiled from measurements of phase shifts with signals of spacecraft of the satellite navigation system (SSS), solving the navigation problem of determining the geodetic coordinates: B, L, H (geodetic B is latitude, L is longitude, N is the height above the ellipsoid) in the WGS-84 coordinate system, characterized in that after flight using a ground computer by absolute positioning according to phase measurements by using accurate ephemeris and accurate satellite time, determined by the International GPS Service (MGS) via the Internet, calculate the satellite position using Kepler elements of the orbit contained in the ephemeris data, and the algorithm for determining the coordinates of the aircraft is implemented in the form of a calculation sequence that includes taking into account the delay of the ionospheric delay according to the Klobuchar model and the troposphere of the delay according to the Black model, fixing an integer solution from the SNA receiver code sequences, determining by the least squares method the coordinates of the aircraft according to the phase measurements of the SNA receiver with the resolution of phase ambiguity, using the algorithm with a floating solution, the conversion of the obtained rhombic coordinates of the location of the aircraft in the geodetic coordinate system. 2. The method of high-precision measurements of the trajectory coordinates of the aircraft in flight research on long-haul routes according to claim 1, characterized in that to ensure convergence in the algorithm for the floating solution of the necessary accuracy, static measurements of the SNA signals are carried out before takeoff and after landing the aircraft.

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