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Dae Hee Won Eunsung Lee Moonbeom Heo Sangkyung Sung Jiyun Lee Young Jae Lee 《GPS Solutions》2014,18(2):177-187
In urban canyons, buildings and other structures often block the line of sight of visible Global Navigation Satellite System (GNSS) satellites, which makes it difficult to obtain four or more satellites to provide a three-dimensional navigation solution. Previous studies on this operational environment have been conducted based on the assumption that GNSS is not available. However, a limited number of satellites can be used with other sensor measurements, although the number is insufficient to derive a navigation solution. The limited number of GNSS measurements can be integrated with vision-based navigation to correct navigation errors. We propose an integrated navigation system that improves the performance of vision-based navigation by integrating the limited GNSS measurements. An integrated model was designed to apply the GNSS range and range rate to vision-based navigation. The possibility of improved navigation performance was evaluated during an observability analysis based on available satellites. According to the observability analysis, each additional satellite decreased the number of unobservable states by one, while vision-based navigation always has three unobservable states. A computer simulation was conducted to verify the improvement in the navigation performance by analyzing the estimated position, which depended on the number of available satellites; additionally, an experimental test was conducted. The results showed that limited GNSS measurements can improve the positioning performance. Thus, our proposed method is expected to improve the positioning performance in urban canyons. 相似文献
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Sergey S. Pospelov Andrey L. Botchkovski Peter A. Krauss Stefan Berberich 《GPS Solutions》2000,4(1):48-55
Software Global Navigation Satellite Systems (GNSS) receivers are those that implement signal correlation processing not in
hardware, but in their software. The main problem for the development of real-time software (SW) multichannel GNSS receivers
is the tremendous amount of calculations to perform signal correlation.
The article reviews recent developments of SW GNSS receivers. The emphasis is made on the computationally effective correlation
processing algorithms and the optimization of processing allocation to the receiver's hardware (HW) and SW.
An architecture is suggested that implements the PRN signals despreading in a special HW preprocessor while all the other
correlation processing functions are still kept in SW. The combination of the most time-consuming processing in HW, and all
signal structure-dependent processing in SW, enables unique flexibility of sophisticated GNSS receiver design based on inexpensive
digital signal processors. ? 2000 John Wiley & Sons, Inc. 相似文献
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GNSS algebraic structures 总被引:4,自引:3,他引:1
The first objective of this paper is to show that some basic concepts used in global navigation satellite systems (GNSS) are
similar to those introduced in Fourier synthesis for handling some phase calibration problems. In experimental astronomy,
the latter are at the heart of what is called ‘phase closure imaging.’ In both cases, the analysis of the related structures
appeals to the algebraic graph theory and the algebraic number theory. For example, the estimable functions of carrier-phase
ambiguities, which were introduced in GNSS to correct some rank defects of the undifferenced equations, prove to be ‘closure-phase
ambiguities:’ the so-called ‘closure-delay’ (CD) ambiguities. The notion of closure delay thus generalizes that of double
difference (DD). The other estimable functional variables involved in the phase and code undifferenced equations are the receiver
and satellite pseudo-clock biases. A related application, which corresponds to the second objective of this paper, concerns
the definition of the clock information to be broadcasted to the network users for their precise point positioning (PPP).
It is shown that this positioning can be achieved by simply having access to the satellite pseudo-clock biases. For simplicity,
the study is restricted to relatively small networks. Concerning the phase for example, these biases then include five components:
a frequency-dependent satellite-clock error, a tropospheric satellite delay, an ionospheric satellite delay, an initial satellite
phase, and an integer satellite ambiguity. The form of the PPP equations to be solved by the network user is then similar
to that of the traditional PPP equations. As soon as the CD ambiguities are fixed and validated, an operation which can be
performed in real time via appropriate decorrelation techniques, estimates of these float biases can be immediately obtained.
