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WO2006108227A1 - Levee d'ambiguite amelioree par l'utilisation de trois signaux gnss - Google Patents

Levee d'ambiguite amelioree par l'utilisation de trois signaux gnss Download PDF

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Publication number
WO2006108227A1
WO2006108227A1 PCT/AU2006/000492 AU2006000492W WO2006108227A1 WO 2006108227 A1 WO2006108227 A1 WO 2006108227A1 AU 2006000492 W AU2006000492 W AU 2006000492W WO 2006108227 A1 WO2006108227 A1 WO 2006108227A1
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Prior art keywords
widelane
signals
ambiguity
ionospheric
narrow
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PCT/AU2006/000492
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English (en)
Inventor
Yanming Feng
Miles P. Moody
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Yanming Feng
Moody Miles P
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Priority claimed from AU2005901769A external-priority patent/AU2005901769A0/en
Application filed by Yanming Feng, Moody Miles P filed Critical Yanming Feng
Publication of WO2006108227A1 publication Critical patent/WO2006108227A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/32—Multimode operation in a single same satellite system, e.g. GPS L1/L2
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/42—Determining position
    • G01S19/43—Determining position using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
    • G01S19/44—Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method

Definitions

  • This invention presents a system for efficient Ambiguity Resolution (AR) and positioning performed with three or more ranging signals from Global Navigation Satellite Systems (GNSS) such as modernized GPS and Galileo satellite systems and Regional Navigation Satellite Systems (RNSS) such as Quasi-Zenith Satellite Systems (QZSS).
  • GNSS Global Navigation Satellite Systems
  • RNSS Regional Navigation Satellite Systems
  • QZSS Quasi-Zenith Satellite Systems
  • the system consists of three subsystems, for GNSS service, GNSS receiver and user terminal respectively.
  • the present invention concerns an ambiguity resolution (AR) method performed with three or more ranging signals from Global Navigation Satellite Systems (GNSS), examples being modernized GPS, Galileo and Quasi-Zenith Satellite Systems
  • GNSS Global Navigation Satellite Systems
  • the invention also concerns a positioning method using specifically combined GNSS signals whose phase ambiguities were correctly determined using the said AR method to support decimeter positioning services on regional to global scales and centimeter level positioning services locally to regionally.
  • the invention is described as a system consisting of three subsystems, using the given GNSS service frequency scheme, a receiver and user/application terminals.
  • GNSS Global Navigation Satellite Systems
  • GPS Global Positioning Systems
  • Glonass Glonass and all future systems such as Galileo systems.
  • Regional Navigation Satellite Systems include the planned Japanese Quasi- Zenith Satellite Systems (QZSS) and the possible Chinese Beidou 2 system.
  • Each GPS satellite transmits continuously using two radio frequencies in the L-band, referred to as L1 and L2, at respective frequencies of 1575.42 Mhz and 1227.60 Mhz.
  • Each GPS signal has a carrier at the L1 and L2 frequency, pseudo-random noise (PRN) codes and satellite navigation data.
  • PRN pseudo-random noise
  • Two different PRN codes are transmitted by each satellite C/A code (P1) and P2 code (PfY).
  • P1 and P2 code P2 code
  • the Galileo system is designed to provide four signals for commercial and civilian use centered on L1 (1575.42MHz), E6 (1278.750MHz), E5B (1207.140Mhz) and E5A (1176.450MHz). Each signal also transmits both carrier phase and PRN codes.
  • the Galileo open service and safety-of-life service will be provided with L1 , E5A and E5B frequencies, while the Galileo commercial service can also access an additional frequency on E6.
  • the planned QZSS system will provide service with L1 , L2 and L5 frequencies as well on regional basis. It has been suggested the Chinese Beidou-2 system also transmits signals at three frequencies in L-band, although details of the frequency allocations remain unpublished.
  • Ambiguity resolution techniques normally involve the use of unambiguous code observations and ambiguous phase observations on multiple satellites together to
  • the geometry-dependent approach to estimate the carrier phase ambiguities is to construct a global estimator that includes four devices:
  • Fig 1 shows the general structure of an ambiguity resolution global estimator. Double-differenced code and phase data set for 2 or more frequencies from 2 or more GNSS receivers 400 will be supplied as ready data set 105 to a global filter 100.
  • physical models defined by observation vector and matrix will be formed.
  • the process 120 defines the a-priori and a-posteriori statistical information of the measurement noises.
  • Estimator 130 supplies floating ambiguity estimates for all the carrier signals.
  • the search engine 140 yields integer solutions for the ambiguity and integer-fixed position solutions for the current epochs, from which the residuals will be supplied to the process 120 for improved statistical information for use in future epochs. This process is optional for some software.
  • a prior-art solution for this class of methods may cover any parts of the global filter
  • Fig 1A shows a prior-art structure of the physical modeling process 110 in terms of measurements and parameters/biases of different types 111a, for the GPS dual case 112a and the GPS three frequency case 113a.
