低频地波传播时延计算的地形优化处理方法

附加二次相位因子(ASPF)是影响长波信号传播时间延迟的主要因素. 积分方程方法计算ASPF适用于地形复杂的路径，是目前广泛使用的计算方法. 它在推导过程中使用了稳定相位积分的近似方法，在地形起伏剧烈地区不再适用. 实际传播路径地形起伏变化巨大，通过数学形态法对实际传播路径修正，可以使路径保留基本几何轮廓并且光滑. 积分方程方法计算结果表明: 利用数学形态法可以有效优化处理实际传播路径. 

Terrain optimization method for low-frequency ground-wave propagation delay calculation

The additional secondary phase factor (ASPF) plays an important role in propagation delay of the low-frequency ground-wave. A method of calculating attenuation for ground-wave propagating over irregular terrain called integral function has been developed recently. It is derived by means of a stationary-phase integration that reduces the dimensionality of the general version, but such an approximation is not valid for all terrain types. The terrain of the actual propagation path changes greatly, and the actual propagation path is corrected by the mathematical morphology method to keep the basic geometric contour and smoothness of the path. The calculation results of the integral equation method show that the actual propagation path can be effectively optimized through the mathematical morphology method.