Double-epoch algorithm in rapid positioning using single frequency GPS receivers

A new algorithm, called as Double-Epoch Algorithm (DEA) is proposed in GPS rapid positioning using two epoch single frequency phase data in this paper. Firstly, the structure characteristic of the normal matrix in GPS rapid positioning is analyzed. Then, in the light of the characteristic, based on TIK-HONOV regularization theorem, a new regularizer is designed to mitigate the ill-condition of the normal matrix. The accurate float ambiguity solutions and their MSEM (Mean Squared Error Matrix) are obtained, using two epoch single frequency phase data. Combined with LAMBDA method, DEA can fix the integer ambiguities correctly and quickly using MSEM instead of the covariance matrix of the ambiguities. Compared with the traditional methods, DEA can improve the efficiency obviously in rapid positioning. So, the new algorithm has an extensive application outlook in deformation monitoring, pseudokinematic relative positioning and attitude determination, etc.     

Integrity monitoring of fixed ambiguity Precise Point Positioning (PPP) solutions

Traditional positioning methods, such as conventional Real Time Kinematic (cRTK) rely upon local reference networks to enable users to achieve high-accuracy positioning. The need for such relatively dense networks has significant cost implications. Precise Point Positioning (PPP) on the other hand is a positioning method capable of centimeter-level positioning without the need for such local networks, hence providing significant cost benefits especially in remote areas. This paper presents the state-of-the-art PPP method using both GPS and GLONASS measurements to estimate the float position solution before attempting to resolve GPS integer ambiguities. Integrity monitoring is carried out using the Imperial College Carrier-phase Receiver Autonomous Integrity Monitoring method. A new method to detect and exclude GPS base-satellite failures is developed. A base-satellite is a satellite whose measurements are differenced from other satellite’s measurements when using between-satellite-differenced measurements to estimate position. The failure detection and exclusion methods are tested using static GNSS data recorded by International GNSS Service stations both in static and dynamic processing modes. The results show that failure detection can be achieved in all cases tested and failure exclusion can be achieved for static cases. In the kinematic processing cases, failure exclusion is more difficult because the higher noise in the measurement residuals increases the difficulty to distinguish between failures associated with the base-satellite and other satellites.     

一种改进的中长基线三频模糊度解算方法研究

研究了一种改进的三频模糊度解算方法。对宽巷和窄巷模糊度固定时受到的噪声误差进行分析得出,选用文中给出的无几何无电离层组合解算的窄巷模糊度噪声标准差均为B3载波波长的8.262 8倍。用实测的北斗三频数据进行了实验验证分析。     

Institutional ambiguity in implementing the European Union Marine Strategy Framework Directive

This article addresses the institutional ambiguity that exists between the European, Regional and Member State levels in the implementation of the Marine Strategy Framework Directive (MSFD). The two main reasons for the emergence of institutional ambiguity are (1) the MSFD being a framework directive and (2) Member States are required to coordinate the implementation of the MFSD through the Regional Sea Conventions. Institutional ambiguity refers to the interference zone between different institutional settings that come together in new policy practices. New rules of the game are needed to bring these institutional settings together and the room to manoeuvre for the actors who negotiate these rules is a defining feature of institutional ambiguity. This article analyses the institutional ambiguity associated with MSFD implementation on the European and regional level for four European Seas: the North Sea, the Baltic Sea, the Mediterranean Sea and the Black Sea. The results indicate different levels of institutional ambiguity in each of the four regions, with the lowest level of ambiguity in the Baltic Sea and the highest in the Mediterranean Sea. Institutional ambiguity also exists on the European level, as coordination efforts have not resulted in clear directions for the implementation of the MSFD as yet. The level of institutional ambiguity is influenced by the relative number of EU member states bordering the particular sea and whether they consider implementation of the MFSD to be urgent. Member States bordering the Mediterranean and the Black Seas lack the support of Regional Sea Conventions in addition to receiving limited direction from the European level.     

基于CORS网络的单频GPS实时精密单点定位新方法

利用单频接收机实现大范围、高精度快速实时定位是卫星大地测量研究的热点和难点问题之一.本文提出了一套基于连续运行参考站系统(CORS)的误差实时建模数据处理方法,设计并实现了一种新的GPS单频接收机实时精密单点定位服务方法.然后,利用山西省CORS网内一组实测动态数据,以及从湖北省CORS网和武汉市CORS网选取的一组实测静态数据进行测试,验证分析了所提出方法用于实时定位服务的可行性.结果表明:对于站间平均距离小于71 km的参考网,网内单频用户按照实时处理模式,在经过数秒钟的初始化后即可获得厘米级的动态精密单点定位结果.这为GPS单频接收机用户实现快速实时精密单点定位提供了一种可行的新方法.     

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The Effects of GPS Carrier Phase Ambiguity Resolution on Jason-1

We have used GPS carrier phase integer ambiguity resolution to investigate improvements in the orbit determination for the Jason-1 satellite altimeter mission. The technique has been implemented in the GIPSY orbit determination software developed by JPL. The radial accuracy of the Jason-1 orbits is already near 1 cm, and thus it is difficult to detect the improvements gained when the carrier phase ambiguities are resolved. Nevertheless, each of the metrics we use to evaluate the orbit accuracy (orbit overlaps, orbit comparisons, satellite laser ranging residuals, altimeter crossover residuals, orbit centering) show modest improvement when the ambiguities are resolved. We conservatively estimate the improvement in the radial orbit accuracy is at the 10–20% level.     

Identification and removal of block ambiguities in sea surface wind field with scatterometers

The solution of the current wind retrieval algorithm for scatterometers has several wind vector ambiguities, due to the bi-harmonic relationship between normalized backscattering cross section and the relative wind direction and the existence of the measurement error. In order to remove the ambiguities for a unique wind field, a circular median filter approach (CMF) is usually adopted. But under the condition for clustering distribution of the false ambiguities in some local areas, the CMF fails and thus engenders block ambiguities, which degrade the precision of the retrieved wind field. For such a situation, a technique of identification and removal of the block ambiguities is presented to further optimize the retrieved wind field after CMF. It is demonstrated in experiment that this technique can identify and remove most of the block ambiguities.     

星载GPS观测数据预处理模型研究

星载GPS不同于地基GPS。为了进行基于星载GPS的低轨卫星精密定轨和地球重力场模型解算,本文研究了星载GPS观测数据的钟差改正、整周模糊度解算、周跳探测、卫星跟踪点改正、GPS天线相位中心偏移和改正等的模型,给出了对应的处理公式和处理过程。     

GPS三频非差观测数据周跳的自动探测与改正研究

在GPS三频非差观测数据的处理中,由于伪距噪声的影响,利用原始的伪距和载波相位观测数据估计的模糊度误差比较大,不能用于探测和改正周跳。对原始观测数据进行平滑或适当的组合处理,可降低观测噪声的影响。因此,本文选择合适的经过平滑或组合处理后的观测数据作为探测周跳的检验量,探测并改正单个频点上的周跳。在分析了一般周跳的特点并在研究双频周跳自动探测与改正方法基础上,提出了选取检验量的四条基本原则。最后,依此原则选取了三个观测值组合作为周跳检验量,利用该组检验量实现三频非差观测数据周跳的自动探测与改正。