RTK GPS在超短基线声学定位系统安装校准中的应用

超短基线（uhra short base line,USBL）声学定位系统的换能器安装是具有一定方向性的,但是,在安装过程中,不能保证换能器方向与船艏方向严格一致,必然存在不可忽视的系统误差,影响了测量精度;因此,必须通过校准消除系统误差。本文应用高精度RTKGPS实现了换能器安装方向的校准,取得了满意的结果。     

GPS RTK技术在滩涂测量中的应用

在黄河口大面积滩涂测量中，采用了GPS实时动态测量(RTK)技术，体现出定位精度高、完成数据采集快、外界因素影响小的特点，成为测量自动化系统的重要组成部分。介绍了控制点精度检核、碎部测量精度比对结果。     

GPS—RTK技术

本文着重介绍了两种GPS—RTK数据处理方法;①利用GPS互相关数据直接求解相位模糊度。②相位模糊度LS搜索解法。简要介绍了RTCM差分格式,讨论了GPS—RTK技术的应用前景及其局限性,最后,对我国如何更好地利用GPS—RTK定位技术提出几点建议。     

GPS精密单点定位精度分析

首先介绍了精密单点定位技术，然后详细分析了这种技术的精度，最后基于这种技术，对现在运行的无线电指向标/差分GPS台站，提出了改进建议。     

基于GPS RTK技术的海岸沙丘动态监测

根据沙丘地形的特点,探讨并实践RTK测量沙丘的基本方法与步骤,同时利用精度为毫米级的全站仪对RTK进行高程精度评定,其误差范围为2~7 cm,证明RTK精度能够满足沙丘动态监测的要求。数据结果分析表明昌黎新开口南侧沙丘高度降低,且整体向西南移动。     

GPS高精度动态测量

高精度动态测量是近年来发展起来的GPS新技术,用于大比例尺测图、港口测量、施工测量等工程中。本文就高精度动态测量中的几个关键问题,如:电文发送速率、电离层效应改正等进行了论述,最后给出为高精度动态测量设置的Type18—Type21四组电文格式和含义。     

星基广域差分GPS的应用与精度分析

简要介绍了星基广域差分GPS定位技术的原理,通过实例对不同差分方式定位精度的对比分析,表明星基广域差分GPS定位技术在中远海水深测量中能满足精度要求,使水深测量作业更加快捷方便。     

RTK布设高精度控制点的可行性分析

GPS RTK可以实时获取流动站的坐标,但无法确定点位坐标精度的可靠性。利用高精度基线检定场对RTK测量成果的精度估计进行了研究,证明在具备高等级已知点位成果时RTK测量可用于获取较高精度的控制点。     

远距离实时差分GPS的精度和作用距离

根据我队3年多来对实时差分GPS在海洋测量工作收集到的资料,分析了差分GPS在远程传输中的精度及作用距离,为今后海洋测量提供了较可靠、有实用价值的依据。     

北斗三号系统与GPS定位性能仿真对比分析

为了解北斗三号系统在国内外及南北极地区的定位性能,在STK仿真平台下建立了北斗三号系统30颗星(3GEO、3IGSO和24MEO)的星座模型,对北京、三亚、新加坡、南北极点等11个站点的平均可见星数和几何精度因子GDOP值进行了分析,并与GPS进行了对比。结果表明,北斗三号系统较GPS在国内外及南北极地区典型站点的定位性能更优。     

机载GPS精密单点定位性能分析

利用地面多基站RTK测量结果和精密单点定位(PPP)测量结果,分析了机载条件下PPP定位、测速性能指标。实验结果表明:机载GPS精密单点定位绝对定位精度在位置、速度上可分别达到0.182 3m和0.024 6m/s,相对定位精度在位置、速度上可分别达到0.1450m和0.0249m/s。     

机载GPS精密单点定位性能分析

利用地面多基站RTK测量结果和精密单点定位（PPP）测量结果,分析了机载条件下PPP定位、测速性能指标.实验结果表明：机载GPS精密单点定位绝对定位精度在位置、速度上可分别达到0.182 3m和0.024 6m/s,相对定位精度在位置、速度上可分别达到0.1450m和0.024 9m/s.     

GPS/GLONASS组合实时动态精密单点定位

针对传统模式下,单系统实时动态精密单点定位精度不高、受环境影响严重等缺点,研究了双系统实时动态精密单点定位的方法,基于非差无电离层组合载波和伪距观测量,依据拓展Kalman滤波进行参数估计,从多种情况进行了实时动态PPP的实验。实测数据解算实验表明,双系统定位较单系统有明显改善,其U、N、E方向收敛后RMS分别为0.224m、0.062m、0.102m,分别较单系统改善了42.9%、26.2%、69.6%,能够满足海上实时动态的厘米至分米级的定位需求。     

转发式卫星导航定位系统性能分析

在介绍我国自主研发的利用通信卫星建立的转发式卫星导航定位系统组成、工作原理的基础上,利用STK软件从系统的几何精度因子、可见性和覆盖性三个方面,对该系统为我国及周边区域服务保障的性能进行了分析,结果表明该系统在中国区域的覆盖率可达到100%,对全球覆盖率可达到40%左右,定位精度随纬度的增加而逐渐降低。可以为我国及亚太地区提供高精度的导航、定位与授时服务,从而也推论该系统不仅可以作为北斗卫星导航定位系统的备份,还可以作为独立的系统自主工作。     

Ambiguity Recovery Using the Triple-Differenced Carrier Phase Type Approach for Long-Range GPS Kinematic Positioning

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.     

Ambiguity Recovery Using the Triple-Differenced Carrier Phase Type Approach for Long-Range GPS Kinematic Positioning

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.     

Sea Surface Determination Using Long-Range Kinematic GPS Positioning and Laser Airborne Depth Sounder Techniques

Precise long-range kinematic GPS positioning requires the use of carrier phase measurements, the data processing of which suffers from the technical challenges of ambiguity resolution and cycle slip repair. In this paper, the combination of an ambiguity recovery technique and a linear bias correction method has been used to overcome such problems. An experiment was conducted to test the utility of this technique to determine aircraft height to high accuracy, over very long baselines (of the order of one thousand kilometres), in support of the Laser Airborne Depth Sounder (LADS). From a comparison of four independently derived trajectories, this airborne GPS kinematic positioning experiment has confirmed that the sea surface can be determined to centimetre accuracy. The sea surface profiles thus obtained can be used to correct the errors introduced by long period ocean swells.