四等水准测量常识（Four level survey common sense）.docVIP

四等水准测量常识（Four level survey common sense） What is the allowable closing error for the four leveling survey? N (+ 6 V that right is the root, do not know how to play) + 20 (the number is the square root of root L, know how to play), how much? What do N and L stand for? 1.N represents the number of stations, L represents the distance (the unit is measured, such as your km) a closed with 9 stations, then the closure should be limited in 6*3=18mm, can also according to the location, if the distance is 1 kilometers, so should be limited in 20*1=20mm Close the point elevation the starting elevation = true elevation difference The algebraic sum of the height difference (back foot readings - front foot readings) of each measurement section Observation elevation difference - true height difference = level measurement closure error The adjustment principle of closing difference of closed and attached level route is that the sign of closing difference is directly proportional to the route length or station number, and is assigned to observation value of each elevation difference. The adjustment principle of branch line level closure is averaged to measure and return the absolute value of the measured height as the height of the two values, and to measure the same symbol; then according to the starting point to Gao Cheng Gao Cheng segment average elevation calculation of each measuring point (1) standard line of support Figure 2-17 (a) branch line level is shown, along the same route from observation, observation due to and from the opposite direction, so to the height measurement and return measured the same absolute value but opposite sign, that is to measure the difference and sum of algebraic sum and difference of back measurement in theory should be equal to zero; but due to various errors in measurement, to measure the sum and difference algebraic sum and difference of back measurement is not equal to zero, which is the closed difference of height difference: (2) closed le