| Gravity measurement has been taken more and more seriously for recent years, establishing the gravity datum of Yunnan is becoming extremely urgent. This paper focuses on designing the basic gravity net of Yunnan and evaluating its precision. The major contents and conclusions are as follows:(1) Studied the gravimeter LCR-G’s precision of reading and correcting. For reading accuracy, analysed the theory of how gravimeter LCR-G surveying, and then introduced the error of reading, instrument leveling,elastic lag and voltage stability one by one that will affect the accuracy of gravimeter, at last, introduced the items that should be noticed in field surveying, the analysis shows the reading accuracy of gravimeter LCR-G can reach7μGal. For correction precision, analysed solid earth tide, case value standardization, null shift etc, and their effections on gravimeter LCR-G’s precision of surveying. Reached a conclusion that the dereferencing of tidal factor bring the maximum error will be less than±2.0μGal mean error will be less than±1.0μGal, scale unit correction precision will be about±2.0μGal,the formula for precision of null shift correction is σ零飘改æ£=0.038(S-30), from the fators above, recched a conclusion on gravimeter LCR-G’s precision of surveying is σ=10+0.038(S-30).(2) Introduced the design condition of Yunnan basic gravity net, evaluated precision of joint survey and gravity stations. Mainly introduced the design of Yunnan basic gravity net, with4instruments and4observation sets to obtain datas, evaluated the precision of joint survey and gravity stations with the method of equal weight and weighting. Got the conclution that the result of weighting was more satisfied, but in the weighting precision evaluation, weight’s confirmation had a great connection with the mean square error of surveying, if there was a system error (in this paper, it means the errors except for the first and the second one) in the surveying datas, accumulation of system error will be grow in the final result, and it perhaps make the result wrong.(3) Introduced the optimal design of Yunnan basic gravity net. Builded the relation of precision and expenses to find a way to build a net with the highest precision when the expenses is the lowest. Designed and optimized the method of equal weight precision evaluation,made it reach the standard of 《National gravity control measurement specifications》... |
