Study on Filtering Algorithm of the Aerial Gravity Measurement Data Processing
|School||PLA Information Engineering University|
|Course||Geodesy and Survey Engineering|
|Keywords||Airborne gravity survey Data processing Hopping Firth correction Horizontal acceleration correction Cross-coupling correction Pretreatment Fourier transform FIR low -pass filter Window function Time-frequency analysis Wigner-Ville distribution|
Airborne gravity measurement, the order of magnitude of the gravity anomaly data generally less than 100 milli-gamma, the magnitude of the noise is often its hundreds even thousands of times, to eliminate the strong noise of the sensor under dynamic conditions and retain full gravity anomaly is airborne gravity measurements into practice the key issues. The filtered extract is an important part of the airborne gravity measurement data processing, reasonable frequency domain passband appropriate filtering method can effectively improve the accuracy of airborne gravity measurement data processing. Studied airborne gravity observation data processing method, focusing on filtering algorithm for processing airborne gravity disturbance, and verified by experiments with real data. Work and innovation of the main points are as follows: 1, combined with Newton's second law, established a mathematical model of the Airborne Vector Gravimetry, aviation scalar gravity measurement data processing method, practical formula given by the model to calculate the gravity disturbance . Airborne gravity data processing flow, hopping Firth correction, horizontal acceleration correction, correction of cross-coupling, measured line than the force vector vertical acceleration, space corrections as well as the calculation of normal gravity model of the correction accuracy. Two methods discussed Airborne Gravimetry horizontal acceleration correction: the two-step and one-step, clear that the raw data should be used to reduce the squared term in the one-step system error caused calculate the horizontal acceleration correction prefiltering processing, and propose a method to determine the scale of the pre-filtering based on a stable platform damping system, determine the pre-filter scale to determine the scale based on the platform stable cycle. FIR low-pass filter, Haar wavelet, db4 the wavelet, db6 wavelet, sym4 wavelet pre-filtering process has been applied to the pre-filtering process wavelet function. 3, using the FIR low-pass filter to filter out the large amount of noise in the observed data, to calculate the part of the measured data. Based on the spectral characteristics of the airborne gravity survey data to determine the technical specifications of the desired filter window function design FIR low-pass filter. 4, to further improve the accuracy of the filtering process of the airborne gravity survey, presented in the audio domain when dealing with airborne gravity survey data, including data, time-frequency analysis, time-frequency support area access pass domain and time-frequency domain filter through design and time-domain data reconstruction, the effect of the filtered extract the audio domain simulation numerical example. Design time-frequency pass domain filter, consistent with the requirements of airborne gravity data filtering process on the part of the measured data, spreadsheets, and verify the calculation of the Wigner-Ville distribution, to determine the feasibility of the audio domain, concluded that the frequency domain filtering dealing with the gravity disturbance data should be noted.