  • the process either has to include the ionosphere biases as parameters to estimate or correct them with other means, in order to reduce the effects to a certain level, for instance, less than 0.5 cycle.
  • the number of the ionospheric parameters is as high as the number of satellites in view minus one. The accuracy requirements for the ionospheric bias estimation/correction are difficult to meet.
  • the existing methods operate over short base-rover distances, typically 10-20km in the single-base real time kinematic (RTK) case.
  • RTK real time kinematic
  • the ionospheric corrections can be better estimated from multiple reference stations, therefore, the base-to-rover distance (equivalent) can be extended to 30 to 40 km.
  • Step 1 the integer ambiguities for the extra-widelanes (EWL) as marked in Table 2 and Table 3 can be fixed by rounding off the difference in cycle unit between the virtual phase and selected virtual code measurements, where the first-order ionospheric delays were deleted.
  • the total noise in the difference is 1/5 cycle or less.
  • the 100% success rate can be expected with the measurement from a single epoch or a few epochs. This has been the first step of almost all existing methods. But this method relies on the code measurements on both L2 and L5 signals, which may not be expected to be available in all circumstances or for all three frequency receivers.
  • Step 2 There are two methods developed for this step: a. Method 1 : After the EWL integer has been fixed, efforts are made to fix the integer for the widelane signals by rounding off the difference in cycle units between the widelane signal and the refined range with the integer-fixed extra- widelane phase measurement. Due to the presence of ionospheric errors in the difference, performance of this method depends on base-to-rover distance. b. Method 2. Applying the same process as Step 1 to the widelane signal instead. The total noise in the difference is about 1/3 to 1/2 cycle. Therefore, high success rate by rounding-off the measurement from a single epoch cannot be expected.
  • Step 3 After the widelane integer has been fixed, the third step is to try to fix the integer for the medium-lane (ML) signal by rounding off the difference in cycle unit between the ML signal and the refined range with the integer-fixed wideiane phase measurement.
  • the idea is the same as in Method 1 , Step 2.
  • the problem is again the large effect of the ionospheric delay in the difference with respect to the wavelength, thus limiting the step to working over short distances only.
  • Feng (2005) and Feng and Rizos (2005) outlined a distance-independent, geometry- free method for performing ambiguity resolution with three GNSS signals, comprising three major processes:
  • Process 1 Geometry-free estimation of the first and second integers: Fixing the integer ambiguities for the extra-widelane (EWL) and WL as marked in Tables 2 and 3 for GPS and Galileo service cases by rounding off the difference between the extra-widelane virtual phase and the virtual code double difference measurements. In these differences, the first-order ionospheric errors are eliminated. The success of the ambiguity fixing depends on the code noise level, which may contain effects of multipath.
  • Process 2 Estimation of the first-order double-differenced ionospheric delay of any ray path from the two integer-fixed widelane signals.
  • the uncertainty of the direct estimate from a single epoch measurement would range from a few centimeters to a few decimeters.
  • the estimate can be improved by modeling over multiple epochs or recursively. This estimation is a distance-independent process.
  • Process 3 Geometry-free estimation of the third independent integer.
  • the third virtual observable must be linearly independent of the two known combinations used in Process 1 , for instance, L1 , being the one in this category.
  • L1 the two known combinations used in Process 1
  • the first-order ionospheric bias can be removed.
  • this distance-sensitive bias term is replaced by the distance- independent noise term magnified by noise in the phase observable.
  • the AR performance of the third signal integer mainly depends on the uncertainty of the ionosphere estimate/correction, which generally consists of bias and random noise components.
  • the integer uncertainty in a cycle is 12 times the residual uncertainty in metres.
  • This invention presents a system for efficient Ambiguity Resolution (AR) and positioning performed with three or more ranging signals from Global Navigation Satellite Systems (GNSS) such as modernized GPS and Galileo satellite systems and Regional Navigation Satellite Systems (RNSS) such as Quasi-Zenith Satellite Systems (QZSS).
  • GNSS Global Navigation Satellite Systems
  • RNSS Regional Navigation Satellite Systems
  • QZSS Quasi-Zenith Satellite Systems
  • the systems consist of three subsystems for GNSS service, GNSS receiver and user terminal respectively. The high-level description of the system is shown in Fig 2.
  • the major advantages in accordance with this invention are the new design for the physical modeling process 110B as shown in Fig 1B. This is compared to the existing design of the physical modeling process 110A as shown in Fig 1A, where the emitting signals L1 , L2 and L5 ( or widelanes (WL)) are used directly.
  • the widelane and a specific narrow-lane are chosen instead of other possible combinations, so that the effects of the residual ionospheric biases are much less sensitive to the base-rover distances.
  • the selected 2 signals can tolerate larger ionosphere errors, thus allowing for more reliable and rapid ambiguity resolution over longer distances.
