Real-time precise point positioning (PPP) based on open-access real-time service (RTS) of the international GNSS service (IGS) has attracted increasing attention in recent years. For offshore applications, the receiving of RTS corrections becomes a major obstacle due to lack of internet-based infrastructures. Short-message communication (SMC) is a particular technique of BeiDou navigation satellite system (BDS), which can provide bidirectional communication between users in a cost-effective way. However, the limited bandwidth and frequency of BDS SMC make it impossible to directly broadcast IGS RTS corrections with BDS SMC. An offshore real-time PPP technique is proposed based on IGS RTS corrections with a single set of BDS SMC devices for communication. RTS orbit corrections in the along-track, cross-track and radial directions, the clock correction and the code bias correction of each satellite are together converted into an equivalent range correction on the basis of user approximate position and will-be-used code observation types. The range corrections within 1 min are fitted into a first-order polynomial. Only the range and range-rate corrections at the reference time are broadcast with BDS SMC. In addition, different from broadcasting corrections of all satellites in the IGS RTS, corrections of only visible satellites are encoded into a BDS SMC correction message to further reduce the data size. The encoding strategy of BDS SMC correction message and a detailed procedure of the offshore real-time PPP technique are presented. The land-simulated and offshore experiment results show that the proposed technique can meet the demands of high-precision offshore applications.

中文翻译：

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基于单套北斗短消息通信设备的海上实时精确点定位技术

近年来，基于国际GNSS服务（IGS）的开放接入实时服务（RTS）的实时精确点定位（PPP）越来越受到关注。对于离岸应用，由于缺乏基于互联网的基础设施，接收 RTS 更正成为主要障碍。短消息通信（SMC）是北斗卫星导航系统（BDS）的一项特殊技术，可以以经济高效的方式提供用户之间的双向通信。但是，BDS SMC 的带宽和频率有限，因此无法通过 BDS SMC 直接广播 IGS RTS 改正。提出了一种基于 IGS RTS 改正的海上实时 PPP 技术，使用一组 BDS SMC 设备进行通信。沿轨道、交叉轨道和径向方向的 RTS 轨道改正，将每颗卫星的时钟校正和码偏校正，根据用户近似位置和将使用的码观测类型，一起转换为等效距离校正。1 分钟内的距离修正被拟合为一阶多项式。BDS SMC 仅广播参考时间的距离和距离速率校正。此外，与IGS RTS中所有卫星的广播改正不同，仅可见卫星的改正被编码到BDS SMC改正消息中，以进一步减小数据量。介绍了BDS SMC修正报文的编码策略和海上实时PPP技术的详细流程。