Research On Polar Airborne Gravity Measurement Data Processing

Based on the analysis of the basic principles and methods of airborne gravity measurement,this paper sunmmarizes the international airborne gravity measurement missions conducted in the Arctic and Arctic regions and takes the airborne gravity measurement system on the "Snow hawk 601" fixed-wing aircraft that was first-time used in the China's 32nd Antarctic Scientific Expedition as the research object.The specific method of extracting the gravity anomaly signal from the airborne gravity measurement system is systematically studied.The main research contents and results are as follows:1)The article systematically elaborated the basic principles and data processing methods of aviation gravity measurement technology,and introduced the specific formulas and application methods of various corrections in aviation gravity measurement and various methods of downward continuation of gravity disturbances.The principle and process of extracting gravity disturbance signals from the raw force measurement data of the airborne gravimeter carried by "Snow hawk 601 "are introduced in detail.2)This paper describes the principle and implementation of GPS Precise Point Positioning(PPP)technology.Using the self-developed PPP software to calculate the GPS data collected by China's 33rd Antarctic Scientific Expedition“Snow hawk 601”fixed-wing aircraft,and its high dynamic and high-precision three-dimensional coordinates were given.Compare the results with the GAMIT TRACK solution.The results show that the static accuracy of PPP mode is 1.57cm,which is better than the TRACK module.The accuracy of the vertical acceleration obtained by the PPP model is also evaluated.The results show that the static accuracy is better than 0.5mGal and the dynamic accuracy is better than 0.71mGal at the filtering scale of 100s,which can meet the precision requirements of airborne gravity measurement.It is considered that the filtering scale of 100s is the appropriate filtering scale for this calculation.3)The "Snow hawk 601" airborne gravity measurement system's measurement data includes GPS data and inertial system attitude data.Stable platform inclination data and gravity instrument specific data.Taking the data measured by F08 as an example,the various corrections were rigorously analyzed and the numerical values,spectrum distribution,and comparison before and after the filtering were given.The results show that both the static and dynamic accuracy are better than 0.7mGal when the vertical acceleration correction based on PPP method is low-pass filtered at a response radius of 8km.The Eotvos correction is only a few tens of milligrams on the same route,only converting the sign when the plane turns east-west.The absolute value of the correction after correction is below 1 mGal,but the change is sharp and the high frequency is dominant.The amplitude of the horizontal acceleration correction is better than 10 mGal after filtering,and only becomes steeper at the time of steering,reaching the order of 104 mGal.In the end,after unified corrections,the airborne gravity anomaly at each point on the survey line was obtained at a cut-off frequency of 100 s.4)In the aerial gravity anomaly reduction method,the gravity correction gradient radial correction method was used,and the radial correction formula was optimized for the special flight conditions of polar aviation gravity measurement.The EGM2008 gravity field model was used to perform the third order at the aerial survey point.Taylor series expansion to improve its accuracy.The internal accuracy of the "Snow hawk 601"aviation gravity measurement system was calculated by using the intersection data.The experimental results show that it is better than 1.6mGal.This study can provide a good reference for the calculation and application of the"Snow hawk 601" aviation gravity data.