Analytic Signal

Use the Grid and Image > Filters > Analytic Signal menu option (GRIDASIG GX) to calculate the analytic signal of a grid.

The option is also available in the 2D Filtering extension under the 2D Filtering menu.

Analytic Signal dialog options

Input grid

Select the input grid.

Script Parameter: GRIDASIG.IN

Output analytic signal grid

Specify the output analytic signal grid.

Script Parameter: GRIDASIG.OUT

Z-derivative method

Select the method for calculating the Z-derivative:

  • FFT (default)

  • Convolution

Script Parameter: GRIDASIG.METHOD [0 - FFT; 1 - Convolution]

Retain derivative grids?

If Yes, the intermediate derivative grids (_dx.grd, _dy.grd, and _dz.grd) are retained and not deleted on exit.

Application Notes

The analytic signal is calculated as the square root of the sum of the squares of the derivatives in the x, y, and z directions:

The analytic signal is useful for locating the edges of magnetic source bodies, particularly in cases where remanence and/or low magnetic latitude complicates interpretation.

The default Z-derivative method is the FFT method. However, for very large grids (greater than 4000 × 4000), using the Convolution method can significantly reduce memory usage and processing time.