Be familiar with the marking rule of the leveling rod, and the reading should be from small to large, and the value should increase in the direction (no matter up or down, from small to large). If it is a mirror, the reading ruler should read from top to bottom.
If a rectangular control network is laid, it is likely that the periphery will not be closed, which exceeds the allowable error. The centering error should not exceed 2-3mm, and the rear-view edge should be selected on the long side.
Extended data
1, general engineering survey generally has no obvious time effect. Foundation pit monitoring is usually coordinated with dewatering and excavation process, which has obvious timeliness. Therefore, the monitoring of deep foundation pit construction needs to be carried out at any time, generally 1 time /d, and it may be carried out several times a day in the critical period when the measured object changes rapidly.
2, choose a more solid place, the tripod should be firmly stepped on, the height should be suitable for the height of the observer, and don't touch the tripod when observing. If the theodolite frame head is not inclined horizontally, the vertical spherical line will deviate from the center of the dial, which will affect the centering accuracy.
3. In the centimeter division, there are still obvious characteristics, and there are obvious laws of real single and virtual double. That is, the all-black area is actually single, and the non-all-black area is imaginary double.
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