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	Input grid. Script Parameter: GRIDASIG.IN
Output analytic signal grid	Output analytic signal grid. Script Parameter: GRIDASIG.OUT
Z-derivative method	Select "FFT" (0) method (default) or "Convolution" method (1). Script Parameter: GRIDASIG.METHOD
Retain derivative grids?	If "yes", the intermediate derivative grids _dx.grd, _dy.grd and dz_grd are not deleted on exit.

Application Notes

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

asig = sqrt ( dx*dx + dy*dy + dz*dz ) 

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

The default Z-derivative method is "FFT method". However, in the case of a very large grid (over 4000x4000) using the "Convolution method" will save a large amount of processing memory and time.