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Already for few decades airborne gravity data has been used in the gravity and geoid modelling. Several countries have used such data for updating national gravity databases and gravimetric geoid development during height reference systems realization. Results related to the processing and usage of the GRAV-D airborne gravity data in the computation of the regional gravimetric geoid model in Colorado (USA) are presented in this study. The focus is to analyse spatial and spectral contributions of airborne gravity. The combination of airborne and terrestrial gravity data is not a straightforward process. Prior to the geoid computations, the data were processed in several procedures, including: filtering of the high-frequency observation noise, outliers removal, downward continuation, bias elimination, estimation of data stochastic properties and data gridding. After data preparation, different versions and solutions of the geoid models are computed by using Least Squares Modification of Stokes' formula with Additive corrections (LSMSA) regional geoid modelling approach. Three types of gravity anomaly grids are used as input data: airborne, terrestrial, and terrestrial-airborne. The accuracy of computed geoid models is estimated by their comparison with available GNSS/levelling points. The results show the geoid accuracy improves by more than 1 cm (20%) when airborne gravity is included in computations compared to the geoid models computed from the terrestrial gravity data only. Furthermore, the spectral analysis provided insights on specific wavelength bands in which airborne gravity data affects the geoid undulation power spectrum.

V tomto príspevku sa diskutuje o regionálnom modelovaní tiažových porúch na strednej geocentrickej sfére blížiacej sa k Zemi v oblasti strednej Európy zo satelitných gravitačných gradientov. Hlavným cieľom tejto štúdie je preskúmať tri numerické prístupy na zníženie vplyvu vzdialených zón pri riešení inverznej gradiometrickej úlohy. Prvý prístup je založený na modifikácii integrálnych vzorcov, t.j., individuálne riešime príspevky v blízkej a vzdialenej zóne. Druhý prístup je jednoduchá modifikácia prvého scenára vyhladením meraných gravitačných gradientov pomocou gravitačného účinku topografických hmôt. V poslednom prístupe, ktorý sa tu nazýva tretí scenár, uplatňujeme dodatočnú úpravu vyhladením gravitačných gradientov o referenčný globálny geopotenciálny model. Pri všetkých troch prístupoch odhadujeme tiažové poruchy každého zo štyroch dobre meraných gravitačných gradientov oddelene, ako aj ich kombinácie. Naše regionálne riešenia gravitačných polí sú založené na gravitačných gradientoch GOCE EGG TRF 2 meraných v období od 1. novembra 2009 do 11. januára 2010. Ako celková referencia bol zvolený model EGM2008. Najlepšia zhoda z týmto modelom bola dosiahnutá pomocou druhého prístupu a komponentu Tzz (RMS 4,4 mGal). In this contribution we discuss a regional recovery of gravity disturbances at the mean geocentric sphere approximating the Earth over the area of Central Europe from satellite gravitational gradients. The main aim of the presented study is to investigate three numerical approaches for reducing the far zone effect for solving an inverse problem. The initial approach is based on the modification of the integral formulas, i. e., we are solving individually the near- and distant-zone contributions. The second approachis a simple modification of the first scenario by reducing measured gravitational gradients for gravitational effects of topographic masses. In the last approach called herein as the third scenario, we apply additional modification by reducing gravitational gradients for the reference global geopotential model. In all three approaches we estimate the gravity disturbances from each of the four well-measured gravitational gradients separately as well as from their combination. Our regional gravity field solutions are based on the GOCE EGG TRF 2 gravitational gradients collected within the period from November 1 2009 until January 11 2010. As an overall reference we choose EGM2008. The best fit, in terms of RMS (4.4 mGal), is achieved using a second approach and Tzz.