Since the launch of the satellite GOCE the gravity field is available globally on earth at a resolution that poses exciting challenges in the study of tectonic and geologic features. The satellite derived gravity fields are published in terms of spherical harmonic expansion, which requires basic knowledge of this technique. Here the essential properties of the field in this formulation are illustrated, with the intent to give sufficient insight to allow the interested reader to calculate the gravity fields in the own area of interest and draw helpful conclusions on the comprehension of the geologic context through qualitative considerations of the gravity field. The gravity models are publicly available as well as the necessary software to compute the fields, offering a useful tool applicable in diverse situations in which subsurface density variations reveal hidden geologic processes, ranging from earth structure and its time variations, earth tides, detection of caves, and the study of earthquakes.
