Research Of The Background Environmental Impact In The Absolute Gravity Measurement

Gravitational acceleration g contains information about Earth's gravity field.Get the exact value of g has important significance for the development of national defense and national economy. However, the value of g obtained by absolute gravity instruments include not only the impact of falling bodies suffered gravity, but also the effects of ambient background environment of the measuring point. Therefore, If we want to obtain the exact value of g the background environmental factors study are required.This paper analyzes the background of environmental factors affecting on absolute gravity measurements, Including tides, hydrology, air pressure, gravity gradient, polar motion, temperature and humidity, etc.We give a brief introduction about each environmental factors principles, and calculate its impact on the absolute gravity measurements magnitude. We analysis some of the environment datas we have already got,and proposed the program to monitor other environmental factors.Firstly, we analysis full-year data of 2015 measured by 2 gphones in our laboratory. Datas show that both of the instrument observations drift in our laboratory are very good, First-order linear fitting is more than 99%,it means the instrument have less interference, and can reduce the drift effectively. This paper assess the impact of environmental factors by analysis the gphones datas and the environmental factors datas together. Such as analysis the rainfalls impact, we find the rain can make the local gravity increase several microgals. We use high-precision barometer recorded the pressure change in room 217 for nearly a month,and give the ressure correction curve is calculated according to the formula Xu Houze, after comparison, we found that changes in air pressure and gravity residual value changes significantly similar trend. It means the changes in barometric pressure do affects the gravitational field of the laboratory, and need to be corrected. In addition, in order to meet the need of monitoring the overall impact of environmental factors through the comparison of absolute gravimeters, I measured the gravity gradient in room 217 by CG5, give the variations of the average gradient in room217. After measure the levelness of the surface of the pier in room 219 by Inclinometer,we find the high difference between two points which apart 1m can produce 2?Gal measurement error. Therefore we must measure the levelness of the pier before the comparison of absolute gravimeter.