MG-GRID

A New Gridding Standard

MG-GRID, is a new, fully automated process that uses measured, or calculated, horizontal magnetic gradients to optimize the gridding of the magnetic total field. This new process, offered exclusively by Scott Hogg & Associates, sets a new standard for the creation of high resolution grids and maps.

See the difference.... compare the maps below!

The geophysical data illustrated above was collected and processed with the support of DREA Canada.

Horizontal gradients show the way...

The MG-GRID process builds upon the SI-GRID interpolation technology introduced in 1998 by Scott Hogg & Associates Ltd. The gridding algorithm uses trend information, measured by horizontal gradients, to optimize the interpolation process. If measured gradient data is not available, supplemental processes can predict values suited to the process. The method does not require filtering or de-sampling of profile detail, nor does it entail any fitting or smoothing of the gridded output. All of the profile detail is preserved, unaltered, in the output grid. An overview of the underlying concepts is presented here.

Measured North and East magnetic gradients provide a means to calculate two angles. Dmax is the up-slope direction of maximum gradient and Dzero, transverse to Dmax, is tangential to the local contour direction.

If a magnetic anomaly is elongated, it has a trend direction that is the same as Dzero within its central region. In contrast, a circular anomaly has a constantly changing Dzero and no associated trend. The MG-GRID process calculates Dzero at each point along a flight line and by comparison from line to line identifies magnetic trend components automatically.

The trends measured are composites of those arising from regional or deep magnetic sources and those from near surface. It is the near surface geology that creates the complex short wavelength information that is the challenge. MG-GRID analyses the Dzero information and derives the trend component needed to control its interpolation process.

In the figure to the right, the measured direction Dzero, as calculated along each flight line, is graphically presented as a yellow vector aligned with the direction Dzero. The length of the yellow ticks varies to reflect the scalar amplitude of the gradient. The MG-GRID process assimilates this information and identifies its interpolation trend component, graphically illustrated by red vectors. The gray shading in the background is a presentation of the MG-GRID total magnetic field created (the high values are light coloured).

The MG-GRID process honours all of the profile detail. There is no de-sampling or pre-filtering of profile data and there is no smoothing of the gridded output.

The MG-GRID process produces a high resolution, minimum complexity grid, consistent with both the total field profile detail and trends derived from the horizontal gradient information. The MG-GRID technology eliminates the needless and confusing "beads-on-a-string" effect and preserves true anomaly cross-section width and detail along strike. Uniform sharp, true detail can be rendered coherently throughout the map.