SYSTEM AND METHOD FOR GRAVITY AND/OR GRAVITY GRADIENT TERRAIN CORRECTIONS

1 . A method for calculating gravity and gravity gradient terrain effects, the method comprising:

receiving a digital relief model (DRM) and gravity and/or gravity gradient data recorded at observation stations;

calculating with a computing device gravity and/or gravity gradient terrain effects at observation stations based on (i) a triangulated surface of the DRM and (ii) an adaptive triangulation method;

removing the gravity and/or gravity gradient terrain effects from the gravity and/or gravity gradient data to obtain gravity and/or gravity gradient terrain corrected data; and

generating gravity and/or gravity gradient anomalies of a surveyed subsurface based on the gravity and/or gravity gradient terrain corrected data.

2 . The method of claim 1 , wherein gravity data is related to any one or more components of a three-component gravity field vector, and gravity gradient data is related to one or more components of a nine-component gravity gradient tensor.

3 . The method of claim 1 , wherein an observation station is a location at which a measurement or observation is made, in air, on land, at sea, in water, at water bottom, or in a borehole.

4 . The method of claim 1 , wherein the adaptive triangulation method is the adaptive Delaunay triangulation.

5 . The method of claim 1 , wherein the adaptive triangulation method is the adaptive quadtree based triangulation.

6 . The method of claim 1 , wherein the adaptive triangulation method uses a roughness of the DRM.

7 . The method of claim 1 , wherein the adaptive triangulation method receives as input an error tolerance.

8 . The method of claim 7 , wherein the adaptive triangulation method also receives as input one or more components of a gravity field vector and/or a gravity gradient tensor to be calculated.

9 . The method of claim 8 , wherein each received component of the gravity field vector or gravity gradient tensor has an associated error tolerance.

10 . The method of claim 1 , wherein the adaptive triangulation method also receives as input a density distribution associated with the DRM.

11 . The method of claim 10 , wherein the density distribution has two or more values when the DRM includes land topography and marine bathymetry, and a density for a land topographic mass or a mass below the water bottom is constant or variable.

12 . The method of claim 1 , wherein the DRM includes land topography and marine bathymetry.

13 . The method of claim 1 , further comprising:

inserting a coastline that defines a boundary between land topography and marine bathymetry or a water body.

14 . The method of claim 1 , further comprising:

calculating the gravity and/or gravity gradient terrain effects due to a triangular prism by using a closed-form formulae or the Gaussian quadrature.

15 . The method of claim 1 , wherein the gravity data include measurements made with a gravimeter directly or a gravity value derived from other measurement results, and gravity gradient data include measurements made with a gravity gradiometer directly or a gravity gradient value derived from other measurement results.

16 . A computing device for calculating gravity and gravity gradient terrain effects, the computing device comprising:

an interface for receiving a digital relief model (DRM) and gravity and/or gravity gradient data recorded at observation stations; and

a processor connected to the interface and configured to,

calculate gravity and/or gravity gradient terrain effects at observation stations based on (i) a triangulated surface of the DRM and (ii) an adaptive triangulation method,

remove the gravity and/or gravity gradient terrain effects from the gravity and/or gravity gradient data to obtain gravity and/or gravity gradient terrain corrected data, and

generate gravity and/or gravity gradient anomalies of a surveyed subsurface based on the gravity and/or gravity gradient terrain corrected data.

17 . The computing device of claim 16 , wherein gravity data is related to any one or more components of a three-component gravity field vector, and gravity gradient data is related to one or more components of a nine-component gravity gradient tensor.

18 . The computing device of claim 16 , wherein the adaptive triangulation method is the adaptive Delaunay triangulation or an adaptive quadtree based triangulation.

19 . The computing device of claim 16 , wherein the adaptive triangulation method receives as input an error tolerance.

20 . A non-transitory computer readable medium including computer executable instructions, wherein the instructions, when executed by a processor, implement instructions for calculating gravity and gravity gradient terrain effects, the instructions comprising:

receiving a digital relief model (DRM) and gravity and/or gravity gradient data recorded at observation stations;

calculating with a computing device gravity and/or gravity gradient terrain effects at observation stations based on (i) a triangulated surface of the DRM and (ii) an adaptive triangulation method;

removing the gravity and/or gravity gradient terrain effects from the gravity and/or gravity gradient data to obtain gravity and/or gravity gradient terrain corrected data; and

generating gravity and/or gravity gradient anomalies of a surveyed subsurface based on the gravity and/or gravity gradient terrain corrected data.