  • the procedures include steps:
  • An additional object of the present invention is to maximize the performance benefits of positioning solutions, achieved using the select GNSS signals whose phase ambiguities were correctly determined using the said steps.
  • the invention can support at least the positioning applications as follows; (1 ) At the regional to global scale, real time kinematic positioning services at decimeter level with three carrier signals from observation of seconds to minutes (2) At the local to regional scale real time kinematic positioning services at centimeter level with three carrier signals from observations of seconds to minutes
  • the positioning performance will then depend on the phase noise level and tropospheric errors.
  • the local, regional and global scales in this context are defined over the base-to-rover distance of tens, hundreds and thousands of kilometers.
  • This invention has significant implications for the future generation GNSS services using three and more frequency bands.
  • Table 1 gives frequencies, wavelengths and assumed noise levels of three GPS civilian signals and four Galileo open and commercial service signals.
  • Table 2 gives frequencies, wavelengths, assumed noise levels and success rates of three GPS virtual WL and EWL signals, of which two are independent.
  • Table 3 gives frequencies, wavelengths, assumed noise levels and success rates of six Galileo virtual WL and EWL signals, of which 2 WL and 2 EWL signals are independent.
  • Table 4 summarizes the error characteristics of the two select EWL and WL combinations for each of the four possible services offered by every combination of three GNSS signals. Of these combinations, two are independent and the first EWL integer can be estimated by a geometry-free method.
  • Table 5 summarizes the error characteristics of the third NL signals combined from each three-signal combination for each GNSS service.
  • Each of the optional signals is independent of the two EWL and /or WL signals in Table 4.
  • the last column is the expected total noise in cycles. It is clear that one or two of the signals have the total noise level lower than 0.25 cycles, which appear superior to all others for ambiguity resolution.
  • Table 6 gives smoothing time epochs for various positioning accuracy levels, showing the comparison between GPS pseudo-ranges and GPS/Galileo widelane phase measurements. It will be noted that the latter require approximately one order of magnitude smaller time duration.
  • Fig 1 shows the general structure of an ambiguity resolution global estimator with inputs of GNSS code and phase data sets for 2, 3 or more carriers and outputs of ambiguity-fixed phase measurements and positioning solutions.
  • Fig 1A shows a prior-art structure of the physical modeling process in terms of measurements and parameters/biases of different types, given examples in both GPS dual case and the three frequency case.
  • Fig 1B shows a summary of the physical modeling process, showing the major difference with respect to the existing process as shown in Fig 1A, in accordance with embodiments of this invention.
  • Fig 2 shows the major components and overall structure of an improved three carrier ambiguity resolution system in accordance with embodiments of the invention, consisting of 3 subsystems.
  • Fig 3 illustrates the key component of Subsystem 1 , a process that identifies the suitable combined/virtual signals for a given GNSS service with signals on 3 or more frequencies in accordance with an embodiment of this invention.
  • Fig 3A is a further architecture in Subsystem 1 , showing the classifications of possible GNSS services in terms of frequencies in accordance with an embodiment of this invention.
  • Fig 4 is a structure of a GNSS receiver that tracks satellites and outputs the code and carrier measurements on 2, 3 and more frequencies for all the satellites in view, in accordance with embodiments of this invention.
  • the Subsystem 2 is set of at least two GNSS receivers 400.
  • Fig 5 shows the structure of Subsystem 3, comprising a computing system that consists of procedures and algorithms to process the measurement outputs from 2 or more receivers for ambiguity resolution and position estimation in accordance with embodiments of this invention.
  • the invention is a system for improved three carrier phase ambiguity resolution, comprising 3 subsystems.
  • Subsystem 1 operates at a navigation satellite system level;
  • Subsystem 2 operates at the receiver level;
  • Subsystem 3 operates at the user/network terminal or application level.
  • Fig 2 shows the major components and overall structure of an improved three carrier ambiguity resolution system in accordance with embodiments of the invention.
  • Subsystem 1 A Processing Device for Identification of Useful GNSS Signals
  • a one-way pseudo-range or phase is defined as the pseudo-range or phase measurement for one receiver-to-satellite pair, which may also be called a "line-of- sight” measurement or "zero difference” measurement.
  • d trop tropospheric delay
  • ⁇ r (t 0 ,L c ) and ⁇ s (r 0 ,Z,,) are receiver and satellite instrument
  • ⁇ the wavelength of the carrier signals
  • ⁇ c phase noise, including maltipath effect
  • Equation (1 ) d orb , d irop , dion , c , dt, dT are the same as for Equation (1 ).
  • the linear combination of three signals can be generally formulated as (Feng, 2004, Abidin, 2000) L(i,j,k) J ⁇ A - 5 . L 5 where i, j, k are any integer coefficients.
  • N(i,j,k) i - N ⁇ + j - N 2 + k - N 5 (6)
  • Ki is a constant depending on the slant total electron content (STEC); ⁇ x is the ionospheric scale factor (ISF).
