This paper investigates the characteristics and the metrological limits of the calibration of spring type gravimeters by using a cylindrical test mass moved vertically around the gravimeter by a lifting device operated in the Mátyáshegy Observatory. The movement of the 3100 kg iron mass generates a sinusoid-like calibrating signal having a peak-to-peak amplitude of 1102 nm s −2 . The careful determination of the geometrical and physical parameters of the test mass combined with the analytical modeling of its gravitational effect and the related uncertainties provides an accuracy of 3 nm s −2 in absolute sense. The overall accuracy, however, is influenced by several other instrumental and environmental factors which are investigated in detail. The conclusions are based on more than 400 experiments with 5 LCR G instruments. As a unique case a Scintrex CG-5 instrument was also involved in the tests what is probably the very first moving mass calibration of this type of gravimeters.Two processing methods, Max-Min and Full-Fit, based on L2 norm adjustment of the observations were developed and applied to obtain instrumental scale factor and other related parameters.The results show that the observations corrected for the disturbing effects still contain a systematic constituent with amplitude of (10-20) nm s −2 regardless which LCR instrument was calibrated. It resembles the second time derivative of the calibrating signal that may indicate the non-uniform elastic response of the spring sensors to the rate of gravity change. Due to the problems mentioned above the overall dispersion of the resultant random and nonrandom residuals of the calibration observations provided by Full-Fit method are typically 10 nm s −2 . The a posteriori standard deviations of the individual scale factors provide, however, measurement accuracy of 2 nm s −2 .

In this paper a systematic, semi-empirical comparison is presented between two-dimensional geoelectric models and their inversion images, obtained by using five different electrical resistivity arrays and an optimized Stummer configuration. Eight different models (more or less in order of growing complexity) are studied and both noise-free and noisy data cases are considered. The results show that (1) the quality of the inversion images obtained with traditional arrays depends significantly on the model and on the noise level, (2) among the traditional arrays it is definitely the dipole-dipole array that provides inversion images mostly similar to the geoelectric models, (3) the inversion images obtained by using the optimized Stummer configuration are even more similar to the original geoelectric model than those obtained by the dipole-dipole array. It means that the optimized Stummer array is even better than the best traditional array, the dipole-dipole array, especially in the deepest part of the inversion images. We conclude that in a general field situation the Stummer configuration is good enough for not being forced to search specific configurations. As presented, optimization procedures, involving null arrays could even further improve the quality of the inversion images obtained by using the Stummer configuration. basis for traditional profiling and sounding techniques they are also important for electrical resistivity tomography (ERT) measurements because the individual arrays serve as a basis for the ERT measurements.ERT measurements, which nowadays play a dominating role in geoelectric probing, should however be handled differently from the individual arrays. In their case the DOI (depth of investigation) introduced by Oldenburg and Li (1999) and the DD (depth of detectability) introduced by values can give information about the depth interval from which one is able to obtain useful information. DOI is the depth, below which any change in the model resistivity has an unobservable effect on the measured signal. The DOI is in theory array-and modeldependent but for the same model, in the case of various arrays, more or less the same DOI value is obtained. At the same time, the DD parameter shows a more significant array-and modeldependence. E.g., the same model by using a given array could be observed from even a four-five times larger depth than by using another array. We supposed a relation between the DD values of the configurations and their imaging properties. The existence of such a relation was verified in this paper.

This paper investigates the effect of electrode positioning errors on the inverted pseudosection. Instead of random spacing errors (as usually assumed in geoelectrics) we exactly measured this effect among field conditions. In the field, in spite of the greatest possible care, the electrode positions contain some inaccuracy: either in case of dense undergrowth, or varied topography, or very rocky field. In all these cases, it is not possible to put the electrodes in their theoretical position. As a consequence, the position data will contain some error. The inaccuracies were exactly determined by using a laser distance meter. The geometrical data from real field conditions and by using Wenner-α, Wenner-β, pole-dipole and pole-pole arrays were then considered over homogeneous half space.As we have found, the positioning errors can be regarded as insignificant, even in case of relatively uncomfortable field conditions. However, in case of very rocky surface the distortions are more significant, but it is still possible to make some corrections: either by neglecting a few electrode positions with the greatest positioning error, or to minimize the inline errors, even on the price that offline deviations are high.

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