No other ambiguity is to be fixed. The satellite pseudo-clock biases can thus be obtained in real time. This is not the case
for the satellite-clock biases. The third objective of this paper is to make the link between the CD approach and the GNSS
methods based on the notion of double difference. In particular, it is shown that the information provided by a maximum set
of independent DDs may not reach that of a complete set of CDs. The corresponding defect is analyzed. One of the main results
of the corresponding analysis concerns the DD–CD relationship. In particular, it is shown that the DD ambiguities, once they
have been fixed and validated, can be used as input data in the ‘undifferenced CD equations.’ The corresponding algebraic
operations are described. The satellite pseudo-clock biases can therefore be also obtained via particular methods in which
the notion of double differencing is involved. 相似文献
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全球卫星导航系统(GNSS)目前得到了十分广泛的应用,但是GNSS信号到达地面的功率很低,同时民用信号的格式是公开的,因此极易受到各种无意和人为故意的干扰,会对GNSS定位和授时的精度造成影响.查找和消除干扰源十分重要,目前通用的干扰源查找手段是采用测向设备实现干扰源的交叉定位,但在不知道GNSS干扰源的大致位置时,采用测向设备查找干扰源将耗费很长的时间.如果能够通过提取一些通用接收机的输出量实现干扰源的粗定位,就可以为测向定位提供初始参考位置和大概的查找范围.本文利用几乎所有的通用接收机都能输出的位置信息实现干扰源的粗定位,随着GNSS接收机逼近干扰源,会造成接收机位置信息的丢失,随着GNSS接收机远离干扰源,接收机又会重新获取位置信息,本文利用一定区域内众多受干扰的接收机的位置信息丢失点和位置信息重捕获点来实现干扰源的粗定位.通过仿真验证,分析了该技术的定位误差,仿真结果表明,该方法能够实现GNSS干扰源的粗定位,为进一步准确查找干扰源提供位置参考. 相似文献
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摘要:地面运动物体、航空与航天飞行器的跟踪量中,GNSS被广泛用于运动轨道的实时跟踪、定位,行两运动体的防撞、对接,地面测控网站的定位及统一时等方面。动态测量的关键技术主要包括:快速捕获解算,零相位天线技术,RAIM技术,超冗余组合接收术,载波相位共同跟踪技术,分集合成抗多径干扰技等。 相似文献
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Penalized GNSS Ambiguity Resolution 总被引:1,自引:1,他引:1
P. J. G. Teunissen 《Journal of Geodesy》2004,78(4-5):235-244
Global Navigation Satellite System (GNSS) carrier phase ambiguity resolution is the process of resolving the carrier phase ambiguities as integers. It is the key to fast and high precision GNSS positioning and it applies to a great variety of GNSS models which are currently in use in navigation, surveying, geodesy and geophysics. A new principle of carrier phase ambiguity resolution is introduced. The idea is to give the user the possibility to assign penalties to the possible outcomes of the ambiguity resolution process: a high penalty for an incorrect integer outcome, a low penalty for a correct integer outcome and a medium penalty for the real valued float solution. As a result of the penalty assignment, each ambiguity resolution process has its own overall penalty. Using this penalty as the objective function which needs to be minimized, it is shown which ambiguity mapping has the smallest possible penalty. The theory presented is formulated using the class of integer aperture estimators as a framework. This class of estimators was introduced elsewhere as a larger class than the class of integer estimators. Integer aperture estimators, being of a hybrid nature, can have integer outcomes as well as non-integer outcomes. The minimal penalty ambiguity estimator is an example of an integer aperture estimator. The computational steps involved for determining the outcome of the minimal penalty estimator are given. The additional complexity in comparison with current practice is minor, since the optimal integer estimator still plays a major role in the solution of the minimal penalty ambiguity estimator. 相似文献
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近年来,由于仪器更换和强震影响,一些长期稳定的GNSS连续站出现了阶跃,严重地影响了参考框架的稳定性和解算精度,理论上这些测站不能再选为参考框架点。针对GNSS连续站阶跃修复及其对数据处理的影响进行了分析,结果表明:1)如果选用未修复阶跃的测站为框架点,将会扭曲解算结果;2)QOCA能够较为便捷地修复测站阶跃;3)修复测站阶跃能够保证参考框架点的稳定性,并能一定程度提高解算精度。 相似文献
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