The results show that the ascent-descent-ascent variations of gravity before earthquake are the obvious reflection of medium-short-term anomaly.

结果表明，震前出现的重力上升下降上升变化是较明显的中短期异常反映；

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What this means is that iFACTS uses data from both aircraft and Nats itself to calculate flight paths, ascent and descent details.

BBC: Why air traffic control still needs the human touch