Process Grids

Use the Euler 3D > Process Grids menu option (E3PREP GX) to compute x, y, and z derivatives of an input grid. This is a necessary first step in Euler deconvolution.

Compute Derivative Grids dialog options

Input Grid	name of input grid file (no default) Script Parameter: E3PREP.GRID
X-derivative output grid	name of output x-derivative grid file (default "dx.grd") Script Parameter: EULER3D.DX
Y-derivative output grid	name of output y-derivative grid file (default "dy.grd") Script Parameter: EULER3D.DY
Z-Derivative output grid	name of output z-derivative grid file (default "dz.grd") Script Parameter: EULER3D.DZ
distance to upward continue	distance to upward continue the input grid (optional) Script Parameter: E3PREP.UPCONT
output upward-continued grid	name of output upward-continued grid file (optional) Script Parameter: E3PREP.UPGRD
Grid expansion in FFT	Option for grid expansion in FFT processing, either "square" or "rectangular", default is square. Script Parameter: E3PREP.XSHAPE

Application Notes

The x and y derivatives are computed in the space domain using a simple nine-point convolution filter. The z derivative filter does not have such a simple spatial representation, so it is implemented in the frequency domain.

To create the (smoothed) DX and DY grids, upward continuation may be necessary if the data contains significant short wavenumber noise. Upward continuation effectively attenuates noise without changing the physical significance of the data (as opposed to a low-pass filter, which does change the significance of the data). A continuation distance of one grid cell is not uncommon, although you should be critical of how much resolution you are losing in the smoothed data when you choose the upward continuation distance.

FFT filtering the original input grid is used to calculate the z-derivative. This involves expanding and filling the input grid before calculating the Fourier transform. The default is to expand to a square grid, but if the input grid is long and narrow, it is more accurate and time-efficient to expand to a rectangle.

Output TRN Grid

The E3PREP process creates a transform (TRN) grid. This TRN grid can now be redirected to a specific location for use in Geosoft Scripts by using this parameter:

E3PREP.TRNGRD="filename.grd"