Title Line

100 /sensor height

45/magnetic inclination

10/magnetic declination

55000 /magnetic field strength

TXYZ0 3 / filter

/===================================================================

/

/Following are descriptions of the MAGMAP process commands. Any number

/of commands may be entered starting in line 6. The order is not important.

/Each command consists of a 4 letter mnemonic followed by a space and a

/number of optional parameters, then a slash character. For example:

/

/BTWR 0.001,6,1 / apply a Butterworth low-pass filter

/DRV1 / first vertical derivative

/

/Parameters are numbered in order following each command:

/

/BPAS Apply a bandpass filter:

/

/ 1. the low wavenumber cutoff in cycles/metre. All wave numbers below

/this value will be removed.

/

/ 2. the high wavenumber cutoff in cycles/metre. All wave numbers

/higher than this will be removed.

/

/ 3. if 1, pass the defined band; if 0, reject the defined band. The

/default is to pass the band.

/

/BTWR Apply a Butterworth filter:

/

/ 1. The central wavenumber of the filter.

/

/ 2. degree of the Butterworth filter function. By default, a degree

/of 8 is used.

/

/ 3. a flag (0 or 1), to specify if a residual (0) high pass or a

/regional (1) low pass is required. By default, a regional filter

/is applied.

/

/CNUP Upward continue the data to a new level:

/

/ 1. the distance, in metres, to continue up relative to the plane of

/observation.

/

/CNDN Downward continue the data to a new level:

/

/ 1. the distance, in metres, to continue down relative to the plane

/of observation.

/

/COSN Apply a cosine rolloff filter:

/

/ 1. low wavenumber starting point of the filter.(Cut-off wavenumber

/for high-pass or start of roll off for low-pass.)

/

/ 2. high wavenumber end point of the filter.(Start of roll off for

/high-pass or cutoff wavenumber for low-pass.)

/

/ 3. the degree of the cosine function. The default is a degree of 2

/for a cosine squared rolloff.

/

/ 4. 0 for residual (high-pass) filter; 1 for regional (low-pass)

/filter. The default is a low-pass filter.

/

/DCOS Apply a directional cosine filter:

/

/ 1. direction of the filter in degrees (0-360 relative to true

/north).

/

/ 2. the degree of the cosine function. By default, a degree of 2 is

/used to give a cosine squared function.

/

/ 3. if 1, apply the filter to pass the specified direction; if 0,

/apply the filter to reject the specified direction. By default,

/the direction is rejected.

/

/DENS Produce an apparent density map:

/

/ 1. thickness, in metres, of the earth model.

/

/ 2. background density in g/cm3, to be added to the density contrast

/map. The default is 0.

/

/DPAS Apply a directional pass/reject filter:

/

/ Angles are measured clockwise relative to north.

/

/ 1. the low cut-off angle in degrees (0-360).

/

/ 2. the high cut-off angle in degrees (0-360).

/

/ 3. if 1, pass the defined band; if 0, reject the defined band. The

/default is to pass the band.

/

/DRVX,DRVY,DRVZ

/

/ Calculate the n'th derivative respective direction (X, Y or Z):

/

/ 1. order of differentiation.

/

/GAUS Apply a Gaussian regional/residual filter:

/

/ 1. the standard deviation of the Gaussian function in cycles/metre

/(similar to cutoff point).

/

/ 2. if 0, the residual component is produced; if 1 the regional

/component is produced.

/

/GNRL Apply a general radially symmetric filter. The filter is defined as

/ a piecewise linear function of wavenumber:

/

/ 1. the wavenumber increment (cycles/metres), starting from zero

/wavenumber, at which the following filter amplitudes are applied.

/

/ 2.-201.

/the coefficients of the filter function at each wavenumber

/increment starting at zero wavenumber. The last value given is

/used for all higher wave numbers. More than one line can be used

/to give the coefficients. A slash character (/) must follow the

/last coefficient.

/

/Normally, filter coefficients are between 0 and 1.For example,

/the following defines a low-pass filter that starts at a

/wavenumber of 0.003 and rolls of to remove all wave numbers above

/0.007:

/

/gnrl 0.001 1. 1. 1. 1. .8 .5 .2 0

/

/HPAS Apply a high-pass filter:

/

/ 1. the cutoff wavenumber in cycles/ metre. All wave numbers below

/this value are removed.

/

/INTG Vertical integration.

/

/LPAS Apply a low-pass filter:

/

/ 1. The cutoff wavenumber in cycles/metre. All wave numbers above

/this value are removed.

/

/NAIV Run MAGMAP using naive default options for all processes.

/

/OPTM Calculate and apply an optimum filter. The optimum filter will

/ remove the effect of all sources that would theoretically lie above

/ the specified filter depth. The filter coefficients are based on

/ analysis of the power spectrum:

/

/ 1. the depth at which to calculate the optimum filter. By default,

/the depth is taken from the flying height in the control file, or

/the continuation depth if specified by the CNDN or SUSC options.

/

/ 2. the wavenumber (cycles/m) at which to start the high-wavenumber

/rolloff. This parameter must be given together with parameter 4.

/By default, this point is calculated from the spectrum.

/

/ 3. the wavenumber (cycles/m) at which to end the high wavenumber

/roll-off. By default, this point is calculated from the

/spectrum.

/

/ 4. spectral density estimate of noise to be removed by the Wiener

/filter. This is in terms of the log of spectral density as

/reported in the second column of the power spectrum. By default

/this is calculated from the power spectrum.

/

/REDE Reduce the magnetic field to the magnetic equator.

/

/REDP Reduce the magnetic field to the magnetic pole:

/

/ 1. Inclination to which to use the phase component only. When

/reducing to the pole from equatorial latitudes, north-south

/features can blow-up due to the strong amplitude correction that

/is applied. By specifying a higher latitude for the amplitude

/correction, this problem can be reduced or eliminated.

/

/A value of 90 causes only the phase component to be used (no

/amplitude correction), and a value of 0 (zero) causes phase and

/amplitude components to be applied over the entire range. The

/default is 20 degrees.

/

/ROFP Rotate the magnetic field from the pole:

/

/ 1. Needs input from Gerry C here

/

/SUSC Produce a susceptibility map. Note that the input grid should have

/ the IGRF removed. This option invokes the REDP and CNDN options as

/ well as applying a filter to convert the magnetic field to

/ susceptibility:

/

/ 1. Depth in metres, relative to the observation level at which to

/calculate the susceptibility. By default the flying height

/reported in line 10 of the MCF constants is used.

/

/ 2. Inclination to which to use the phase component only in the

/reduction to the pole. The default is 20.

/

/TXYZ Convert magnetic field from T component (total field) or

/ Z component (vertical field) to another (X,Y,Z or T) component.

/

/ 1. Input transform field:

/0 total field.

/1 X field (not recommended for input, see note)

/2 Y field (not recommended for input, see note)

/3 vertical field (positive down)

/

/ 2. Output transform field, as above.

/

/ Note: The X and Y fields cannot be used to calculate the

/other fields because they do not contain information

/in the orthogonal direction, which is required. See

/the DXDYTF program, which can be used to calculate the

/total field if you have both the X and Y derivative fields.

/

/ Examples:

/

/ TXYZ 0 1 / calculate X field from total field

/ TXYZ 0 2 / calculate Y field from total field

/ TXYZ 0 3 / calculate vertical field from total field

/

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