航空测量场景下的中长基线动态定位方法

单基站中长基线动态相对定位受到大气残余误差影响,无法快速固定整周模糊度,定位精度和可靠性不如短基线场景。在航空测量场景下,流动站与基准站之间的基线由短到长变化,利用短基线场景下固定的整周模糊度反算得到高精度的电离层延迟量,并对其进行建模预报。随着基线变长,利用预报的电离层延迟约束中长基线定位模型,实现快速模糊度固定。本文分析了动态长基线情形下的电离层延迟的时变特性,采用滑动窗口进行电离层建模预报,讨论了该方法在航空测量实际作业中的实施条件、定位精度及模糊度固定情况。实测机载数据的解算结果表明,使用该方法,当测量载体出发阶段处于短基线场景下,单基站相对定位结果就可以达到接近100%的模糊度固定率,且定位精度保持在厘米级,显著减小了航空测量任务的作业成本。

A method of dynamic positioning with the medium and long baseline for aerial measurement scenarios

Medium and long baseline kinematic relative positioning with a single base station will be affected by atmospheric residual errors and the ambiguities could not be fixed fast. Therefore, the performance of long-baseline relative positioning with low ambiguity-fixed rate is not as good as short-baseline situations. While considering baselines varying from short to long in airborne scenes, we propose a new method to improve the performance of kinematic relative positioning. First, high precision ionospheric delays can be easily obtained from the ambiguity-fixed resolutions in short-baseline scenes when the air just taking off. Second, the subsequent ionospheric delays are predicated epoch by epoch based on previous ionospheric delays. At last, filter with ionosphere predication constrained is implemented to fix the ambiguities quickly and obtain continuous high-precision positioning results. In this paper, the characteristics of double-differenced ionospheric residual errors for the dynamic measurement scenarios with long-baseline are analyzed. A sliding window will be applied for modeling and prediction of ionospheric delays. Next, we have discussed the implementation conditions, performance of positioning and the ambiguity resolution with this proposed method. The presented algorithm is evaluated by a set of airborne data and the results show that the new scheme can obtain the 100% fixing rate nearly and centimeter-level positioning accuracy in long baseline relative positioning with single base station as long as a few minutes short-baseline data. With this method, the costs of airborne measurement tasks will be significantly reduced.