  • the integers i, j and k take the choices of 0 or 1 only.
  • the magnitude of the ionospheric effects on the linear combination (7) can be expressed the same as (5).
  • the noise level of the combined code is expressed as
  • FIG 3A shows the classifications of possible GNSS services in terms of service frequencies in accordance with an embodiment of this invention.
  • a GNSS signal data set 310 gives the groups of possible services using 2 and 3 frequencies from the processing unit 310a.
  • the data set 310b lists five dual- frequency and four three-frequency options:
  • Galileo service with L1 , E5B, E5A open and safe-of-life
  • Galileo service with L1 , E6, E5A commercial
  • Equation (3) there is an infinite number of linear combinations defined by Equation (3). To assure the integer nature of the combined signals, only combinations with integers i, j, and k are considered, of which three are linearly independent.
  • the end goal of three carrier ambiguity resolution (TCAR) is to find three combinations, whose integer ambiguities can be easily and reliably determined, then leading to recovery of the integer ambiguity solutions of the three natural phase measurements, for instance, in the GPS case, L1, L2 and L5.
  • Fig 3 illustrates the processing elements of the system 300 to identify the most useful virtual signals for the given service classified in the data set 310.
  • the functions of the five elements in the system 300 are described as follows:
  • Element 310 identifies the first EWL signal, which is L(0,1 ,-1), assuming that f(1 ,0,0)>f(0,1 ,0)>f(0,0,1) and [(f( ⁇ ' i > O)-f(O,O,1))]>[f(1 ,O,O)-f(O,1 > O)].
  • the characteristics of this EWL are provided in the first line of each block of Table 4.
  • Element 320 examines the options for the second most useful signals. Table
  • the virtual frequency and wavelength are given in Columns 4 and 5 of Table 4; the ionospheric scale factor (ISF) and the phase noise factor (PNF) in Columns 7 and 8.
  • Columns 9, 10 and 11 give the total noise levels in cycle units computed from the ISF and PNF using three different assumptions for the ionospheric delay on the L1 carrier and the 1 ⁇ phase noise level and residual tropospheric delay.
  • Element 325 decides which is the optimal second EWL signal from Table 4.
  • each service there is one superior EWL having a minimum ionospheric scale factor, which reduces the effects of the first-order ionospheric delay to the factor of 0.0744 in the GPS case, and 0.3035, 0.2454 and 0.0227 in the three Galileo cases respectively.
  • Ambiguity resolutions using these EWL signals should outperform the use of any other combinations over long distances.
  • Element 325 also decides one more additional EWL signal, for consistence check purposes if applicable.
  • Element 330 examines the options for the third most useful signals from a new category of combinations, of which each must be independent of the previous two or their derivatives.
  • Table 5 lists the characteristics of the most interesting NL combinations whose ISF are much less than 0.10 in magnitude, and any one is linearly independent of the previous two EWL or WL signals in Table 4 within each service case. After examination of all the possible combinations at EWL, WL, ML and NL levels, it is recognized that there are many EWL, WL and ML signals in this category, but none of these is evidently more useful for ambiguity resolution purposes over longer distances.
  • L(-3, 4,0) is a widelane of 1.628 m wavelength and independent of L(1 ,0,-1 ) and L(0, 1 ,-1) and their derivatives.
  • ISF the ionospheric scale factor
  • PNF phase noise factor
  • an ionospheric delay of 1 m level leads to a ranging error of 1 cm or less in these NL measurements. With respect to the wavelength of 11 cm, the ionospheric effect is only less than 0.1 cycles. If the other effects such as relative tropospheric errors and phase noise are controlled within a few centimeters, these NLs can be used for more effective ambiguity resolution over longer baselines. Fortunately, the tropospheric delay is less distance-sensitive.
  • Useful NL signals are also identified in a number of dual frequency service cases, such as GPS L1 and L2, GPS L1 and L5, Galileo L1 and E6, Galileo L1 and E5A and Galileo L1 and E5B. This implies that long-range ambiguity resolution may be achieved using dual-frequency receivers as well. For instance, in the GPS dual carrier case, the useful NLs are L(4,-3) and L(5,-4), where the respective ISFs are 0.0902 and 0.0708.
  • Element 335 decides which NL signal is used as the third signal for ambiguity resolution.
  • the one with minimal noise to wavelength ratio (total noise in cycle) is the best choice.
  • the one with the next lowest noise to wavelength ratio may be selected for consistence check purposes if possible.
  • the two narrow-lane choices are L(5,-3,1 ) and L(4,1 ,-4) e.
  • the two narrow-lane choices are L(4,0,-3) and L(4,-1 ,-2) f.
  • the narrow-lane choice is L(5,-4)
  • the results of the process 300 would be the data set 340, which gives 3 sets of coefficients for the 3 best EWL/NL signals for ambiguity resolutions.
