This free (for Geometrics magnetometer owners) powerful data processing and modelling package provides data base management, file importation, girding, contouring and dipole pattern matching source body modelling for the experienced geophysicist or potential field data processor. Output includes a table of target anomaly locations and depths. Includes pre-processing of GPS locations and data reformatting.
MagMap2000 - Pre-Processing Tool
Reads GPS/ Geometrics Mag records and converts them into UTM/Transverse Mercator system based on standard or custom ellipsoids. Filters GPS positions to eliminate errors and smoothes the track as required.
Layback calculations are included. Exports results in the format suitable for other girding and contouring programs and for usage by MagPick.
MagPick - Processing And Interpretation Tool
Provides visual analysis of the magnetic map and manual or automatic selection of anomalies. Includes: Viewing the magnetic map with dynamic adjustment of colour scale in accordance with min/max of the data. Program allows enlarging or zooming into different parts of the map and presenting zoomed sections in separate windows with automatic change of the colour scale to fit the data range.
IGRF (Earth's magnetic field) model till 2005 plus UTM transformation is included MagPick interpolates the map grid based on profile data using splines in a tension algorithm or by triangulation. The map can be viewed in different modes including colours, contours, shaded or illuminated relief. MagPick allows the user to increase resolution of existing maps with a bi-linear or spline interpolation and also provides a utility to smooth the grid using a relaxation algorithm.
For residual (total field minus local IGRF field) magnetic maps, MagPick provides tools for upward/downward continuation, reduction to the pole and synthetic gradient calculation.
Additional information such as lines, polygons and annotated points can be drawn and then loaded as an overlay on top of the magnetic map.
Visual analysis of the profile data includes loading of initial (profile) measurements and plotting their geometrical positions on the top of the map. The observed magnetic field can be viewed as a set of linear graphs such as T(x), T(y), T(l) and T(p) where T is the field, x,y are planar co-ordinates of observed points, l is the distance along the profile, p is the projection of the profile on a line selected by user. Markings on the profile automatically appear on the map view and vice versa.
The following operations are available for profile data:
- Spline smoothing and regional field removal.
- Erasing parts of the profile.
- Exporting profile data in user-drawn a polygon, thus creating a new set of profiles.
- Scaling of the profile data.
- Allows plotting of annotated stacked profiles.
- Shifting profile positions.
- Layback calculation (as in MagMap2000).
Locating Magnetic Source Bodies
MagPick does a quantitative interpretation based on fitting of the observed magnetic anomaly using the field of a simple source. Both map or profile information can be used, and geometrical and magnetic parameters of the source can be estimated. Presently it is possible to locate two types of sources.
A. Magnetic dipole (magnetised sphere). The position and depth of the centre are estimated.
B. A horizontal magnetic line of finite length.
- Pipe sections can be modelled by such a source.
- Positions of the ends and depth of the pipe are to be estimated.
- In order for the Dipole Interpretation package to function properly, it requires starting points from which to converge on the source body location.
That data is supplied by the following two techniques:
Simple Magnetic Anomaly Picking
Allows the user to select two points with a mouse and store their positions in a file. Interpretation routine assumes that the X-Y position of the body is between the local minimum and maximum of the field.
Advanced Magnetic Anomaly Picking
User selects rectangular regions of maxima and minima field values and the program automatically locates the precise position.
During interpretation, MagPick provides interactive selection of the data by using the zoom window or by restriction of the polygonal shape.
Results of the interpretation are presented in the form of a worksheet and are plotted on the magnetic maps. QC analysis is performed by comparing observed and synthetic magnetic fields.