共查询到20条相似文献，搜索用时 31 毫秒
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Performance analysis of triple-frequency ambiguity resolution with BeiDou observations 总被引：5，自引：1，他引：4
We investigate triple-frequency ambiguity resolution performance using real BeiDou data. We test four ambiguity resolution (AR) methods which are applicable to triple-frequency observations. These are least squares ambiguity decorrelation adjustment (LAMBDA), GF-TCAR (geometry-free three-carrier ambiguity resolution), GB-TCAR (geometry-based three-carrier ambiguity resolution) and GIF-TCAR (three-carrier ambiguity resolution based on the geometry-free and ionospheric-free combination). A comparison between LAMBDA, GF-TCAR and GB-TCAR was conducted over three short baselines and two medium baselines. The results indicated that LAMBDA is optimal in both short baseline and medium baseline cases. However, the performances of GB-TCAR and LAMBDA differ slightly for short baselines. Compared with GF-TCAR, which uses the geometry-free model, the GB-TCAR using the geometry-based model improves the AR performance significantly. Compared with dual-frequency observations, the LAMBDA AR results show a significant improvement when using triple-frequency observations over short baselines. The performance of GIF-TCAR is evaluated using multi-epoch observations. The results indicated that multi-path errors on carrier phases will have a significant influence on GIF-TCAR AR results, which leads to different GIF-TCAR AR performance for different type of satellites. For GEO (Geostationary Orbit) satellites, the ambiguities can barely be correctly fixed because the multi-path errors on carrier phases are very systematic. For IGSO (Inclined Geosynchronous Orbit) and MEO (Medium Earth Orbit) satellites, when the elevation cutoff angle is set as 30°, several tens to several hundreds of epochs are needed for correctly fixing the narrow lane ambiguities. The comparison of positioning performance between dual-frequency observations and triple-frequency observations was also conducted. The results indicated that a minor improvement can be achieved by using triple-frequency observations compared with using dual-frequency observations. 相似文献
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一种短基线GNSS的三频模糊度解算(TCAR)方法 总被引：3，自引：2，他引：1
TCAR或综合TCAR是GNSS中常用的快速确定三频模糊度的方法,其原理简单,计算方便。根据不同的噪声背景和多径条件,给出综合TCAR单历元实时解算模糊度的误差分析及仿真结果。针对模糊度估计成功概率不高的情况,结合双频相关法(DUFCOM),并根据综合TCAR的特点,对综合TCAR进行改进。最后,将此方法与基于整数最小二乘准则搜索的LAMBDA方法进行比较。仿真结果表明,利用该方法成功搜索到正确模糊度值的概率与LAMBDA方法相当,但降低计算量,有效提高用综合TCAR单历元实时解算模糊度的可靠性。 相似文献
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Partial integer decorrelation: optimum trade-off between variance reduction and bias amplification 总被引：2，自引：2，他引：0
Different techniques have been developed for determining carrier phase ambiguities, ranging from float approximations to the
efficient solution of the integer least square problem by the LAMBDA method. The focus so far was on double-differenced measurements.