  • Fig 4. schematically illustrates a generic multiple frequency scenario of GNSS receiving system, which is known as Subsystem 2 as shown in Fig 2.
  • Receiver 400 receives GNSS signals from any number of satellites in view such as SV1 , SV2, SV K, shown respectively at 411 , 412 and 410.
  • Each signal has 2, 3 or more than three frequencies, produces 2, 3, and more sets of code and carrier measurements.
  • this Subsystem must have a set of at least two multiple frequency GNSS receiver, that can track signals from more than four GNSS satellites.
  • Use of existing dual-frequency GPS receivers can also partially achieve improved ambiguity resolutions.
  • Subsystem 3 A Processing Device for Carrier Phase Ambiguity Resolution
  • Fig 5 shows the structure of Subsystem 3, which has a core processing device 500 comprised of procedures and algorithms to process the measurement outputs from 2 or more receivers for ambiguity resolution and position estimation in accordance with embodiments of this invention.
  • a core processing device 500 comprised of procedures and algorithms to process the measurement outputs from 2 or more receivers for ambiguity resolution and position estimation in accordance with embodiments of this invention.
  • Two data sets 430 and 340 will be supplied to the device 500.
  • Data set 430 contains code and carrier phase measurements from 2 or more GNSS receivers 400.
  • Data set 340 contains 3 sets of coefficient parameters for the select EWL and NL virtual signals as determined in Subsystem 1.
  • the subsystem resolves three carrier ambiguities at two levels: a) At the regional-to-global level, estimate the first type of EWL and WL ambiguities using distance-independent geometry-free approaches; estimate the second type of EWL and WL ambiguities using geometry-dependent methods, over distances of up to a few thousands of kilometers; b) At the local level, estimate the third NL ambiguity using geometry-dependent methods, over baselines of up to a few hundred kilometers.
  • the device 500 completes ambiguity and positioning tasks with operation of six processing elements: 510, 515, 520, 525, 530 and 535.
  • Processing Element 510 prepares data sets of double-differenced code and phase measurements for the select EWL, WL and ML and NL signals for use in the generic process 100. Other elements are described in the following sections.
  • Processing Element 520 is an estimator of the ambiguity of the first and second EWL signals comprising three steps. Step 1 of Processing Element 520 performs determination of the first EWL ambiguity using the geometry-free method as outlined in Feng (2004) and other authors (Hatch, 2000) etc. For double-differenced phase observations, the first EWL is constructed as follows: where the double differenced range is expressed as:
  • the probability of the correct integer can be given as follows:
  • EWL integers with two STDs ⁇ ⁇ V ⁇ for measurements from a single epoch and— ⁇ AV ft for improved measurements (for instance, by averaging over several
  • the above process is a geometry-free and distance-independent estimator, giving the correct integers in the simplest manner.
  • This method is desirable and reliable for these specific EWLs, as the distance-related ionospheric errors do not have any effects.
  • the problem is that this method requires the code measurements on the second and third emitting signals, which may not be available at all times or in all circumstances. Therefore, this step is optional.
  • Step 2 of Processing Element 520 is a physical modeling process for the second select EWL signals. According to Table 4, the preferred second EWL signals in the four GPS/Galileo services studied are
  • ⁇ VP I/2 ⁇ V;5+£ ⁇ VPi/2
  • ⁇ VI(l,-6,5) ⁇ Vp+0.0744 ⁇ -A(l,-6,5) ⁇ VN(l,-6,5)+ ⁇ ⁇ Vi(I ⁇ 5) (1 7) where ⁇ VP 1/2 is the double-differenced, ionospheric-free code measurements.
  • ⁇ X is the 3-by-1 state correction term to be estimated.
  • ⁇ VP ionospheric-free code measurement ⁇ VP 1/2 . Therefore, ⁇ VP (Ui0) may be used
  • ⁇ VP 1/2 ⁇ Vp+s ⁇ Wu2
  • Step 3 of the Processing Element 520 performs estimation of the ambiguities ⁇ V N(0, 1 ,-1) and ⁇ V N(1 , -6, 5) using an existing global estimator as schematically shown in Fig 1.
  • Section 3.5 outlines the popularly used least square ambiguity decorrelation adjustments (LAMDA) procedures as one option. Any other existing improved method can be employed.
  • LAMDA least square ambiguity decorrelation adjustments
  • the EWLs L(1-3,2), L(1 ,-10,9) and L(1 ,-4,3) are used instead of L(1 ,-6,5).
  • Processing Element 530 will perform the positioning estimation using ambiguity fixed observations. This process comprises three steps.
  • Step 1 of Processing Element 530 estimates the 1st-order ionospheric-bias using two ambiguity-fixed observations. First of all, with the correct EWL integers for
  • the first-order ionospheric bias can be given as follows (Feng, 2004)
  • This equation allows the first-order ionospheric delay to be estimated directly from the three carrier signals in receiver, playing an important role in three carrier ambiguity resolution and positioning.
