We have surveyed the Earth's surface using gravity anomalies and second-order radial derivatives of the disturbing gravitational potential computed from the gravitational model EGM2008 complete to degree and order 2159 (for selected degrees up to 2190). It corresponds to 5 arcmin resolution on the ground. Over most well known impact crater sites on the Earth we found the second-order derivatives (not available from ordinary gravity surveys) offered finer discrimination of circular features than the gravity anomalies themselves. We also discovered that some of the sites show evidence of double or multiple craters which will need further ground verification. Some of these signatures (in hilly or mountainous terrain) may also need to be corrected for the gravitational effect of topography to sharpen their hidden features., Jaroslav Klokočník, Jan Kostelecký, Pavel Novák and Carl A. Wagner., and Obsahuje bibliografii
Since 2002, the US-German GRACE (Gravity Recovery and Climate Experiment) mission has been providing a precise survey of the Earth's time-variable gravity field, with unprecedented temporal and spatial sampling. GRACE time-variable gravity fields provide a means of measuring the temporal and spatial variations of mass redistribution within the Earth system. The GRACE mission has started a new era in studying a series of geophysical problems ranging from deep Earth structure to tracking mass redistribution on and near the surface of the Earth. Time variability of the gravity field presented here is based on the transformation of “monthly gravity field models” to the geoid. We show the changes caused by the global water cycle and land hydrology., Jan Kostelecký, Aleš Bezděk and Jaroslav Klokočník., and Obsahuje bibliografii