Mag, Derivative and Analytical Signal Grids

Use the Calculate and Display Analytical Signal Grid option (UXMAGASI GX) to create a grid (GRD) file of the total field magnetic data using the minimum curvature gridding method, and then calculate the derivative grids and finally the analytic signal grid.

Mag, Derivative and Analytical Signal Grids dialog options

Mag channel to grid

Magnetic data channel to grid

Script Parameter: UXMGRGRD.CHAN

Output total field grid

Output grid (*.grd)

Script Parameter: UXMGRGRD.GRID

Output X-derivative
grid

X-derivative grid

Script Parameter: UXDXDYDZ.DX

Output Y-derivative
grid

Y-derivative grid

Script Parameter: UXDXDYDZ.DY

Output Z-derivative
grid

Z-derivative grid

Script Parameter: UXDXDYDZ.DZ

Z-derivative method

0 – FFT method (default)

1 – Convolution method

Script Parameter: UXDXDYDZ.METHOD

No. of passes of
smoothing filter

Number of passes

Script Parameter: UXMGRGRD.PASS

Output analytic signal
grid

Analytic signal grid

Script Parameter: UXASIG.ASIG

Display analytic signal grid

Display analytic signal in a single grid (1), colour shaded grid (2) or don't display (0)

Script Parameter: UXMGRGRD.DISPL

Display colour bar

Display colour bar vertically (1), horizontally (2) or don't display (0)

Script Parameter: UXMGRGRD.COLORBAR

[Controls]

Click this button to set up the minimum curvature gridding (RANGRID GX) controls dialog.

Application Notes

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

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 )

This GX provides interfaces for you to set parameters to grid the total field magnetic data. It then uses other GX’s in UXO package to grid the data and display the grids in the current map.

If the grids are to be displayed, and no map is current, an additional dialog will appear requesting a map name.

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.

See Also: