It is one of the key techniques how to correct the additional second-phase factors (ASF) which indicate the affection of land on the speed of ground wave for developing the accuracies of timing and navigation of Loran-C signal in long-wave.

• 如何修正用以表征陆地对罗兰C信号电波(地波)传播速度影响的附加二次相位因子(ASF),是提高长波无线电导航定位和高精度授时的关键技术之一。