Reduce to Magnetic Equator (REDE)

Use the Reduce to Magnetic Equator option to apply the reduce to the magnetic equator filter.

Reduce to Magnetic Equator dialog options

Date (YYYY/MM/DD)	Enter the date when the survey was 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
Amplitude correction inclination	Amplitude correction inclination Ia in degrees. Default is +20.0 in the northern hemisphere and –20.0 in the southern hemisphere

Application Notes

Reduction to the equator is used in low magnetic latitudes to centre the peaks of magnetic anomalies over their sources. This can make the data easier to interpret while not losing any geophysical meaning. Reducing the data to the pole (REDP) does much the same thing, but at low latitudes, a separate amplitude correction is usually required to prevent North-South signal in the data from dominating the results. As a result, reduced to the pole data may present a less 'honest' view of the data

Reduction to the equator has an amplitude component (sin(I) ) and a phase component ( i cos(I) cos(D-θ) ). When reducing to the equator, features normal to the declination direction can blow up due to the strong amplitude correction that is applied. A strong discontinuity occurs in the direction normal to the declination D. By specifying a higher latitude for the amplitude correction alone, this problem can be reduced. This is however at the expense of under-correcting the amplitudes of features along the declination direction.

If a date is entered to calculate the inclination and declination, and if the grid does not have a coordinate system assigned, you will be prompted to defined it. The IGRF date and parameters, once defined, become the values used in other controls that require them. The field strength is only required for apparent susceptibility calculation, but is re-calculated along with the inclination and declination in the other controls, so the values are always synchronized.

Reduce to the magnetic equator

if (| Ia | < | I |), Ia = I

Where:

I	Geomagnetic inclination in °
D	Geomagnetic declination in ° azimuth
Ia	inclination for amplitude correction (never less than I) Default is ± 20 degrees. If |Ia| is specified to be less than |I|, it is set to I.