Import UBC Mag3D Model(s)

Use the Database > Import > UBC Mag3D Model(s) menu option (IMPUBCMODMSH GX) to import UBC 3D Model & MSH files to a Geosoft Database.

Import UBC Mag3D Model(s) dialog options

Model file(s)	Select one or more MOD files to import. Each will be imported to a single channel. Those ending in ".den" will be imported to "Density"; those ending in ".sus" will be imported to "Susceptibility" and all others will be imported to a channel with the given extension; e.g. "test.mag" would be imported to the channel "mag". See below for the format. Script Parameter: IMPUBSMODMSH.MOD: Multiple files delimited with "|"
MSH header file	The Mesh file, containing a description of the 3D mesh. See below for the format. Script Parameter: IMPUBSMODMSH.MSH
Import as planes in	Select "X", "Y" or "Z" to select how the data is imported. Each slice or plane of blocks is imported to a single line in the database, beginning at L0. The slices can be defined as parallel to any of the three axes. Selecting "Z" means that you can select any individual line and grid and plot that elevation directly. If you specify "X" or "Y" each line represents a vertical section in the model. In order to grid "X" or "Y" lines, you must reset the Current X and Y channels (under the Coordinates menu) to be "Y" and "Z" for the "X" slices, or "X" and "Z" for the "Y" slices. Then you may select an inidividual line for gridding and display. Script Parameter: IMPUBSMODMSH.DIR: 0: "X", 1: "Y", 2: "Z"
Value to interpret as dummy	There is no fixed dummy value in UBC mod files; it normally is set as -9.0, but it can be -90.0, for instance, if there is real data smaller than -9.0. Script Parameter: IMPUBSMODMSH.DUMMY (default -9.0)

MSH Header File Format

This file contains the 3D mesh which defines the model region. The mesh has the following structure:

NE  Number of cells in the East direction.

NN  Number of cells in the North direction.

NV  Number of cells in the vertical direction.

E0, N0, V0  Coordinates, in meters, of the southwest top corner, specified in (Easting, Northing, Elevation).

Model File Format

Model files consist of a total of NE*NN*NV values, one per line, as in the following example:

[i j k]=[1 1 1] is defined as the cell at the top-south-west corner of total number of lines in this file should equal NN NE NV, where NN is the in the North direction, NE is the number of cells in the East direction, and NV cells in the vertical direction. The lines must be ordered so that k changes the 1 to NV), followed by j (from 1 to NE), then followed by i (from 1 to NN).

The dummy value is -9.0, and is automatically converted to a Geosoft dummy on import.

The above descriptions are derived from the following document:

MAG3D

A Program Library for Forward Modelling and

Inversion of Magnetic Data over 3D Structures

VERSION 3.0

Developed under the consortium research project

JOINT/COOPERATIVE INVERSION OF

GEOPHYSICAL AND GEOLOGICAL DATA

UBC–Geophysical Inversion Facility

Department of Geophysics and Astronomy

University of British Columbia

Vancouver, British Columbia