  • the effects of the second-order ionospheric errors could be partially reduced as well over shorter base-to-rover distances.
  • the problem is the large uncertainty of the estimate (24) due to carrier phase multipath and receiver noise in the widelane combinations ⁇ V L(1 ,-1 ,0) and ⁇ V L(1 ,0,-1 ). This uncertainty can reach the level of a few to several decimeters, for ⁇ ⁇ Vil ranging from 2 mm to 5 mm.
  • Step 2 of Processing Element 530 is to correct the ionospheric bias in the Widelane signals and refine WL measurements with phase smoothing procedures.
  • phase noise standard deviation of this phase measurement is about 3 ⁇ ⁇ _.
  • n is the number of measurement epochs.
  • the technique was first proposed by Hatch (1982) for smoothing pseudo-range measurements and can be readily generalized to provide real time recursive estimation of the ambiguity-fixed phase measurements, or over a sliding/moving observation window.
  • Table 6 outlines the minimum number of samples or time epochs required to achieve the different accuracy levels of double-differenced (DD) measurements given in the first column. It is seen that, to achieve the same DD ranging accuracy, the smoothing period required for the widelane phase measurements is typically over 10 times smaller than required for smoothing the code measurements.
  • decimeter positioning accuracy can be achieved within 1 to 3 minutes with the ambiguity- resolved widelane phase measurements, instead of 10 to 30 minutes of convergence time to the same levels as compared to use of DD ionosphere-free code measurements.
  • This technological advance is remarkable, promising much wider regional and global scale applications which have not been offered by existing GPS technologies.
  • Step 3 of Processing Element 530 carries out estimation of the user states using the ionosphere corrected and/or smoothed WL measurements using least-square estimation. After the first two EWL ambiguities ⁇ vN(o,i,-i) and ⁇ VN(i,-6,5) or their
  • positioning can be done without the resolution of the third ambiguity, if only decimeter accuracy is concerned. This positioning is performed over any distances.
  • Processing Elements 515 and 535 deal with both cases respectively.
  • the estimation is based on the models using one NL measurement in Table 5, for instance, L(4,0,-3). This narrow-lane must be used together with other virtual measurements to allow the over-determined ambiguity estimation with measurements from a single epoch.
  • the first step of this Element 515 is to form the physical models with one WL and one NL signals.
  • the observation models for ambiguity resolution are directly written as
  • ⁇ W(l,O,l) ⁇ VJ ⁇ + +s ⁇ W(1 ⁇ 1)
  • Step 2 of Processing Element 315 is estimation of the ambiguities ⁇ V N(1 ,0,-1) and ⁇ V N(4, 0, -3) using an existing a global estimator as schematically shown in Fig 1.
  • Section 3.5 outlines the least square ambiguity decorrelation adjustments (LAMDA) procedures as one of the option to complete this estimation.
  • the success in estimation of the integer ambiguity of L(4,0,-3) depends upon the quality of the WL and NL measurements.
  • the direct phase noise would be typically at the level of 1 to 2 centimeters while the ionospheric term can be controlled to 1 cm or less, either via bounding the ionospheric error on L1 to 1 m, or bounding the base-to-rover baseline. The tropospheric error seems the most dominating factor.
  • Processing Element 515 covers the case of Dual Carrier Ambiguity Resolution (DCAR ) using the WL and NL signals.
  • DCAR Dual Carrier Ambiguity Resolution
  • L(1 ,-1) measurements may be determined first and the positioning results are used as constraints for reduced integer search space.
  • the Widelane L(1,-1) and Narrow-laneNarrow-lane L(4,-3) or L(5,-4) are used together to resolve the ambiguities for GPS L1 and L2 signals.
  • the measurements include
  • ⁇ VL(1,-1) ⁇ Vp + 1.2833 - A(I - 1) ⁇ VN(I,- l) + f ⁇ VL(1 ,- 1 ,o, f. 2 (34)
  • ⁇ VZ(4 -3) ⁇ Vp - 0.0902 ⁇ L - A(4,-3) ⁇ VN(4,-3) + £ ⁇ VL(4, . 3)
  • Equation (26) can be used to resolve ambiguities more efficiently, if the effect of multipath in carrier phase is normal.
  • Processing Element 535 resolve the NL ambiguities after the process 530, where two EWL ambiguities (their dependent WL ambiguities) have been fixed and WL have been corrected and refined through Step 2. Therefore, the observation models for ambiguity resolution are directly written as:
  • the final step of Processing Element 535 performs the positioning process after the third ambiguity is resolved.
  • the ambiguities for the three original signals eg L1 , L2, and L5
  • the first-order ionospheric delay can be estimated precisely and correction can apply to any combinations.
  • those with minimum phase noise factor should be used for positioning.
  • Good examples are the ionospheric free measurements L(77,-60,0) with a phase noise factor of 3 and L(4,0,-3) with a phase noise factor of 2.6, while worse examples are the ionospheric free signal L(0,24,-23) with a phase noise factor 16.
