Input data can be sourced from (1) GIS or other 3-dimensional modelling software which produce MIF (MapInfo Interchange Format) or DXF formatted files, (2) from spreadsheet software which produce ASCII files, column-formatted (each column corresponding to eg: location [X,Y,Z], structural measurements, grade, petrophysical properties such density and magnetic susceptibility, etc), and (3) from the interactive manual capture of structural information at one locality.
Figure 1 shows the dialog box allowing to import MapInfo Interchange Format files into gOcad and the resulting object in the gOcad camera. The input file corresponds to the MapInfo provided political boundary file of the world in the latitude-longitude coordinate system. The dialog box to import DXF formatted file is also shown.
Both converters will allow input for any point or line objects. The Mapinfo to gOcad® converter allows to import any numerical properties (floating point or integer values) previously assigned to MapInfo objects. Properties such as structural measurements (planar surfaces) are converted into a vectorial property which can then be used to constrain the geometry of a model (see Fig. 2).
Structural measurement can be entered using three different convention: (1) right hand rule (looking in the direction of the strike, the dip is on the right hand side, eg: 135 50), (2) dip / dip-direction (50 225, and (3) strike, dip, dip-direction (135 50 SW).
These functions were specifically designed to allow an easy input of structural data (foliation and lineation measurements) from measurements taken in the field and digitally captured within a spreadsheet software.
Structural information is converted into a gOcad point (Fig. 2) associated to a vector property (normal to the measured plane and/or lineation) and any other numerical properties assigned to the points in the ASCII file. The structural points are used to constrain the model using normal gOcad® functions. Table 1 shows the ASCII file used to create the points in Figure 2.
A common format used to exchange 3-dimensional models or objects is via the Virtual Reality Modelling Language (VRML). The gOcad® software already proposes to generate VRML models from a list of objects. Still under development, these filters do not allow to export a set of points which are color-coded according to a property. Since hard-rock geology data are very often sparse and discrete, it appeared necessary to be able to save clouds of points as VRML objects corresponding to (1) a stand alone VRML file or (2) a VRML object to be incorporated in a bigger VRML model by further file handling.
Figure 3 the dialog box allowing to output VRML sets of points. The generated VRML model is a spherical representation of the seismicity in the Banda Arc region and along the Australian / Indonesian subduction system. Political boundaries have been added using the classical gOcad function. Depth of hypocentres is color-coded.