GAMIT/GLOBK在高精度长基线像控点解算中的应用

Application of the GAMIT/GLOBK in high-precision long baseline as photo-control-point calculation

青海省藏区大比例尺基础地理信息都兰测区数据采集项目,航摄结束后摄区像控点布设南北基线跨度160 km,东西基线跨度135 km,基线跨度很大,如果采用传统RTK方法,受基线距离的限制,测区必须重新建设多个基准站,外业工作效率将大幅度降低,并且常规坐标解算方法很难保障解算精度。为了解决长基线像控点高精度解算问题,利用GAMIT/GLOBK解算方式,引入了9个IGS基准站、精密星历及精密钟差对测区106个静态观测的像控点进行坐标解算,用另外一组以摄区高精度CORS(连续运行基准站)站作为控制点,区域网平差后cm级的解算成果检验GAMIT/GLOBK的解算精度。通过分析发现,采用GAMIT/GLOBK解算模式,在不依赖摄区CORS站及已知控制点的情况下,其基线解算所有单天的NRMS标准化均方根值精度值均小于0.25,基线重复率相对重复性精度达到了10^-3 m、绝对重复性精度达到了10^-8 m,通过TBC成果对GLOBK坐标平差精度进行评定,得出N,E,U等3方向的中误差分别为:11.9,10.4,4.2 cm,通过利用距测区150 km范围内的3个已知CORS站点对上述N,E方向中的系统性共模误差进行改正,改正后中误差为-0.728 4,-1.995 cm.解算精度满足1∶1万外业像控点要求,说明利用GAMIT/GLOBK解算方式,可以为青海省大部分无基准、无控制的地区开展GPS像控点数据测量及解算工作提供实践精度参考。

For the project of basic geographic information data acquisition in Dulan area of Qinghai Tibetan,the span of baselines formed by photo-control-point is quite large,with 160 km from north to south and 135 km from east to west.If the traditional RTK method is used,some reference stations must be built in the survey area to overcome the effects of baseline distance.Thus,the efficiency of field work will be greatly reduced,and the accuracy of coordinate calculation is difficult to be guaranteed.In order to solve the problem about the high-precision positioning for long baseline photo-control-point,this paper used the GAMIT/GLOBK mode,while nine IGS reference stations,precise ephemeris and precise clock bias were introduced,to calculate the photo-control-point for 106 static observations in the survey area.Using another set of high accuracy Continuously Operating Reference Stations(CORS)stations as control points,to check the accuracy of GAMIT/GLOBK mode by the cm level solution results after block adjustment.Based on the analysis,we found the baseline accuracy of all single day Normalized Root-Mean-Square value(NRMS)is less than 0.25 by using GAMIT/GLOBK mode without depending on the CORS station and the known control points.The relative repeatability accuracy of baseline repetition rate has reached 10^-3 m,absolute repeatability accuracy has reached 10^-8 m.By evaluating the accuracy of GLOBK coordinate adjustment through TBC results,we concluded the mean error of N,E and U in three directions is 0.119,0.104,0.042 m respectively.The systematic common-mode errors in the N and E directions are corrected by using three known CORS stations within the range of 150 km from the measuring area.The standard deviation is-0.728 4,-1.995 cm after correction.The accuracy of the solution meets the requirements of 1∶10 000 external photo-control-point,It means the GAMIT/GLOBK mode,can provide a reference for the GPS photo-control-point data measurement and calculation in most areas of Qinghai Province without datum and control.