This study develops a three‐step Monte Carlo method to evaluate the worst possible integrity risk of ionospheric spatial gradients for GAST D GBAS. Impact simulation parameters are classified into two groups, “worst‐case” and “average,” based on the underlying integrity requirements. Unlike “average” parameters, “worst‐case” parameters are those for which a clear basis for averaging could not be established because the probabilistic distribution of these parameters cannot be developed with sufficient confidence due to the lack of observation data. In calculating integrity risk, these “worst‐case” parameters use the worst‐case value that maximizes the integrity risk. Each step of the randomized search narrows down the parameter ranges in sequence and identifies the two worst‐case parameter sets (based on the largest position error and the largest missed‐detection probability) for each worst‐case region identified in the initial step. The resulting integrity risk values are well below 10⁻⁹, showing that the GAST D SARPs integrity requirement is met.

中文翻译：

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电离层异常对GAST D GBAS影响的完整性风险评估

这项研究开发了一种三步蒙特卡洛方法来评估GAST D GBAS的电离层空间梯度的最坏完整性风险。根据基本完整性要求，影响模拟参数分为“最坏情况”和“平均”两类。与“平均”参数不同，“最坏情况”参数是无法为其建立清晰平均基础的参数，因为由于缺乏观测数据，这些参数的概率分布无法得到足够的置信度。在计算完整性风险时，这些“最坏情况”参数使用最坏情况值来使完整性风险最大化。随机搜索的每个步骤依次缩小参数范围，并为在初始步骤中确定的每个最坏情况区域识别两个最坏情况参数集（基于最大位置误差和最大的漏检概率）。产生的完整性风险值远低于10^-9，表明满足GAST D SARPs完整性要求。