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Ⅰ.特大桥测量工作大桥的测量工作，比较重要的是桥址三角网施工测量和水文测量。桥址三角网的类型和布置，首先决定于两岸地形。成果精度应符合施工测量的要求。图形以简单而易于平差为原则，一般是采用四边形为控制网，其中一边为桥位线，两岸两边为基线。观测角度的误差规定不超过仪器精确度的2倍。然后按照几何条件作总的平差。基线方面，我们以往是采用铟钢尺比长校对的钢尺，用基线架、重锤丈量，其精度能达到1/25000。桥长的相对误差，当桥的长度500公尺左右时，约为±20～±30mm，故相应的桥长精度亦能达到1/10000以上，如黄河上的三道坎三盛公、广西省的邕江郁江大桥等都是采用该项方法丈量的，经过施工考验证明都能符合精度要求。去年在郑州黄河桥勘测时，由于桥位长度在一公里以上，才开始采用铟钢基线尺丈量。该铟钢尺的相对精度能达到1/750000～1/1，000，000以上，完全能满足一公里以上大桥的精度要求（精度计算方法详施工测量部份）。
Ⅰ. Measurement work of super large bridge The measurement work of the bridge is more important than the bridge site triangulation construction measurement and hydrological measurement. The type and layout of the bridge site triangulation, first decided by the two sides of the terrain. The accuracy of the results should be consistent with the requirements of construction measurement. Graphics to simple and easy to adjust the principle of the general is the use of quadrilateral control network, one side of the bridge bit line, both sides of the cross-strait as the baseline. The error of observation angle does not exceed 2 times the accuracy of the instrument. Then according to the geometric conditions for the total adjustment. Baseline, we used to use indium ruler than the length of the school ruler, with a baseline frame, heavy hammer measurement, the accuracy can reach 1/25000. The relative error of bridge length is about ± 20 ~ ± 30mm when the length of the bridge is about 500 meters, so the precision of the corresponding bridge length can reach 1/10000 or above. For example, Province Yujiang River Yujiang Bridge, etc. are all measured by this method, after construction test proved to meet the accuracy requirements. When surveying the Yellow River Bridge in Zhengzhou last year, it began to use the indium-steel baseline ruler to measure because of the bridge length of more than one kilometer. The relative accuracy of the indium ruler can reach 1/750000 ~ 1 / 1,000,000 or more, fully meet the accuracy requirements of more than one kilometer of the bridge (precision calculation method detailed construction measurement part).