Performance Evaluation of the Early CNAV Navigation Message
Performance Evaluation of the Early CNAV Navigation Message
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DOI：
10.1002/navi.111
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发表时间：
2015-01
影响因子：
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通讯作者：
P. Steigenberger;O. Montenbruck;U. Hessels
中科院分区：
文献类型：
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作者：
P. Steigenberger;O. Montenbruck;U. Hessels
在2013年6月进行初步测试活动后，全球定位系统局于2014年4月28日开始进行民用导航电文CNAV的运行前例行生成和传输。新消息由IIR-M组卫星在L2C信号以及IIF组卫星的L2C和L5信号上广播。新的CNAV星历报文中的改进的分辨率和更多的参数提供了显著减少的星历拟合误差，并且在很大程度上避免了来自同一上载的连续星历报文的不连续性。Block IIR-M和IIF卫星的CNAV数据自传输开始以来一直使用一小组全球分布的接收器进行收集，这些接收器提供几乎连续的覆盖范围。基于与国际GNSS服务（IGS）的精确星历的比较，对于CNAV消息获得约1.1 m的空间信号距离误差（SISRE），而对于传统导航消息（LNAV）获得0.6 m。这种性能下降与CNAV更新频率较低有关，导致预测时间长达四天。对于三个星期的时间，每天CNAV更新率几乎相同的SISRE获得LNAV。作为SISRE分析的补充，新的信号间校正（ISC）已经被监测，这使用户能够在实时定位应用中使用L1/L2 P（Y）码观测值以外的其他信号时正确地考虑差分码偏差（DCB）。广播ISC值与IGS多GNSS实验框架中得出的DCB和欧洲轨道确定中心的DCB在0.1 - 2 ns水平上（取决于ISC类型）一致。虽然到目前为止，民用L1C/A和L2C信号的用户经历了明显的定位降级，但ISC现在能够实现与半无码P（Y）码接收机完全竞争的单点定位精度。
Following an initial test campaign in June 2013, the GPS Directorate has initiated a pre-operational routine generation and transmission of the Civil Navigation Message CNAV starting on 28 April 2014. The new message is broadcast by Block IIR-M satellites on the L2C signal as well as the L2C and L5 signals of the Block IIF satellites. The improved resolution and larger number of parameters in the new CNAV ephemeris message offers a notably reduced ephemeris fitting error and largely avoids the discontinuities of consecutive ephemeris messages from the same upload. CNAV data of the Block IIR-M and IIF satellites have been collected since the start of transmission using a small set of globally distributed receivers offering an almost continuous coverage. Based on comparison with precise ephemerides of the International GNSS Service (IGS), a Signal-in-Space Range Error (SISRE) of about 1.1 m is obtained for the CNAV message whereas it is 0.6 m for the legacy navigation message (LNAV). This degraded performance is related to less frequent CNAV updates resulting in prediction times of up to four days. For a three week period with a daily CNAV update rate almost the same SISRE is obtained as for LNAV. Complementary to the SISRE analysis, the new Inter-Signal Corrections (ISCs) have been monitored, which enable users to correctly account for differential code biases (DCBs) when using other signals than the L1/L2 P(Y)-code observations in real-time positioning applications. The broadcast ISC values agree with DCBs derived in the frame of the IGS Multi-GNSS Experiment and DCBs from the Center for Orbit Determination in Europe on the 0.1 – 2 ns level depending on the ISC type. While users of the the civil L1C/A and L2C signals have, so far, experienced a notably degraded positioning, the ISCs now enable a single point positioning accuracy that is fully competitive with that of semi-codeless P(Y)-code receivers.