What is base level measurement
When the line is long, in order to ensure the accuracy of measuring the elevation of each point of the middle stake, it is usually necessary to survey the known elevation points near the whole line, and measure a point every certain distance as the base leveling point of the line. This point can be used as the foundation elevation to measure the elevation of the middle stake of the line near this point. This measurement process is called base level measurement.
matters needing attention:
1. Leveling should be paid attention to when the level is placed. The point position should be close to the distance between the front view and the back view as far as possible, so as to eliminate the internal error of the instrument.
2. After aiming at the backward looking reading, turn to the aiming forward looking immediately. At this time, the leveling state must be maintained. If the leveling bubble is staggered at this time, the fine leveling must be carried out in this state after aiming at the forward looking, and then the reading can be made.
3. In order to ensure the accuracy of measurement, round-trip measurement is required. The reading can be used only when the accuracy is within the requirements of general surveying. It can also be checked by the method of double-sided ruler, and each station should be checked as much as possible in the measurement.
4. The datum of base leveling survey should be adjusted before use. For specific adjustment method, please refer to general survey knowledge.
5. During the measurement, the level ruler should be vertical. When reading, the parallax should be eliminated first. The master of ceremonies should read the minimum data of the middle wire clamp to ensure the most accurate reading.
6. The surveyor must ensure that there is no soil at the bottom of the ruler. When using the tower ruler, attention should be paid to the non-contact between the rulers.