嫩江是松花江的北源，是东北地区的重要河流。
The Nen river, the northern source of the Songhua river, is the important river of northeast region.
长江发源于世界屋脊--青藏高原的各拉丹冬雪山西南侧，正源沱沱河，南源当曲河，北源楚玛尔河。
It originates from the Tuotuo River on the southwestern side of the snow-draped Geladandong.
分析表明：天文找北系统结构简单，精度高，对外部误差源不敏感。
It is showed that the north-finder has simple structure, high precision, and is not sensitive to outer error sources.
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