本文运用数理统计学原理分析了南通市一级导线网（B区）单位权中误差偏大的原因；
This paper analysis the reason why the middle error of unit weight in first class traverse of Nan Tong City (B area) is bigger with the principle of mathematic statistics;
通过与自由网平差结果对比表明，两种平差计算得到的单位权中误差相差不大，近似相等。
Compare to the free net adjustment result, these two unit weighted errors are closely approximated.
新的抗差方案试图实现如下三阶段目标：1）选取抗差性能很强的初值，包括定位参数和单位权中误差的初值。
The new scheme put forward in the present paper can realize this object by the following stages:1)to select the suitable beginning values for iterative solution ;
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