Magnetic Data Processing

All routine processing steps can be performed:

  1. Compensation:
    Generally fluxgate measurements are used to remove manoeuvre noise of the aircraft. This can be done with a compensator or using software either in real-time or as a separate post-processing step. We can offer a recalibration of compensation coefficients and perform a compensation to reduce manoeuvre effects.
  2. Dynamic lag time correction:

    There are often two reasons for some time delay in the magnetic data set, (i) a used compensator produces the mag data with a short delay or/and a Butterworth filter employed may delay the signal slightly and (ii) the mag sensor is not at the same forward position as the reference point of the stored positional data. A dynamic lag time correction can correct for these effects using the speed of the aircraft calculated for each individual position.

  3. Removal of Diurnals

    Magnetic ground station data is scanned for artifacts (gaps, passing vehicles) and then subtracted from the airborne data without changing the general data level.

  4. International Geomagnetic Reference Field IGRF:

    The data is merged with coordinates of the flight path which can be in any projection and datum. The IGRF program converts on the fly the coordinates and datum to WGS-84 lon-lat-height and calculates for each record separately for the given epoch all necessary elements of the geomagnetic field, generally only total magnetic intensity.

  5. Levelling

    A database of intersection data (a standard c++ container of objects) is used to get a balanced set of correction values for traverse and control line intersections using a specially designed relaxation process. A file for manual corrections can be provided for a priori values at intersections or at additional points along lines. These can be applied before or after the relaxation process, absolute or relative. An interpolation polynomial is employed between correction positions giving a continuous differential function over the whole flight line with extremely small overshooting matching the provided values exactly at intersections. This polynomial can be be chosen as tightly as desired to follow a linear interpolation or similar to a spline interpolation. A parameter can control the maximum deviation from a linear interpolation.

  6. Gridding

    Data will be gridded using the continuous curvature gridding algorithm surface of Generic Mapping Tools. This routine allows for a tension factor between 0 and 1 giving a minimum curvature grid if set to 0.

  7. Micro-levelling/Decorrugation

    Specifically designed filter on grid data can reveal further subtle levelling issues. These generally small corrections can be added to the line data to get superior levelled line data retaining the along-line details.

  8. Derivatives

    Most advanced Fast Fourier Transformation techniques (FFTW3) will be employed for the application of any Fourier domain filter at line or grid data. A great number of derivatives can be carried out at highest efficiency like First Vertical Derivative or any higher order, directional filters, Hilbert transforms, upward continuation and more.

  9. Reduction to the pole

    Reduction to the pole can be done in the Fourier domain using the FFTW3 library. The development of a dynamic version which can be used for a large area with changing inclination and declination is considered.

  10. Euler Deconvolution

    A simple Euler Deconvolution can be carried out and maps can be produced of the results. Some more sophisticated methods in this field may be developed.

  11. Tilt-angle depth analysis

    This method is similar to the Euler Deconvolution using higher derivatives and calculating locations without the need of values for the Structural Index. Estimates for the Structural Index can be derived from this analysis and could be used for the Euler Deconvolution.