Practical implementations of the LAMBDA method lead to a residual probability of wrong fixing of the order one percent. For
safety critical applications, this probability had to be reduced by eight orders of magnitude, which could be achieved by
linear multi-frequency code–carrier combinations. Scenarios with single or no differences include biases due to orbit errors,
satellite clock offsets, as well as residual code and phase biases. For this case, a linear combination of Galileo E1 and
E5 code and carrier phase measurements with a wavelength of 3.285 m and a noise level of a few centimeters is derived. This
ionosphere-free combination preserves the orbit and clock errors, and suppresses the E1 code multipath by 12.6 dB. Since integer
decorrelation transformations, as used in the LAMBDA method, inflate biases, the number of such transformations must be limited,
and applied in a judicious order. With a Galileo type constellation, this leads to a vertical standard deviation of ca. 20 cm,
while keeping the probability of wrong fixing extremely low for code biases of 10 cm, and phase biases of 0.1 cycle, combined
in a worst case. 相似文献
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用遗传算法搜索GPS单频单历元整周模糊度 总被引：10，自引：2，他引：10
介绍了短基线利用单频单历元双差载波相位定位时模糊度固定的基本理论，探讨了利用遗传算法快速搜索GPS单频单历元整周模糊度的一些理论和实现的方法．提出了用改进的正则化方法改善浮动解来提高搜索成功率的新思路。算例分析表明，在一定的条件下．应用遗传算法搜索整周模糊度成功率高、稳键性较好。 相似文献
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Precise GRACE baseline determination using GPS 总被引：13，自引：1，他引：13
Precision relative navigation is an essential aspect of spacecraft formation flying missions, both from an operational and a scientific point of view. When using GPS as a relative distance sensor, dual-frequency receivers are required for high accuracy at large inter-satellite separations. This allows for a correction of the relative ionospheric path delay and enables double difference integer ambiguity resolution. Although kinematic relative positioning techniques demonstrate promising results for hardware-in-the-loop simulations, they were found to lack an adequate robustness in real-world applications. To overcome this limitation, an extended Kalman Filter modeling the relative spacecraft dynamics has been developed. The filter processes single difference GPS pseudorange and carrier phase observations to estimate the relative position and velocity along with empirical accelerations and carrier phase ambiguities. In parallel, double difference carrier phase ambiguities are resolved on both frequencies using the least square ambiguity decorrelation adjustment (LAMBDA) method in order to fully exploit the inherent measurement accuracy. The combination of reduced dynamic filtering with the LAMBDA method results in smooth relative position estimates as well as fast and reliable ambiguity resolution. The proposed method has been validated with data from the gravity recovery and climate experiment (GRACE) mission. For an 11-day data arc, the resulting solution matches the GRACE K-Band Ranging System measurements with an accuracy of 1 mm, whereby 83% of the double difference ambiguities are resolved. 相似文献
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根据GNSS不同频率间整周模糊度的约束关系,提出一种基于多频整周模糊度间关系约束的模糊度新算法(dual-frequency integer relationship constrained ambiguity resolution,FirCAR)。FirCAR可快速动态解算出高高度角卫星的整周模糊度,将已经固定的整周模糊度视为高精度的伪距观测值应用到下一步的浮点解重算中。结合模糊度搜索算法,如LAMBDA,在模糊度搜索方面的高效性,根据重算后的浮点解进一步解算其他未固定的模糊度解。模糊度固定成功后,即可实现OTF(on the fly)快速定位。实测数据表明,FirCAR算法在静态和动态观测条件下,模糊度初始化所用的平均观测历元数分别为1.04和1.10。与常规的模糊度搜索算法的对比试验表明,结合FirCAR算法模糊度固定所用的观测历元数分别减少了39%和18%。 相似文献
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Traditional carrier phase combinations are linear functions of the original carrier phases. We develop a new way of carrier phase combination that regards carrier phases of different frequencies as the basis of the carrier phase space. The combined carrier phase is a point of this space. Then, this point, i.e., the combined carrier phase, is mapped back to a single-dimensional carrier phase by a bidirectional mapping. The new single-dimensional carrier phase is called mapped carrier phase. The advantages of this combination approach are a long wavelength and small noise of the mapped carrier phase, which make ambiguity resolution easy. Unfortunately, the mapped carrier phase value is not well determined due to the noise in the observed phases. On the contrary, a set of possible mapped carrier phase values are attained; however, only one value is correct. To reduce the number of candidates and fix the correct value of the mapped carrier phase, the following steps are discussed: (1) The integer nature of the original carrier ambiguity is used to attain an initial set of possible mapped carrier phase values; (2) the distribution of the mapped carrier phase ambiguity is included to reduce the possible values; and (3) the Gaussian least-squares objective function is introduced to fix the correct value. As a result of these steps, a single-epoch positioning algorithm is established. Two experiments are carried out to preliminarily compare the new algorithm with LAMBDA. The results show that the new algorithm is slightly below LAMBDA in resolution success rate, but computationally more efficient than LAMBDA. 相似文献
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针对常规GNSS解算模糊度存在的问题,该文提出了一种新的GNSS宽巷模糊度单历元求解算法。利用单历元双频码伪距观测值和载波相位观测值得到双差宽巷模糊度浮点解,将所有浮点宽巷模糊度分别向上、向下取整建立模糊度搜索空间;将模糊度空间中的所有备选组合代入双差宽巷观测方程中进行最小二乘解算,其中单位权中误差最小的组合就是最优的宽巷模糊度组合;然后对最优组合进行正确性检验以确定宽巷模糊度。确定宽巷模糊度后,可以利用宽巷观测值和载波观测值求出基础模糊度整周解。实验表明,该文提出的模糊度固定方法具有较高的成功率和可靠性,静态数据中模糊度固定成功率达到98.84%,动态数据中模糊度固定成功率达到了99.60%。 相似文献
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GPS载波相位观测值作为高精度观测量在姿态测量中得到广泛应用。姿态测量系统中,基线长度可以通过提前量测精确求得。作为约束条件,可以用于模糊度搜索,提高模糊度搜索效率和准确度。本文介绍了传统的LAMBDA方法,且在此基础上提出了附有基线长度约束的LAMBDA搜索方法,并比较了两者的搜索效率。 相似文献
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下三角Cholesky分解的整数高斯变换算法 总被引：1，自引：0，他引：1
针对全球导航卫星系统(GNSS)载波相位测量中,基于整数最小二乘估计准则解算整周模糊度问题。目前以LAMBDA降相关算法和Lenstra-Lenstra-Lovász(LLL)为代表的规约算法应用最为广泛。由于不同算法采用的模糊度方差-协方差阵的分解方式不同,导致难以合理地进行不同算法性能的比较。该文通过分析LAMBDA算法的降相关特点,从理论上推出基于下三角Cholesky分解多维情形下的整数高斯变换的降相关条件及相应公式,并与分解方式不同的LAMBDA和LLL算法作了对比。实验结果表明,降相关采用的分解方式将会直接影响计算复杂度和解算性能,因此该文推导的整数高斯变换算法便于今后基于下三角Cholesky分解的降相关算法间的合理比较。 相似文献
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为了充分利用各频率观测值信息,提出了一种非差非组合的北斗卫星导航系统长距离基准站间整周模糊度解算方法。首先,直接利用不同频率的观测值建立误差观测方程,并采用随机游走策略估计相对天顶对流层湿延迟误差和电离层延迟误差,增加历元间的约束;然后,采用一种非差整周模糊度实时线性计算方法,依次得到基准站网当前历元所有卫星的非差整周模糊度,解决了在基准星变换时,模糊度需要承接或者重新进行法方程叠加的问题;最后,使用实测数据进行方法验证,结果表明,各基准站模糊度平均固定速度为20个历元（采样间隔1 s）,可快速实现基准站载波相位整周模糊度解算。由于所提方法充分利用了各频率观测值信息,避免了线性组合放大噪声对整周模糊度固定的影响,其模糊度固定成功率与无电离层组合法相比有较大的提高。 相似文献
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The Indian Regional Navigation Satellite System (IRNSS), which is being developed for positioning services in and around India, is the latest addition to the global family of satellite-based navigation systems. As IRNSS only shares the L5-frequency with GPS, the European Galileo, and the Japanese Quasi-Zenith Satellite System (QZSS), it has at least at present a limited interoperability with the existing systems. Noting that the L5-frequency capability is under development even for GPS, this contribution assesses the interoperability of the IRNSS L5-signal with the GPS, Galileo, and QZSS L5/E5a-signals for positioning and navigation using real data collected in Perth, Australia. First, the noise characteristic of the