Data Processing And Application Research Of Airborne Gravimetry

Global warming,melting of polar ice sheets,sea levels rising and major geological hazards are the major concerns and the issues of the scientific community over the world.The basic geospatial information including earth gravity field structure and high preci-sion high resolution geoid are needed to process these problems.To determine the high precision global gravity field model and gravimetric geoid have became the important jobs of geodesy.Airborne gravimetry is an effective way to improve the spatial resolu-tion of gravity field and the accuracy of short-wave signal.It is also the only viable and the easiest way to get ultra-high resolution gravity acquisitions on large scale.Airborne gravimetry played an important role conducting gravity survey in uninhabited areas all over the world.With the coming and outstanding development of airborne gravimetry technique,airborne gravimetry has became a useful way for geodetic scientists to im-prove the precision of geoid model.In the beginning of this century,many countries conduct airborne gravity project of the geoid model determination and the global grav-ity field modeling(platform system).In the meantime strapdown system experiments are also conducted.Therefore,the study of airborne gravimetry and application of airborne airborne gravity data have became the new idea for geodetic scientists.Hence we choose airborne gravimetry as the subject of my thesis.The objective is airborne gravimetry data processing and application by various methods,particularly,research on the platform modeling correction formula of the tilt error,combination the gravity data between strapdown system and platform system,proposing system error correc-tion based on semi-parametric model,designing and validation of a plan to merge many kinds of gravity data and geoid determination,proposing questions and suggestions for further research.The finished tasks in this thesis include these parts:1.We have reviewed airborne gravity of geodesy in past years and analyzed the relationship between airborne gravimetry and earth science.The events of airborne gravimetry development have been summarized.The unified theory behind many air-borne gravimetry methods is given.Finally,many issues related to airborne gravimetry processing and application have be addressed to my experience.2.Studying and summarizing the theory of specific force generated by airborne gravimeter and acceleration determination theory,involving the formulas for the trans-formation of coordinate systems in different space and time,study of the pendulum motion equation of the gravimeter,summarizing all kinds of the mathematical model of error correction,the key points are formula derivation and the theoretical analysis.Studying and summarizing the specific force principle of the inertial navigation system,the model and direct methods,the concept and computational model of the inertial navigation are calculated.The key points are providing the precision requirements of inertial navigation system(gyro and accelerometer)by airborne gravimetry.The clas-sification and reasons of zero deviation error caused by accelerometer are analyzed in detail.3.Investigating and summarizing several post-processing methods for systematic error of airborne gravimetry.Summarizing and studying the error effects on airborne gravity downward continuation.The calculation formulas of the influence of systematic and random errors are derived.The purpose of all above mentioned work in this item is to prepare for quantitative analysis of systematic and random errors.The inverse poisson integration method based on the semi-parametric model is proposed.It is tested by the experimental using actual data.4.Summarizing and developing a software system with multi-function for airborne gravimetry processing and application is developed.The software system can be used for scalar data processing,combination of strapdown and platform gravity,downward continuation,multi-type gravity fusion and gravimetric geoid determination.The achievements in this thesis are these points:1.The theory of scalar airborne gravity data processing is studied in detail.The tilt error correction formula problem of Arne Olesen doctoral thesis has been found which is not preciseness considering the force acquisition merely.We derived the complete formula to tilt error correction.The actual data verifies its correctness of the new formula.2.The characteristics of random zero bias of the SINS accelerometer is investigated in detail.The combination of strapdown and platform airborne gravity is proposed.We have derived the related theoretical equations are which used to correct the mentioned bias with the help of the long-term stability of the platform instrument.Moreover,the Antarctic airborne gravity experiment has been conducted to test the method.As a result,the precision of SINS airborne gravimetry has been improved from 4.1mGal to 3.1mGal.3.The random and systematic errors of airborne gravity effects on downward con-tinuation(DWC)are analyzed.Systematic and random error effects were calculated based on theoretical deductions and numerical simulations.The results show the linear relationships between systematic error effects or random errors effects and grid spaces or DWC heights.It is concluded that the smaller grid spaces and higher DWC heights will increase the systematic error effects and random error effects.4.The inverse Poisson integral based on the semi-parametric model is proposed to process systematic errors.Laying stress on optimization algorithm with compensation least square and smoothing parameter.The new method can estimate systematic errors and ground gravity at the same time.Finally,it is proved that the new method is supe-rior to the traditional inverse poisson integral taking advantage of data from Louisiana(NGS airborne gravity project)and the Tibetan plateau(simulated airborne gravity).5.The combined algorithm of semi-parametric model and regularization method is proposed to estimate systematic error and to weaken random error effects.The new method can also improve the accuracy of downward continuation results.And the experimental results show the combined algorithm is more effective dealing with DWC error effects than semi-parametric model and regularization method separately.The DWC height is 6.3 km and the resolution is 6.And the combined algorithm experimental accuracy can reach about 2.922mgal.6.The results of comparison between this method and the combined algorithm proposed in this paper,showed the combined algorithm performs better in the Louisiana state DWC test,while this method is superior in Tibetan Plateau DWC test.From the experimental results,it is found that the accuracy of this method depends on the priori parameters.Since the three parameters of the Tibetan Plateau are more close to the actual situation so the DWC accuracy is better.As a result,the precision of Taiwan's airborne gravity DWC was increased from 19.653mGal(Hwang et al.,2007)to 11.653 mgal.7.GOCE,airborne,shipborne and land gravity are used to determine gravimetric geoid of Taiwan.Many kinds of gravity data are combined by least squares colloca-tion.And the residual topographic correction is used to calculate the terrain effect.In addition the gravity field model is used in the remove-compute-restore approach.Fi-nally,two-dimensional FFT is applied to compute Stokes integral to determine Taiwan gravimetric geoid,GPS leveling comparison results showing the 0.126 m std which is as same as the accuracy of geoid model released by the Taiwan(Hwang et al.,2007)with similar data.8.A software system with multi-function for airborne gravimetry processing and application is summarized.The software system can be used for scalar data processing,combination of strapdown and platform gravity,downward continuation,multi-type gravity fusion and gravimetric geoid determination.