  • the effect of phase noise is 3 ⁇ or less, the effect of the tropospheric error will be the dominant factor. In other words, if the effect can be restricted to the centimeter level, centimeter positioning performance is achievable.
  • An efficient method is to restrict the base-to-rover baselines to 100 km or so, over which the relative tropospheric biases in the double differenced ranges could be bounded to a few centimeters.
  • LAMBDA Least-squares ambiguity decorrelation adjustment
  • the central point of the LAMBDA method is to introduce a hypothetical transformation Z in the restricted class of transformation which diagonalises the matrix WN.
  • Processing Element 525 is responsible for recovering the integer ambiguities of three emitting signals. It is the final process for complete ambiguity resolutions. In dual-frequency cases, given two known integers, for instance, ⁇ VN(l,-l) and
  • the present invention for three carrier ambiguity resolution use two select EWL signal and one NL signal instead of other possible combined signals. These EWL and NL signals can tolerate much larger ionospheric errors than others, thus allowing for more reliable and rapid ambiguity resolution over longer distances. In the least-square estimator, no ionospheric and tropospheric parameters are needed, the computational effort for statistical search and validation is minimal.
  • the subsystem resolves three carrier ambiguities at two levels
  • the above improved ambiguity resolution techniques support kinematic positioning services at the regional to global scales for decimeter accuracy and at the local to regional scales for centimeter accuracy, achieved in real time or post-processing.
  • the present invention will have significant impact on the future GNSS services at all global, regional and levels.

Landscapes

  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)

Abstract

L'invention concerne un système permettant une levée d'ambiguïté et un positionnement améliorés, effectués à l'aide d'au moins trois signaux de mesure de la distance en provenance d'une ou de plusieurs constellations GNSS, telles que des systèmes GPS et Galiléo modernisés. Pour un service GNSS donné disposant de chacune des trois fréquences, le sous-système 1 du système recherche et sélectionne au moins deux signaux virtuels à couloir ultralarge (EWL: extrawide lane; longueur d'onde supérieure à 290 cm), et un signal virtuel à couloir étroit (NL: narrow lane, longueur d'onde d'environ 11 cm), qui présentent des facteurs d'échelle ionosphériques minimaux en amplitude par rapport à leurs longueurs d'onde. Il en résulte que ces signaux EWL et NL sont capables de tolérer des erreurs ionosphériques beaucoup plus importantes que les autre signaux, permettant ainsi une levée d'ambiguïté plus fiable et plus rapide sur des distances base-station mobile beaucoup plus grandes. Etant donné que l'estimation des paramètres ionosphériques et troposhpériques n'est plus nécessaire, l'effort de calcul pour la recherche statistique et la validation est minime. Le sous-système 2 du système se compose d'un groupe d'au moins 2 récepteurs GNSS génériques, permettant de poursuivre les satellites GNSS à vue, et produit les mesures de code et de porteuses associées à chacune des trois fréquences. Le sous-système 3 du système est un système de traitement qui effectue la levée d'ambiguïté et l'estimation de position en utilisant des doubles différences des mesures de phase et de code d'au moins deux récepteurs. Le sous-système 3 comprend quatre procédures consistant à:1) lever deux ambiguïtés EWL à l'aide de mesures associées à seule ou à plusieurs époques, avec une certitude de presque 100 %; (2) estimer la correction ionosphérique de premier ordre en utilisant des deux signaux EWL dont l'ambiguïté a été levée, et en appliquant la correction estimée au signal WL (wide lane); (3) lever l'ambiguïté du couloir NL choisi sur des distance pouvant atteindre quelques centaines de kilomètres; et (4) utiliser les signaux virtuels dont l'ambiguïté a été levée pour effectuer le positionnement cinématique en temps réel, avec une précision de l'orde du décimètre pour les échelles régionale à planétaire, et avec une précision de l'ordre du centimètre pour les échelles locale à régionale. Ce système fournit les algorithmes techniques clés pour les services GNSS locaux, régionaux et planétaires de la prochaine génération faisant appel à au moins trois signaux de porteuses.
