Quis enim aut eum diligat quem metuat, aut eum a quo se metui putet? Coluntur tamen simulatione dumtaxat ad tempus. Quod si forte, ut fit plerumque, ceciderunt, tum intellegitur quam fuerint inopes amicorum. Quod Tarquinium dixisse ferunt, tum exsulantem se intellexisse quos fidos amicos habuisset, quos infidos, cum iam neutris gratiam referre posset.

Quis enim aut eum diligat quem metuat, aut eum a quo se metui putet? Coluntur tamen simulatione dumtaxat ad tempus. Quod si forte, ut fit plerumque, ceciderunt, tum intellegitur quam fuerint inopes amicorum. Quod Tarquinium dixisse ferunt, tum exsulantem se intellexisse quos fidos amicos habuisset, quos infidos, cum iam neutris gratiam referre posset.

Quis enim aut eum diligat quem metuat, aut eum a quo se metui putet? Coluntur tamen simulatione dumtaxat ad tempus. Quod si forte, ut fit plerumque, ceciderunt, tum intellegitur quam fuerint inopes amicorum. Quod Tarquinium dixisse ferunt, tum exsulantem se intellexisse quos fidos amicos habuisset, quos infidos, cum iam neutris gratiam referre posset.
The gravity technique is based on measuring localised variations in the Earth’s gravitational field which are caused by materials of different densities. Typical targets for high resolution ‘microgravity’ surveys include (i) low density targets such as caves, fault zones, mine-workings and basements, and  high density targets such as dykes, shallow rock, buried walls etc.

The presence of an anomalously high (or low) density body in the subsurface causes a localised high (or low) anomaly in the measured gravitational field.
Example 1 gravity anomaly created by a gallery 
(modeling of an infinite cylinder of 2.00m of diameter in a homogeneous medium of 2.2g / cm3 whose roof is located at different depths)

The gravity effects described can be extremely small, however, modern instrumentation and exhaustive data processing techniques enable detection of both geological and artificial structures or voids. GEMSOL UK Ltd also carries out regional gravity surveys targeting hydrocarbon traps or groundwater resources for local supply or geothermal energy.
Example Cavity Detection Threshold 
(modeling of a sphere in a homogeneous medium of density 2.2 g / cm3 whose roof is located at different depth Z)

               <  Gravimeter

                                                                                   Maps map of the anomaly of bouguer >