U. S. Army soldiers from the 27th Infantry Regiment pull a bobcat tractor out of the mud at their mountaintop position at Observation Post Mustang in Kunar Province, Afghanistan.
在阿富汗库纳尔省的野马观测站，美国陆军第27步兵团的士兵正在山顶将轻型拖拉机从淤泥中拖出来。
During 1981-1987, the fixed position observation was conducted in different patterns of multiple cropping system of paddy fields.
1981年至1987年，对稻田不同多熟种植方式进行了定位观察。
An explicit functional relation of the point position variance of angular resection with observation value was derived.
推导了测角后交点位方差与观测值的显函数关系式。
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