PCT/AU2006/000492 2005-04-11 2006-04-11 Levee d'ambiguite amelioree par l'utilisation de trois signaux gnss WO2006108227A1 (fr)

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EP1972958A1 (fr) * 2007-03-22 2008-09-24 Technische Universität München Méthode de traitement d'un ensemble de signaux d'un système général de navigation par satellite ayant au moins trois fréquences porteuses
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WO2014011792A1 (fr) * 2012-07-12 2014-01-16 California Institute Of Technology Analyse de contenu électronique total d'inclinaison ionosphérique utilisant une estimation basée sur système de positionnement global
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WO2017181221A1 (fr) * 2016-04-18 2017-10-26 Spatial Information Systems Research Ltd Procédé d'analyse de multiples signaux émis par des systèmes mondiaux de satellites de navigation discrets
CN109313268A (zh) * 2016-03-18 2019-02-05 迪尔公司 具有宽巷偏差校正值和窄巷偏差校正值的导航卫星的轨道和低延时时钟的确定
CN109765589A (zh) * 2019-02-21 2019-05-17 哈尔滨工程大学 一种基于无电离层组合的三频gnss实时周跳固定技术
CN110346823A (zh) * 2019-07-17 2019-10-18 广西大学 可用于北斗精密单点定位的三频模糊度解算方法
US10495727B2 (en) 2017-02-07 2019-12-03 Raytheon Company Phase difference estimator and method for estimating a phase difference between signals
FR3087569A1 (fr) * 2018-10-18 2020-04-24 Airbus Operations Procede et systeme de guidage d’un aeronef lors d’une procedure d’approche en vue d’un atterrissage sur une piste d’atterrissage.
CN111708060A (zh) * 2020-05-29 2020-09-25 广州南方卫星导航仪器有限公司 一种基于gnss系统的亚米级定位方法、设备及介质
CN112285745A (zh) * 2020-11-18 2021-01-29 青岛杰瑞自动化有限公司 基于北斗三号卫星导航系统的三频模糊度固定方法及系统
CN112485813A (zh) * 2020-11-17 2021-03-12 中国人民解放军战略支援部队航天工程大学 Glonass测站间非组合测距码频间偏差校正方法及系统
CN113805211A (zh) * 2021-07-26 2021-12-17 广州南方卫星导航仪器有限公司 一种rtk多频观测值数据处理方法、设备、介质及产品
CN114675314A (zh) * 2022-05-30 2022-06-28 深圳市智联时空科技有限公司 一种重新收敛的精密单点定位方法
CN115097493A (zh) * 2022-06-20 2022-09-23 涟漪位置(广州)科技有限公司 Gnss相位偏差产品的完好性监测方法、服务端及存储介质
US11645156B1 (en) 2021-10-29 2023-05-09 Hewlett Packard Enterprise Development Lp Updating error policy
CN116359968A (zh) * 2023-05-10 2023-06-30 立得空间信息技术股份有限公司 一种联合北斗二号和北斗三号的三频差分定位方法
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CN117607906A (zh) * 2023-11-24 2024-02-27 中交一公局厦门工程有限公司 基于北斗/uwb云端数据处理的快速静态测量放样系统
CN118859269A (zh) * 2024-09-24 2024-10-29 长江三峡集团实业发展(北京)有限公司 基于电离层相关的宽巷模糊度整网固定方法、装置和系统

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EP1972959A1 (fr) * 2007-03-22 2008-09-24 Technische Universität München Méthode de traitement d'un ensemble de signaux d'un système de navigation par satellite ayant au moins trois fréquences porteuses
WO2008113828A1 (fr) * 2007-03-22 2008-09-25 Technische Universität München Procédé de traitement d'un ensemble de signaux d'un système mondial de navigation par satellite avec au moins trois porteuses
US8094065B2 (en) 2007-03-22 2012-01-10 Technische Universitaet Muenchen Method for processing a set of signals of a global navigation satellite system with at least three carriers
EP1972958A1 (fr) * 2007-03-22 2008-09-24 Technische Universität München Méthode de traitement d'un ensemble de signaux d'un système général de navigation par satellite ayant au moins trois fréquences porteuses
US9255993B2 (en) 2012-02-08 2016-02-09 California Institute Of Technology Processing satellite data for slant total electron content measurements
US9576082B2 (en) 2012-02-08 2017-02-21 California Institute Of Technology Ionospheric slant total electron content analysis using global positioning system based estimation
WO2014011792A1 (fr) * 2012-07-12 2014-01-16 California Institute Of Technology Analyse de contenu électronique total d'inclinaison ionosphérique utilisant une estimation basée sur système de positionnement global
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US9071234B2 (en) 2013-03-07 2015-06-30 Raytheon Company High-resolution link-path delay estimator and method for estimating a signal-path delay
US9198150B2 (en) 2013-03-07 2015-11-24 Raytheon Company Link path delay estimator that combines coarse and fine delay estimates
CN103217698A (zh) * 2013-04-16 2013-07-24 武汉大学 一种基于北斗卫星导航系统三频信号模糊度的确定方法
DE112013007301B4 (de) 2013-08-07 2023-08-31 Topcon Positioning Systems, lnc. Abschwächung der Szintillationen in Signalen von globalen Navigationssatellitensystemen, welche durch ionosphärische Unregelmäßigkeiten verursacht werden
CN105277958A (zh) * 2014-07-16 2016-01-27 上海双微导航技术有限公司 一种采用三频数据进行相对定位解算的方法
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WO2017181221A1 (fr) * 2016-04-18 2017-10-26 Spatial Information Systems Research Ltd Procédé d'analyse de multiples signaux émis par des systèmes mondiaux de satellites de navigation discrets
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