Algorithm for carrier-adjusted DGPS positioning and some numerical results

This paper derives a DGPS positioning algorithm, referred to as the algorithm for carrier-adjusted DGPS positioning. This algorithm can be applied by a DGPS user when code and carrier observations are available and when the dynamic behaviours of both mobile positions and receiver-clock biases can and cannot be modelled. Since the algorithm directly uses code and carrier observations, the stochastic model of observations has a simple structure and can be easily specified. When the dynamic behaviour of mobile positions can be modelled, the algorithm can provide recursive solutions of the positions, on the other hand, when the behaviour cannot be modelled, it can provide their instantaneous solutions. Furthermore, the algorithm can integrate with a real-time quality-control procedure so that the quality of the position estimates can be guaranteed with a certain probability. Since in the use of the algorithm there always exist redundant observations unless the position parameters are inestimable, the quality control can even be performed when only four satellites are tracked. Using the algorithm and real GPS data collected at a 100-km baseline, this contribution investigates how DGPS positioning accuracies vary with the type of observables used at reference and mobile stations, and how important it is to choose an elevation-dependent standard deviation for code observations in DGPS data reduction. It was found that using carrier observations along with code observations is more important at the reference station than at the mobile station. Choosing an elevation-dependent standard deviation for code observations can result in better positioning accuracy than choosing a constant standard deviation for code observations. For the 100-km baseline, half-metre single-epoch positioning accuracy was achieved when dual-frequency data was used at both reference and mobile stations. The positioning accuracy became better than 0.75m when the types of observable used at the mobile station were replaced by L1 code and carrier. Received: 9 April 1996 / Accepted: 6 February 1997     

Artificial neural networks for predicting DGPS carrier phase and pseudorange correction

Artificial neural networks (ANNs) were used to predict the differential global positioning system (DGPS) pseudorange and carrier phase correction information. Autoregressive moving average (ARMA) and autoregressive (AR) models were bounded with neural networks to provide predictions of the correction. The neural network was employed to realize time-varying implementation. Online training for real-time prediction of the carrier phase enhances the continuity of service of the differential correction signals and, therefore, improves the positioning accuracy. When the correction signal from the DGPS was lost, the artificial neural networks predicted the correction data with good accuracy for the navigation system during a limited period. Comparisons of the prediction results using the two models are given.

IMU／DGPS辅助ADS40影像直接定位及其精度分析

阐述了IMU/DGPS辅助ADS40影像直接定位的基本方法,针对不同ADS40扫描条带采用不同的局部空间直角坐标系的现状,推导了航带间外方位元素的统一化处理算法.试验结果表明,ADS40影像直接定位的误差是系统性的,因此在生产作业中引入少量控制点参与平差仍是必需的.     

舰载卫星导航接收机海上试验与鉴定方法研究

介绍了舰载卫星导航接收机海上试验与鉴定所要解决的一些具体问题;总结了以往靶场对无线电定位系统和DGPS舰栽机海上鉴定试验的经验,提出了一些有益的建议.     

舰载卫星导航接收机海上试验与鉴定方法研究

介绍舰载卫星导航接收机海上试验与鉴定所要解决的一些具体问题,在总结以往靶场对无线电定位系统和DGPS舰载机的海上鉴定试验方法的基础七,提出一些相关建议,供专家学者参考.     

矩阵体积法原理及其在水下差分GPS定位中的应用

给出了矩阵体积法的原理和方法,并使用矩阵体积法研究了水下差分GPS定位中设计矩阵的态性,导出了星形空间网中设计矩阵的体积与观测向量高度角参数的函数关系式,为研究星形空间网图形强度提供了数学模型。     

潮间带地形测量的新途径

潮间带,特别是宽阔的浅滩或淤泥滩地带是海洋测绘中的困难地带。本文提出用ＤＧＰＳ定位结合杆测水深的地形测量方法,代替常规水深地形测量方法,使潮间带水深地形测量变得越来越简便快速。     

信标机在海上钻探定位中的应用

通过近两年3个以上项目的工作实践,对信标机在海洋钻探定位进行了总结,通过和RTK的比较来探索信标的操作特点,探索了信标机在1954北京坐标系和地方坐标系中平面定位的应用。     

相对GPS的精度校验方法探讨

首先介绍了相对GPS（RGPS）概念与工作原理,进而提出了三种RGPS的精度校验方法,即移动法、半移动法与静态法。通过分别研究三种方法的数据采集、数据处理与精度分析,得出了由于时间延迟的影响,采用第二种方法,能有效地提高校验结果的准确性与效率。     

载波相位平滑伪距及其在差分定位中的应用

推导了单频和双频载波相位平滑伪距的Hatch滤波公式,利用两组实测数据进行了载波相位平滑伪距,然后将平滑后的不同观测类型的伪距用于实时差分定位。定位结果表明,C／A码Hatch滤波的差分定位精度高于P码;无电离层组合的Hatch滤波差分定位精度低于C／A码。