Pseudo-Gravity (GPSD)

Use the Pseudo-Gravity option to apply the pseudo-gravity filter.

Pseudo-Gravity Filter dialog options

Date (YYYY/MM/DD)	Enter the date when the survey has been conducted to automatically calculate and populate the inclination and declination of the IGRF field. The calculate button appears to the right of the date entry once a valid date is entered. This is an optional field.
Inclination	Geomagnetic inclination (I) in degrees from the horizon.
Declination	Geomagnetic declination (D) in degrees azimuth.
Density contrast	Density contrast (d) in g/cm³ (Default 1.0).
Magnetization	Magnetization (J) in nT (Default 50000).
Amplitude correction inclination	Inclination to be used for the amplitude correction (Ia). Default is $image\ebx_-132491598.jpg$ 20 degrees. If \|Ia\| is specified to be less than \|I\|, it is set to I.

Application Notes

In general, on input you would supply the TMI grid. You could, however, start with the pole reduced grid. In this case you should set the inclination to 90; the declination is immaterial and can be set to 0.

Pseudo-Gravity

if (|I_ɑ| < |I|), I_ɑ=I

Where:

I	geomagnetic inclination
I_ɑ	inclination for amplitude correction (never less than I) Default is ± 20 degrees. If \|I_ɑ\| is specified to be less than \|I\|, it is set to I.
d	density contrast in g/cm³
G	gravitational constant, 6.6738
J	magnetization in nT
D	geomagnetic declination

Parameters:

direction of wavenumber in degrees azimuth

wavenumber (radians/ground_unit)

Note: r = 2pk where k is cycles/ground_unit.

Wavenumber domain variable definition


k	Wavenumber domain increment, used to depict a radially symmetrical variable.	where: np is the number of points cs is the cell size
u	X component in the wavenumber domain.	k = 2π ( i μ+j ν )
v	Y component in the wavenumber domain.
r	Radial component in the wavenumber domain.	also 2πk
θ	Polar component in the wavenumber domain.

Ground_unit is the survey ground units used in your grid (eg. metre, feet etc.).

Output Pseudo-Gravity is in unit of mGal if ground_unit is metre or 0.3mGal if ground_unit is feet.