IRNSS L5-signal and its comparison with that of the GPS, Galileo, and QZSS L1/E1- and L5/E5a-signals is presented. Then, the L5-observables of combined systems (formed from IRNSS, GPS, Galileo, and QZSS) are assessed for real-time kinematic positioning using the standard LAMBDA method and for instantaneous attitude determination using the constrained LAMBDA method. The results show that the IRNSS L5-signal has comparable noise characteristics as that of the other L5/E5a-signals. For single-frequency carrier phase-based positioning and navigation, the results show better ambiguity resolution performance of L5/E5a-only processing than that of L1/E1-only processing. 相似文献
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利用北斗三频超宽巷模糊度波长较长易于固定的优势,提出一种基于北斗三频的BDS/GPS宽巷模糊度逐级单历元固定方法。首先利用载波和伪距组合固定BDS(0,-1,1)和(1,4,-5)两个超宽巷模糊度,根据固定后的超宽巷模糊度变换得到BDS宽巷模糊度(1,-1,0),然后将BDS宽巷模糊度作为约束条件与GPS宽巷观测方程联立得到GPS宽巷模糊度浮点解和其方差协方差阵,最后采用LAMBDA算法实现GPS宽巷模糊度的固定。实验结果表明,BDS超宽巷组合可实现100%固定,采用BDS约束GPS宽巷模糊度固定时ratio值均大于2,大于5的占97.8%以上,因此文中提出的方法可实现BDS/GPS双系统宽巷模糊度单历元固定,有效提升GNSS模糊度解算的时效性。 相似文献
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ZHANG Yongjun LIU Jingnan 《地球空间信息科学学报》2002,5(4):32-36
To obtain the GLONASS satellite position at an epoch other than reference time,the satellite‘s equation of motion has to be integrated with broadcasting ephemerides.The iterative detecting and repairing method of cycle slips based on triple difference residuals for combined GPS/GLONASS positioning and the iterative ambiguity resolution approach suitable for combined post processing positioning are discussed systematically.Experiments show that millimter accuracy can be achieved in short baselines with a few hours‘ dual frequency or even single frequency GPS/GLONASS carrier phase observation,and the precision of dual frequency observations is distinctly higher than that of single frequency observations. 相似文献
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The Indian Regional Navigation Satellite System (IRNSS) has recently (May 2016) reached its full operational capability. In this contribution, we provide the very first L5 attitude determination analyses of the fully operational IRNSS as a standalone system and also in combination with the fully operational GPS Block IIF along with the corresponding ambiguity resolution results. Our analyses are carried out for both a linear array of two antennas and a planar array of three antennas at Curtin University, Perth, Australia. We study the noise characteristics (carrier-to-noise density, measurement precision, time correlation), the integer ambiguity resolution performance (LAMBDA, MC-LAMBDA) and the attitude determination performance (ambiguity float and ambiguity fixed). A prerequisite for precise and fast IRNSS attitude determination is the successful resolution of the double-differenced integer carrier-phase ambiguities. In this contribution, we will compare the performance of the unconstrained and the multivariate-constrained LAMBDA method. It is therefore also shown what improvements are achieved when the known body geometry of the antenna array is rigorously incorporated into the ambiguity objective function. As our ambiguity-fixed outcomes show consistency between empirical and formal results, we also formally assess the precise attitude determination performance for several locations within the IRNSS service area. 相似文献
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单频GPS快速定位方程是严重病态的,应用最小二乘原理得到的模糊度浮点解大大偏离其准确值,应用LAMBDA方法难以正确地固定模糊度。本文将GPS载波相位双差观测量在不同的小波空间和尺度空间进行分解和重构,去除高频测量噪声,可减小测量噪声对GPS快速定位中病态方程解的影响,提高模糊度浮点解的精度,缩小模糊度搜索空间。实验表明,对于GPS短基线,仅利用1min左右的单频载波观测数据,经过基于haar、db4、coif4和sym4小波的5尺度小波变换后,可获得较准确的模糊度浮点解,应用LAMBDA法可正确地固定模糊度,达到厘米级定位精度。 相似文献