大比例尺测图两点法已知边推未知边精度分析

大比例尺地形图在实际工程中有较大的作用．而两点法已知边推未知边在大比例尺测图中有很重要的作用，特别是在城市房屋和矩形建筑物等地物的测量中有重要的意义。本文对两点法已知边推未知边的平面精度进行了分析。从碎部点的平面精度出发，分析了平板测图时碎部点和数字测图时碎部点的平面精度，根据误差传播定律，结合测绘的实际情况，从而推导出两点法已知边推未知边的边长比精度。结合工程测量规范的要求，给出两点法已知边推未知边在各种大比例尺应用中的限差。

PRECISION ANALYSIS OF DEDUCING UNKNOWN-SIDE FROM KNOWN-SIDE BY TWO-POINT METHOD IN LARGE-SCALE MAP-SURVEYING

Large scale map plays an important role in engineering, because it's the foundation of design and construction. The two point method of deducing unknown side from known side is widely used in large scale map surveying, esp. in the survey of city buildings and other rectangular structures. This essay analyses horizontal precision of the unknown side, which was deduced from the known side by two point method. According to the horizontal precision of detail point, it analyzes the horizontal precision of the detail point when using flat, and the horizontal precision of the detail point when using the total station and computer. According to the principle of error transmission, combining the practical engineering, we gained the ratio of unknown side, which was deduced from the known side by two point method. Due to the standard of engineering surveying, we conclude the restrictive errors in each large scale map surveying when deducing the unknown point from known point by two point method.