We present a toolbox expressly written for MATLAB platform to provide terrain corrections of gravity data. The program performs the complete Bouguer computations, including the Bullard A, the Bullard B and the Bullard C corrections, from any kind of free air datasets (offshore or on land stations). The gravity contribution due to the relief is computed starting from a gridded topography in which any each grid point corresponds to the thickness of a right rectangular prism having its base at the sea level. The computation is carried out on a circular region having its centre in the point station and divided in three different concentric sectors. The contribution due to the relief delimited in the external sector is calculated by means of the harmonic spherical expansion of the potential of each prism. The gravity effect due to the relief enclosed within the intermediate sector is computed by summation of the contributions of any single prism located in this area by means of an analytical formula. In a third phase, is calculated the gravity effect due to the inner zone, bounded by the eight nearest grid points and forming four squares located around the point station. It is computed following two steps: Firstly, the contribution of a flat prism having its top at the elevation of the point station is computed. Finally, the result is added to the effect due to a conic prism divided in four different quadrants. Each of them slopes continuously from each square of the inner zone toward the point station. The complete terrain correction results by adding tha values resulting from eachy step. The program results suitable because it allows to modify all the parameters playing a role in the calculation (i.e., radius of the circular search area, extent of the external and intermediate sectors, reference density, etc.,) and is really easy-to-use because all input data are enclosed in a single command line that can be fastly modified. Finally, a real case is presented to show the reliability of the method.
A MATLAB toolbox for computation of complete Bouguer anomalies from free air anomalies.
CELLA, Federico
2011-01-01
Abstract
We present a toolbox expressly written for MATLAB platform to provide terrain corrections of gravity data. The program performs the complete Bouguer computations, including the Bullard A, the Bullard B and the Bullard C corrections, from any kind of free air datasets (offshore or on land stations). The gravity contribution due to the relief is computed starting from a gridded topography in which any each grid point corresponds to the thickness of a right rectangular prism having its base at the sea level. The computation is carried out on a circular region having its centre in the point station and divided in three different concentric sectors. The contribution due to the relief delimited in the external sector is calculated by means of the harmonic spherical expansion of the potential of each prism. The gravity effect due to the relief enclosed within the intermediate sector is computed by summation of the contributions of any single prism located in this area by means of an analytical formula. In a third phase, is calculated the gravity effect due to the inner zone, bounded by the eight nearest grid points and forming four squares located around the point station. It is computed following two steps: Firstly, the contribution of a flat prism having its top at the elevation of the point station is computed. Finally, the result is added to the effect due to a conic prism divided in four different quadrants. Each of them slopes continuously from each square of the inner zone toward the point station. The complete terrain correction results by adding tha values resulting from eachy step. The program results suitable because it allows to modify all the parameters playing a role in the calculation (i.e., radius of the circular search area, extent of the external and intermediate sectors, reference density, etc.,) and is really easy-to-use because all input data are enclosed in a single command line that can be fastly modified. Finally, a real case is presented to show the reliability of the method.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
