{"thcode":2,"term":{"code":501,"name":"gravitational field (earth)","parent":287,"scope":"Region or space around earth's mass which exerts a force that mutually attracts other masses in proportion to the product of the two masses and the distance between them."},"uf":[{"name":"gravity","usewith":false},{"name":"gravity anomaly maps","usewith":{"code":700,"name":"maps and atlases","parent":808,"scope":"Representation, usually on a flat surface, of a part or whole of the Earth or other parts of the universe.  Collections of maps linked digitally or bound together in a book are called atlases."}},{"name":"gravity field","usewith":false}],"bt":[{"code":287,"name":"earth characteristics","parent":1174,"scope":"The measurable, definable properties and features of the earth."},{"code":1174,"name":"topics","parent":1,"scope":"Themes, subjects, and concerns for which USGS information resources are relevant."},{"code":1,"name":"Categories","parent":null,"scope":"Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."}],"nt":[{"code":1675,"name":"bouguer anomaly","parent":501,"scope":"Gravity anomaly corrected to remove the effects of topography using knowledge of the terrain in the area surrounding the measurement station."},{"code":1674,"name":"free-air anomaly","parent":501,"scope":"Gravity anomaly corrected for elevation of the location at which the measurements were made."},{"code":2291,"name":"gravity gradient","parent":501,"scope":"Lateral variation of the three-dimensional vector components of gravity, typically measured using airborne sensors."},{"code":1673,"name":"isostatic anomaly","parent":501,"scope":"Gravity anomaly corrected for the effects of low-density rocks underlying mountains."}],"rt":[{"code":470,"name":"geophysics","parent":291,"scope":"Branch of geology studying the physical characteristics and phenomena of the earth and its atmosphere."},{"code":2298,"name":"inverse modeling","parent":713,"scope":"An iterative approach to estimate the form and characteristics of a physical system explained by observations or measurements. Frequently used to determine a subsurface geological structure from measurements of physical properties obtained at or near the earth's surface."}]}