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采用载波无几何组合和星间单差无电离层组合的历元间高次差作为周跳检验量,因组合观测值中不包含伪距,其理论噪声与波长相比几乎可以忽略。利用两种组合观测值联合进行周跳探测,可避免各自的探测盲点。将两个载波组合联立进行周跳的求解,由于组合噪声较小,直接取整即可求得周跳的大小。提出的方法在一定程度上克服了传统周跳探测与修复算法中,由于引入伪距带来的探测能力不强、修复精度不高等问题。通过对IGS站观测数据模拟周跳探测与修复情况的统计,新提出算法的周跳探测成功率为99%,周跳修复成功率为94%。 相似文献
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针对海洋测高卫星未来发展趋势,提出了Ku/Ka/C三频高度计进行组合测距的设想。给出了高度计相位中心至海面距离的随机误差模型,分析表明电离层延迟改正是影响海面高测量分辨率和精度的重要因素。其次利用典型电离层参数计算表明电离层2阶以上项对高度计测距的影响在毫米级以下,可忽略其影响。通过计算分析,在1Hz采样且不滤波条件下,Ka/C组合改正电离层1阶项精度可优于3mm,基本消除电离层的影响,测距总精度达到3.5cm。通过Ku/C/Ka三频组合测距误差分析,三频电离层改正残余误差比双频改正更大,因此如果采用三频组合测距体制,则建议在数据处理中采取Ku/C、Ka/C组合形式改正电离层,这种体制可充分利用各频段特点,进一步提高宽阔海域、冰区、近海区域的海面测量精度和有效数据比例。 相似文献
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With the rapid development of BeiDou satellite navigation system (BDS), high-quality service has been provided in the Asia-Pacific region currently, which will be extended to the whole world very soon. BDS is the first Global Navigation Satellite System that all satellites broadcast the triple-frequency signals. The triple-frequency signals in theory can improve the cycle slip detection that is one of the preconditions in precise positioning by making use of carrier phase. This paper discusses the development of a cycle slip detection method for undifferenced BDS triple-frequency observations in kinematic scenario. In this method, two geometry-free extra-wide-lane combinations and one geometry-free narrow-lane (NL) combinations are employed. The key is to mitigate the between-epoch ionospheric biases in the geometry-free NL combinations. We propose to predict the ionospheric biases of current epoch by using those from its consecutive foregoing epochs. The method is tested with extensive experiments in varying observation scenarios. The results show that in case of sampling interval as small as 5 s, the between-epoch ionospheric biases can be ignored and the correct cycle slips can be determined. Meanwhile in case of lower sampling frequency, one needs to compensate the ionospheric biases of current epoch by using the predicted ionospheric biases. The presented method can correctly detect all cycle slips even if they are as small as 1 cycle. 相似文献
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Precise, long-range GPS kinematic positioning to centimeter accuracy requires that carrier phase ambiguities be resolved correctly during an initialization period, and subsequently to recover the “lost" ambiguities in the event of a cycle slip. Furthermore, to maximize navigational efficiency, ambiguity resolution and carrier phase-based positioning need to be carried out in real-time. Due to the presence of the ionospheric signal delay, satellite orbit errors, and the tropospheric delay, so-called absolute ambiguity resolution “on-the-fly” for long-range applications becomes very difficult, and largely impossible. However, all of these errors exhibit a high degree of spatial and temporal correlation. In the case of short-range ambiguity resolution, because of the high spatial correlation, their effect can be neglected, but their influence will dramatically increase as the baseline length increases. On the other hand, between discrete trajectory epochs, they will still exhibit a large degree of similarity for short time spans. In this article, a method is described in which similar triple-differenced observables formed between one epoch with unknown ambiguities and another epoch with fixed ambiguities can be used to derive relative ambiguity values, which are ordinarily equal to zero (or to the number of cycles that have slipped when loss-of-lock occurred). Because of the temporal correlation characteristics of the error sources, the cycle slips can be recovered using the proposed methodology. In order to test the performance of this algorithm an experiment involving the precise positioning of an aircraft, over distances ranging from a few hundred meters up to 700 kilometres, was carried out. The results indicate that the proposed technique can successfully resolve relative ambiguities (or cycle slips) over long distances in an efficient manner that can be implemented in real-time. 相似文献
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Precise, long-range GPS kinematic positioning to centimeter accuracy requires that carrier phase ambiguities be resolved correctly during an initialization period, and subsequently to recover the “lost" ambiguities in the event of a cycle slip. Furthermore, to maximize navigational efficiency, ambiguity resolution and carrier phase-based positioning need to be carried out in real-time. Due to the presence of the ionospheric signal delay, satellite orbit errors, and the tropospheric delay, so-called absolute ambiguity resolution “on-the-fly” for long-range applications becomes very difficult, and largely impossible. However, all of these errors exhibit a high degree of spatial and temporal correlation. In the case of short-range ambiguity resolution, because of the high spatial correlation, their effect can be neglected, but their influence will dramatically increase as the baseline length increases. On the other hand, between discrete trajectory epochs, they will still exhibit a large degree of similarity for short time spans. In this article, a method is described in which similar triple-differenced observables formed between one epoch with unknown ambiguities and another epoch with fixed ambiguities can be used to derive relative ambiguity values, which are ordinarily equal to zero (or to the number of cycles that have slipped when loss-of-lock occurred). Because of the temporal correlation characteristics of the error sources, the cycle slips can be recovered using the proposed methodology. In order to test the performance of this algorithm an experiment involving the precise positioning of an aircraft, over distances ranging from a few hundred meters up to 700 kilometres, was carried out. The results indicate that the proposed technique can successfully resolve relative ambiguities (or cycle slips) over long distances in an efficient manner that can be implemented in real-time. 相似文献
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Kun Lu Xingzhao Liu Yongtan Liu 《Oceanic Engineering, IEEE Journal of》2005,30(2):455-462
In this paper, a cascaded correction and suppression method of reducing ionospheric phase path contamination and sea clutter to enable detection of targets travelling at speeds near the Bragg Doppler is addressed. The Hankel rank reduction (HRR) technique based on singular value decomposition (SVD) has been used to estimate the ionospheric phase distortion and suppress the sea clutter. Simulation results show that such a technique is helpful for the worse conditions when the target masking effect happens even after ionospheric phase decontamination. Finally, an attempt to combine another phase decontamination algorithm based on the piecewise polynomial phase modeling with the clutter cancellation stage for faster phase fluctuation is discussed briefly and some results are given. 相似文献