高频GPS单历元定位精度及噪声特征

PRECISION AND NOISE CHARACTERISTICS OF HIGH-FREQUENCY GPS EPOCH-BY-EPOCH POSITIONING

采用精密单点定位与相对定位模式,对天津地区GPS连续站高频观测数据进行处理,利用改进的恒星日滤波方法削弱多路径噪声的影响,并对定位精度和噪声特征进行分析。精密单点定位坐标时间序列的EW、NS和垂直向精度分别为7.3、7.1和16.0 mm,相对定位的EW、NS和垂直向精度分别为5.0、5.2和14.7 mm,总体上相对定位精度较精密单点定位精度高1.9～2.3 mm。采用功率谱密度方法研究两种定位模式的噪声模型,显示出白噪声模型无法表达时间序列的噪声特征。对于精密单点定位,在频率低于0.1 Hz的区域噪声与频率相关,而在高于0.1 Hz的区域趋向于高斯白噪声;相对定位模式结果显示噪声随频率的降低而增加。基于最大似然法,采用幂律噪声与白噪声组合模型估计幂律噪声的谱指数和白噪声的振幅,表明相对定位模式的噪声趋向于随机漫步噪声加白噪声组合模型,而精密单点定位的噪声趋向于闪烁噪声加白噪声组合模型。

High-frequency observations of 12 Continuous Operational Reference System（ CORS） GPS stations in Tianjin were processed with precise point positioning（ PPP） and relative difference positioning（ PRP） to estimate the absolute and relative epoch-by-epoch positions. The Modified sidereal filtering was used to correct multipath effect of high-frequency position time series. Positioning precision of PPP for east,north and vertical components are 7. 3mm,7. 1 mm and 16. 0 mm,respectively. The precision of PRP for east,north and vertical components are 5. 0 mm,5. 2 mm and 14. 7 mm,respectively. Compare to PPP,the precision of PRP is improved as 1. 3 mm to 2. 3 mm. According to the power spectral density,the noise is not only white noise. For PPP,the noise at frequencies below 0. 1Hz decreases with frequency and becomes flat at higher frequencies. However,for PPP,the noise at whole frequency band decreases with frequency. The difference of noise between PPP and PRP occur at high frequencies up0. 1Hz. And then,the spectral indexes of power law noise are estimated simultaneously with amplitude of white noise using maximum likelihood estimation. The white noise amplitude of PRP is much larger than PPP＇s. The noise of PRP can be best described by a combination of white noise plus random walk noise. However,the noise of PPP can be best described by a combination of flicker noise plus white noise.